I:\MEPC\55\2-4.doc 

For reasons of economy, this document is printed in a limited number. Delegates are 

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INTERNATIONAL MARITIME ORGANIZATION

IMO 

E

MARINE ENVIRONMENT PROTECTION 

COMMITTEE 

55th session 

Agenda item 2 

MEPC 55/2/4

 21 April 2006

 Original: ENGLISH

HARMFUL AQUATIC ORGANISMS IN BALLAST WATER 

Basic Approval of Active Substances used by EctoSysô electrochemical system 

Submitted by Sweden 

SUMMARY 

Executive summary: This document contains non-confidential information for Basic 

Approval of Active Substances used by EctoSysô electrochemical 

system as required by the Procedure for approval of Ballast Water 

Management systems that make use of Active Substances (G9). 

Relevant documents together with the application dossier have been 

submitted to Marine Environment Division of the Organization for 

review by the GESAMP ñ Ballast Water Working Group in 

accordance with the provisions of the above mentioned procedure. 

Action to be taken: Paragraph 6 

Related documents: BWM/CONF/36, MEPC 53/24/Add.1, BWM.2/Circ.4 

Introduction 

1 Regulation D-3.2 of the International Convention for the Control and Management of 

Shipsí Ballast Water and Sediments stipulates that Ballast Water Management sytems that make 

use of Active Substances to comply with the Convention shall be approved by the Organization. 

2 The Procedure for approval of Ballast Water Management systems that make use of 

Active Substances (G9) adopted by resolution MEPC.126(53) defines principle aspects to be 

documented by data or testing (MEPC 53/24/Add.1, annex 4, paragraph 4.2.1) and some basic 

principles for risk evaluation (MEPC 53/24/Add.1, annex 4, paragraph 5.3). According to 

section 6 of the Procedure (G9) the Organization should evaluate the information provided in the 

application. 

3 According to BWM.2/Circ.4 proposals for approval of Ballast Water Management systems 

that make use of Active Substances are to be submitted to Marine Environment Division of the 

Organization to be reviewed by the GESAMP-Ballast Water Working Group. In the meantime, a 

document on the proposal for approval containing all the non-confidential data related to the 

respective Active Substance needs to be submitted to MEPC 55. 
MEPC 55/2/4 - 2 - 

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4 The competent authority in Sweden has verified the application dossiers prepared by 

Permascand AB and believes them to satisfy the data requirements of the Procedure (G9). 

5 Sweden therefore submits the non-confidential part of the applicantís dossier in the annex 

of this document to the Organization for evaluation according to the Procedure (G9). 

The complete dossier will be made available to the experts of the GESAMP-Ballast Water 

Working Group with the understanding of confidential treatment. 

Action requested of the Committee

6 The Committee is invited to consider the proposal for approval and decide as appropriate. 

*** 
MEPC 55/2/4 

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ANNEX

1 INTRODUCTION 

The applicant is proposing an electrochemical system, the EctoSysô, as the disinfection step in a 

complete system for ballast water treatment. EctoSysô is an electrochemical system utilizing 

electrodes with high oxygen overpotential, and therefore producing powerful disinfectants such 

as the hydroxyl radical directly into the media and also providing direct oxidation of 

microorganisms and other contaminants on the electrode surface. In addition, small amounts of 

harmless disinfecting by-products (i.e. free active chlorine) from the cell prevent regrowth in the 

tanks and biofouling, and by the cell design and electrode configuration preventing the formation 

of secondary chlorinated organics such as for example trihalomethanes (THM:s). The EctoSysô 

is designed for purification and disinfection in high flow applications with conductive medias 

such as natural sea water or brackish water. One single, compact module can be dimensioned for 

treatment of flows up to 500 m3

/h, with no additional chemicals and a minimum of maintenance 

needed. The EctoSysô is typically used for ballast water treatment as the disinfecting step after 

mechanical separation (e.g. filters, hydrocyclones) of contaminants down to 40-45 μm scale. The 

water is typically treated both during ballasting and deballasting. 

An electrochemical cell working with a natural water media such as sea water could theoretically 

produce an endless number of various oxidative species. However, the oxidative species and 

by-products produced in the EctoSysô either has a very short degradation time, are produced in 

extremely low concentrations (in the order of natural occurrence in sea water) or are completely 

harmless. The air emissions resulting from treatment will contain oxygen gas and small amounts 

of hydrogen gas and carbon dioxide. Neither the Active Substances nor any of the relevant 

chemicals are bio accumulative or persistent and will ultimately degrade under environmental 

conditions to oxygen, water, carbon-dioxide and chloride in detectable levels. 

The key factors for the EctoSysô electrochemical system are the electrode type and the cell 

design. Permascand AB has over 30 years of experience in developing, producing and 

characterizing different kinds of electrochemical cells, electrodes and catalytic coatings used by 

the electrochemical industry. Different kinds of electrodes and coatings are used for different 

industrial applications and - in the case of treating ballast water - by using catalytically inactive 

electrodes with high oxygen- and hydrogen overpotentials it is possible to selectively produce the 

desired highly oxidative species (i.e. hydroxyl radicals) without the problems associated with 

conventional chlorine electrolysis. 

2 APPLICATION FOR THE USE OF CHEMICAL ACTIVE SUBSTANCE 

The use of ìActive Substancesî by this electrochemical system refers to the descriptions and 

definitions given in the Procedure for approval of Ballast Water Management systems that make 

use of Active Substances (G9) adopted by resolution MEPC.126(53) and does not fall under the 

Directive 98/8/EC of the European Parliament and of the Council of 16 February 1998 

concerning the placing of biocidal products on the market (the Biocidal Products Directive, 

BPD). Article 1 of Directive 98/8/EC lays down the scope of the Directive, which concerns the 

authorization and placing on the market for the use of biocidal products. According to 

Article 3(1), Member States shall prescribe that a biocidal product shall not be placed on the 

market and used in their territory unless it has been authorized in accordance with the Directive. 

Authorization is defined in Article 2(1)(i) as an administrative act by which a Member State 

authorizes the placing on the market of a biocidal product. On the basis of the definition of 

authorization in Article 2(1)(l) there is an explicit link between authorization and the placing on 
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the market, whereas at present, no reference is made to the use of the product. Placing on the 

market is defined in Article 2(1)(h) as a supply and there is no reference to the use. There is no 

supply when the production of the Active Substance takes place in situ without involving 

precursors that are not placed on the market. Our interpretation of ìManual of Decisions for 

Implementation of Directive 98/8/EC concerning the placing on the market of biocidal productsî 

is that placing on the market of hydroxyl radical- and active chlorine producing equipment (for 

waters naturally containing chloride) does not fall within the scope of BPD to the extent that no 

biocidal products or precursors for biocidal products are placed on the market. The users of the 

EctoSysô equipment are not within the scope of the BPD to the extent that they use the 

equipment to produce and use the Active Substances on their own site, without placing them on 

the market. 

Due to the fact that the proposed electrochemical ballast water disinfection system EctoSysô is 

not based on the supply or addition of any chemicals to the water to be treated, the testing and 

characterization of the Active Substances in the Procedure (G9) may not be applicable at all 

points. Furthermore, one of the Active Substances (i.e. hydroxyl radicals) in question has such a 

short half-life that it is not possible to characterize it from the point of view of persistency, 

bioaccumulation, endocrine disruption etc. which is a major part of the Procedure (G9). The main 

disinfecting effect of the hydroxyl radicals produced will take place inside the electrochemical 

system itself (within a few micrometers from the electrodes), and will not (beside some residual 

regrowth preventing effect originating from active chlorine species) occur in other parts of the 

ballast water system either on the ship or after discharge of the ballast water back to the sea. 

This application for the use of an electrochemical system, EctoSysô, which makes use of Active 

Substances to treat ballast water, will focus on whole effluent toxicity testing and chemical 

specification of ballast water treated under relevant conditions. However, characterization of the 

function and environmental fate of the Active Substances and relevant chemicals will also, if 

applicable, be shown in this application for Basic Approval. The whole-effluent toxicity testing 

will be supplemented by a computer model of the dilution of the ballast water in the sea or in 

harbours after discharge. 

3 IDENTIFICATION (THE PROCEDURE (G9), SECTION 4.1) 

EctoSysô generates the Active Substances in situ in the ballast water stream without adding any 

precursors, active or non-active, to the water. No commercial formulation, including additives or 

not, are added in the Ballast Water Management system in order to comply with the Convention. 

The highly oxidative Active Substance primarily produced by EctoSysô in natural waters such 

as marine sea water/brackish waters is the hydroxyl radical, OHï. This species under normal 

circumstances has a half-life in the order of nanoseconds, and thus never leaves the cell (or the 

reaction zone) with the water flow. The hydroxyl radical very efficiently inactivates and breaks 

down microorganisms and other contaminants. No chemically active long-lived residuals are 

formed at relevant concentrations in this process using this electrochemical treatment method and 

specially developed electrochemical cell. Indirect disinfection and also direct oxidation of 

microorganisms on the electrodes will only contribute to the Total Organic Carbon (TOC) level. 

Because of the nature of an electrochemical treatment and the complexity of natural waters, it is 

not possible to make a complete account of all chemical species formed in the reactor. However, 

the Active Substances and relevant chemicals that can be produced at detectable concentrations 

are easily identified. These are as follows: 
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• Hydroxyl radical, OHï: a very reactive oxidative species with half-life in the order of 

nanoseconds, thus never leaving the reactor. Secondary radicals may also be formed in 

very small amounts as intermediates in the degradation processes of other oxidative 

species. The hydroxyl radical will be referred to as an ìActive Substanceî of this 

electrochemical ballast water disinfection method. 

• Free Active Chlorine: due to the sea water content of chloride ions, small amounts of 

chlorine gas (Cl2) will form as a by-product on the anode surface and will further, by 

favourable interactions with the cathode due to the EctoSysô cell design, immediately 

form other free active chlorine species (0.05-2 ppm) HOCl and/or OCl- depending on the 

pH. These small amounts of free active chlorine will contribute to prevent 

regrowth/biofouling in the ballast tanks and to the most extent ultimately degrade back 

into chloride ions. Due to the composition of the EctoSysô electrochemical cell, the 

primary produced chlorine gas will very rapidly (by cathodic interactions and water) form 

the active chlorine species, thus preventing the formation of harmful chlorinated organics 

such as for example THM:s. Free active chlorine will be referred to as ìActive 

Substanceî due to their oxidative and disinfecting abilities. 

• Hydrogen gas, H2(g): will be formed at the cathode due to water electrolysis ñ however, 

due to the composition of the electrochemical cell, the main cathode reactions will be 

reduction of oxygen gas (O2) and the small amounts of chlorine. Hydrogen gas will be 

referred to as a ìRelevant chemicalî in this application due to the safety aspects of this 

gas. 

As will be shown by this proposal, none of the Active Substances or Relevant Chemicals used in 

or caused by EctoSysô ballast water treatment will form any kind of threat to the ship, crew or 

environment. 

4 ELECTROCHEMICAL DISINFECTION PROCESSES 

4.1 The ballast water problem 

The need for ballast water treatment (BWT) originates in the hazardous introduction of alien 

species (e.g. algaes, copepods, vertebrates etc.) into new biotopes, where they may cause 

enormous damage to the local eco system and its populations of native species. Planktons and 

microorganisms as a total group vary greatly in form, colour, and habits, as well as in size. 

The variety is enormous. For example, in one classification alone, the Diatomacea, it is estimated 

that there are over 10,000 species, each of which has its own distinctive shape, pattern or design. 

Some microorganisms live only in sunlight, others in the dark. Some are aerobic requiring 

oxygen for their existence; others are anaerobic and grow in the absence of air. They may be 

mobile or non-mobile. Microorganisms grow, in cold or hot water and even under ice. This 

variety results in very high demands on universally functional BWT systems. No ballast water 

treatment system, using Active Substances or not, will ever be able to guarantee a 100% 

efficiency (kill rate) on all types of aquatic organisms. Surviving bacteria, spores and viruses etc. 

will start to reproduce again as soon as the right conditions are provided. By the applicant, it is 

considered necessary to include some residual treatment effect, at least while ballast water is 

stored in the tanks to prevent regrowth. 
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4.2 Oxidation processes in water treatment 

Oxidation processes are commonly used in water treatment for disinfection and removal of 

obnoxious or potentially toxic contaminants in the water, and for some industrial purposes such 

as pulp bleaching and purification of wastewater before discharge into the environment. The 

most familiar chemical oxidant is oxygen from air; other examples of oxidants used in water 

treatment are e.g. chlorine, chloramines, ozone, chlorine dioxide, hydrogen peroxide and 

potassium permanganate. Sometimes these oxidants are used in combination with each other 

(e.g. ozone with hydrogen peroxide) or with photons from irradiation lamps (i.e. UV treatment). 

4.3 Electrochemical oxidation 

During several years, there has been great interest in developing effective disinfection processes 

based on electrochemistry, since it is an environmentally friendly, low-cost, and convenient 

disinfection strategy to operate. In addition, electrochemical oxidation has been known to destroy 

a wide variety of microorganisms from planktons and bacteria to virus and algae. There are 

various electrochemical disinfection processes, including the in situ electro generation of 

disinfection agents (oxidative species), electro-sorption of bacteria on the electrode surface, 

electrocution and electrophoresis. Especially, in situ production of chemical disinfectants has 

been intensively studied because it has an obvious appeal in that dangerous chemicals are not 

transported and stored. The EctoSysô is an electrochemical system utilizing electrodes with high 

oxygen overpotential, and therefore producing powerful disinfectants such as the hydroxyl 

radical directly into the media and also providing direct oxidation of microorganisms and other 

contaminants on the electrode surface. 

One of the most common electrochemical water treatment processes generating a variety of 

oxidants is the anodic oxidation. In the area of wastewater treatment, the anodic oxidation 

process has been widely used as the most simple and convenient method due to its high 

efficiency for degrading the chemical pollutants. This efficiency is provided by dual oxidation 

pathways involving the direct electron transfer between target chemical compounds and anode 

surface, and also indirect electron transfer mediated by reactive intermediate species formed from 

water oxidation and other reactants, such as for instance the hydroxyl radical (ïOH) and chlorine 

(Cl2). By an electrochemical treatment of waters, either a partial (reduction of toxicity) or a 

complete decomposition of the pollutants can be achieved. In the case of organic materials, 

complete decomposition means the oxidation to carbon dioxide and as consequence a relatively 

high energy consumption for large organic molecules [1]. The attempts for an electrochemical 

oxidizing water treatment can be classified into two categories: direct oxidation at the anode or 

indirect oxidation mediated by oxidative species produced at the anode. 

4.3.1 Direct Oxidation at the Anode 

A model has been developed [2] to describe the course of the anodic oxidation of an organic 

molecule assuming three major steps (a-c): (S indicates surface) 

Discharge of water forming an adsorbed hydroxyl species: 

S[ ] + H2O → S[OH] + H+

 + e- (a) 
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The adsorbed OH is the ìactivated stateî of water in oxygen-transfer reactions to the organic 

molecule R: 

S[OH] + R → S[ ] + RO + H+ + e- (b) 

 

Co-evolution of O2 by oxidation of water diminishing the current efficiency: 

S[OH] + H2O → S[ ] + O2 + 3H+ + 3e- (c) 

An organic contaminant (such as e.g. a microorganism in ballast water) may this way be rendered 

harmless by direct oxidation at the anode surface in an electrochemical cell. The electrodes used 

in EctoSysô works at high overpotentials and thus have a high efficiency for direct oxidation 

(i.e ìcombustionî). The mechanism is induced even further by the favourable mass transport 

characteristics of the EctoSysô cell and by the fact that the cell wall of pathogenic 

microorganisms is negatively charged by nature and will be electrically attracted to the anode 

surface. 

4.3.2 Indirect oxidation 

In pure water medium, the most typical anodic reaction is the oxygen evolution resulting from 

water oxidation through two-electron transfer reaction as described below by (Equation 1) similar 

to (c) above. This reaction is composed of two one-electron transfer reactions expressed by 

equations (2) & (3), involving the production of ïOH as the reactive intermediate. At a high 

anodic potential, also some ozone can be generated by a six electron transfer mechanism 

(Equation 4). This ozone production is negligibly small (non detectable by standard analysis 

methods) in the case of sea water electrolysis because of the content of dissolved ions. When 

chloride ions (Cl -) are present in the electrolyte (like in marine or brackish water), chlorine gas 

evolution can occur simultaneously as described by (Equation 5) below. 

 

 H2O → 1

/2O2 + 2H+ + 2e - E0 = + 1.23 V (vs. NHE) (1) 

 H2O → ïOH + H+

 + e - (2) 

 ïOH → 1

/2O2 + H+ + e - (3) 

 3H2O → O3 + 6H+

 + 6e - E0 = +1.51 V (vs. NHE) (4) 

 2Cl -

→ Cl2 + 2e - E0 = + 1.36 V (vs. NHE) (5) 

 

Even though many kinds of oxidants can be generated by anodic oxidation processes, most 

research and practical application of electrochemical disinfection for water has only paid 

attention to and focused on the production of free active chlorine species and related compounds 

as disinfectant agents. However, bearing the problems with disinfection by-products associated 

with conventional chlorine disinfection in mind, during the development of the EctoSysô 

electrochemical disinfection system for treatment of marine waters focus has been laid on the 

potential of anodic oxidation processes as a powerful disinfection tool without considerable net 

production of chlorine gas, free active chlorine species and consequently no harmful by-products. 

The factor above others influencing the selectivity for anodic production of different kinds of 

oxidative species is the electrode type used in the system. Conventional electrodes used in the 

electrochemical industry, such as for instance the DSAô type electrodes used in chlorine 

electrolysis, are in general strongly catalytically active in order to reduce the cell voltage and 

hence the power consumption of the electrolysis. The catalytic activity of these conventional 

electrodes entails the fact that they will, in water-based electrolytes, work at low electrode 

potentials because of the discharge mechanism of common water electrolysis where oxygen gas 
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(O2) is formed at the anode and hydrogen gas (H2) at the cathode. The total voltage span (the cell 

voltage) between the negative potential of the cathode (at which H2 is formed) and the positive 

potential of the anode (at which O2 is formed) is called the ìelectrochemical windowî of the 

electrode type in question. Of course, different electrode types and coatings can be used as anode 

and cathode respectively. The factors influencing the catalytic activity of different electrodes and 

coatings are many including chemical factors such as content of different elements but also 

physical such as e.g. wetability of the surface. 

The electrochemical windows of conventional, catalytically active, electrode types are small 

because of the low cell voltages and low absolute values of electrode potentials at which water 

electrolysis occurs. When these electrodes work with low potential absolute values, no highly 

oxidative species (e.g. hydroxyl radicals) can be produced on the electrode surface because other 

reactions (common water electrolysis and oxidation of chloride) are thermodynamically favored 

under these conditions. The absolute dominant result of sea water electrolysis with conventional 

electrochemical cells and electrodes is anodic production of oxygen gas and chlorine, and 

cathodic production of hydrogen gas. 

On the other hand, available on the market is also non-catalytically active electrodes with large 

electrochemical windows, i.e. electrodes that during electrolysis discharges in oxygen- and 

hydrogen evolution at high electrode potentials. When using non-catalytically active electrodes 

(such as for instance electrodes with conductive boron-doped diamond coatings) working at high 

absolute values of potential, it is possible to create selectivity for the anodic production of highly 

oxidative species others than oxygen and chlorine. The selectivity for each theoretically possible 

species among each other is determined by factors such as the complexity of mechanism 

rendering the species in question. Hydroxyl radicals are highly thermodynamically favoured due 

to simple reaction mechanisms. Table 1 shows the oxidation potential of some oxidative species. 

 

 Table 1: Oxidation potential of different oxidative species 

Oxidative species Oxidation potential, E0 (V) 

Hydroxyl radical, ïOH 2.8 

Superoxide, ïO2

-

 2.4 

Ozone, O3 2.1 

Persulphate, S2O8

2- 2.0 

Hydrogen peroxide, H2O2 1.8 

Hypochlorite, OCl- 1.7 

Chlorine dioxide, ClO2 1.5 

Oxygen, O2 1.2 

The power of a chemical oxidant to cause a chemical oxidation reaction is measured by two 

properties: (1) the thermodynamic driving force and (2) the rate constant of oxidation. The 

thermodynamic driving force of the oxidation process for one oxidant compared to another is 

determined by its oxidation potential. 

The oxidation potential is a measure of a chemicalís oxidizing (or reducing) power; the more 

positive the value of E 0, the more likely is the chemical reaction to take place as written. The 

parameter E 0

 is related to the free energy ∆G 0 by the formula ∆G 0 = ñ nFE 0, where n is the 

number of electrons transferred and F is the Faraday constant (9.648×104

 J/V). For example, a 

large positive value of E 0

 indicates that the substance in question is a powerful oxidizing agent, 

thus the hydroxyl radical is one of the most effective oxidants known.
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4.4 Biological efficiency

Generally in water treatment, the ability to oxidize biological molecules and the ability to diffuse 

through the cell walls of microorganisms are requirements of any effective disinfectant. The cell 

wall of pathogenic microorganisms is negatively charged by nature. This means for example, in 

the case of disinfection processes using free active chlorine, that the cell wall can be penetrated 

by the neutral hypochlorous acid (HOCl) rather than by the negatively charged hypochlorite ion 

(ClO-). Hence the hypochlorous acid is a more effective disinfection species than hypochlorite 

ion. The equilibrium HOCl/OCl- is strongly pH dependent (see figure 1) and due to a pH of 

around 8 in sea water environment, BWT disinfection using free active chlorine will be less 

efficient than the equivalent treatment of e.g. drinking water. The surface charge of the 

contaminants/microorganisms is not influencing the disinfection efficiency of radicals such as 

e.g. hydroxyl radicals. 

The issue of pH dependence is also irrelevant concerning electrochemical disinfection using 

hydroxyl radicals. Hydroxyl radicals produced in sea water is neither influenced by pH nor is 

influencing pH value themselves as long as the water contains oxidisable material. Thus 

EctoSysô treatment of sea water/brackish water will not have any impact on the pH value to a 

relevant extent. 

5 DATA-SET FOR ACTIVE SUBSTANCES AND PREPARATIONS (THE 

PROCEDURE (G9), SECTION 4.2) 

5.1 Hydroxyl radicals 

5.1.1 Properties (the Procedure (G9), paragraph 4.2.1.5) 

5.1.1.1 Chemical identity

CAS No.: 3352-57-6 

IUPAC International Chemical Identifer: InChI=1/HO/h1H 

Name: Hydroxyl radical 

Chemical structure: O*H 

Molecular formula: HO 

Molecular mass (g/mol): 17.01 

(Source: NIST (National Institute of Standards and Technology, USA) Standard Reference Database 69, June 2005 Release: NIST 

Chemistry WebBook) 

5.1.1.2 Physical and chemical properties 

The physical properties of the hydroxyl radical, ïOH, are very hard to specify and the chemical 

properties are probably best described in terms of reaction rate constants in interacting with other 

species. It can be concluded that the reactivity is extremely high and the half-life is in the order 

of nanoseconds. Hydroxyl radicals are very common in the environment due to their involvement 

as an intermediate species in various reaction chains occurring naturally, such as photochemical 

and biochemical processes. 
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The most covering way to characterize the chemical properties of hydroxyl radicals is to describe 

the reaction kinetics and proposed reaction mechanisms to various species. This has been studied 

in ìCritical Review of Rate Constants for Reactions of Hydrated Electrons, Hydrogen Atoms and 

Hydroxyl Radicals (.OH/.Oñ) in Aqueous Solutionî, George V. Buxton et al., J. Phys. Chem. Ref. 

Data 17: 513-886 (1988). The kinetic data for the ïOH in aqueous solution and the corresponding 

radical anions, ïOñ

 and eaqñ, have been critically reviewed and can also be found at 

http://www.rcdc.nd.edu/compilations/Hydroxyl/OH.HTM. Reactions of the radicals in aqueous 

solution have been studied by pulse radiolysis, flash photolysis and other methods. Rate 

constants for over 4400 reactions, more than 6100 measured values are tabulated, including 

reactions with molecules, ions and other radicals derived from inorganic and organic solutes. 

5.1.1.3 Disinfection properties 

The immediate biocide action of the hydroxyl radical has been well recognized from massive 

experimental evidences, which demonstrate that disinfection processes using hydroxyl radicals 

are technically feasible. It is generally accepted that reactive oxygen species (ROS) and hydroxyl 

radicals play the role of disinfectants. For instance, studies have determined how the ïOH, acting 

either independently or in collaboration with other ROS, is quantitatively related to the 

inactivation of E. coli. The results indicates that the ïOH is the primary oxidant species 

responsible for inactivating E. coli (in this specific study produced in the UV/TiO2 process). 

The exact mode of hydroxyl radicals (which belongs to the surface phase of the anode material) 

inactivating microorganisms is not fully understood. In attempts to understand the mode of 

hydroxyl radicals inactivating microorganisms, some research has been made with MS-2 phage 

and E. coli, which are frequently used as indicators of virus and bacteria in disinfection study, 

respectively. MS-2 phage was inactivated mainly by hydroxyl radical in bulk phase, whereas 

E. coli was inactivated by hydroxyl radical in both bulk and surface phases, and possibly some 

other reactive oxygen species such as ïO2

-

. Possible oxidants and mechanisms responsible for 

inactivating microorganisms in anodic oxidation processes have been identified in some cases. 

For instance, the role of hydroxyl radical on the inactivation of E. coli in anodic oxidation 

process under conditions where chlorine species can not be formed (by using excess methanol as 

hydroxyl radical scavenger) has been investigated. It was observed that the inactivationof E. coli

occurred through two distinct stages independently from the current density applied, which are 

characterized by the rapid inactivation at an initial stage of electrolysis (1st stage inactivation) 

and a slower inactivation as the electrolysis proceeds further (2nd stage inactivation). The two 

stages of inactivation seem to be related to the competition of two kinds of electron transfer 

reaction, which are similar to the degradation of chemical pollutants. In addition, as the evidence 

for the occurrence of direct electron transfer reaction, the existence of electro-sorption of E. coli

cells facilitating the electron transfer between microbial cells and electrode surface was 

identified. 

5.1.2 Risk characterization and analysis of hydroxyl radicals (the Procedure (G9), section 5.3)

5.1.2.1 Screening for persistence, bioaccumulation and toxicity 

Persistence tests and bioaccumulation tests according to the Procedure (G9), paragraphs 5.1.1.1 

and 5.1.1.2, are not applicable on hydroxyl radicals due to their physical and chemical properties. 

The Active Substance of hydroxyl radicals used in the EctoSysô disinfection system does not 

fulfil the PBT criteria as outlined by the Procedure (G9) and EC, 2003a: 
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Criterion PBT criteria 

P (persistence) Half-life > 60d in marine water or > 40d in fresh water 

or half-life > 180d in marine sediment or > 120d in 

fresh water sediment or readily biodegradable 

B (bioaccumulation) BCF > 2000 or lgKOW > 4.5 

T (toxicity) Chronic NOEC < 0.01mg/l or CMR or endocrine 

disruption effects. 

Due to the extremely short half-life of the radical, it is obvious that it is not persistent in the 

environment. The octanol-water partition coefficient (the Procedure (G9), paragraphs 5.3.7 and 

5.3.11) is for the same reason not possible to calculate; therefore the issue of bioaccumulation is 

not relevant for hydroxyl radicals. The direct toxicity of hydroxyl radicals to microorganisms is 

discussed below, but will never be a concern outside the electrochemical cell and therefore not 

after discharge of the ballast water. 

Due to the nature of the electrochemical technology used, humans will not be exposed to 

hydroxyl radicals during any part of the ballast water treatment process. Hydroxyl radicals will 

never be handled and due to the short lifetime never leave the electrochemical reactor, thus will 

the discharge concentration (the Procedure (G9), paragraph 5.3.8) be zero at all times. The risk 

assessment will conclude no existent threats posed by the Active Substance to the environment, 

crew or ship. 

Concerning direct toxicity tests on hydroxyl radicals, according to the Procedure (G9) 

(paragraphs 5.1.1.3, 5.3.9, and 5.3.10) in the case of hydroxyl radicals is very limited, also 

regarding data on mammalian toxicity (the Procedure (G9), paragraph 4.2.1.2). Again, due to the 

material properties (short life time) of the hydroxyl radical, regular toxicity tests, tests for 

bioaccumulation or endocrine disruption are impossible to perform or not relevant. The tests 

recommended by the Procedure (G9) are therefore not applicable. The main approach to 

investigating/evaluating and arguing about the toxicity is based on a whole-effluent discharge 

toxicity test approach described under section 6 of this document, and on the comprehensive 

material regarding free active chlorine, which is also included. The mechanism of hydroxyl 

radical disinfection (i.e. acute ìtoxicityî to living organisms) is not fully understood but some 

theories are included above under section 5.1.1.3 of this document. 

5.1.2.2 Formation of hydroxyl radicals in the EctoSysô system (the Procedure (G9), 

paragraph 5.3.3) 

The current exchange for hydroxyl radical formation on electrodes used as anodes in the 

EctoSysô has been analyzed using a spectrophotometric radical spin-trap technique (using N, 

N-dimetyl-4-nitrosoanilin, RNO, as spin trap molecule selective to hydroxyl radicals) that is 

commonly accepted and has been described in literature [3]. The method has been modified by 

the applicant to simulate BWT conditions regarding salinity and electrochemical operating 

parameters of the EctoSysô. Experiments where performed at bench-scale. 

The results from these tests show that the current efficiency for hydroxyl radicals on electrode 

materials used in EctoSysô can reach 25%, i.e. 25% of the applied current is used for anodic 

production of hydroxyl radicals on this type of electrode surface. The actual efficiency in the 

EctoSysô under relevant treatment conditions is believed to be higher due to favourable mass 

transport induced by the cell design. With this basic estimation of the electrode performance 

(25% current efficiency) and bearing in mind that hydroxyl radical formation from water is a one 

electron transfer operation, approximately 1.6*10-3 moles of hydroxyl radicals should be formed 

each second in an EctoSysô electrochemical cell dimensioned for treatment of 500 m3/h ballast 
MEPC 55/2/4 

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water. A rough estimation of the content of microorganisms (of all classes) is 1*109 per litre. 

This would give an average dose of about 7*109

 hydroxyl radicals per microorganism if 100% 

efficiency for this purpose is reached. Hydroxyl radicals will are not selective to certain species, 

and in sea water especially carbonate is a main scavenger. The remaining 75% of the applied 

current will mainly induce oxygen evolution, but also direct oxidation of organic and inorganic 

materials on the electrode surface and small production of chlorine (Cl2) as by-product. 

The actual production of hydroxyl radicals in the EctoSysô electrochemical cell during ballast 

water treatment under relevant conditions is not known. The influence of physical parameters 

such as e.g. flow rate on the formation of hydroxyl radicals has not been investigated. However 

this is not important from an environmental point of view or concerning safety aspects because 

the hydroxyl radicals will never leave the reactor due to their short half-life. It is noted that the 

hydroxyl radicals produced, along with the mass transfer efficiency of the cell, is suited to meet 

the criteria of sufficient ballast water treatment (Standard D-2 in IMO Ballast Water 

Management Convention). The total influence of the EctoSysô treatment of ballast water 

regarding change of physical properties and toxicity is instead analysed taking a whole-effluent 

approach. 

5.1.2.3 Produced secondary by-products from hydroxyl radicals 

Hydroxyl radicals will act as oxidizing agent in various redox reactions involving all kinds of 

species present in the media. Hydroxyl radicals does not form halogenated disinfection 

by-products (DBP:s) when participating in oxidation/reduction reactions with natural organic 

material. However, if bromide ion is present in raw water treated with hydroxyl radicals (such as 

sea water) halogenated DBPs may be formed to a higher extent than under normal environmental 

conditions. THM in sea water will ultimately to the most extent consist of bromoform, due to the 

stability of this substance and the sea water content of bromide ion, Br-

. The total formation of 

THM in sea water during EctoSysô treatment is quantified and discussed under section 5.3.2 

below. 

5.2 Free active chlorine 

Hypochlorite concentration should normally be expressed as % NaClO in common water 

disinfection applications. However, to allow a comparison between this document and legal 

criteria (which express NaClO solutions in terms of active chlorine content) the term ìFree 

Active Chlorineî is used in this dossier. 

5.2.1 Properties (the Procedure (G9), paragraph 4.2.1.5)

The common physical properties of the free active chlorine species are not possible to account 

for specifically, because they will always form equilibrium in a solution and never (except Cl2

gas) exist in their pure form. Therefore, the physical properties of the (relevant in this case) 

corresponding substance for sea water, sodium hypochlorite, will be shown accordingly. 

(Note: Free active chlorine (in practice Cl2+HOCl+ClO-) is expressed as equivalent content of 

Cl2. As the molecular weight of Cl2 is 71 g/mol and the molecular weight of NaClO is 

74.4 g/mol, for sodium hypochlorite the equivalent active chlorine measured as the oxidizing 

power represents 95% of the sodium hypochlorite weight (M.W.Cl2/M.W.NaClO x 100 = 71 x 

100/74.4).) 
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5.2.1.1 Chemical identity (the Procedure (G9), section 4.1) 

CAS No.: 7681-52-9 

EINECS No.: 231-668-3 

Name: Sodium hypochlorite 

Chemical structure: Na+

ClOMolecular formula: ClO.Na 

Molecular mass (g/mol): 74.4 

(Source: RISK ASSESSMENT REPORT FOR SODIUM HYPOCHLORITE, DRAFT. Akzo Nobel NV, November 2005[7])

5.2.1.2 Physical and chemical properties 

During storage of commercial solutions, hypochlorite is slowly transformed into chlorate and 

chloride. The following data are valid for an aqueous solution with a content of 15% (w/w) 

available chlorine (IUCLID, 2001). 

Table 2: Physical properties of sodium hypochlorite 

Property Value References 

Physical state Liquid 

Melting point - 20 to -30°C Safety data sheet Hoechst AG 1994 

Boiling point 96 ñ 120 °C Safety data sheet Hoechst AG 1994 

Relative density 1.23 g/cm3 at 25°C Sicherheitsdatenblatt der Bayer AG 

Vapour pressure 17.4 - 20 hPa at 20°C Safety Data Sheet Rhone Poulenc 

Water solubility Miscible [29.3 g/100 g (0 deg 

C) in water] 

HSDB 

Partition 

coefficient 

n-octanol/water 

(log value) 

n.a. 

(logKow = -3.42, estimated) (online software at: 

http://syrres.com/esc/kowdemo.htm)

Granulometry n.a. 

Conversion factors 

Flash point n.a. 

Autoflammability 

Flammability 

Explosive 

properties 

Anhydrous sodium 

hypochlorite is very explosive 

HSDB 

Oxidizing 

properties 

Strong oxidizing agent usually 

stored and used in solution 

HSDB 

Viscosity 

Henryís constant 

(Source: RISK ASSESSMENT REPORT FOR SODIUM HYPOCHLORITE, DRAFT. Akzo Nobel NV, November 2005[7])

5.2.1.3 Disinfection properties 

When diluted in water, depending on pH value (see figure 1 below), hypochlorite is partly 

transformed into hypochlorous acid (HOCl). This product is an extremely efficient biocide for 
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prions, viruses, bacteria, parasites and fungi. HOCl reacts actively by chlorination of nitrogen on 

compounds like amino acids. It is thus very reactive to proteins. With adapted levels of 

concentration and contact times it can kill all the microorganisms. At much lower concentrations 

in water (0.1 to 1 mg/l) it is able to inhibit bacterial growth. In this last case the proteins of the 

membrane are partly destroyed and the bacteria are not able to multiply (Techware Report, 1996; 

Venkobachar et al., 1977) 

The disinfecting properties of free active chlorine species in water are based on the oxidizing 

power of the free oxygen atoms and on chlorine substitution reactions. Free active chlorine 

species kills pathogens such as bacteria and viruses by breaking the chemical bonds in their 

molecules. Disinfectants that are used for this purpose consist of chlorine compounds which can 

exchange atoms with other compounds, such as enzymes in bacteria and other cells. When 

enzymes come in contact with chlorine, one or more of the hydrogen atoms in the molecule are 

replaced by chlorine. This causes the entire molecule to change shape or fall apart. When 

enzymes do not function properly, a cell or bacterium will die. Hypochlorous acid (HOCl) can 

easily penetrate protective slime layers and cell walls of microorganisms, causing them to die or 

suffer from reproductive failure. 

5.2.2 Classification 

According to Directive EEC 67/548, annex 1 and its amendments sodium hypochlorite 

(Index-No. 017-011-00-1) is classified as follow: 

Current classification according to Annex 1 (29th ATP): 

Classification: C, N 

R-sentences: 31-34-50 

S-sentences: (1/2)-28-45-50 

Specific limits: 

C≥ 10%: C R31-34 

5% ≤ C < 10%: Xi R31-36/38 

The C&L Technical Group at the 15-18 March 2005 meeting, decided to maintain the above 

classification. According to the Dangerous Substances Directive 67/548/EEC and subsequent 

amendments and to the Dangerous Preparation Directive 88/379/EEC, sodium hypochlorite 

solutions are classified as follows: 

• Solution less than 5%: Not classified; 

• Solution from 5% to 10% available chlorine: Irritant with the risk phrases R 31: 

contact with acids liberates toxic gases and R 36/38: irritating to eyes and skin; and 

• Solution above 10% available chlorine: corrosive with the risk phrases R 31: contact 

with acids liberates toxic gases and R 34: causes burns. 

(Note: This classification includes the risk related to the sodium hydroxide always present as a 

stabilizer in concentrations up to 1% when sold in solution and used in common applications. 

The free active chlorine related to EctoSysô BWT is formed in situ.) 

Theoretical pure sodium hypochlorite should be classified as ìvery toxic to aquatic organismsî 

(N, R50) based on aquatic toxicity data, and as ìharmful for ingestionî (Xn, R22) on the basis of 

the oral LD50 data. This classification does not apply to solutions as their concentration is always 
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below 25%, and especially not to the sea water treated with EctoSysô since the maximum 

concentration of free active chlorine will never exceed 2 ppm (2 mg/l equivalent Cl2). 

5.2.3 Electrochemical formation of free active chlorine 

On the anode surfaces of an electrochemical cell, oxidative species will be produced from the 

reactants available in the electrolyte. In the case of a sea water electrolyte, the most common 

reactant available will of course be water, H2O. When using conventional electrodes (such as 

DSAô types) the main product of this electrochemical process would be oxygen gas (O2) 

evolving from the anode due to common water electrolysis (Half-cell reaction: Equation 1 

above). When chloride ions (Cl -) are present in the electrolyte (like in marine or brackish water), 

chlorine gas (Cl2) evolution can occur simultaneously with the formation of hydroxyl radicals on 

the anode as described by (Equation 5) above. When Cl2 is present, OCl-

 and HOCl will form 

spontaneously with water (Equation 6). Cl2 will also have some selectivity to reactions with other 

substances (organic or inorganic) present in the water, thus forming by-products that might be 

harmful such as for instance trihalomethanes, THM:s. However, in the EctoSysô 

electrochemical cell, the reduction of chlorine (oxidation number: 0) as Cl2 to HOCl (oxidation 

number: -1) is mediated by interactions on the cathode, due to that the cell design and electrode 

configuration is especially developed to favour this purpose: 

Cl2 + H2O → HOCl + H+

 + Cl - (6) 

(EctoSysô cell: this electron transfer mediated through rapid interaction of Cl2/H2O with 

cathode surface) 

Equilibrium depending on the pH-value sets between hypochlorous acid and hypochlorite ions: 

Cl2 + 2H2O → HOCl + H3O+

 + Cl- (7) 

HOCl + H2O → H3O+

 + OCl- (8) 

The ratio between these two species of free active chlorine will distribute according to pH as 

described in figure 1. If the hypochlorite ions do not interact with/oxidize material present in the 

water, it will ultimately fall apart to chloride ions and oxygen atoms (Equation 9): 

OCl - → Cl -

 + O (9) 

Hypochlorous acid (HOCl, which is electrically neutral) and hypochlorite ions (OCl-, electrically 

negative) will together form free active chlorine. Both substances have very distinctive 

behaviour. Hypochlorous acid is more reactive and is a stronger disinfectant than hypochlorite. 

Hypochlorous acid can split into hydrochloric acid (HCl) and atomair oxygen (O). The oxygen 

atom is also a powerful disinfectant. 

The small amounts of free active chlorine will contribute to prevent regrowth/biofouling in the 

ballast tanks and will thus also to the most extent ultimately degrade back into chloride ions. Due 

to the composition of the EctoSysô electrochemical cell, the primary produced chlorine gas will 

very rapidly, by cathodic interactions and water, form the active chlorine species thus preventing 

the formation of harmful chlorinated organics such as for example THM:s. 
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5.2.4 Chemistry of free active chlorine in sea water 

5.2.4.1 Chlorine equilibrium 

Free active chlorine express the oxidizing power of a chlorine containing solution as if all the 

chlorine species present were available as Cl2, transformed according to reactions such as those 

given below: 

Cl2 + H2O = HClO +HCl (10) 

Cl2 + 2 OH- → ClO- + Cl- + H2 O (11) 

Chlorine and its entire derived species are oxidative and very reactive compounds. Chlorine gas 

is a more efficient oxidiser than hypochlorous acid (HOCl), and hypochlorous acid is more 

efficient than the hypochlorite ion (ClO-

). The balance between HOCl and ClO- can be studied in 

polluted water with pH between 4 and 10. In this case, the kinetic of the reactions and the final 

products obtained depend to a large extent on the percentage of each of the two species 

(HOCl, ClO-

). 

There are three species of chlorine in equilibrium in water: gaseous chlorine Cl2, HOCl (also a 

gas at room temperature and pressure), and ClO-. An example of the distribution between them as 

a function of pH is shown in figure 1. For example, at pH 7.5 half of the chlorine is active as 

HOCl and half is available as ClO-. The pH of sea water is normally 8-8.2 and the only species 

effectively present is ClO-. 

pH

2 4 6 8 10

Form in which available chlorine is present (%)

0

20

40

60

80

100

OCl- HOCl

Cl2

Figure 1: Calculated variation in composition of a chlorine solution with degree of acidity or 

alkalinity for 0.1 M Cl2 in water at standard temperature and pressure (the data in this 

figure are based on general chemistry handbooks).

Hypochlorite (OCl-), which will be the free active chlorine specie most common in seawater due 

to a pH on the alkaline side, is an oxidant which oxidizes other substances and thereby reduces 

itself to chloride ions. However, since sea water naturally contains 65ppb Br-, HOCl will 

normally transform to HOBr (Equation 12) that is the more stable substance in sea water at pH 

around 8. 
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HOCl + Br- → HOBr + Cl - (12)

Halogenated organic compounds may be formed by the reactions of hypochlorite with organic 

substances. The possible reaction products include trihalomethanes, THMs (ultimately in sea 

water mainly as bromoform) and Haloacetic acids, HAAs formed at low pH. Some of these 

halogenated compounds may be toxic and slowly degradable in the aquatic environment, and is a 

mayor concern for conventional chlorine water treatment processes. For the EctoSysô BWT 

case, see further section 5.3 and also especially section 5.3.2. 

5.2.4.2 Main reaction routes 

There are mainly four routes for the transformation of free active chlorine in sea water: 

• Chlorination with amines R-NH2 or ammonium NH4

+

 is very rapid and explains the 

very fast disappearance of free active chlorine in for instance waste water. The 

chlorine atom linked with a nitrogen atom is expressed as combined active chlorine. 

R-NH2 + Cl2 ! R-NHCl + H+ + Cl- (13) 

If there is, at one point, a large excess of active chlorine over -NH2, chloramines like 

R-NCl2 and NCl3 are formed. 

• Oxidation reactions occur with many inorganic or organic compounds. Thus, for 

example, ferrous ion can be transformed into ferric ion, organic radicals can be 

transformed through hydrolysis, and C-C bonds can be broken. If there are no 

nitrogen compounds in the solution, this type of reaction is predominant. 

• Chlorination of C atoms from organic molecules is easier for molecules with a shorter 

carbon skeleton. Three typical reactions are: Reaction with phenol giving 

monochlorophenols; Reaction with molecules containing two carbon atoms: 

acetaldehyde, acetonitrile, and acetic acid, which are chlorinated on the CH3, and give 

chloroacetaldehydes, chloroacetonitriles and chloroacetic acids; Reaction with final 

degradation of the carbon chain giving THMs and especially CHCl3 (chloroform) in 

the case of fresh water but main stable THM in the sea water case is CHBr3

(bromoform). 

Free active chlorine can both be maintained constantly in excess, as well as rapidly transform 

into combined chlorine species depending on the sea water properties. Both rapid and slow 

reactions can take place and both oxidation and carbon or nitrogen chlorination processes are 

found. The main reaction where free active chlorine is transformed is the nitrogen chlorination 

with the formation of mainly mono chloramines. The chemical degradation of combined active 

chlorine in this type of scenario takes a few hours. It also produces a number of long chain 

chlorinated molecules (chlorination of C) but to a lesser extent (only 1 or 2% conversion of the 

free active chlorine). These molecules only represent the start of the chemical degradation 

process. After a certain time, the remaining AOX part would include volatile compounds such as 

chloroform but due to the sea water content of bromide, the final main contribution (after a very 

long decay period) to the Total Residual Oxidant (TRO) will be HOBr. See further section 5.6. 
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5.2.4.3 Naturally occurring hypochlorite production 

Hypochlorite is also produced naturally in vivo for cell defence processes. The natural production 

of halo-oxo acids is widespread and related to haloperoxidases, which is well documented in the 

literature. A good overview of biohalogenation is given by Neidleman and Geigert (1986) and 

more recently by Winterton (1997). Hypochlorite is produced by chloroperoxidases, which are, 

among others, produced by mammals (in white blood cells), lichens and in many fungal species 

(Vollenbroek et al., 1995). Active chlorine species representing chlorine at a formal +I oxidation 

state (HOCl, Cl2, N-chloroamide, etc.) have been quantified to some extent in one study looking 

at the rate of conversion of oxygen into polymorphonuclear leukocytes when phagocytozing a 

micro-organism. It was demonstrated that 28% of the consumed oxygen is converted into active 

chlorinating agents (Foote et al., 1983). Even chlorine gas species have been identified in 

neutrophiles during phagocytosis (Hazen et al., 1996). Hypochlorite and active chlorine species 

(as well as other oxidants) will thus always be present in natural sea water due to dissolved 

chloride ions and naturally occurring bio reactions and equilibriums. 

5.2.5 Analysis of free active chlorine 

The analysis methods for free active chlorine approved by the Standard Methods Committee in 

1993 (APHA, 1995) for fresh water use iodine, DPD (N,N-diethyl-p-phenylene-diamine) or 

syringaldazine. The DPD methods are commonly used for treated and waste water using ferrous 

ammonium sulphate or by colorimetry. Spectrophotometric colorimetry was chosen due to its 

feasibility to on site analysis. However, with colorimetric methods, organic contaminants and 

may produce a false free chlorine reading, and sample colour and turbidity may interfere. Sea 

water is not an ideal media due to the high content of dissolved ions. It is also very well known 

that the DPD reagents are highly unselective to the active chlorine species that is to be analysed, 

but instead indicates the total amount of oxidants available with an oxidizing power above a 

certain potential. This is especially important to keep in mind when interpreting free active 

chlorine readings from DPD analysis on electrochemically treated waters, because of the vast 

number of oxidative species that can potentially form during electrolysis. The term ìfree active 

chlorineî should consequently in the following section 5.2.6 rather be interpreted as ìtotal 

oxidants capable of reacting with DPDî or similarly the commonly used term ìTotal Residual 

Oxidantsî (TRO). 

5.2.6 Free active chlorine formation during EctoSysô ballast water treatment

The formation of free active chlorine species in the EctoSysô system has been analysed during 

artificial- and natural sea water treatment (Sweden, 2003-04), as well as during small scale real 

case ballast water treatment conditions in Bremerhaven, Germany during 2005. The analysis 

techniques that have been used are standardized colorimetric methods based on well established 

DPD reagents (see section 5.2.5), and also monitored by on-line measurement probes based on 

electrochemical analysis techniques (ProMinent). All tests were performed using EctoSysô 

systems dimensioned for treatment of 10m3

/h. 

It was shown and verified that the free active chlorine formation during EctoSysô treatment of 

natural (and also artificial) sea water was well below drinking water standards (USA/EPA: 4 mg/l 

free active chlorine) even under worst case conditions. It was also shown that the free active 

chlorine formation was, at a fixed flow rate through the cell, directly proportional to the applied 

current at relevant current densities. Thus, it is possible to at all times predict the formation of 

free active chlorine during EctoSysô treatment at specified flow rates and current densities. 
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DPD respons (as Free Active Chlorine, DPD1), 

natural sea water treatment at flow rate 10m3/h

0,00

0,10

0,20

0,30

0,40

0,50

0,60

0,70

0 5 10 15 20

Current (A)

DPD respons (ppm)

DPD respons (as Free Active Chlorine, DPD1), 

artificial sea water with different salinitys, 

treatment at flow rate 10m3/h, current 12A

0,3

0,35

0,4

0,45

0,5

0,55

15 20 25 30 35 40 45

Salinity (PSU)

DPD respons (ppm)

Figure 2 illustrates the free active chlorine, in terms of DPD1 (Dr. Lange) response, during 

EctoSysô treatment of natural sea water (west coast of Sweden, 32 PSU) at nominal flow rate. 

Nominal current density applied for effective hydroxyl radical production and sea water 

treatment at nominal flow rate in terms of meeting the standard D-2 criteria is 2.5kA/m2, thus 

generating approximately 0.5 ppm free active chlorine as by-product to the main production of 

the Active Substance of hydroxyl radicals. The temperature was 11°C. The pH was measured 

to 8.1, and thus the free active chlorine was to 80% in the form of OCl- (see figure 1). The worst 

case scenario includes an applied current density of 4kA/m2

 and thus a predicted free active 

chlorine formation of below 2 ppm. 

 Figure 2: DPD 1 response, current dependency Figure 3: DPD 1 response, salinity dependency

Figure 3 illustrates the free active chlorine formation as a function of the salinity of the media. 

The tests were performed using artificial sea water produced by dissolving appropriate amounts 

of NaCl (technical quality, Akzo Nobel) with tap water. The water was room-tempered with a pH 

of 7.1. The tests were performed in multiple and figure 3 shows a typical result. The conclusion 

is that the salinity of the sea water influences the by-production of free active chlorine by 

increasing its current exchange up to salinity levels of approximately 30PSU. Below this, less 

free active chlorine will be formed due to mass transport limitations for dissolved chloride ions to 

reach the reaction zone. With lower salinities (< 30PSU), anodic current efficiencies will instead 

rise for the production of hydroxyl radicals and oxygen gas. 

Figure 4, below, illustrates the free active chlorine (or TRO) formation at nominal applied current 

as a function of the flow rate through the cell, during small scale real case ballast water treatment 

conditions in Bremerhaven, Germany. It was concluded that the flow rate is a very important 

parameter in a specified interval, i.e. below the nominal flow rate. At higher flow velocities of 

the media, the flow rate has less importance for the total concentration of free active chlorine, 

because the mass transport improvement induced by increased turbulence will be 

counterbalanced by a larger total treated volume. 
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DPD respons (as Free Active Chlorine, DPD 1) 

natural sea water treatment at current 15A

0,0

0,2

0,4

0,6

0,8

1,0

1,2

1,4

1,6

2 4 6 8 10 12

Flow rate (m3/h)

DPD response (ppm)

 Figure 4: DPD 1 response as a function of treatment flow-rate (nominal 10m3

/h)

5.2.7 Decay of free active chlorine and TRO in natural waters 

It is well known that chlorine-induced oxidants in waters with wide salinity and ammonia ranges 

are toxic to aquatic organisms and that the toxicity depend upon the persistence as well as their 

chemical form (reference 4). In view of lack of knowledge and modelling difficulty on the 

theoretical rates of oxidant disappearance in natural waters, most studies take an empirical 

approach in investigating the decay rates and products. A model of the HOCl/OCl-

 has been 

developed in Appendix II to reference 7. 

5.2.7.1 Predictions and models 

Studies of the self decomposition (no interactions with organics/inorganics) of hypochlorite in 

distilled water without the influence of photolysis have been studied [4]. It was concluded that 

this mode of free active chlorine decay can be omitted in calculations of real case scenarios and 

waters, however the decomposition of hypochlorite is accelerated by the presence of 

hypobromite. The natural presence of ammonia in the water will immediately consume oxidants 

according to eq.I, 

CR = C0 - rCN (I) 

where CR is the concentration of free oxidants (mg/l) after initial interactions with ammonia, C0

is the initial free oxidant concentration, r is a weight ratio chlorine and ammonia content which is 

estimated to 6.2 in sea water, and CN is the concentration of ammonia nitrogen (mg/l). After this 

immediate consumption, the further decay can be modelled as a second order reaction [5]: 

2 k C

dt

dC − = ⋅ (II) 

where C is the concentration of free oxidants at time t, and k is the reaction rate constant 

depending on a number of factors, e.g C0. It can thus be concluded that the decay of total 

oxidants formed by electrochemical ballast water treatment of sea water undergoes one very 

rapid phase and one decay phase over time. If Cí0 is defined as Cí0 = C0 ñ CR (which also equals 

rCN in eq. I), integration of eq. II yields: 
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'

0

1 1

C

k t

C = ⋅ + (III) 

that gives a theoretical expression of the total oxidant concentration in sea water at time t (min) 

after treatment. As an indication of the value of the constant k at relevant conditions, k has been 

measured to 0.52 (l/mg*min) at C0 = 0.84 mg/l free active chlorine dose in natural sea water. 

5.2.7.2 Experiments and analysis

The decay of free active chlorine/TRO levels was investigated in relevant natural sea water 

environment after EctoSysô treatment under simulated BWT conditions in Bremerhaven 

harbour, Germany. The analysis technique used was the standard DPD method as described 

above in section 5.2.5. The results clearly show that the free active chlorine content 

(DPD response) in treated natural sea water rapidly start to drop from an initial concentration of 

0.55 ppm during the first 20 minutes after treatment. The influence of sun light (photolysis) was 

prevented by storage of the treated water in a dark container, temperature about 15-20°C. 

The DPD reading of free active chlorine (or rather total oxidant level) as described under 

section 5.2.4.3 corresponds in this particular case more likely to a disturbance to the 

spectrophotometric analysis induced by the high turbidity of the water. Figure 5 shows the decay 

of free active chlorine/TRO down to reach background levels (continuously measured and shown 

as ìEctoSys influentî) after 50 minutes. 

DPD response (as Free Active Chlorine, DPD1) 

decay in natural sea water, stored after EctoSys 

treatment

0,10

0,15

0,20

0,25

0,30

0,35

0,40

0,45

0,50

0,55

0,60

0 20 40 60 80

Time (min)

DPD response (ppm)

EctoSys effluent

EctoSys influent

Figure 5: Decay of oxidants produced during EctoSysô nominal treatment of natural 

sea water 

The two phases of free oxidant decay (see section 5.2.7.1) is clearly shown in this figure. 

The back-ground ìzeroî level (0.20-0.25 ppm) of free oxidants (in this particular case, where the 

treated ballast water is stored under dark conditions in accordance with real case ballast water 

tanks) is reached at approximately 1h after nominal EctoSysô treatment. 

5.2.8 Risk characterization and analysis of free active chlorine (the Procedure (G9), section 5.3) 

5.2.8.1 Screening for persistence, bioaccumulation and toxicity 

The Active Substance of free active chlorine species produced as a by-product in the EctoSysô 

disinfection system does not fulfil the PBT criteria as outlined G9 and EC, 2003a: 
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Criterion PBT criteria 

P (persistence) Half-life > 60d in marine water or > 40d in fresh water or 

half-life > 180d in marine sediment or > 120d in fresh 

water sediment or readily biodegradable 

B (bioaccumulation) BCF > 2000 or l gKOW > 4.5 

T (toxicity) Chronic NOEC < 0.01 mg/l or CMR or endocrine 

disruption effects. 

Due to the rapid breakdown of all free active chlorine species in natural waters (section 5.2.7) it 

is concluded that they are not persistent in the environment. The octanol-water partition 

coefficient (log KOW, the Procedure (G9), paragraphs 5.3.7 and 5.3.11) for hypochlorite has been 

calculated to a negative value of -3.42, therefore bioaccumulation is not an issue for hypochlorite 

and further testing not considered relevant. The toxicity of chlorine species have been thoroughly 

investigated in accordance with the Procedure (G9), and will in this application be shown not to 

pose threat to the environment in the case of the small by-production during EctoSysô treatment 

of ballast water. This statement is based on facts such as the low initial concentrations, the rapid 

decay (section 5.2.7.1), predicted PEC values of zero (section 5.2.11.2) and low PEC further 

supported by modelling ballast water dilution after discharge in harbours (section 8). 

5.2.9 Effect assessment of free active chlorine to marine environment 

5.2.9.1 General information about the toxicity data 

Chlorine and sodium hypochlorite are listed for registration as biocide by the EuroChlor group of 

which Akzo Nobel NV is a member. Both substances are currently also under evaluation in the 

EU Existing Substances Program which evaluates all uses of the compounds, including biocidal. 

This activity is co-ordinated by EuroChlor. Common principals of risk assessment apply and 

need IUCLID data files. As all environmental data for chlorine is based on data already 

mentioned in the hypochlorite dossier, the EU chlorine evaluation awaits the completion of 

hypochlorite. Hypochlorite and chlorine are both in there final stages and are expected to be 

completed soon. 

 

The Akzo Nobel strategy for the Biocidal Products Directive (BPD) is to make use of the 

finalized risk assessment and discuss with the authorities what additional work should be 

performed and in how far is reworking of documents for BPD required. The IUCLID data files 

are scheduled to be updated after the EU Risk Assessment Report (RAR) is finished (during 

2006) to make this database consistent with RAR. 

 

Therefore, at the moment there is no documentation finalized. The most consistent 

documentation is the running draft Risk Assessment Report on hypochlorite (May 2004) which 

data included in this proposal refers to. There is a general consensus on the conclusions of the 

risk assessment. The produced concentrations of free active chlorine in the EctoSys during ballast 

water management are below drinking water standards and will never reach levels dangerous to 

the environment when discharged. Toxicity evaluations are made under natural sea water 

environmental conditions (e.g. considering effect of sun light, pH, temperatures etc.). 

There is a large amount of documented data available on the aquatic toxicity of hypochlorite, 

from a number of sources, including general reviews (e.g. Brungs, 1973; Mattice & Zittel, 1976; 

Kalmaz & Kalmaz, 1981), peer-reviewed literature, personal communications and IUCLID 

(updated version 03/06/94) which is available to the public. The references are only indicated in 
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the text of this dossier and not listed specifically in the reference list ñ however they are available 

through the separate Akzo Nobel Risk Assessment Report (reference 7) on hypochlorite. IUCLID 

data have been checked, and included alongside additional data from other references that were 

obtained from literature. For each study, experimental conditions and main results are 

summarized in tables 3, 4 and 5. As the data available on the aquatic toxicity of hypochlorite 

have been generated over several decades using different testing methods, species and conditions, 

they need to be carefully evaluated for validity. 

The validity of the aquatic toxicity data was evaluated according to the criteria recommended by 

the European authorities and present in IUCLID. The evaluation criteria are defined as: 

- Rated 1 = valid without restriction 

- Rated 2 = valid with restriction 

- Rated 3 = invalid 

- Rated 4 = not assignable 

The main parameters that need to be documented when describing aquatic toxicity tests for 

sodium hypochlorite are: 

(a) The pH and temperature 

The experimental pH and temperature have an important role in the evaluation of aquatic toxicity 

data as they determine the chemical species present. In water, the hypochlorite ion is in 

equilibrium with hypochlorous acid, the ratio of each species being pH and temperature 

dependent. The amount of hypochlorous acid decreases as pH and temperature increase 

(Hellawell, 1986). At pH 7.0 70% is HOCl whereas at pH 8.0 80% is ClO-

 when the temperature 

is 25o

C (Taylor, 1993). Therefore in freshwater (characteristic pH range of 6.5-7.2) the dominant 

form is the more toxic HOCl while at estuarine pHís (7.5-8.2) the reverse is true (Gentile et al., 

1976). At pH values above 4.0, Cl2 does not exist - hence when authors have reported that they 

used chlorine in aquatic toxicity studies conducted at a pH of about pH 7.0, the chemical species 

present are a mixture of HOCl and ClO-

. Temperature also affects the equilibrium between 

hypochlorous acid and hypochlorite, but to a much lesser extent than pH, with the ionization 

content (pKa) for hypochlorous acid decreasing from 7.75 at 5o

C to 7.63 at 15oC and 7.54 at 

25o

C (Alabaster & Lloyd, 1980). Aquatic organisms are generally more sensitive to chlorine at 

higher temperature; an inverse relationship between LC50 and temperature was found in fish 

(Brooks and Seegert, 1977; Scott and Middaugh, 1977). It has been demonstrated that a thermal 

stress combined with exposure to chlorinated compounds produces a synergetic effect 

(Thatcher et al., 1976).

 

(b) The characteristics of the test media 

Some characteristics of the test media may also affect the evaluation of aquatic toxicity data 

e.g. presence of ammonia and organic compounds, hardness and salinity. In clean aqueous test 

media the chlorine present is likely to exist as hypochlorous acid/hypochlorite ion (i.e. detectable 

as ìfree active chlorineî) decaying rapidly due to reduction reactions and photolysis, e.g. half-life 

< 2 hours for both hypochlorous acid and the hypochlorite ion (Taylor, 1993). In natural water 

there will be more interactions with nitrogen and organic compounds so that the hypochlorous 

acid/hypochlorite ion decays faster and the chlorine present is likely to be a mixture of free active 

chlorine and chloramines (Ewell et al, 1986; Klerks & Fraleigh, 1991). The products formed 

from chlorination of natural water are also a function of salinity. Since sea water typically 
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contains 65 mg/l bromide, bromination rather than chlorination may predominate as salinity 

increases (Scott and Middaugh, 1977). 

The effect of the hardness of the test media on the aquatic toxicity of sodium hypochlorite has 

not been systematically studied. However it is not considered to be substantial as the dissociation 

of calcium hypochlorite to the hypochlorite ion is reported as reversible suggesting that the 

availability of the hypochlorite ion in test media would not be reduced by the presence of calcium 

ions (Alabaster & Lloyd, 1980). 

(c) The measured test concentration 

Hypochlorous acid/hypochlorite ion concentrations will under environmental conditions always 

decay over the duration of the test, by mechanisms shown in section 5.2.4.2. Therefore the initial 

dosed concentration is not representative of the concentration to which the test organisms have 

been exposed for the duration of the test. For example Taylor (1993) has shown that the aquatic 

toxicity of hypochlorite to Ceriodaphnia dubia in a flow-through test was 24h LC50 = 

0.006 mg/l compared to 0.048 mg/l in a static test - in the latter case the concentration of 

hypochlorite was believed to be poorly maintained. In saltwater, measured concentrations are 

often expressed as Total Residual Oxidant (TRO) or Chlorine-Produced Oxidant (CPO), which 

encompass free and combined chlorine as well, but also include other oxidative products such as 

brominated species). 

For data to be considered: 

* valid without restriction (i.e. rated 1) the test details should include the use of standard, or 

well-documented methodology, standard or known species, standard end-points for short and 

long-term toxicity, flow-through system, information on the pH, temperature, dissolved oxygen, 

number of concentrations, number of animals, duration of the test, measured concentrations of 

the test substance, performance of the control, clear concentration-effect relationship, statistical 

method used for calculating the endpoint. 

* valid with restriction (i.e. rated 2) 

the test report should include a description of the methodology, information on the taxonomy of 

the species, number of concentrations, number of animals, pH, temperature, test duration, 

oxygen concentration (or the use of a flow-through method such to guarantee its adequate 

maintenance), measured test concentrations. A semi -static exposure regime can be considered 

satisfactory provided that the chemical concentration has been adequately maintained and its 

fluctuations have properly been monitored and taken into account in the calculation of the 

endpoint. 

* invalid (i.e. rated 3) 

the test methodology is poorly documented or does not include all the major information needed 

for ëvalid with restrictioní rating, or bad performance of the control(s). 

* not assignable (i.e. rated 4) 

the test details reported are insufficient to give the test any rate.

* supportive information. Examples are tests conducted under intermittent exposure, where effect 

are evaluated after a standard period (e.g. 96h) but refer to a much shorter and discontinuous 

exposure (in the order of minutes for few times a day), or cases when no clearly identified 

endpoint can be retrieved for short or long-term toxicity (e.g. LC50/NOEC can only be expressed 
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as ìsmaller thanî or ìgreater thanî). These kind of data, although not adequate as such to derive a 

PNEC, can provide useful indication of toxicity and are retrieved as supportive information. 

The valid data for marine organisms have each been used to determine Predicted No Effect 

Concentrations (PNECs) for the aquatic compartment based on the Technical Guidance 

Document for New & Existing Substances - 1996 (Commission Regulation 1488/94/EC) 

(See further 5.2.10). 

5.2.9.2 Toxicity data on hypochlorite for brackish- and sea water species

Fish ñ short term toxicity 

The short-term toxicity of chlorinated salt water has been tested on many estuarine and marine 

fish species in bioassays conducted at different exposure regimes, from a single pulse dose of a 

few minutes to a continuous 96 hours standard exposure. Data valid for the assessment were 

retrieved from the papers by Bellanca and Bailey (1977), Thatcher (1978) and Roberts et al.

(1975). 

Bellanca and Bailey (1977) evaluated the short-term toxicity of chlorine to the estuarine fish 

Leiostomus xanthurus (ocean spot) in a flow through laboratory experiment, using a continuous 

flow serial diluter fed with river water. The authors calculated a 96h-TLm (equivalent to an 

LC50) = 0.090 mg/l of TRC, which consisted principally of free active chlorine. This data is 

rated 1. 

Thatcher (1978) conducted many laboratory flow-through bioassays on 8 species of estuarine and 

marine fish, belonging to different families including salmonidae, clupeidae and percidae. Since 

the main purpose of the study was to investigate the impact of chlorinated effluents from power 

plants, fish were simultaneously exposed to hypochlorite and to a 5°C thermal stress. 

The 96 h LC50 ranged from 0.032 mg/l (as TRO), for the most sensitive species (Oncorhynchus 

kisutch), to 0.167 mg/l (Gasterosteous aculeatus). These data were considered relevant for the 

assessment because heat is usually associated to free active chlorine in power plants effluents, 

but they were rated 2 because the authors report that in a previous study the addition of thermal 

stress resulted in a toxicity higher than chlorine alone and, moreover, LC50 was calculated 

pooling data from different tests. 

Roberts et al. (1975) tested the toxicity of continuous exposure of chlorinated river water 

(salinity 20%o) to three estuarine fish species. The lowest LC50 was calculated for Menidia

menidia: 96 h LC50= 37 μg/l (as TRC). This data was judged ìvalid with restrictionî (2) because 

Ca(OCl2) was applied as chlorine source and some information on the experimental procedure is 

lacking. 

Middaugh et al. (1977) tested the toxicity of chlorinated brackish pond water to early-life stages 

of Morone saxatilis in a flow-through test. Only data relative to eggs hatchability could be 

retrieved. A rough estimate of the 48 h LC50 = 8 μg/l TRC was calculated by us using the 

authorsí raw data relative to percentages of hatched eggs per test concentration. This data can be 

used as indicative information of eggs sensitivity. 

Fish ñ long term toxicity 

Goodman et al. (1983) developed a method for testing the early-life stages of Menidia 

peninsulae, an estuarine fish of the Atherinidae family. They carried out a 28d test starting 
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with 36 h old eggs, under flow through conditions using natural seawater diluted with freshwater 

to a 20% salinity, and measured the effects of sodium hypochlorite on eggs survival and fry 

survival and growth. Fry were the most sensitive stage. The authors calculated a NOEC (fry 

survival) = 0.04 mg CPO/l (CPO is to be considered analogous to TRC measured by other 

authors in saline waters), a concentration at which only 5% of fish died. At this concentration no 

sublethal effects were evident. The results of this test are considered fully valid (rated 1). 

One prolonged field study has been carried out by Liden et al. (1980) on two different estuarine 

fish species Brevoortia tyrannus and Leiostomus xanthurus exposed to chlorinated condenser 

cooling effluents for 19 and 20 days, respectively. All experiments were carried out in long 

troughs system where discharge waters, at three levels of chlorination, were continuously 

pumped, with inflow rates maintained at 0.038 l/s to simulate cooling water retention times 

observed in the plantís discharge canal. Up to the highest concentration (62 μg/l as TRO) a 

negligible mortality occurred among B. tyrannus, whereas at all TRO concentrations, the survival 

of L. xanthurus was significantly lower than that of control fish. At the lowest concentration 

(14 μg/l) mortality occurred in 26% of animals but, because of the lack of a clear 

concentration-effect relationship, no NOEC or EC10 can be calculated or extrapolated. 

These data are therefore not usable for assessment. 

Invertebrates ñ short term toxicity 

The acute toxicity of sodium hypochlorite to saltwater invertebrates has been widely studied with 

many organisms, including rotifers, mollusks, crustaceans and worms, but data adequate for the 

assessment are available only for a few classes. 

Thatcher (1978) tested seven species, including shrimps, mysids, amphipods and crabs, in flow 

through apparatus where animals were simultaneously exposed to chlorinated unfiltered seawater 

and 5°C thermal stress to mimic a common scenario in the real environment. The most sensitive 

species was the shrimp Pandalus goniurus for which a 96 h LC50= 90 μg/l was calculated 

pooling data from different tests. These data have been rated 2 because of data pooling and, 

above all, because the additional thermal shock might have influenced the sensitivity to 

hypochlorite. 

Very short-term exposure to pulse chlorination, with and without thermal stress, has been 

evaluated by Capuzzo and coworkers (1976, 1979a,b), who conducted flow-through bioassays 

with Brachionus plicatilis, Acartia tonsa, and larvae of Crassostrea virginica with exposure 

periods of 30-60 minutes at various temperatures. In bioassays performed at acclimation 

temperatures, lethality (measured 48 h after exposure) was LC50= 820, 180 and 120 μg/l,

respectively. For all species tested, except the copepods, the thermal stress showed a synergistic 

effect with residual chlorine concentration, lowering LC50 values down to 10 μg/l (∆T=7.5°C) 

for B. plicatilis and 80 μg/l (∆T=5°C) for C. virginica.

Four invertebrate species were tested by Roberts et al. (1975) using estuarine river water, 

chlorinated by addition of Ca(OCl)2 in flow through or static systems. When static systems were 

used the TRC concentrations were kept as stable as possible by constant addition of the chemical 

and average values were used to calculate the endpoints. The lowest lethal concentrations to be 

used as supportive information are extrapolated values for Mercenaria mercenaria larvae 

(48 h TL50=1 μg/l TRC, in the static test) and Crassostrea virginica juveniles 96 h EC50 (shell 

deposition)=23 μg/l TRC, in the flow through test). The authors report that when oyster larvae 

were exposed intermittently (manual additions at 6-8h intervals) the 48 h LT50 was 0.11 mg/l, 

i.e. two orders of magnitude higher. 
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In later experiments Roberts and Gleeson (1978) observed a similar toxicity in oyster and 

copepods continuously exposed for 48 hours to Ca (OCl)2 in flowing estuarine river water. For 

Crassostrea virginica larvae the 48 h EC50 was 26 μg/l and for adults of Acartia tonsa the

lowest 48 h LC50 was 29 μg/l as residual chlorine measured amperometrically. In the absence of 

other, more reliable studies with the relevant chemical species (sodium hypochlorite) it was 

decided to use these data in the assessment, because they provide valuable information for the 

toxicity assessment of chlorinated natural water, and assigned these data the rate ëvalid with 

restrictioní because of the different parent compound. 

The range of acute toxicity of chlorinated seawater to invertebrates appears therefore to span 

almost two orders of magnitude. 

Invertebrates ñ long term toxicity 

In the scientific literature, three studies investigating the long-term toxicity of sodium 

hypochlorite have been found. In a field study on chlorinated condenser cooling effluents using 

mollusk bivalves (Liden et al., 1980), the survival of oysters (Crassostrea virginica) and clams 

(Rangia cuneata) maintained at three TRO concentrations for 15 days was not affected at 

concentration as high as 62 μg/l, while oyster mean shell deposition was significantly reduced in 

the treated animals. At the lowest test concentration (14 μg/l) a 14% reduction in shell deposition 

was observed, so that following Technical Guidance Documents (TGD) the NOEC can be 

estimated as LOEC/2, i.e. 7 μg/l. This data is rated 2 because it was obtained from a non-standard 

test. 

Scott and Middaugh (1977) examined the lethal and sublethal effects of chlorine to adult oyster 

(Crassostrea virginica) during seasonal chronic exposures (45-75 days) to incoming estuarine 

sea water, whose temperature, pH and salinity was naturally fluctuating. Survival was reduced at 

relatively high concentrations of Chlorine- Produced Oxidants (CPO); a rough estimation of 

LC10≅160 μg/l CPO was made on the basis of the concentration-effect curves. On the other 

hand, severe sublethal effects (mean condition index and gonadal index) were observed also at 

the lowest tested concentration (140 μg/l CPO), so it is expected that the NOEC for these effects 

would be << 140 μg/l CPO. Because of the lack of a clear endpoint, these data cannot be used in 

a risk assessment. 

In another experiment Scott et al. (1979) found that mortality of C. virginica was not 

significantly reduced at 110 μg/l but the high mortality observed in the control make this result 

unreliable. At the same concentration marked sublethal effects were observed, but no direct 

concentration-effects relationship was found (not valid data). 

Algae: Phytoplankton ñ short term toxicity 

Data on short-term toxicity to algae were retrieved from the literature but they were not 

considered adequate for the effects assessment of hypochlorite. 

The effects of chlorine to three phytoplanktonic algae species were tested by Videau et al. (1979) 

in static tests with filtered sea water, aimed to evaluate a number of variables. The most sensitive 

species was Dunaliella primolecta, for which an initial dose of 400 μg/l TRO caused 50% 

mortality in 24 hours. After 3 hours from dosing, free active chlorine had disappeared in 

chlorinated water below 50 μg/l. Based on their experimental results, the authors extrapolated 
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that in a natural medium, having a population of 1cell/ml, mortality would reach 65% after 24 h 

exposure at 200 μg/l. 

Gentile et al. (1976) report the Cl2 concentrations causing 50% growth reduction in a series of 

24 h static tests on 11 phytoplankton species; the LC50 ranged from 75 to 330 μg/l. Only the 

highly concentrated stock solution was measured. Other tests performed on the diatom 

Thalassiosira pseudonana showed that, 48 h after exposure to 200 μg/l chlorine, growth was 

reduced by about 60%. 

Algae: Phytoplankton ñ long term toxicity 

Sanders et al. (1981) studied the effects of prolonged chlorination on natural marine 

phytoplankton communities cultivated in large tanks under flow through conditions (semi-field 

test). To achieve measurable concentration in the exposure tanks, HOCl was added by single 

daily additions directly to the tanks, where it degraded within 2 hours (an intermittent exposure 

was therefore resulting). A 50% reduction in cell density (the most sensitive endpoint) was 

observed in the 21 day test at concentrations as low as 1-10 μg/l TRC. These data provide 

evidence of the severe impact of free chlorine on phytoplankton at very low concentrations, even 

at intermittent exposure (data used as supportive information). 

Microcosms ñ long term toxicity 

Erickson and Foulk (1980) used outdoor and indoor flow-through systems to evaluate the effects 

of continuous chlorination (1 year) on entrained estuarine plankton communities consisting of 

eggs, larvae, algae and juveniles (not better specified). NaOCl was continuously applied at dose 

levels of 125 to 1441 μg/l, which resulted in concentrations of residual chlorine in the systems 

below the detection limits of the amperometric analyzer used (10 μg/l). In all treatments a 

reduction of ATP, measured as indication of biomass, was observed (from 13% to 58%). This 

data can be used as supportive information. 
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5.2.9.3 Summary of ecotoxicology study results with sodium hypochlorite in sea water 

Table 3: Toxicity data on fish 

 

Species System Comments Duration Anal. Parameter Results Val Reference 

(Short term studies) T°/pH meas. (mg/l) 

Alburnus alburnus S 10°C/7.8 96 h (-) LC50 32-37 3 Linden et al. (1979) 

Ammodytes hexapterus FT 14.8°C/8.0 96 h (+) TRO LC50 0.082 2 Thatcher (1978) 

Clupea harengus FT 14.8°C/8.0 96 h (+) TRO LC50 0.065 2 Thatcher (1978) 

Cymatogaster aggregata FT 14.8°C/8.0 96 h (+) TRO LC50 0.071 2 Thatcher (1978) 

Cymatogaster aggregata FT 13°C//7.9-8.1 60 min (+)TRO LC50 0.308 3 Stober et al. (1980) 

Cymatogaster aggregata FT 20°C//7.9-8.1 60 min (+)TRO LC50 0.230 3 Stober et al. (1980) 

Cynoscion nebulosus S 25°C/7.8 48 h (+) TRC LC50 0.17 +/- 0.28 3 Johnson et al. (1977) 

Cynoscion nebulosus S 25°C/7.8 48 h (+) TRC Hatch (LC50) 0.21 +/- 0.01 3 Johnson et al. (1977) 

Cynoscion nebulosus S 25°C/7.8 48 h (+) TRC Hatch (LC50) 0.21 +/- 0.01 3 Johnson et al. (1977) 

Fundulus heteroclitus FT 24°C/7.9-8.1 30 min (+) TRO 

100% mortality 

at 48h 0.65 3 Capuzzo et al. (1977) 

Gasterosteus aculeatus FT 14.8°C/8.0 96 h (+) TRO LC50 0.167 2 Thatcher (1978) 

Menidia menidia FT 17-28/river water 96h (+) TRC TL50 0.037 2 Roberts et al. (1975) 

Morone saxatilis FT 18°C/6.8 ---- (+) TRC incipient LC50 0.04 3 Middaugh et al. (1977) 

Morone saxatilis FT 18°C/6.8 ---- (+) TRC incipient LC50 0.07 3 Middaugh et al. (1977) 

Morone saxatilis FT 18°C/6.8 ---- (+) TRC incipient LC50 0.04 3 Middaugh et al. (1977) 

Morone saxatilis FT 18°C/6.8 48 h (+) TRC LC50 * 0.008 s Middaugh et al. (1977) 

Mugil cephalus ----- >48h (-) TLM50 8.0 3 Parella et al. (1986) 

Oncorhynchus gorbuscha FT 14.8°C/8.0 96 h (+) TRO LC50 0.052<x<0.023 3 Thatcher (1978) 

Oncorhynchus gorbuscha FT 18.6-23.5°C/7.53 7.5-60 min (+)Cl2 24h LC50 0.5-0.1 3 Stober et Hanson (1974) 

Oncorhynchus kisutch FT 14.8°C/8.0 96 h (+) TRO LC50 0.032 2 Thatcher (1978) 

Oncorhynchus kisutch FT 13°C//7.9-8.1 60 min (+)TRO LC50 0.208 3 Stober et al. (1980) 

Oncorhynchus kisutch FT 20°C//7.9-8.1 60 min (+)TRO LC50 0.130 3 Stober et al. (1980) 

Oncorhynchus tshawytscha FT 14.8°C/8.0 96 h (+) TRO LC50 0.065<x>0.038 3 Thatcher (1978) 

Oncorhynchus tshawytscha FT 11.7-21.7°C/7.2-7.8 7.5-60 min (+)Cl2 24h LC50 0.5-0.005 3 Stober et Hanson (1974) 

Parophrys vetulus FT 14.8°C/8.0 96 h (+) TRO LC50 0.073 2 Thatcher (1978) 

Pseudopleuronectes 

americanus FT 24°C/7.9-8.1 30 min (+) TRO 

100% mortality 

at 48h 0.55 3 Capuzzo et al. (1977) 

Stenotomus versicolor FT 24°C/7.9-8.1 30 min (+) TRO 

100% mortality 

at 48h 0.65 3 Capuzzo et al. (1977) 

Leiostomus xanthurus 

FT 14.2-16°C/7,5 96h (+)TRC TLm(=LC50) 0.09 1 Bellanca & Bailey (1977) 

Species System Comments Duration Anal. Parameter Results Val Reference 

(Long term studies) T°/pH meas. (mg/l) 

Brevoortia tyrannus FT 31.2°C/7.1 19 d (+) TRO 0% mortality 0.062 s Liden et al. (1980) 

Leiostomus xanthurus FT 31.2°C/7.1 20 d (+) TRO 26% mortality 0.014 s Liden et al. (1980) 

Menidia peninsulae FT 25°C/7.9-8.0 28d (+) CPO NOEC 0,04 1 Goodman et al. (1983) 

Validity System Analytical measurement 

1 = valid without restriction S = Static TRO = total residual oxidant 

2 = valid with restriction SS = Semi static TRC = total residual chlorine 

3 = invalid FT = flow-through Cl2 = available chlorine 

4 = not assignable DA = daily chemical addition 

s = supportive 

* calculated using raw data provided by the authors 

 

(a) the time is that when the effect has been measured, in those cases when it does not coincide with the duration of exposure. 
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Table 4: Toxicity data on invertebrates 

Species System Comments Duration Anal. Parameter Results Val Reference 

(Short term studies) T°/pH meas. (mg/l) 

Crassostrea virginica (MB) FT 17-28/river water 96h (+) TRC EC50 0.023 (b) s 

Roberts et al. 

(1975) 

Crassostrea virginica (MB) S, CA 17-28/river water 48h (+) TRC TL50 <0.005 s 

Roberts et al. 

(1975) 

Mercenaria mercenaria (MB) S, CA 17-28/river water 48h (+) TRC TL50 0.001 (b) s 

Roberts et al. 

(1975) 

Acartia tonsa (CCP) S, CA 17-28/river water 48h (+) TRC TL50 <0.005 s 

Roberts et al. 

(1975) 

Acartia tonsa (CCP) FT 20/25°C/+ 48h (+) Cl2 LC50 0.029/0.067 2 

Robert and 

Gleeson (1978) 

Crassostrea virginica (MB) FT 20/25°C/+ 48h (+) Cl2 EC50 0,026 2 

Robert and 

Gleeson (1978) 

Crassostrea virginica (MB) FT 20°/25°C//7.9-8.1 30 min (+)TRO 48h LC50 0.08-0.12 s Capuzzo (1979a) 

Crassostrea virginica (MB) FT 20°/25°C//7.9-8.1 30 min (+)TRO 48h LC100 0.86-1.40 s Capuzzo (1979a) 

Crassostrea virginica (MB) FT 48h (+)CPO LC50 0.027 4 Roberts (1980) 

Mulina lateralis(MB) FT 48h (+)CPO LC50 0.038 4 Roberts (1980) 

Brachionus calyciflorus (R) S 25°C/7.5 24 h (-) LC50 0.37 3 Snell (1991) 

Brachionus plicatilis (R) FT 20°/25°/27.5°C/7.9-8.1 30 min (+) TRO LC50 0.01-0.18 s Capuzzo (1979b) 

Brachionus plicatilis (R) FT 20°/25°/27.5°C/7.9-8.1 30 min (+) TRO LC100 0.46-1.76 s Capuzzo (1979b) 

Crangon nigricauda (CD) FT 14.8°C/8.0 96 h (+) TRO LC50 0.134 2 Thatcher (1978) 

Crangon 

septemspinosis(CD) S 10°C/8.4 5min (+) 24h TL50 10 3 

Gentile et al. 

(1976) 

Hemigramus nudus (CD) FT 14.8°C/8.0 96 h (+) TRO LC50 1.418 2 Thatcher (1978) 

Hemigrammus oregonensis 

(CD) FT 14.8°C/8.0 96 h (+) TRO LC50 1.418 2 Thatcher (1978) 

Pandalus danae (CD) FT 14.8°C/8.0 96 h (+) TRO LC50 0.178 2 Thatcher (1978) 

Palaemonetes pugio (CD) S 22°C/8.3-8.7 96 h (+) LC50 52 (c) 3 

Curtis and 

Ward(1981) 

Homarus americanus (CD) FT 60 min (+) TRC 48h LC50 0.41-2.89 s Capuzzo (1976) 

Neomysis sp. (CD) FT 14.8°C/8.0 96 h (+) TRO LC50 0.162 2 Thatcher (1978) 

Pandalus goniurus (CD) FT 14.8°C/8.0 96 h (+) TRO LC50 0.090 2 Thatcher (1978) 

Anonyx sp. (CA) FT 14.8°C/8.0 96 h (+) TRO LC50 0.145 2 Thatcher (1978) 

Pontogenia sp. (CA) FT 14.8°C/8.0 96 h (+) TRO LC50 0.687 2 Thatcher (1978) 

Gammarus fasciatus (CA) S 20°C/7.5 96 h (-) LC50 4.0 3 Ewell (1986) 

Asella intermedius (CA) S 20°C/7.5 96 h (-) LC50 32 3 Ewell (1986) 

Nitocra spinipes (CCP) SS 10°C/7.8 96 h (-) LC50 40 3 

Bengtsson 

(1983) 

Nitocra spinipes (CCP) S 10°C/7.8 96 h (-) LC50 40 3 Linden (1979) 

Acartia tonsa (CCP) FT 10°/15°/20°/25°/28°C/8.0 30 min (+) TRO 48h LC50 0.82-0.86 s Capuzzo (1979)a 

Acartia tonsa (CCP) FT 10°/15°/20°/25°/28°C/8.0 30 min (+) TRO 48h LC100 3.5-3.6 s Capuzzo (1979)a 

Acartia tonsa(CCP) S 15°C/--- 120min ? 

24h 50% 

mortality 1 3 

Gentile et al. 

(1976) 

Eurytemora affinis(CCP) S 15°C/--- 360 min ? 

24h 50% 

mortality 1 3 

Gentile et al. 

(1976) 

Pseudodiaptomus 

coronatus(CCP) S 15°C/--- 9 min ? 

24h 50% 

mortality 2.5 3 

Gentile et al. 

(1976) 

Arcatia tonsa (CCP) FT 31°C 24 h (+) TRO mortality > 0.085 3 Liden (1980) 

Perna viridis FT 28,9-29,4°C/#8,0 30h Cl2 100% Killed 10 2 

Rajagopal et al. 

(1995) 

Perna viridis FT 28,9-29,4°C/#8,0 48h Cl2 100% Killed 10 2 

Rajagopal et al. 

(1995) 
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Species System Comments Duration Anal. Parameter Results Val Reference 

(Long term studies) T°/pH meas. (mg/l) 

Crassostrea virginica (MB) FT 24-31°C/--- 60 d (+) TRC 63% effect 0,11 3 Scott et al. (1979) 

Crassostrea virginica (MB) FT 24-31°C/--- 60 d (+) TRC NOEC mortality 0,11 3 Scott et al. (1979) 

Crassostrea virginica (MB) FT (field) 31.2 °C/7.1 15 d (+) TRO 14% effect 0,014 2 Liden et al. (1980) 

Brachidontes striatulus FT 29,2-29,8°C/#8,0 20d Cl2 100% killed 1 2 Rajagopal et al. (1997) 

Brachidontes striatulus FT 29,2-29,8°C/#8,0 24d Cl2 100%Killed 1 2 Rajagopal et al. (1997) 

Brachidontes striatulus FT 29,2-29,8°C/#8,0 102h Cl2 100%Killed 5 2 Rajagopal et al. (1997) 

Brachidontes striatulus FT 29,2-29,8°C/#8,0 156h Cl2 100%Killed 5 2 Rajagopal et al. (1997) 

Perna viridis FT 28,9-29,4°C/#8,0 21d Cl2 100% Killed 1 2 Rajagopal et al. (1995) 

Perna viridis FT 28,9-29,4°C/#8,0 33d Cl2 100% Killed 1 2 Rajagopal et al. (1995) 

Crassostrea virginica (MB) FT 11-27°C/7.4-8.3 45-75 d (+) CPO 0.160-0.250 3 

Scott and Middaugh 

(1977) 

Crassostrea virginica (MB) FT 11-27°C/7.4-8.3 45-75 d (+) CPO NOEC <<0.140 3 

Scott and Middaugh 

(1977) 

Rangia cuneata (MB) FT (field) 31.2 °C/7.1 15 d 0% effect 0.062 3 Liden et al. (1980) 

Validity System Analytical measurement 

1 = valid without restriction S = Static TRO = total residual oxidant 

2 = valid with restriction S, CA = static with constant addition system TRC = total residual chlorine 

3 = invalid SS = Semi static CPO = chlorine-produced oxidant 

4 = not assignable FT = flow-through Cl2 = available chlorine 

s = supportive 

Species

MB = Mollusc bivalve; MG = Mollusc gasteropod; R = Rotifer; CD = Crustacea decapod; CA = Crustacea amphipod; CPP = Crustacea copepod; 

CCL = Crustacea cladocere 

(a) the time is that when the effect has been measured, in those cases when it does not coincide with the duration of exposure 

(b) extrapolated value 

(c) 4-6% aqueous solution 

(d) rough estimate on raw data 
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Table 5: Toxicity data on algae 

Species System Comments Duration Anal. Parameter Results Val Reference 

(Short term studies) T°/pH Meas. (mg/l) 

Dunaliella primolecta S 20°C 24 h (+)TRO 50% mortality 0.4 3 Videau et al. (1978.79) 

Pavlova lutheri S 20°C 24 h (+)TRO 50% mortality 4 3 Videau et al. (1978.79) 

Phaeodactylum 

tricornutum S 20°C 24 h (+)TRO 100% mortality 0.8 3 Videau et al. (1978.79) 

Skeletonema costatum S 20°C 24 h (+) (a) LC50 0.095 3 Gentile et al. (1976) 

Rhodomonas baltica S 20°C 24 h (+) (a) LC50 0.11 3 Gentile (1976) 

Dunaliella tertiolecta S 20°C 24 h (+) (a) LC50 0.11 3 Gentile (1976) 

Monochrysis lutheri S 20°C 24 h (+) (a) LC50 0.200 3 Gentile (1976) 

Thalassiosira pseudonana S 20°C 24 h (+) (a) LC50 0.075 3 Gentile (1976) 

Thalassiosira pseudonana S 20 min 60% effect at 48h 0,2 3 Gentile (1976) 

Chaetoceros decipiens S 10°C 24h (+) (a) LC50 0.140 3 Gentile (1976) 

Thalassiora nordensholdii S 10°C 24h (+) (a) LC50 0.195 3 Gentile (1976) 

Thalassiosira rotula S 10°C 24h (+) (a) LC50 0.330 3 Gentile (1976) 

Asterionella japonica S 10°C 24h (+) (a) LC50 0.250 3 Gentile (1976) 

Chaetoceros didyum S 10°C 24h (+) (a) LC50 0.125 3 Gentile (1976) 

Detonula confervacea S 10°C 24h (+) (a) LC50 0.200 3 Gentile (1976) 

Phytoplankton FT 9-18°C//8.4 12h (+)TRO 

Primary 

productivity(EC98) 1.2 3 Carpenter (1972) 

Phytoplankton SS 7-19.7°C//8.4 3x1.5h (+)TRO 

Primary 

productivity(EC86) 1.2 3 Carpenter (1972) 

Species System Comments Duration Anal. Parameter Results Val Reference 

(Long term studies) T°/pH Meas. (mg/l) 

Phytoplankton 

(microcosm) FT, DA 6-8°C/7.7-7.9 21 d (+)TRC (b) 

50% cell density 

reduction 0.001-0.01 s Sanders et al. (1981) 

Microcosm study FT 10.1- 30.8 °C/ 1 y (+)TRC 

13-58% ATP 

reduction < 0.01 s 

Ericksson and Foulk 

(1980) 

Validity System Analytical measurement

1 = valid without restriction S = Static TRO = total residual oxidant 

2 = valid with restriction SS = Semi static TRC = total residual chlorine 

3 = invalid FT = flow-through Cl2 = available chlorine 

4 = not assignable DA = daily chemical addition 

s = supportive 

(a) only the stock solution (100 mg/l) was measured 

(b) free active chlorine as HOCL was administered 
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5.2.9.4 Summary of Ecotoxicity Data Selected for the Determination of the PNEC for Brackish 

and Sea Water Organisms 

The valid and supporting data discussed in sections 5.2.9.3 to 5.2.9.4, which are acceptable for 

use in the determination of the PNEC for brackish and sea water organisms, are collected and 

summarized in table 6. 

Table 6: Summary of ecotoxicity data selected for the determination of the PNEC 

for brackish and sea water organism. 

SHORT-TERM TOXICITY

Valid data Supportive information

Endpoint 

Study 

Details/Reference

Endpoint Study 

Details/Reference 

Fish 96hLC50 = 32 μg 

TRO/l (rated 2) 

Thatcher, 1978 48hEC50 = 

8 μg TRC/l 

(eggs) 

Middaugh et al., 1977

Fish 96hLC50 = 90 μg 

TRC/l (rated 1) 

Bellanca and 

Bailey, 1977 

 

Crustaceans - - - - 

Mollusks 48h EC50 = 26 μg 

TRC/l (rated 2) 

Roberts and 

Glason, 1978 

 

Algae - - - - 

LONG TERM TOXICITY

Endpoint 

Study 

Details/Reference

Endpoint Study 

Details/Reference 

Fish 28d NOEC = 40 μg 

CPO /l (rated 1) 

(fry survival) 

Goodman et al., 

1983 

 

Crustaceans - - - - 

Mollusks 15d NOEC = 7 μg 

TRO/l (rated 2) 

(shell deposit) 

Liden et al., 1980 

 

Algae - 21d EC50 = 1-

10 μg TRC/l 

(periphytic 

community, 

intermittent 

exposure) 

Sanders et al., 1981 

Phyto and Zooplankton 

- 1y EC50 

< 10 μg TRC/l 

(biomass reduction) 

(microcosm study) 

Erickson and Foulk, 

1980 

TRO =Total residual oxidant 

TRC= total residual chlorine 

CPO = Chlorine-produced oxidants 

Validity rates: 

1= valid 

2= valid with restriction 

s= supportive information 
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5.2.9.5 Terrestrial compartment 

The possible exposure routes of soils to free active chlorine are via contaminated sludges or via 

direct application of chlorinated water. OCl-

/ HOCl are highly soluble molecules not likely to 

sorb onto activated sludges. Therefore, there is no evidence that free active chlorine species have 

the potential to contaminate activated sludges. As a consequence also, contamination of soils due 

to dumping of with free active chlorine polluted sludges can be excluded. 

Contamination of soils due to direct application of chlorinated water will not be of permanent 

origin. The high content of organic matter in a soil will allow a quick (order of seconds) 

reduction of OCl-

/ HOCl. 

5.2.10 Conclusion and PNEC determination 

5.2.10.1 General consensus 

In the scientific literature of the last 30 years, a great number of short and long term aquatic 

toxicity studies on hypochlorite, conducted with fresh and saltwater organisms belonging to all 

trophic levels, have been found. Section 5.2.9.4 gives, for each study, details on experimental 

conditions and test results are reported for fish, invertebrates, algae and microorganisms. 

Nevertheless, after their evaluation following the criteria indicated in the European Commission 

TGD, the number of valid data judged adequate for risk assessment was drastically reduced 

because many of them did not meet the validity criteria specified at the beginning of this chapter. 

In spite of the high number of studies conducted, only a few provide reliable information useful 

for the assessment. This is because most of the studies were carried out in the 70ís and 80ís and 

were tailored to answer specific questions such as, for example the efficacy of sodium 

hypochlorite as biofouling agent, the effect of temperature stress and/or of intermittent exposure 

of very short pulse additions of hypochlorite. Hence, their evaluation is not straightforward. From 

many of these studies, although good and reliable, it was not possible to retrieve the proper endpoint requested for derivation of PNEC (e.g. the NOEC for long-term studies), so that, following 

the TGD indications, they were used as additional information in support of valid toxicity data 

(rated 1 or 2) used in the PNEC calculation. In addition, it should be noted that none of the 

evaluated experiments were conducted in GLP, due to the fact that most of them were carried out 

long before the requirements of the Directive 87/18/EEC. Short and long term toxicity data are 

available for microorganisms, algae, invertebrates and fish. The evaluation and comparison of 

toxicity data are made difficult by the complexity of sodium hypochlorite chemistry in water and 

by the different analytical methods used to measure its concentration. Total Residual Chlorine, 

TRC, is a measure of both free active and combined active chlorine (such as chloramines). It is 

difficult to separate the contribution to toxicity of the free available chlorine such as HOCl/-

OCl 

from that of the combined chlorine species. Also, the relative amounts of the different chlorine 

species will be different for each test, due to pH and other medium related effects, test duration 

and ammonium level effects, etc. For those studies where the percentage of free active chlorine 

(FAC) out of the TRC had been measured and reported the toxicity endpoints have also been 

expressed as concentration of FAC/l. In chlorinated salt water, toxicant concentration is often 

expressed as Total Residual Oxidant (TRO) or Chlorine Produced Oxidants (CPO), which 

include, in addition to free end combined chlorine, also other oxidative products. This makes the 

assessment task and the comparability of fresh and salt water toxicity data harder. Ballast water 

represents waters with high salinity ranges. In the following the results for sea water are 

summarized and attempt to derive the PNEC for this environment. 
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In table 6, toxicity data adequate for risk assessment have been listed together with supportive 

data. Valid short-term toxicity data have been collected for mollusks and fish, which show a 

similar sensitivity: 48 h EC50 = 26 μg TRC/l and 96 h LC50 = 32 μg TRO/l, respectively. 

Supportive information indicates that acute toxicity is higher for fish eggs: 48 h EC50 = 8 μg 

TRC/l. No data for crustaceans or algae are available, so that it is not possible to determine which 

trophic level is the most sensitive in short-term tests. 

For the same groups, molluscs and fish, long-term toxicity data have also been found. Molluscs 

(15d NOEC = 7 μg TRO/l) are more sensitive than fish fry (28d NOEC (fry survival) = 40 μg 

CPO/l) For crustaceans and algae, adequate data for risk assessment are again not available. 

Anyhow a study conducted on periphytic community under intermittent exposure provides a 21d 

EC50 lying between 1 and 10 μg TRC/l, suggesting that following continuous exposure the 

NOEC for algae is likely to be lower than that. 

5.2.10.2 PNEC derivation 

Considering the specific mode of action of hypochlorite, which is a strong oxidizer, and the 

recommendations given in the EC technical guidance documents (TGD) (final version 

May 2002), short- and long-term toxicity data for saltwater organisms have been pooled. In this 

way a set of three valid NOEC values is obtained, one for each trophic level: fish, molluscs and 

algae. 

When, after pooling the data from fresh and salt water the dataset consists of two long-term 

NOECs representing two trophic levels (e.g. algae and fish) plus a NOEC from an additional 

marine taxonomic group (e.g. molluscs), as it is the case in the present assessment, the TGD 

recommends that a factor of 50 is applied to the lowest figure. Hence, PNEC = 3 μg TRC/l/50 = 

0.06 μg TRC/l corresponding to 2.1 μg FAC/l/50 = 0.04 μg FAC/l. 

5.2.11 PEC values of active chlorine species due to BWT 

A general PEC derivation for active chlorine/TRO in the case of ballast water discharge is not 

possible to calculate, because of the vast amount of possible scenarios and different physical 

conditions of the harbours, waters, ships etc. PEClocal values would have to be predicted in each 

particular case. However, the most relevant and comparable case to ballast water discharge (in 

terms of discharge concentrations found in the literature is regular cooling water discharge from 

coastal power plants. The cooling water is taken from the sea, chlorinated due to e.g. biofouling 

of the condensers etc., and discharged back directly to the sea. The free active chlorine level will 

be in the same range as the maximum result from by-production using EctoSysô in ballast water 

treatment. The power plant cooling water case has been extensively studied due to the large 

volumes of water and due to the limited receiving local area. 

Quite recently, some data on TRO concentrations in the discharge plumes in sea water of various 

power stations have been published (Jenner et al, 1997). These data vary from 0.02 mg/l TRO in 

the near vicinity of power stations to zero at further distances. Moreover it must be noted, that 

these data most likely do not represent hypochlorite but a variety of other oxidants. In general, 

observed concentrations will be variable and to a large extent influenced by local conditions. 

Local regulations are usually designed to prevent acute effects in the vicinity of the discharges. 
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Therefore a PEC value for hypochlorite in a worst-case regular cooling water scenario will 

rapidly drop to zero when reaching surface water. This can be expected based on the model 

calculations for the comprehensive household/sewage scenario predicted by Akzo Nobel 

(reference 7) and is also supported by measurements (Jenner et al., 1997, 1998). It means that 

potential effects - if any - may only be expected in the near vicinity of the outlet of the cooling 

water system and thus not even at all relevant in the ballast water discharge case where the exact 

point of discharge will vary. 

The calculation model presented in section 5.2.7.1 and discharge/decay model (appendix 2 to 

reference 7) for the sewage exposure scenario clearly show that concentrations of 0.5 mg/l TRO 

(maximum value at the power plant cooling water condensers, worst-case regular scenario) as 

well as concentrations up to 8 mg/l (extreme worst-case shock dosing regime) will fall below the 

detection limit within seconds upon reaching the surface water. Thus, this will certainly also be 

the case for discharge of treated ballast water containing < 2 mg/l TRO and can easily be verified 

during on-board installation and test phase. 

5.2.12 Free active chlorine PEC/PNEC derivation 

The normal approach to risk assessment considers the ratio PEC/PNEC as an important factor. 

This ratio normally includes safety factors of 50-100. However, in this case where PEC is 

predicted to rapidly drop to zero when reaching surface water, the PEC/PNEC is not relevant to 

estimate. 

5.2.13 Discharge exposure model 

Modelling of the decay and exposure of free active chlorine in sewer and river water have been 

performed by Akzo Nobel (reference 7). It was concluded that dilution from low (< 10 ppm) 

concentrations to background levels will occur within seconds in all relevant, natural cases when 

the chlorinated waters are discharged. This implies for the EctoSysô ballast water discharge 

case a dilution period also will be very short. See further section 7. 

5.2.14 Mammalian toxicity (the Procedures (G9), paragraph 4.2.1.2) 

The worst-case maximum concentration (2 ppm) in EctoSysô ballast water effluents motivates 

no studies on mammalian toxicity, taking into account the rapid decay (section 5.2.7) of FAC and 

TRO in natural waters. However, such data on FAC is included in the Akzo Nobel Risk 

Assessment Report [7] readily available. 

5.3 Secondary disinfection by-products

5.3.1 General 

Disinfection by-products (DBP:s) are chemical (organic and inorganic) substances that can form 

when disinfectants, such as e.g. free active chlorine, react with naturally present compounds in 

the water. The formation of these products mainly takes place during reactions in which organic 

substances play a major part. These materials end up in water during the decomposition of plant 

and animal matter. Little general information can be given on the chemical structures of all kinds 

of organic substances present in marine sea water and thus being precursors for the formation of 

possible disinfection by-products during disinfection of ballast water. The mechanisms of 

formation of DBP:s therefore remains unclear and impossible to generalize. Research is also 
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difficult because of the extensive number of substances that make up organic matter. For this 

reasons, methods for disinfection of natural waters must be carefully evaluated through 

effect assessment. 

The types of DBP:s that are formed depend on a number of influencial factors: 

• the type of disinfectant 

• the disinfection dose 

• the disinfection residuals 

When the dose and residuals of the disinfectant are higher, more disinfection by-products are 

formed. 

• circumstances of disinfection: temperature and pH 

When temperatures increase, reactions take place faster and causing a higher chlorine 

concentration in conventional chlorine electrolysis to be required for a proper disinfection. This 

causes more halogenic disinfection byproducts to form. At higher pH values, more THM 

(Trihalomethanes ñ see below) is also formed from conventional chlorine electrolysis, whereas 

more haloacetic acids (HAA) are formed when pH values are lower (in fresh water applications). 

• the constituents of water 

• concentrations and properties of naturally present organic matter in the water 

The level of organic matter is usually registered as the ìtotal organic carbonî (TOC) 

concentration or the ìdissolved organic carbonî (DOC) concentration. The composition and 

concentration of naturally present organic matter determine the types and concentrations of 

DBP:s that will eventually be formed. Location and seasons may influence the naturally present 

organic carbon concentration, causing the concentrations of DBP:s to vary. The formed 

concentrations of disinfection by-products in litoral and pelagial water may also be different 

(reference 11). 

Adsorbable Organic halogens (AOX) is a measure of the number of C-Cl bonds formed in a 

reaction, expressed as Cl2 consumed to form these bonds. Part of the AOX content is volatile; 

the main representative in this case is chloroform. It is very important to distinguish between the 

volatile and the non-volatile part in order to analyse the AOX. The non-volatile part is of high 

importance due to the potential stability of some of the components (mainly the chloroacetic and 

chloroaromatic compounds). 

Trihalomethanes (THM) are a group of (mainly) four chemicals that are formed along with other 

disinfection by-products when chlorine or other disinfectants used to control microbial 

contaminants in water react with naturally occurring organic and inorganic matter. The 

trihalomethanes are: chloroform, bromodichloromethane, dibromochloromethane and 

bromoform. In the case of drinking water, different regulations are currently active 

internationally. For example, EPA has published the Stage 1 Disinfectants/Disinfection 

Byproducts Rule to regulate total trihalomethanes (TTHM) at a maximum allowable annual 

average level of 80 ppb (parts per billion). This standard replaced the current standard of a 

maximum allowable annual average level of 100 parts per billion in December 2001 for large 

surface water public water systems. The standard became effective for the first time in 

December 2003 for small surface water and all ground water systems. The drinking water 

regulation is mentioned here to serve as comparative value in the complete risk assessment of 
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by-products formation in ballast water treatment using EctoSysô as a disinfecting step, knowing 

the worst case concentrations of THM produced. 

Bromate (BrO3

-

) is a chemical that is mainly formed when ozone used for disinfection reacts with 

naturally occurring bromide found in source water. Bromate is well known to be carcinogenic 

and must be controlled at all sea water treatment with oxidative methods. The Stage 1 

Disinfectants/Disinfection Byproducts Rule regulates bromate at an annual average of 10 ppb

in the case of drinking water. 

5.3.2 Secondary disinfection by-products in the EctoSysô ballast water treatment process 

The problems with disinfection by-products associated with conventional disinfection techniques 

can effectively be avoided using the EctoSysô treatment technique. The reactive intermediates 

producing by-products are degraded cathodically before they form stable and possibly harmful 

by-products. 

THM can (in natural waters) be used as an indicator of the total amounts of formed disinfection 

by-products. The formation of HAA is in the EctoSysô case not considered relevant because of 

the low levels of chlorine that are formed (< 2 ppm) combined with the high pH of sea water. 

However, several analyses of both THM levels and AOX (Absorbable Organic Halogens) levels 

have been performed during nominal EctoSysô treatment conditions, and also taking a ìworst 

caseî approach, at different locations and waters. The results show that the THM levels are well 

under EPA drinking water standards even at ìworst caseî (i.e. low flow rate, very high current). 

The dominant THM species formed is bromoform due to its relative stability and the sea water 

content of bromide. Table 7 summarizes some typical data for THM and AOX formation in sea 

water due to EctoSysô treatment. The THM analysis were made at a laboratory accredited 

according to DIN ISO / EC 17025, using method: DIN EN ISO 10301 (F4). AOX was measured 

according to EN 1485. The analyses were performed approximately 24 h after treatment, thus the 

total residual chlorine (TRC) and free active chlorine (FAC) levels are totally decomposed. 

Table 7: Summary of AOX and THM formation in sea water 

during EctoSysô treatment with different currents applied 

control 2.2A 8A 15A

AOX (ppm) 0.06 0.2 0.2 0.2 

THM

(ppb): 

 

CHCl3 < 5 < 5 < 5 < 5 

CHCl2Br < 5 < 5 < 5 < 5 

CHClBr2 < 5 < 5 < 5 < 5 

CHBr3 < 5 39 42 71 

TRC (ppm) < 0.05 < 0.05 < 0.05 < 0.05 

FAC (ppm) < 0.05 < 0.05 < 0.05 < 0.05 

Figure 6 illustrates the typical influence of flow rate to the formation of THM under EctoSysô 

nominal applied current and natural sea water treatment in Bremerhaven harbour 

(salinity 11-20 PSU), Germany. It can be concluded that the formation of total THM is negligible 

at nominal parameters and also in the order of drinking water standards (EPA) at worst case 

conditions. The TTHM consisted of bromoform to 85-100% in all cases. In combination with 

other measurements (see section 5.2.6) of the formation of free active chlorine, it can also be 

concluded that, using EctoSysô treatment, the free active chlorine (DPD measured ìTROî) level 
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can be in the order of 0.6-0.8 ppm without producing THM levels that would pose any threat to 

the environment. 

THM formation in sea water after EctoSys treatment, nominal + 

worst-case conditions

0

20

40

60

80

100

120

140

0 20 40 60 80 100 120

Flow rate, % of nominal (=10m3/h)

Total THM, ppb 

July tests, nominal current, turbidity

12FNU

November tests, worst case current,

turbidity 122FNU

 Figure 6: THM concentration as a function of flow rate, nominal- and worst-case current 

(THM analysis by lab accredited according to DIN ISO / EC 17025, method: DIN EN ISO 10301 (F4)) 

5.3.3 PNEC secondary disinfection by-products 

Trihalomethanes 

In most fresh water situations the dominant trihalomethane produced during hypochlorite use is 

chloroform: only in high bromide situations, such as chlorination of sea-water used for cooling, 

do the brominated trihalomethanes become major components. 

It is beyond the scope of this risk assessment to derive PNECs for the brominated 

trihalomethanes individually. However, ecotoxicological data (gathered by e.g. Khalanski et al.) 

in connection with assessment of seawater chlorination suggest that the ecotoxicities of the 

brominated THMs are not markedly different from chloroform. Table 8 below highlights some 

published studies with useful comparative data: 
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Table 8: Examples of ecotoxicological data for THM:s, aquatic species

Species, 

biological stage 

Compound Toxicity mg/l Reference 

Daphnia magna 

(Freshwater) 

Chloroform 

Bromoform 

48 hr LC50 = 29 

48 hr LC50 = 46 

Le Blanc 1980 

Lepomis 

macrochirus 

(Freshwater) 

Chloroform 

Bromoform 

96 hr LC50 = 13 ñ 22 

96 hr LC50 = 29 

Anderson & Lusty 1980 

Buccafusco et al. 1980 

Cyprinus carpio

(Carp embryos) 

Chloroform 

BDCM 

DBCM 

Bromoform 

96 hr LC50 = 161 

96 hr LC50 = 119 

96 hr LC50 = 53 

96 hr LC50 = 76 

Trebalka et al. 1981 

Cyprinus carpio

(Carp embryos) 

Chloroform 

BDCM 

DBCM 

Bromoform 

96 hr LC50 = 97 

96 hr LC50 = 67 

96 hr LC50 = 34 

96 hr LC50 = 52 

Mattice et al. 1981 

In view of the above, it seems reasonable for the purposes of a broad assessment to regard the 

trihalomethanes as of similar aquatic toxicity and to use the chloroform PNEC for total 

trihalomethanes. The Akzo Nobel draft Risk Assessment (reference 7) for chloroform estimates a 

PNECaquatic of 146 μg/l (see section 3.2.1.4 in reference 7) 

5.3.4 PEC secondary disinfection by-products 

The most important factor for the potential environmental impact of free active chlorine 

discharged in sea water is the formation of by-products, consisting of other oxidants (included in 

the TRO concept) and other chemicals. The power plant cooling water application of 

hypochlorite use is also here the most useful and comparable case for the EctoSysô ballast water 

treatment. The formation of by-products will vary strongly, both quantitatively and qualitatively, 

due to the fluctuations in surface water composition, temperature, residence time, etc. The impact 

of different environmental factors on the mechanism of by-product formation has been studied 

extensively (e.g. Handbook of American Water Works, 1982). A summary of the main 

by-products generated by hypochlorite use in seawater cooling systems is given in table 9. The 

data represent actual measurements. In all situations it is observed that elevated by-product 

concentrations only occur in the near vicinity of the discharges. 

Table 9: Measurement of by-products of hypochlorite application in cooling water 

 in sea water, summarizing data from Jenner et al. 1997 

Power stations No. of 

samples 

Bromoform (μg/l) Dibromoacetonitrile(μg/l) 

 Average range Average range 

Several in UK, 90 16.32±2.1 0.72ñ29.2 

F and NL 29 1.48±0.56 < 0.1-3.15 
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For the marine cooling water scenario PEC values of TRO between 0 and 20 μg/l were measured. 

Since hypochlorite is added at the beginning of the cooling system it is expected that the TRO 

measured after discharge will be mainly a mixture of oxidative compounds other than 

hypochlorite. Since the nature of TRO is not identified it is not useful nor possible to determine a 

PEC/PNEC ratio. 

The actual formation of inorganic and organohalogen by-products will be highly dependant on 

specific local conditions and dosing regimes, which are normally under control of local permits. 

The use of hypochlorite in cooling water is recently described in the reference document on the 

application of best available techniques (BAT) in industrial cooling systems (IPPC, 2000). 

Another useful recent publication was published by ElectricitÈ de France (Khalanski, 2002) on 

organic by-products from cooling water chlorination from EDF marine power stations. 

Measurements of the main trihalomethane formed (bromoform) in cooling water samples from 

three power station showed bromoform levels up to 26.8 ug/l. The report assesses the risks of the 

main organic CBPís, concluding that the margins between the most sensitive toxicity thresholds 

and the observed environmental concentrations for these power stations have safety factors of 

103

 to 107 for the local scale and 104 to 109 for the regional scale. 

In situ measurements (plume sampling in the field) for 10 coastal power stations in France, the 

United Kingdom and the Netherlands were carried out for the following chemical class of 

compounds: haloforms, haloacetonitriles and halophenols. Five compounds were found at mean 

chlorine dosage levels of 0.5-1.5 mg/l (as Cl2) of which 2 were consistently present above the 

detection limit. Bromoform was present in all effluents as well as dibromoacetonitrile. 

Dibromochloromethane, bromodichloromethane and 2,4,6-trichlorophenol were detected in a few 

cases at very low levels. 

For by-product risk assessment, the chlorination of seawater (where brominated species 

predominate), probably represents a worse case in terms of by-product loads in effluents than 

freshwater chlorination. The environmental properties and toxicity of brominated and chlorinated 

species are similar, but the brominated oxidants formed are more reactive and have been 

observed to yield somewhat elevated levels of by-products, notably THMs (Pourmoghaddas and 

Stevens, 1995). This may to some extent be counteracted because by-product formation will be 

somewhat reduced at the higher pH that is typical of seawater. 

The by-product concentrations from the EdF study (Khalanski, 2002) together with data in 

Table 9 would indicate conservative THM concentrations in the discharge during continuous 

dosing of approximately 30 μg/l. Risk characterization can then consider the case for sea water: 

For marine discharges in coastal zones the technical guidance documentation suggests a dilution 

factor of 100 can be considered as a worst case. This gives PEC local values of 0.3 μg/l for 

THMs, which well serves as an indicative ìworst-caseî value for the ballast water discharge 

case. A conservative PEC/PNEClocal for THM can thus be estimated (PNEC = 146 μg/l, see 

section 5.3.3) and indicates no possible harm to the environment from THM originating in 

EctoSysô ballast water treatment. 

5.3.5 Disinfection by-products associated with conventional chlorination 

Chlorination disinfection by-products (CDBPs) are chemical compounds that normally form 

when water containing natural organic matter (i.e all natural waters) is chlorinated. In 

conventional chlorination of natural waters, the high concentrations of free active chlorine 

species (i.e. Cl2, OCl-

, HOCl) present inevitably leads to the formation of a number of 
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chlorination by-products of which trihalomethanes (THM:s) are only one subgroup. Among the 

many disinfection by-products caused by conventional chlorination (electrochemical or not), 

THM:s are most often present and in the greatest concentration and as such are used as indicators 

of total disinfection by-product formation. THM:s have been shown to be carcinogenic. It will be 

formed in unacceptable quantities using conventional electrochemical chlorine generators in 

ballast water management if special technical measures will not be taken to prevent formation or 

remove CDBPs. 

5.3.6 Disinfection by-products associated with ozonation 

Using ozone as a disinfectant, bromate ion (BrO3

-

) formation is a big potential concern with 

source waters containing bromide ions. Bromate is a chemical that is formed when ozone used to 

disinfect water reacts with naturally occurring bromide found in source water. The oxidation 

reaction of bromide ion (Br-

) to hypobromite ion (BrO-) and bromite ion (BrO2

-

) and 

subsequently to bromate ion occurs due to direct reaction with ozone. Intermediate reactions can 

also occur through hydroxide radical mediated mechanisms if bromide is not present. 

5.3.7 Disinfection by-product health effects, additional information

Some studies have been performed on disinfection by-products health effects, but only 

concerning drinking water. However, it certainly raises concern over the use of conventional 

chlorination/ozonation in ballast water treatment systems. Since the discovery of chlorinated 

by-products in drinking water in 1974, numerous toxicological studies (studies on the health 

effects from exposure to high dosages contaminants usually involving animals in a lab) have 

been conducted. These studies have shown several disinfection by-products to be carcinogenic in 

laboratory animals (e.g., including bromate, certain trihalomethanes and haloacetic acids). Some 

disinfection by-products have also been shown to cause adverse reproductive or developmental 

effects in laboratory animals (e.g., chlorite and certain trihalomethanes and haloacetic acids). 

However, there is considerable uncertainty involved in the results of high-dose, toxicological 

studies of some by-products occurring in disinfected drinking water to estimate the risk to 

humans from chronic exposure to low doses of these and other by-products. 

In the area of epidemiology (studies of the factors that influence disease in human populations), a 

number of studies have been completed investigating the relationship between exposure to 

chlorinated surface water and cancer. Some have suggested an increased cancer risk to those 

exposed to chlorinated waters while others have demonstrated none. In issuing the Stage 1 

Disinfectants/Disinfection By-products Rule based on evidence then available, EPA stated that 

while the agency cannot conclude that there is a causal link between exposure to chlorinated 

surface water and cancer; these studies have suggested an association, albeit small, between 

bladder, rectal, and colon cancer and exposure to chlorinated surface water. There are fewer 

epidemiology studies evaluating the association between exposure to disinfection by-products 

and reproductive and developmental effects. Again, some have suggested an increased risk from 

exposure to disinfection by-products while others have shown none. There remains considerable 

debate in the scientific community on the significance of these contradictory findings concerning 

chlorinated water and disinfection by-products. As with cancer, EPA stated in its Stage 1 

Disinfectants/Disinfection By-products Rule that, based on data then available, the agency can 

not conclude there is a causal link between exposure to disinfection by-products and reproductive 

and developmental effects. In sum, EPA believes the weight-of-evidence presented by the 

available epidemiological studies on chlorinated drinking water and toxicological studies on 

individual disinfection by-products support a potential hazard concern and warrant regulatory 

action at this time such as that taken in the Stage 1 Disinfectants/Disinfection By-products Rule. 
MEPC 55/2/4 

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In the case of disinfection systems for ballast/sea water treatment, it is concluded that measures 

have to be made to monitor and keep the disinfection by-product levels to a minimum. 

6 TOXICITY TESTING OF THE TREATED BALLAST WATER (THE 

PROCEDURE (G9), SECTION 5.2) 

6.1 Whole effluent toxicity testing 

Brixham Environmental Laboratory (BEL), AstraZeneca UK Limited, have run a series of 

aquatic toxicity tests on whole-effluents of sea water treated with the Ectosysô ballast water 

treatment system [8]. The laboratory is certified according to GLP and consequently has archive 

dossiers of the complete experiment and raw-data, not included in this application. 

Organisms representing three trophic levels (Algae, crustacean and fish) have been used to 

represent species variations and lifestyles with different feeding strategies, which account for 

differences in sensitivity among different organisms. Acute toxicity testing was selected to 

determine any short term effects from the effluent. This in itself provides a significant safety 

factor since the timescale of dilution of the discharged effluent will be much shorter (of the order 

of a few hours) than the timescale of the tests (72 or 96 hours). Chronic toxicity data (the 

Procedure (G9), paragraph 5.2.2) was consequently not considered necessary. 

These toxicity tests have been carried out for four different cases representing different 

environmental conditions and different operating conditions of the unit; these conditions were 

full salinity (~35PSU) and half salinity (~17.5PSU) at both nominal treatment conditions and by 

applying high (150% of nominal) current representing a ìworst caseî scenario. The treatments 

and storage time of the water was designed to simulate a relevant real case of ballast water 

treatment using Ectosysô as a disinfecting step: the water was filtered down to 20-40 μm and 

filled in a storage tank (1 m3

), then treated by the Ectosysô unit (5m3/h) and stored for 48 h in a 

second tank, then treated again by the Ectosysô unit immediately before the toxicological 

studies. 

The tests were conducted during the period 9th January to 1st February 2006 and in each case the 

effluents produced from the Ectosysô unit were tested at two series of dilutions (100, 30, 10, 3 

and 1 % v/v, and 30, 10, 3, 1 and 0.3 % v/v respectively). The results from the three trophic 

levels and the four test conditions were very consistent. The worst case results from the tests 

were: 

Parameter % v/v Test 

Concentration causing 50% kill (LC50) 5.5 turbot and rainbow trout 

Concentration causing 50% effect (EC50) 3.6 Algae (biomass) 

No effect concentration (NOEC) 3.0 All 

Lowest effect concentration (LOEC)* 10 All 

*LOEC not possible to define further, since the statistical model does not have the proper input values (data from measurements between 3 

and 10%) 

A No Effect Concentration of 3% v/v translates to a requirement in the receiving water for a 

dilution of 33 times (100% ÷ 3%) for there to be potentially no effect on the environment. The 

LOEC value should be considered as indicative. These levels of toxicity are well in range with 

the expected from the worst case concentrations of TRO resulting from sea water treatment with 

the Ectosysô. Dilution in the environment varies spatially and with parameters such as the 

discharge rate, the ambient water speed and the turbulence. Therefore there is a need to combine 
MEPC 55/2/4 

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the toxicity results with predictions of dilution to make a risk assessment for the Ectosysô 

process (see section 7). 

Table 10: Summary of whole effluent toxicity test results (% v/v) 

Start date, 

Treatment 

Algae, 72h 

(biomass) 

Algae, 72 h 

(growth rate) 

Tisbe, 24 & 48 h Fish, 24 h 

9/1/2006 

Full salinity, 

high current 

EbC50 5.1% 

CI (2.8-7.4)% 

NOEC 

(3.0%)* 

ErC50 8.8% 

CI (0-20)% 

NOEC 3.0% 

24 h LC50 9.7% 

CI (5.4-17)% 

48 h LC50 8.1% 

CI (4.4-14)% 

Turbot: 

LC50 5.5% 

CI (3-10)% 

16/1/2006 

Full salinity, 

normal current 

EbC50 9.2% 

CI (0-19)% 

NOEC 3.0% 

ErC50 11% 

CI (5.4-16)% 

NOEC 3.0% 

24 h LC50 11% 

CI (6.0-19)% 

48 h LC50 8.1% 

CI (4.4-14)% 

-- 

23/1/2006 

Half salinity, 

high current 

EbC50 5.5% 

CI (1.7-9.4)% 

NOEC 3.0% 

ErC50 6.4% 

CI (5.3-7.6)% 

NOEC 3.0% 

24 h LC50 8.1% 

CI (5.3-13)% 

48 h LC50 5.5% 

CI (3-10)% 

Rainbow Trout: 

LC50 5.5% 

CI (3-10)% 

30/1/2006 

Half salinity, 

normal current 

EbC50 3.6% 

CI (2.1-5.0)% 

NOEC 3.0% 

ErC50 7.1% 

CI (4.1-10)% 

NOEC 3.0% 

24 h LC50 14% 

CI (10-22)% 

48 h LC50 14% 

CI (10-22)% 

-- 

LC50 ñ concentration causing 50% kill (fish and Tisbe). 

CI ñ 95% confidence interval. 

EbC50 - concentration causing a 50% reduction in the Algae growth based on the biomass 

measurements. 

ErC50 - concentration causing a 50% reduction in the Algae growth rates. 

NOEC ñ No Observable Effect Concentration. 

LOEC ñ Lowest Observable Effect Concentration. 

* NOEC, LOEC could not be defined statistically, values given are as perceived by the operator 

(see Appendix 3 of reference [8]). 

6.2 Ecotoxicity test of treated natural sea water (the Procedure (G9), section 5.1.1) 

The persistence of total toxicity in Ectosysô treated natural sea water has been screened during 

2003 with a ecotoxicity test, performed by marine biologist and consultant Dr. F. NorÈn. The 

Ectosysô unit was running under nominal operating conditions treating natural sea water at the 

west coast of Sweden. Three different test organisms were added after different storage periods 

after treatment, and the survival was analysed with the ìlive-deadî method. Storage was made at 

approx. 5-10°C, in dark, closed 1 litre containers. The test organisms were unfortunately chosen 

due to convenience of other surrounding efficiency tests. The results are shown in figure 7. 
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Ekotox- test of stored natural sea water treated with EctoSys, nominal 

conditions

0

10

20

30

40

50

60

70

80

90

100

Controll t=0 min t=30min t=60 min t=5 h

Storage time before addition of organisms

survival rate, % 

Isochrysis 

Pavlova

Artemia

Figure 7: Ecotox test results from testing remaining toxicity of Ectosysô treated sea water 

Any conclusions that can be drawn from this study have to be made from the Pavlova results, 

while the Artemia survived to almost 100% through the experiment, and Isochrysis died instantly 

even in the untreated water (The ìcontrollî). The Pavlova results indicate that toxicity of 

Ectosysô treated water is decreased after approx. 1-5h under conditions similar to the ballast 

water storage case. 

7 MODELLING OF BALLAST WATER DISCHARGE INTO RECEIVING 

WATERS 

Versatile computer software has been developed to predict discharge dilution scenarios in generic 

harbours. Both harbours of ìopenî and ìclosedî types can be simulated, the number of 

discharging ships, different discharge rates and total volumes of treated ballast water along with 

decay, traffic, tidal flows etc. are considered by the model. The software has been developed (and 

calculations carried out) by Astra Zeneca Brixham Environmental Laboratory in Brixham, the 

United Kingdom, a GLP certified laboratory with expertise in the area. Table 11 in section 7.2 

are some results from these calculations, ranging from reasonable ìreal caseî discharge to 

unreasonable high discharge volumes. In these examples, the discharge from one ship has been 

modelled for simplicity and overview. Simulations were allowed to run to predict the time 

duration after discharge for concentration to fall below 3% (NOEC) everywhere in the water 

volume. An overall whole effluent NOEC of 3% was indicated by the whole-effluent toxicity 

tests (see section 6.1). 

7.1 Definitions of generic harbours: 

Closed: 

800 m × 190 m, depth 12 m. Ship at 400 m, 10 m with discharge onto surface 

Open: 

Model domain is 7000 m × 300 m, depth 12 m. Ship at 3500 m, 10 m with discharge onto 

surface 
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7.2 Model results 

Table 11: Predicted time to reach NOEC (3%) dilution 

after discharge of different rates and volumes of ballast water treated with EctoSysô 

Discharge Closed harbour Open harbour 

1,000 m3/h, 5 h 19 h 1 h 

1,000 m3/h, 10 h 24 h 1 h 

5,000 m3/h, 5 h 114 h 6 h 

5,000 m3/h, 10 h > 500 h* 20 h 

* 500 hrs after discharge end (Concentrations in % neat effluent)

7.3 The influence of decay to overall toxicity reduction, example 

Some examples taking the toxicity reduction over time (see section 6.2) have been carried out. 

Assuming (as an absolute worst case) toxicity degrades in 24 hrs and follows 1st order 

degradation, and run the simulation at the 5,000 m3

/h, 10 h, closed harbour-case, gives: 

3%=100%.exp(-kdeg.24) 

Which implies that kdeg=0.146 hr-1

Rerun of a specific case (5,000 m3

/h, 10 h, closed harbour) with this degradation rate gives the 

answer 12 hrs after discharge until concentrations below 3% of neat effluent. (3% = NOEC). This 

can be compared to the result > 500 h without considering any decay of the toxic substances. 

8 SHIP AND PERSONAL SAFETY (THE PROCEDURE (G9), SECTION 6.3) 

8.1 General 

No risks with handling chemicals can be associated with the EctoSysô ballast water treatment 

system. Active Substances and relevant chemicals are produced in situ and not handled by the 

crew or suppliers at any part of the process. The water is typically treated both during ballasting 

and deballasting. Concentration of hydroxyl radicals in the effluent water to the ballast water 

tank will be zero, and concentration of by-produced free active chlorine species will be negligible 

small and therefore not a threat to human health, ship or environment. All electrical equipments 

are built from CE labelled parts and no voltages dangerous to human health will be applied. The 

electrical wiring and current feeders will be totally screened off externally, and no voltage will be 

applied between parts that are subject to handling by the crew or supplier. The EctoSysô ballast 

water treatment system is equipped with a number of automatic safety clamping devices that will 

shut the system off if an external emergency (such as for instance pump failure causing decreased 

flow rates) occurs. All parts are built from metallic or non-flammable materials, approved for use 

on ships. Maintenance procedures will not pose threats to operating personnel, surrounding 

equipment, the environment or to the general operation of the ship. 
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8.2 Corrosion 

The corrosive properties of water treated by the EctoSysô ballast water treatment system will 

not differ significantly from untreated water. The redox potential of natural sea water (35 PSU) 

treated under relevant conditions by the EctoSysô will increase a maximum of 100 mV 

immediately after treatment and, because of the chemical diversity of natural waters and the 

degradation of free active chlorine, rapidly decrease again back to natural values. 

Corrosion tests according to ASTM standard test procedures have been considered. The most 

relevant in the case of electrochemically treated marine and brackish waters used on ships would 

be the ASTM G31-72: ìStandard Practice for Laboratory Immersion Corrosion Testing of 

Materialsî and ASTM D1654-05: ìStandard Test Method for Evaluation of Painted or Coated 

Specimens Subjected to Corrosive Environmentsî. However, the data achieved from such tests 

would naturally not be of any use in the evaluation of possible actual corrosion cases on-board 

ships. The Applicant has approached this problem by instead launching long-term corrosion 

studies that will proceed during both land-based type approval test phase and also verified at the 

shipboard type approval test phase (see below). 

The claim that the corrosive properties of water treated with the EctoSysô ballast water 

treatment system will not change has been partly confirmed during on-going case studies in 

Bremerhaven where the short term effects on different kinds of steel (non-coated or painted with 

standard protective coatings) have been evaluated. The physiochemical properties relevant to 

corrosiveness (e.g. redox potential and pH) have been measured continuously at relevant running 

conditions. Batch tests were carried out according to DIN EN 12502 with piping parts (St37-2, 

zinc plated) exposed to influent water and effluents treated by EctoSysô over five weeks. The 

water was renewed every 2 ñ 7 days simulating ballasting operation. No significant changes in 

the parameters temperature, conductivity, redox potential, oxygen content or pH could be 

detected. Besides a small formation of protecting zinc carbonate layers no corrosion was visible 

on the piping parts. Batch tests on corrosion do not represent the complex interaction between 

abrasion and corrosion, which occur in flow through systems. Consequently, new long-term 

(> 6months) tests are planned in real scale with ballast water tank design, linked to the 

land-based type approval experimental setup. The results along with in-house expertise opinions 

will be reported continuously during these trials in 2006-08. 

Hydroxyl radicals produced in the water is neither influenced by pH nor influencing pH value 

themselves in natural waters. The construction of the EctoSysô electrochemical cell with 

periodic oxidation/reduction throughout the treatment prevents a net change of the balance 

between H+

/OH- ions. Thus, EctoSysô treatment of sea water/brackish water will not have any 

impact on the pH value of the water. The theoretical, small, influence there might be is also 

effectively counterbalanced by the buffering capacity of natural sea water. Figure 8 shows the pH 

difference between influent- and effluent water of the EctoSysô during treatment, nominal 

operating flow rate, of natural sea water in Bremerhaven harbour, Germany. It was thus 

concluded that the main parameters influencing the corrosive properties of the sea water remains 

practically unchanged from EctoSysô treatment. 
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6

7

8

9

0 5 10 15 20 25

current in A

pH

influent

effluent

Figure 8: Influence of EctoSysô treatment on the pH of sea water (measured on-line, ProMinent 

test probes) 

8.3 Production of hydrogen gas 

Beside preventing chlorinated disinfection by-products, such as THM:s, to form, the EctoSysô 

cell design and electrode configuration also has positive effects on the net-production of 

hydrogen gas. Instead of only producing hydrogen gas (H2) on the cathode, oxygen gas (O2) and 

also the small amounts of chlorine gas (Cl2) produced at the anode will undergo reduction 

reactions on the cathode. This is possible due to the short distance between the electrodes, 

electrode configuration and turbulence promoting structure. (Patent application no.: 

WO2005058761(A1)). The reduction of oxygen dissolved in the water as competitive reaction to 

formation of hydrogen gas on relevant electrode materials have been theoretically studied using 

cyclic voltammetry in solutions with varying concentrations of NaCl [8]. It was concluded that 

oxygen reduction was a major cathode reaction in oxygen saturated electrolytes such as e.g. sea 

water/ballast water. 

Hydrogen gas may theoretically be formed during an electrolysis process in water. However, in 

the case of electrochemical in-line ballast water treatment such as EctoSysô where all the ballast 

water is treated during a single flow through the cell, no harmful concentrations will build up in 

the ballast water tanks or surrounding systems. This is partly because continuous venting of the 

ballast water tanks are necessary during ballasting and deballasting, making it impossible to build 

up explosive concentrations (4%) of hydrogen gas in the ballast water tanks. For surrounding 

systems (pipings etc.) a reliable degassing will be also included to the complete ballast water 

treatment system. In the particular case of EctoSysô, it is both theoretically and practically 

confirmed that much less hydrogen gas will be produced compared to conventional in-line sea 

water electrolysis. The actual production of and current exchange for hydrogen gas during 

EctoSysô treatment of water with relevant salinities have been preliminary analysed according 

to the following procedure: An effluent tank with a total volume of 1100 l was installed at the 

effluent of a pilot plant (EctoSysô 10m3

/h unit treating natural sea water, Bremerhaven, 

Germany). The effluent was continuously flown through with the same flow rate used in the 

influent to the pilot plant. The water volume in the effluent tank was approx. 735 l and the gas 

phase volume approx. 365 l. The effluent tank was closed by a cover, and the hydrogen gas in the 

gas phase above the water was measured by a Draeger PAC III H2-sensor at different flow rates 
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and each maximum hydrogen concentration was recorded. The concentrations formed in the 

closed tank never achieved dangerous levels. Hydrogen and oxygen gas mixture is ignitable 

when the hydrogen reaches at least 4 %, which never occurred. Figure 9 shows the built up 

hydrogen gas concentration in the tank gas phase at worst case operational parameters. For 

onboard installations a reliable degassing will be also included to the complete ballast water 

treatment system. 

Hydrogen formation, EctoSys treatment at worstcase applied current 

0

500

1000

1500

2000

2500

3000

3500

4000

0123456789

Flow rate, m3/h, (nominal: 10m3/h)

H2 conc. in tank gas-phase, 

ppm

Figure 9: Built up hydrogen gas (H2) concentration in the tank gas phase after EctoSysô 

treatment at worst- case operational parameters. Nominal flow rate for this system is 

10m3

/h, explosive/dangerous level of hydrogen concentration is 4,000 ppm. 

Bench scale tests using authentic EctoSysô cells and electrodes will be conducted to more in 

detail investigate the influence of the physical parameters (e.g. salinity, TOC, pH) of the water to 

the formation of hydrogen. Field tests (using natural sea water) on the hydrogen formation will 

also be conducted linked to life-time tests of EctoSysô cells and electrodes. All these tests will 

be continuously on-going and reported during the type-approval/shipboard testing process, along 

with mathematical case-study modelling. 

9 ASSESSMENT REPORT (THE PROCEDURE (G9), SECTION 4.3) 

Handling of the Active Substances and Preparations (the Procedure (G9), section 7.1) is not an 

issue for the system proposed by the applicant, where the Active Substances are formed in situ. 

The Akzo Nobel comprehensive documentation over free active chlorine includes a complete risk 

assessment report over such substances (see reference 7) and is available as stated in 

paragraph 4.2.5 of the Procedure (G9). The whole-effluent tests and analysis on toxicity for the 

EctoSysô BWT treatment system are based on both nominal treatment conditions as well as 

worst-case scenarios, and have been performed by certified laboratory accredited to GLP. 

Analysis results combined with toxicity data, degradation data/predictions and risk assessment 

shows that even if high safety factors are applied, we assess that no harm will be done to the 

surrounding environment, ship or crew using the EctoSysô as a disinfection step in ballast water 

management systems. However, since certain toxicity, specified in this document, was found in 

the effluent water; it might be considered necessary to assess this local immediate marine 

environmental impact against the potentially catastrophic environmental impact of introducing 

alien species into new biotopes. The WHO type of risk/benefit analysis can be used based on the 

Convention on Biological Diversity (CBD), Article 14, and also publications in the area 
MEPC 55/2/4 

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[see reference 10]. The vital data of this application (whole effluent toxicity, water quality 

control and influence of all relevant water parameters) will be confirmed during the following 

performance tests, including the land-based full scale type approval procedure. The chemistry of 

the Active Substances in natural waters is considered well-known as far as formation of toxic 

substances, and also concerning by-products that will form in detectable quantities. Uncertainties 

(the Procedure (G9), paragraph 6.4.3) of this assessment are mainly linked to possible up-scaling 

problems, while the data given in this document are mainly based on small-scale pilot 

equipments. This will however be thoroughly investigated and reported during the following test 

phases. The GESAMP- Ballast Water Working Group is invited give their view of this, and to 

continue assessment of the nominal and worst-case approach and the relevancy and quality of 

performed tests in this document. 

10 REFERENCES 

.1 ìUllmannís Encyclopedia of Industrial Chemistryî, Copyright © 2002 by Wiley-VCH 

Verlag GmbH & Co. KGaA. All rights reserved. DOI:10.1002/14356007.a09_183, 

Article Online Posting Date: January 15, 2003. 

.2 D. C. Johnson, N. Popovic, J. Feng, L. L. Houk, K. T. Kawagoe, The Electrochem. 

Society, Proc. Volume 95 ñ 26, 176 ñ 188 (1996). 

.3 C. Comninellis, ìElectrolysis in the electrochemical conversion/combustion of organic 

pollutants for waste water treatmentî, Electrochemical Society, Proceedings pp.75-86 

(1994). 

.4 K. Yamamoto et al. ìEmpirical model for disappearance of free oxidants in natural water 

with wide salinity and ammonia rangesî, Water Res.Vol.19, No. 12, pp.1595-1599 

(1985). 

.5 M. H. Lietzke, ìA kinetic model for predicting the composition of chlorinated water 

discharged from power plant cooling systemsî, Water Chlorination, Vol. 2, pp.707-716 

(1978). 

.6 P. Hoestgaard-Jensen et al. ìChlorine decay in cooling water and discharge into 

seawaterî, Water Pollut. Control Fed., Vol. 49, pp.1832-1841 (1977). 

.7 ìRISK ASSESSMENT REPORT FOR SODIUM HYPOCHLORITE, DRAFT.î Akzo 

Nobel NV, November 2005. 

.8 A M Riddle, A D Lillicrap, P J Nicholson, ìAssessment of the toxicity of the effluent 

from the EctoSysô bilge water treatment systemî, Brixham Environmental Laboratory 

study number Z0457, Report No BL8298/B, March 2006. 

.9 M. Behm, ìGrundl‰ggande studie av BDD-elektroder i natriumkloridlˆsningî, The Royal 

Institute of Technology KTH, March 2006. 

.10 Jeff McNeely, ìInvasive species: a costly catastrophe for native biodiversityî, Land Use 

and Water Resource Research 1, 2, pp.1-10 (2001). 
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.11 M. Fabbricino, G.V. Korshin, ìFormation of disinfection by-products and applicability of 

absorbance spectroscopy to monitor halogenation in chlorinated coastal and deep ocean 

seawaterî, Desalination 176, pp 57-69 (2005). 

11 ABBREVIATIONS

AOX: Absorbable Organic halogens 

BAT: Best Available Techniques 

BPD: Biocidal Products Directive 

BWT: Ballast Water Treatment 

CBD: Convention on Biological Diversity 

CPO: Chlorine Produced Oxidants 

(C)DBP: (Chlorinated) Disinfection By-Products 

DSAô: Dimensionally Stable Anodes 

FAC: Free Active Chlorine 

GLP: Good Laboratory Practice 

HAA: Haloacetic acids 

NOEC: No Observable Effect Concentration 

PEC: Predicted Environmental Concentration 

PNEC: Predicted No Effect Concentration 

ROS: Reactive Oxidative Species 

TGD: Technical Guidance Documents 

(T)THM: (Total) Trihalomethanes 

TOC: Total Organic Carbon 

TRC: Total Residual Chlorine 

TRO: Total Residual Oxidants 

TSS: Total Suspended Solids 

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