### United States Environmental Protection Agency Office of Wastewater Management Washington, DC 20460

EPA

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‐ R

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‐ 006 November 2011 

# Exhaust Gas Scrubber Washwater EffluentExhaust Gas Scrubber Washwater Effluent Contents

i CONTENTS

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S ECTION 1 I NTRODUCTION ............................................................................................................... 1

S ECTION 2 E XHAUST G AS S CRUBBER T ECHNOLOGY ....................................................................... 4 2.1 Seawater Scrubbers ................................................................................................. 5 2.2 Freshwater Scrubbers .............................................................................................. 7 2.3 Hybrid and Dry Scrubbers ...................................................................................... 8

S ECTION 3 E XHAUST G AS S CRUBBER W ASHWATER T REATMENT .................................................... 9

S ECTION 4 IMO G UIDELINES FOR EGCS S , W ASHWATER M ONITORING AND D ISCHARGE C RITERIA ........................................................................................................................... 10 4.1 Washwater Monitoring ......................................................................................... 10 4.2 Continuous Discharge Limits ............................................................................... 10 4.2.1 pH .............................................................................................................. 10 4.2.2 PAHs ......................................................................................................... 11 4.2.3 Turbidity/Suspended Particulate Matter (Solids) ...................................... 11 4.3 Other Discharge Limits ......................................................................................... 12 4.3.1 Nitrates ...................................................................................................... 12 4.3.2 Washwater Additives and Other Substances ............................................ 12 4.3.3 Washwater Residue ................................................................................... 12 4.4 Periodic Monitoring .............................................................................................. 12

S ECTION 5 C HARACTERIZATION OF P OLLUTANTS IN EGCS W ASHWATER D ISCHARGES ............... 13 5.1 The MS Zaandam Seawater Scrubber Trials ........................................................ 13 5.2 The Pride of Kent Seawater Scrubber trials .......................................................... 18 5.3 The Suula Freshwater Scrubber Trial ................................................................... 23 5.4 Summary of Marine EGCS Scrubber Trials ......................................................... 25

S ECTION 6 A SSESSMENT OF P OLLUTANTS D ISCHARGED IN S CRUBBER W ASHWATER AND P ROTECTIVENESS OF IMO G UIDELINES ............................................................................. 26 6.1 pH .......................................................................................................................... 2 8 6.2 PAH....................................................................................................................... 30 6.3 Turbidity ............................................................................................................... 32 6.4 Nitrate ................................................................................................................... 33 6.5 Sulfate, COD and Dissolved Oxygen ................................................................... 34 6.6 Metals .................................................................................................................... 35 6.7 Summary ............................................................................................................... 36

S ECTION 7 A CRONYMS ................................................................................................................... 38

S ECTION 8 R EFERENCES ................................................................................................................. 40Exhaust Gas Scrubber Washwater Effluent Contents

ii LIST OF TABLES

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1 PAH Discharge Concentration Limit by Flow Rate ..........................................................11

2 Concentrations of Metals in the Wa shwater Discharge from the Zaandam Scrubber Trial ................................................................................................................ ....17

3 Concentrations of PAHs in the Seawat er Intake and Washwater Discharge from the Pride of Kent Scrubber Trial ........................................................................................22 4 Approximate Amount of Water (t/hr) Af fected by a Scrubber for a 12 MW Engine ........................................................................................................................ ........30

LIST OF FIGURES

Page

1 SOx Scrubber Components ..................................................................................................4

2 The EcoSilencer ® Scrubber Installed on the Pride of Kent .................................................5 3 Open Type Wet Scrubber .....................................................................................................6 4 Closed Type Wet Scrubber ..................................................................................................7

The EPA contacts for this document are Ryan Albert (202) 564-0763 and Shirley Fan (202) 564- 2425.Exhaust Gas Scrubber Washwater Effluent Executive Summary

iii EXECUTIVE SUMMARY

This document contains information about effl uent washwater discharges associated with the operation of exhaust gas cleaning systems (EGCSs), also known as sulfur oxide (SOx) scrubbers, onboard vessels. The us e of scrubbers to clean the exha ust from marine engines using high sulfur residual oil and diesel fuels is an option for reducing SOx air emissions required by Annex VI of the MARPOL International Conventi on for the Prevention of Pollution from Ships. Washwater generated by an EGCS can c ontain contaminants from three sources:

1. Pollutants scavenged from the exhaus t gas exiting the engine (combustion products, fuel and lubricants);

2. The source of washwater used to clean th e exhaust (seawater or freshwater); and

3. The scrubber itself (dissolution of materi als, possible reactio n products and/or chemical additives).

The deployment of SOx scrubbe rs to treat emissions from diesel engines on large ocean going vessels has been so far limited to a handful of ships. However, the use of SOx scrubbers in combination with high sulfur residual oil fuel s may be an economically attractive option in Sulfur Oxide Emission Control Areas (SECAs) and worldwide. As the deadlines for SOx reduction 1 draw nearer, some vessels may begin usi ng scrubbers to reduce SOx emissions rather than burning low sulfur fuel oil.

This document describes the basic technology of EGCS, treatment processes used to remove pollutants from washwater prior to discha rge, guidelines established by the International Maritime Organization (IMO) for washwater mo nitoring and discharge criteria, available onboard sampling data characterizi ng the constituent con centrations in washwater discharge, and impacts of scrubber washwater discharge on water quality and aquatic life and protectiveness of IMO guidelines.

1 The revised Annex VI entered into force on July 1, 2010 . The sulfur content of fuel will fall in the Emission Control Areas (ECAs), which include the Baltic Sea, the No rth Sea and the English Channel, from 1.5% to 1% in July 2010 and to 0.1% in January 2015. A North American ECA, which includes waters adjacent to the Pacific, Atlantic and Gulf coasts and the 8 main Hawaiian Islands, will become enforceable in 2012. Globally, the highest permitted sulfur content of fuel will fall from 4.5% to 3.5% in January 2012 and to 0.5% in January 2020.Exhaust Gas Scrubber Washwater Effluent Section 1 - Introduction

1 

## SECTION 1
INTRODUCTION

The International Convention for the Prev ention of Pollution from Ships (MARPOL), 1973 as modified by the Protocol of 1978, also known as MARPOL 73/78, Annex VI Prevention of Air Pollution from Ships, requi res the reduction of SOx emissions either by burning low sulfur fuel oil or cleaning the exhaust gas. Cleaning, or scrubbing, the e xhaust gas is generally accepted to be more economical. According to EGCS ma nufacturer Wärtsilä, th e cost saved by using heavy fuel oil instead of low sulfur fuel oil can pay back the cost of installing and operating EGCS in about one year (Hatley, 2010). The EGCS s used today for sulfur control are commonly known as SOx scrubbers. In a wet scrubber, the e xhaust gas is mixed with washwater, and the water-soluble components of the exhaust gas ar e removed by dissolution into the washwater. SOx scrubbers are capable of removing up to 95 percent of SOx from ship exhaust (EGCSA, 2010). By removing sulfur from the exhaust, the sc rubber also removes most of the direct sulfate particulate matter (PM). Sulfat es are a large portion of the PM from ships operating on high sulfur fuels. By reducing the SOx emissions, the scrubber also controls much of the secondary PM that is formed in the atmosphere from these emissions.

There are two main types of wet scrubbe r technologies. The first wet scrubber technology, referred to as seawater scrubbing, is an open-loop de sign which uses seawater to scrub the exhaust before discharging the washwa ter back to the sea following treatment. In a seawater scrubber, the exhaust gases are brough t into contact with s eawater, either through spraying seawater into the exhaust stream or r outing the exhaust gases through a water bath. The sulfur dioxide (SO 2 ) in the exhaust gas dissolves in the washwater, where it is ionized to bisulphate and sulfite, which are then readily oxidized to sulfate (Hassellöv and Turner, 2007). The ionization of SO 2 and the sulfuric acid formed from sulfur trioxide (SO 3 ) also produces acidity. The sulfuric acid in the water then react s with carbonates and other salts in the seawater to form sulfates (USEPA, 2009a). The washwater is treated to remove solids and raise the pH prior to discharge back to sea. The removed solids are stored onboard for shoreside disposal.

The second wet scrubber technology is a cl osed-loop system. Freshwater is used as washwater, and caustic soda is injected into the washwater to neutralize the sulfur in the exhaust. A small portion of the washwater is bled off a nd treated to remove suspended solids. The suspended solids are held as sludge and disposed of shoreside as with the open loop design. The treated bleed-off washwater can be discharged at open sea or held onboard for disposal shoreside. Additional freshwater is added to th e system as needed. While this design is not a completely closed loop, it can be operated in ze ro discharge mode for a period of time (USEPA, 2009a).Exhaust Gas Scrubber Washwater Effluent Section 1 - Introduction

2 Wet scrubbers are a well-est ablished technology for SOx and PM reduction that are widely used in stationa ry sources such as land

‐ based oil

‐ and coal

‐ fired power plants. In these applications, lime and caustic soda are typically used to neutralize the sulfuric acid in the washwater. The first use of exhaust gas scr ubbers in the marine industry was not for SOx emission control but rather as an inexpensive means to produce inert gas for reducing the fire hazard in the cargo tanks of tankers while unl oading. By the 1970s, their use was widespread (Entec, 2005).

The first prototype seawater scrubber system for exhaust gas cont rol onboard a vessel was installed in 1991 (Entec, 2005). A comprehe nsive seawater scrubber field trial was conducted in May 1998 onboard the Canadian ice breaker Louis S. St.-Laurent . The trials were conducted during 22 days of a 6-week transatlantic voyage. Around the same time, a different scrubber prototype, the Eco-Silencer ® , was fitted for testing onboard the Canadian freight and passenger ferry Leif Ericson. This was a full-scale plant and tr eated the entire exhaust stream from the engine. One of the specific aims of the Leif Ericson trials was to investigate washwater quality though a water treatment plant and, if necessary, apply alte rnate water treatment processes (Entec, 2005). More recen t prototype SOx scrubber insta llations aboard three ships, the Zaandam , the Pride of Kent and the Suula , have demonstrated their viability in this application and provided data to characterize pollutant concentr ations in scrubber washwater discharges. These demonstrations have shown th at scrubbers can replace and fit into the space occupied by the exhaust silencer units and can work well in marine applications (USEPA, 2009a).

The deployment of SOx scrubbe rs to treat emissions from the diesel engines on large ocean going vessels is currently limited to a ha ndful of ships. Although the installation of an EGCS allows a ship operator to continue to use high sulfur fuel after the 2015 and 2020 deadlines for ECAs and worldwide, respectively, there is uncertainty associated with this compliance solution (Kehoe et al., 2010). The co ntinued use of EGCS depends on the successful completion of monitoring specified in the IM O Guidelines (see Section 4) and long-term scientific studies to prove they do not negatively impact the environment. In the interim, a ship owner installing EGCS undertakes a risk that th e EGCS may need to be removed in favor of using low-sulfur fuel if in the future it is found that scrubbers ha ve unacceptable impacts.

The use of SOx scrubbers in combination with high sulfur residual oil and diesel fuels may be economically beneficial in SECAs and wo rldwide; therefore, a large number of vessels may begin using scrubbers. In June 2010, th e Motorship Newsletter announced the first commercial order for seawater scrubbers capab le of meeting new European Union (EU) regulations on fuel emissions from ships, wit hout requiring low sulfur fuel oil (Motorship Newsletter, 2010). Seawater scrubbers were in stalled on four new 45,000-ton ferries burning residual fuel oil to meet rules demanding sulfur emissions equivalent to 0.1 percent fuel-sulfur

content.Exhaust Gas Scrubber Washwater Effluent Section 1 - Introduction

3 This document describes the constituent con centrations in the wa shwater discharged by vessels operating wet scrubber EGCSs. This discharge can contain material from:

 Pollutants scavenged from the exhaus t gas exiting the engine (combustion products, fuel and lubricants);

 The seawater used to clean the exhaust (i n the case of a seawater scrubber); and

 The scrubber itself (dissolution of system materials, possible reaction products and/or chemical additives).

The use of scrubbers to clean the exhaust fr om marine engines using high sulfur residual oil and diesel fuels may lead to high concentrat ions of a number of harmful compounds in the water body around the ships (AEA, 2009). Several trials were conducted onboard vessels to characterize the constituent concentrations in washwater discharge. Section 5 summarizes the results of the trials and assessm ents of the potential impacts of scrubber washwater discharge on water quality and aquatic life. Sectio n 6 presents a comparison of the results of the trials with the
2009 Guidelines for Exhaust Gas Cleaning Systems (IMO Annex 9, Resolution MEPC.184(59), adopted July 17, 2009), criteria intended to pr otect aquatic resources from adverse impacts resulting from scrubber washwater discharges.Exhaust Gas Scrubber Washwater Effluent Section 2 - Exhaust Gas Scrubber Technology

4 

## SECTION 2
EXHAUST GAS SCRUBBER TECHNOLOGY

As described in Section 1, there are severa l different designs of SOx scrubbers that remove sulfur oxides from the exhaust gases of vessel engines and boilers. The majority of wet scrubber systems have three basic components, illustrated in Figure 1 and described below.

Source: EGCSA. 2010

Figure 1. SOx Scrubber Components

1. Exhaust gas cleaning unit serves as a contact chamber that enables the exhaust stream from an engine or boiler to be intimately mixed with water, either seawater, freshwater, or both. Due to sp ace and access limitations, the exhaust gas cleaning units tend to be high up in the ship, in or around the funnel area.

2. Wash water treatment to remove water-soluble polluta nts, such as sulfur dioxide (SO 2 ), sulfur trioxide (SO 3 ) and nitrogen dioxide (NO 2 ), which form sulfates and nitrates that dissolve in the washwate r after the scrubbing process. Scrubber washwater also contains suspended solids, heavy metals, hydrocarbons and polycyclic aromatic hydrocarbons (PAHs). Be fore the washwater is discharged, it must be treated to remove solids. The treatment process typically includes a multicyclone, a cyclonic separator similar to that used to separate water fromExhaust Gas Scrubber Washwater Effluent Section 2 - Exhaust Gas Scrubber Technology

5 residual fuel prior to delivery to the engi ne. Heavier particles may also be trapped in a settling or sludge tank for disposal.

3. Sludge handling to retain sludge removed by the washwater treatment process for disposal shoreside.

Figure 2 shows the EcoSilencer ® scrubber incorporated into the exhaust train on the ferry Pride of Kent

.

Source: Entec, 2005
Figure 2. The EcoSilencer ® Scrubber Installed on the Pride of Kent

2.1 S EAWATER S CRUBBERS
In a seawater or “open” type scrubber (see Fi gure 3), seawater is used as wash water for scrubbing, and the resulting wastew ater is treated and discharged back to sea. The natural alkalinity of the seawater is used to neutra lize the acidity that results from SOx removal. 2

2 Alkalinity in the open ocean is typically 2,200 to 2,300 μ mol CaCO 3 /L (Hassellöv and Turner, 2007). Alkalinity in some coastal areas, ports, rivers and estuaries can be affect ed by the different drainage areas of the inflowing rivers, resulting in large variations in the chemistry. Rivers ru nning through soil rich in carbonates will be high in alkalinity. For example, the southern rivers of the Baltic Sea run through calcite bedrock resulting in high carbonate concentrations with consequently high alkalinity (approximately 1,650 -1,950 μ mol/L), whereas the northern rivers run through granite bedrock resulting in low alkalinity (approximately 800-1,300 μ mol/L) (Hassellöv and Turner, 2007). In general, the alkalinity in the Baltic Sea is lowe r than the open sea because of the minimal exchange of water through the Danish straits. Seawater scrubbers can ope rate at low alkalinity levels, but in some cases the SO 2 removal efficiency may be reduced (Henriksson, 2007).Exhaust Gas Scrubber Washwater Effluent Section 2 - Exhaust Gas Scrubber Technology

6 Source: EGCSA. 2010

Figure 3. Open Type Wet Scrubber

Typically, seawater systems use 45 m 3 of washwater per megawatt-hour 3 (MWh) for scrubbing (MEPC, 2008). Seawater scrubbing of the exhaust from a representative 10 MWh engine would generate 450 m 3 /hr or 2.8 million gallons per day (MGD) of washwater effluent. The volume of washwater required for a given sc rubbing efficiency increases with elevated alkalinity and with higher water temperature (DNV, 2009). The energy consumption of a seawater scrubber is 2 to 3 percent of the engine power output (Filancia, 2009).

Seawater scrubbing requires the exhaust gases to be mixed wi th seawater to dissolve the sulfur oxides. Manufacturers use various te chniques to achieve mixing without unduly obstructing the passage of exhaust gas, which co uld result in a “back pr essure” outside of the engine builder’s limits and adve rsely affect engine operation. The sulfur oxides of engine exhausts typically consist of approximately 95 percent SO 2 and 5 percent SO 3 (EGCSA, 2010). When dissolved, a reaction occurs whereby the sulf ur dioxide is ionized to bisulfite and sulfite, which is then readily oxidized to sulfate in seawater containing oxyge n (Hassellöv and Turner, 2007).

The ionization to bisulfite and sulfite and the sulfuric acid formed from sulfur trioxide produces acidity (Karle and Turner, 2007). The acid ity is neutralized initially by the alkalinity of the seawater, due to its natural bicarbonate co ntent. After the initial buffering capacity is consumed, the pH of washwater is reduced to approximately 3. At low pH, the ionization of sulfur to sulfite is negligible and exha ust gas cleaning is limited (EGCSA, 2010).

3 Maximum continuous rating (MCR) or 80% of the power rating of the fuel oil combustion unit.Exhaust Gas Scrubber Washwater Effluent Section 2 - Exhaust Gas Scrubber Technology

7 2.2 F RESHWATER S CRUBBERS

In a freshwater or “closed” t ype scrubber, freshwater treate d with an alkaline chemical such as caustic soda is used for neutralization and scrubbing. As shown in Figure 4, washwater is recirculated and any evaporative loss is replaced with additional freshwater. A small quantity of the washwater is bled off to a treatment plant a nd then discharged. Typical ly, closed freshwater systems have much smaller discharge rates than seawater scrubbers (approximately 0.1 to 0.3

m 3 /MWh) and treat a smaller volume of effluent (MEPC, 2008). Closed freshwater systems can periodically be operated in a “zero discharge mode” without discharging any washwater overboard (SSG, 2007).

Source: EGCSA. 2010

Figure 4. Closed Type Wet Scrubber

Freshwater scrubbers are used when high efficiency cleaning is needed or when the variable alkalinity associated wi th seawater precludes use of seaw ater scrubbers. The ability to operate an EGCS without discharging washwate r for short periods of time, using available holding tank capacity, may be advantageous in wa ter bodies that are especially sensitive or vulnerable, such as enclosed water bodies and/ or those with low alkalinity. The SOx exhaust gas removal efficiency of a freshwater scrubber is typically greater than 90 percent and removal efficiencies as high as 97 percent can be obt ained for exhaust from generator engines. The energy consumption of freshwater scrubbers is reported to be a bout 0.5 percent of the engine power output (Hatley, 2010).Exhaust Gas Scrubber Washwater Effluent Section 2 - Exhaust Gas Scrubber Technology

8 2.3 H YBRID AND D RY S CRUBBERS
Hybrid scrubbers can operate us ing either seawater or freshw ater as source water, while dry scrubbers operate using chemisorption. Hybrid systems can operate in either an open loop (seawater) at sea or closed loop (freshwater) in harbors, estuar ies, and other sensitive water bodies (Aalborg, 2010). The advantages of a hybrid EG CS include the ability to operate in either freshwater or seawater and the ability to main tain scrubber efficiency in low alkalinity water bodies, such as the Baltic Sea, estuaries and rivers. A hybrid scrubber was installed on the 21 MW diesel engine aboard the ferry Tor Ficaria. The Tor Ficaria ’s scrubber has operated over 1,000 hours since May 2010 and is reported to be the largest EGCS inst alled onboard a ship (Aalborg, 2010).

Dry scrubbers use solid media rather than wa shwater to capture su lfur oxides from the exhaust gas. Exhaust gas in a dry scrubber is pass ed through a bed of granul ar solid media, such as calcium carbonate (CaCO 3 ), burnt lime (CaO), or hydrated lime (Ca(OH) 2 ), to which the sulfur oxides absorb and react to form gypsum (CaSO 4 ) (Couple Systems, 2010). The advantage of dry scrubbing technology is that pollutants are not transferred from air to water, as they are in wet scrubbers, but instead react with the soli d media to form a byproduct. The byproduct can be reused for high-temperature desu lfurization at power plants, as a raw material for cement and steel making, or as fertilizer (Couple Syst ems, 2010). There are over 500 dry scrubber installations for exhaust gas captu re at power plants. A dry scr ubber was installed to clean the exhaust gas from the 3.6 MW main engine a board the German cellulose freighter MS Timbus in
2009.Exhaust Gas Scrubber Washwater Effluent Secti on 3 - Exhaust Gas Scrubber Washwater Treatment

9 

## SECTION 3
EXHAUST GAS SCRUBBER WASHWATER TREATMENT

Operating or cleaning a wet exhaust gas scr ubber for marine diesel engines and boilers generates effluent (washwater) that must be tr eated prior to discharg e. Washwater contains gaseous and particulate emissions removed from the exhaust in the funnel by the scrubber. The SOx and nitrogen oxides (NOx) dissolved in the sc rubber washwater react to form sulfuric and nitric acids, which significantly reduce the pH of the washwater leaving the scrubber. Washwater constituents can also include PM emissions captu red by the scrubbers, as well as traces of oil, PAHs, heavy metals and nitrate.

Washwater effluent from seawater systems is treated, blended with reaction water to neutralize the pH, and discharged overboard. For freshwater sc rubbers, only a fraction (e.g., 10 percent) of the washwater is bled off for trea tment and discharged. Alternatively, freshwater scrubber washwater can be routed to a bilge water ta nk not destined for discharge or other suitable holding tank for treatment and disc harge, or for disposal shoreside.

Treatment of scrubber washwater normally c onsists of suspended solids removal and pH neutralization. In curren t marine EGCS installations, such as the scrubbers aboard the Pride of
Kent and Zaandam , the washwater leaving the scrubbers is passed through a multicyclone, a prefiltration device that predomin antly separates particles larg er than 30-40 μm from the washwater using centrifugal force (WATERCO, 2010). The solids from the multicyclone are collected and concentrated in a sludge tank. The amount of sludge generated by washwater treatment depends on the amount of solids capt ured and the water c ontent of the sludge following settling. Solids generation for a seaw ater scrubber system are approximately 0.6 percent by weight of residual fu el consumed (EGCSA, 2010).

The effectiveness of centrifugal separation and settling depends on the particle size distribution and particle density (USEPA, 2009a). Additional treatment processes can be added to improve the efficiency of solids removal, including various filtration methods and/or coagulation and flocculation. Coagulation and flocculation remove pa rticles too small for gravitational settling by aggregati ng them into large, more readily separable particles. Such additional treatment has been used to treat the wa shwater bled from closed freshwater scrubbers, such as the EGCS installed on the Suula

.

After the washwater is treated to remove so lids, it is blended with reaction water, typically seawater used for engine cooling (E GCSA, 2010). The function of the reaction water is to neutralize the pH of the washwater prio r to discharge overboa rd. Reaction water and washwater can be mixed in nearly equal pr oportions, although increa sing the proportion of reaction water can improve the neutralizati on of the acidic washwater (HA & H-K, 2010).Exhaust Gas Scrubber Washwater Effluent Section 4 – IMO Guidelines for EGCSs, Washwater Monitoring and Discharge Criteria

10 

## SECTION 4 IMO GUIDELINES FOR EGCSS, WASHWATER MONITORING
AND DISCHARGE CRITERIA

On October 9 th , 2008, the 168 member states of the In ternational Maritime Organization (IMO) adopted more stringent standards to cont rol exhaust emissions from the engines that power ocean going vessels. The engine and fuel st andards are included in amendments to Annex VI of MARPOL. The revised Annex VI entered in to force on July 1, 2010. The sulfur content of fuel decreased in the ECAs, including the Baltic Sea, the North Sea and the English Channel, from 1.5 percent to 1 percent in July of 2010 a nd will decrease to 0.1 percent in January of 2015. A North American ECA (including wa ters adjacent to the Pacific, Atlantic and Gulf coasts and the 8 main Hawaiian Islands) will become en forceable in 2012 (USEPA, 2010b). Globally, the highest permitted sulfur content of fuel will fall from 4.5 to 3.5 percent in January of 2012 and to 0.5 percent in January of 2020. The IMO developed guidance criteria for the use of exhaust gas cleaning devices, such as SOx scr ubbers, as an alternative to oper ating on low sulfur fuel. As a component of their analyses, the IMO also se t scrubber washwater monitoring and discharge criteria in Section 10 of the Guidelines fo r EGCSs (Resolution MEPC .170(57)). The current Guidelines for EGCSs were adopted on July 17 th , 2009 though Resolution MEPC.184(59), and are summarized in Sections 4.1through 4.3 below.

4.1 W ASHWATER M ONITORING
The IMO guideline recommends pH, PAH c oncentration, turbidity and temperature should be continuously monitored a nd recorded when the EGCS is operated in ports, harbors, or estuaries. In other areas, these parameters s hould be continuously monitored and recorded whenever the EGCS is in operation, except for s hort periods of maintenance and cleaning of the equipment.

4.2 C ONTINUOUS D ISCHARGE L IMITS

4.2.1 pH

The washwater pH must meet one of the follo wing requirements and the results recorded in the vessel’s EGCS Technical Manual (ETM ) as applicable (Resolution MEPC.184(59)):

 The discharge washwater should have a pH of no less than 6 .5 measured at the ship’s overboard discharge with th e exception that during maneuvering and transit, a maximum difference of 2 pH is allowed between the ship’s inlet and overboard discharge; or

 During commissioning of the unit(s) after installation, the discharged washwater plume should be measured externally from the ship (at rest in a harbor) and theExhaust Gas Scrubber Washwater Effluent Section 4 – IMO Guidelines for EGCSs, Washwater Monitoring and Discharge Criteria

11 discharge pH at the ship’s overboard pH monitoring point will be recorded when the plume at a distance of 4 meters from the discharge point equals or exceeds a pH of 6.5. This discharge pH, which is found to achieve a minimum pH of 6.5 in the washwater plume 4 meters from the ship, will become the overboard pH discharge limit.

4.2.2 PAHs

The maximum continuous PAH concentration in the discharged washwater should not be greater than 50 μ g/L phenanthrene equivalence (PAH phe) above the inlet water PAH concentration. For the purposes of this criteria, the PAH concen tration in the washwater should be measured downstream of the water treatme nt equipment but upstream of any washwater dilution or other reactant dosing unit, if used, prior to discharge. The 50 μ g/L limit is normalized for a washwater flow rate thr ough the EGCS unit of 45 tons/MWh. This limit should be adjusted for washwater flow rates, as shown in Table 1.

Table 1. PAH Discharge Concentration Limit by Flow Rate

Flow Rate (t/MWh) Discharge Concentration Limit ( μ g/L PAHphe equivalents) Measurement Technology

0 - 1 2250 Ultraviolet Light

2.5 900 Ultraviolet Light

5 450 Fluorescence a

11.25 200 Fluorescence a

22.5 100 Fluorescence a

45 50 Fluorescence a

90 25 Fluorescence a

Source: Resolution MEPC.184(59) a. Fluorescence technology should be used for any flow rate > 2.5 t/MWh

.
For a 15-minute period in any 12-hour peri od, the continuous PAH phe concentration limit may exceed the limit described above by up to 100 percent, to allow for an abnormal start up of the EGCS (Resolution MEPC.184(59)).

4.2.3 Turbidity/Suspended Part iculate Matter (Solids)

The washwater treatment system should be designed to minimize suspended PM, including heavy metals and ash. The maximum con tinuous turbidity in washwater should not be greater than 25 formazin nephlomet ric units (FNU) or 25 nephlometr ic turbidity units (NTU) or equivalent units, above the inlet water turbidity. However, during periods of high inlet turbidity, the precision of the measurement device and the time lapse between inlet measurement andExhaust Gas Scrubber Washwater Effluent Section 4 – IMO Guidelines for EGCSs, Washwater Monitoring and Discharge Criteria

12 discharge measurement are such that the use of a difference limit is unreliable. Therefore, all turbidity difference readings s hould be a rolling average over a 15-minute period to a maximum of 25 FNU. For the purposes of this criteria, th e turbidity in the washwater should be measured downstream of the water treatment equipment but upstream of washwater dilution (or other reactant dosing) prior to discharge. For a 15-minute period in any 12-hour period, the continuous turbidity discharge limit may be exceeded by 20 percent (Resolution MEPC.184(59)).

4.3 O THER D ISCHARGE L IMITS

4.3.1 Nitrates

The washwater treatment system should prev ent the discharge of nitrates beyond that associated with a 12 percent removal of NOx from the exhaust, or beyond 60 mg/L (1 mM) normalized for a washwater discharge rate of 45 t/MWh (similar to the adjustment tabulated above for PAHs), whichever is greater. All system s should be tested for n itrates in the discharge

water.

4.3.2 Washwater Additives and Other Substances

An assessment of the washwater is require d for those EGCS technologies which make use of chemicals, additives, prepara tions or create relevant chemicals in situ

.

4.3.3 Washwater Residue

Residues (sludge) generated by the EGCS should be delivered shoreside to adequate reception facilities. Such residue s should not be discharged to the sea nor incinerated onboard.

4.4 P ERIODIC M ONITORING
The IMO washwater discharge criteria are intended to act as initial guidance for implementing EGCS designs. The IMO Guidelines stat e that the criteria s hould be revised in the future as more data become available on the conten ts of the discharge and its effects, taking into account any advice given by the Group of Expe rts on the Scientific Aspects of Marine Environmental Protection (GESAM P). Administrations (i.e., signa ture nations) should therefore provide for collection of relevant data. To this end, IMO requests ship owners, in conjunction with the EGCS manufacturer, to sample inlet water (for back ground), water after the scrubber (but before any treatment system) and discharg e water and to analyze these samples using EPA or ISO test procedures for the followi ng parameters (Resolution MEPC.184(59)):

 pH;

 PAH and oil (detailed GC-MS analysis);

 Nitrate and nitrite; and

 Metals (Cd, Cu, Ni, Pb, Zn, As, Cr and V).Exhaust Gas Scrubber Washwater Effluent Section 5 – Characterization of Pollutants in EGCS Washwater Discharges

13 

## SECTION 5
CHARACTERIZATION OF POLLUTANTS IN EGCS
WASHWATER DISCHARGES

Prototype SOx scrubbers have been installe d onboard three large ocean-going vessels: the Zaandam, the Pride of Kent , and the Suula (USEPA, 2009a). The scrubber trials aboard these vessels also provided data to ch aracterize constituent concentra tions in washwater discharges. These data represent the best available informati on regarding pollutant conc entrations that can be expected in scrubber washwa ter discharges, including:

 pH,

 Temperature,

 Turbidity,

 Nutrients,

 Metals, and

 PAHs.

The results from the scrubber trials (summarized below) are published as project reports, which have not been peer reviewed. Samples were analyzed by certifi ed laboratories or by academic institutions.

5.1 T HE MS Z AANDAM S EAWATER S CRUBBER T RIALS
In November 2006, the Puget Sound Clean Air Agency received funding from the EPA to evaluate whether a seawater scrubbing system could be successfully designed, installed/retrofitted and operated within the tight confines of an existing cruise ship. In April 2007, Holland America Line installed a seawater scrubber in the stack of one of the five 9 MW diesel generators on the cruise ship MS Zaandam when she was in drydock in Victoria, Canada (HA & H-K, 2010).

The study was designed to answer a number of basic questions about seawater scrubbing, including:

 How much washwater is ge nerated by this scrubber?

 What pollutants are present in the washwa ter discharge and what are their concentrations or values?

 How are these pollutants dissipated into the environment when the ship is at dock?

 How much sludge is generated by this scr ubber (in grams per ton of fuel burned)?

 What are the pollutants that end up in the sludge and what are th eir concentrations?Exhaust Gas Scrubber Washwater Effluent Section 5 – Characterization of Pollutants in EGCS Washwater Discharges

14 Both continuous and periodic sampling of washwater was conducted onboard the
Zaandam . In

‐ line monitoring occurred nearly con tinuously between August 2007 and January 2008, and during scrubber operations between Fe bruary and September 2008 and in February 2009. During these periods, the Zaandam operated in the Pacific Ocean, including coastal waters of Alaska, British Columbia, California, and Ha waii. Periodic samples were also collected as follows:

 August 18, 2007

‐ Skagway, Alaska

 August 24, 2007

‐ Juneau, Alaska

 September 12, 2007

‐ Vancouver, British Columbia

 August 30, 2008

‐ Vancouver, British Columbia

 September 3, 2008

‐ Juneau, Alaska

 September 4, 2008

‐ Skagway, Alaska.

Washwater sample collection followed the pr ocedures from the Environmental Impact Assessment work performed on the ferry the Pride of Kent by Newcastle University and the Terramare Institute. Samples of raw seawater and scrubber washwater were collected at the inlet and discharge of the system, respectively, to a ssess the changes that occurred as a result of scrubbing. Samples were analyzed by certified labo ratories in the jurisdictions where they were collected.

The average washwater flow rate during the scrubber trials aboard the Zaandam was 390

m 3 /hr (2.5 MGD). The following is a summary of the pollutant concentrations and other parameters measured in the raw seawater inta ke and the washwater samples, based upon the presentation of data in Appendix F of the final project report to EPA (HA & H-K, 2010).

pH

The washwater discharge pH was approximately 2 standard units lower than the intake. The mean pH measured in the washwater discharg ed in coastal waters of California and Hawaii in 2008 was 5.8; the minimum measured value was 5.4. Over this period, it was noted that problems with pumps reduced the flow rates in th e scrubber system. Higher discharge pH values were measured in Alaskan coastal waters in 2008; the mean discharge pH was 6.3. The increase in pH was achieved by raising th e volume of reaction water being blended with washwater and lower engine loads (HA & H-K, 2010).

Temperature

The increase in washwater temperature between the inlet and the discharge was less than 3.5°C throughout the duration of the project (HA & H-K, 2010).Exhaust Gas Scrubber Washwater Effluent Section 5 – Characterization of Pollutants in EGCS Washwater Discharges

15 Turbidity

In

‐ line continuous measurement of turbidity wa s found to be unreliabl e as air bubbles in
the washwater interfered with the function of the turbidity probe. Results from periodic (discrete) sampling in 2007 indicated that turbidity and total suspended solids (TSS) decreased in concentration between the intake and the discharge. Maximum tu rbidity in the discharge was 8 NTUs, and the maximum change between intake and discharge was

‐ 9 percent (HA & H-K, 2010).

Dissolved Oxygen (DO)

DO concentration in the disc harge ranged from 4.0 mg/L in the warmer waters off California and Hawaii to 10.0 mg/L in the colder waters of Alaska. Although these concentrations represent varying degrees of saturation, they also suggest that re

‐ oxygenation of washwater prior to overboard discharge was generally successful (HA & H-K, 2010).

Alkalinity

As expected, alkalinity decreased between th e seawater inlet and the washwater discharge as carbonates and bicarbonates were consumed during scrubbing. Alkalinity was reduced between 76 to 98 percent with a minimum alka linity measured in the discharge of 21 mg CaCO 3 /L (HA & H-K, 2010).

Chemical Oxygen Demand (COD)

COD generally increased between inlet and discharge as a result of the presence of sulfites in the discharge. COD increased between the discharge and the intake between 33 and 91 percent with a maximum concentration in th e discharge of 130 mg/L (HA & H-K, 2010).

Conductivity

There was no clear trend of increasing or decreasing conductivity between the inlet and discharge. The scrubber did not add new salts into the marine environment (HA & H-K, 2010).

Total Suspended Solids

TSS decreased between inlet and discharge samples. In 2007, the maximum TSS in the discharge was 17 mg/L, and the maximum change was

‐ 73 percent. Results of periodic sampling
in 2008 indicated no consistent trend for TSS be tween inlet and discharge samples (HA & H-K, 2010).Exhaust Gas Scrubber Washwater Effluent Section 5 – Characterization of Pollutants in EGCS Washwater Discharges

16 Ammonia, Nitrate/Nitrit e, Kjeldhal Nitrogen

According to the project report (HA & H-K, 2010), the scrubber installed aboard the Zaandam did not remove NOx from engine emissi ons. For the most part, nitrogen compounds (ammonia, nitrite/nitrate and total Kjeldahl nitr ogen (TKN)) were not det ected in the washwater of this EGCS. Nitrite/nitrate was measured in the washwater discharge in Skagway at a concentration of 146 μg/L, while a TKN concentrat ion of 45 μg/L was meas ured in the discharge sampled in Vancouver (HA & H-K, 2010).

Sulfites

Sulfites (compounds containing sulfide ion, SO 2 -3 ) were analyzed in Alaska in 2008 using a Hach field test kit. Sulfites were not detected in the intake, but were measured in the discharge at concentrations ranging from 32 to 48.6 mg/L . These are the compounds likely contributing to the COD measured in the discharge (HA & H-K, 2010).

PAHs

The in-line discharge probe de tected PAHs at approximately 100 parts per billion (ppb, equivalent to μ g/L) in California and Hawaii, and 134 ppb in Alaska. The study authors believe that the in-line measurements were not reliable as the air bubbles in the washwater interfered with the probe’s ability to detect the PAHs. PA Hs were not detected in any of the washwater discharge samples collected in Alaska in 2007 and analyzed by the laboratory. PAHs were detected in one discharge sample in Vancouve r, at a concentration of 1.3 ppb phenanthrene equivalents (HA & H-K, 2010).

Organic Compounds

Volatile organics were not detected in wa shwater discharge samples collected in 2008 (HA & H-K, 2010).

BTEX, HEM and TPH-D/G

BTEX (benzene, toluene, ethylbenzene and xyl ene), hexane extractable material (HEM), and TPH-D/G (total petroleum hydr ocarbon –diesel and gasoline co mponents) were not detected in the washwater discharge (HA & H-K, 2010).

Metals

Dissolved (filtered) and total metals concentrations were measured in 7 paired influent/effluent samples 4 . For several metals (arsenic, copper, lead, nickel and selenium), total

4 Data from samples collected in 2008 during tests using a flocculant chemical to treat washwater were excluded from this analysis.Exhaust Gas Scrubber Washwater Effluent Section 5 – Characterization of Pollutants in EGCS Washwater Discharges

17 and/or dissolved concentrations were measured in the washwate r discharge at concentrations exceeding EPA’s National Recommended Water Qua lity Criteria for the protection of aquatic life (NRWQC) for saltwater organisms (USEPA , 2005). In general, when exceedances were detected in the discharge, they were also detect ed in the intake at similar concentrations. This indicates that the ambient seawater was a likely source of the metals. Discharge concentrations exceeding the intake concentration by more th an 50 percent were interpreted as a stronger indication that a metal was being added to the wa shwater by the scrubbing process. Details of the exceedances of water quality crite ria for metals are described be low and presented in Table 2 (HA & H-K, 2010):

Table 2. Concentrations of Metals in the Washwater Discharge from the Zaandam Scrubber Trial

Metal Median Total Discharge Concentration (μg/L) (n=7) Median Filtered Discharge Concentration

(μg/L) (n=7) # Samples Exceeding

150% of Intake Concentration EPA NRWQC Saltwater

Acute (μg/L) # Samples Exceeding Acute Criterion EPA NRWQC Saltwater Chronic

(μg/L) # Samples Exceeding

Chronic Criterion

Arsenic 81 81 1 69 6 36 7

Chromium 22 12 0 570 0 74 0
Copper 18 15 1 4.8 7 3.1 7

Lead 0.4 0.4 0 210 0 8.1 2

Nickel 20 12 5 74 2 8.2 7

Selenium 100 94 2 290 0 71 6

Source: HA & H-K. 2010 n – Number of samples

 Arsenic concentrations in all samples 5 (intake and discharge) exceeded acute and chronic criteria. Discharge concentrations ex ceeded intake concentrations in half of the samples; in one sample the total di scharge concentration exceeded the intake concentration by more than 50 percent.

 All intake and discharge samples exceeded acu te and chronic criteria for copper. In the majority of samples, influent copp er concentrations exceeded discharge concentrations. In one sample the total e ffluent copper concentration exceeded the influent concentration by more than 50 percent.

5 In EPA’s 2009 Study of Discharges Incidental to Normal Operation of Commercial Fishing Vessels and Other Non-Recreational Vessels Less Than 79 Feet (USEPA, 2010), the high concentrations of chloride and other cations in seawater were found to interfere with the analytical de termination of arsenic, as well as selenium. It is possible that a similar problem occurred in this study, and would explain the unexpectedly high concentrations of these metals in these samples of seawater and washwater.Exhaust Gas Scrubber Washwater Effluent Section 5 – Characterization of Pollutants in EGCS Washwater Discharges

18  Effluent lead concentrations sampled in Juneau and Skagway in 2007 exceeded acute and chronic criteria, although the paired infl uent samples had similar or higher lead concentrations. Lead criteria were not exceeded in samples collected at Juneau and Skagway in 2008.

 Total and dissolved nickel effluent concen trations exceeded the chronic criterion in all samples. In two discharge samples, tota l nickel concentrations also exceeded the acute criterion. In 5 of 7 paired data sets , the total discharge concentration exceeded the intake concentration by more than 50 percent.

 Six total and 4 dissolved effluent samp les exceeded the chronic criterion for selenium. In 2 of the sample pairs, the total discharge concentration exceeded the intake concentration by mo re than 50 percent.

 Washwater samples were also analyzed for antimony, beryllium, cadmium, chromium, mercury, thallium and zinc; no exceedances of water quality criteria were noted for these metals.

During operation of the seawater scrubber on the Zaandam in ports in Hawaii and Alaska, sooty deposits were observed rising to th e surface in the washwater discharge plume, and a slight sheen was witnessed. Th ese visible pollutants appeared to be caused from combustionderived carbon deposits. These carbon deposits, wh ich were nearly neutral in buoyancy, passed with the washwater through the multicyclone, attached to entrained air bubbles, and rose to the sea surface at the point of discharge. The washwa ter discharge contained very little petroleum hydrocarbon, but it appeared to fl oat to the surf ace resulting in the slight sheen observed. The addition of an oil-water separator to the washwa ter treatment process ahea d of the multicyclone in later trials appeared to prevent the reoccurre nce of this visible soot/sheen (HA & H-K, 2010).

5.2 T HE P RIDE OF K ENT S EAWATER S CRUBBER TRIALS

Trials of seawater scrubbers were conducted aboard the P&O Lines Pride of Kent , a ferry operating between the harbors of Dover and Calais . Seawater scrubbers we re installed on four 1.2 MW auxiliary engines onboard the Pride of Kent . The trials lasted over 16 months, during which the auxiliary engines ran almost conti nuously (Hufnagl et al., 2005). The ability of seawater scrubbers to reduce atmospheric emissi ons was examined, and the impacts of scrubber washwater discharges on the water quality in the harbors were studied. When all engines operated at full power, the washwater flow rate was 216 m 3 /hr (1.4 MGD). Sampling was conducted during five events held in February 6 , March, July, September and November of 2004, when the seawater scrubbers for the auxiliary engi nes were partially in use (Hufnagl et al., 2005).

6 The scrubbers were not operating during sampling in the ports of Dover and Calais in February, so data for those samples have been excluded from consideration in this document.Exhaust Gas Scrubber Washwater Effluent Section 5 – Characterization of Pollutants in EGCS Washwater Discharges

19 In each sampling event, discrete grab samples were collected at various locations in each harbor, including a transect 5 to 700 meters from the wash water discharge, at the seawater intake, and in the washwater discharge. Additional samples were collected at 6 locations throughout the seawater/washwater treatment system during the Pride of Kent’s crossings of the English Channel. The ambient and washwater samples were analyzed for a suite of constituents and other parameters similar to those measured on the Zaandam. Results from the final project report (Hufnagl et al., 2005) are summarized in S ections 0 through 0 (Huf nagl et al., 2005).

Temperature

Washwater temperatures in the discharge were significantly higher than those measured at the seawater inlet. The temp erature increases ranged from 1.9 to 4.1°C in March and July, and from 11.9 to 16.9°C in September and November. Discharge temperatures were greater than 37°C (99°F) in both ports and the channel during the September sampling event. In the July and September sampling events, a 1 °C temperature increase was measured in the ambient harbor water closest to the ship. Alt hough the report authors expected no adverse effects to result from the discharge of heated washwater, they also noted that the buoyancy of the discharge plume resulting from the difference in temperature (a nd hence density) with the ambient water would have an effect on mixing in the upper water column. Note that the IMO does not provide guidelines for washwater discharge temperature (Hufnagl et al., 2005).

pH

The SOx and NOx dissolved in the scrubber wa shwater form sulfuric and nitric acids, which significantly reduce the pH of the wash water leaving the scrubber. The washwater samples taken downstream from the scrubbers, prio r to blending with reaction water, had low pH values, ranging from 2.67 to 3.79. The buffering capaci ty of seawater used as reaction water was partially effective in neutralizing the washwater acidity. The average decrease in washwater pH between inlet and discharge samples was 1.39. Disc harge pH values in all of the September samples were less than 6.5, as were two-thirds of the November samples. The lowest pH measured in the overboard discharge was 6.15. Thes e values are below the lower limit of 6.5 in the IMO Guidelines for washwater discharge, wh ich is also the lower limit of the EPA NRWQC pH criteria for marine aquatic life. Howeve r, ambient water sampled along the discharge transects of the harbor (includi ng directly in front of the wa shwater discharge at 1 to 5 m distance) indicated no observable de crease in pH (Hufnagl et al., 2005).

Sulfate

In addition to washwater acidification, the dissolved SOx increased the sulfate concentration in the effluent. Sulfate concentr ations measured in washwater downstream from the scrubber were 14 to 19 percen t higher than those measured at the seawater intake. In the discharge samples, sulfate concentrations ranged between 2,600 and 3,052 mg/L, which accountsExhaust Gas Scrubber Washwater Effluent Section 5 – Characterization of Pollutants in EGCS Washwater Discharges

20 for an increase of 0.4 to 6 percent. This may not be a significant increase, since the analytical error associated with these measurements was re ported to be approximately 6 percent (Hufnagl et al., 2005).

Nitrate

Nitrate, an important aquatic nutrient, is fo rmed in the scrubbing process when NOx is dissolved in the washwater. In the washwater samples taken downstream from the scrubber, the nitrate concentrations were two to thirteen time s higher than in the seawater inlet samples. The washwater treatment processes (multicyclone and filtration) did not reduce these concentrations because the treatment is designed to remove su spended solids and particulate pollutants, not dissolved pollutants such as nitrate. Nitrate co ncentrations increased be tween the influent and effluent discharge in 10 of 12 washwater sample s. The average discharg e nitrate concentration was 638 μg/L (or 144 μg NO 3 -N/L), 21 percent greater than the average influent concentration (Hufnagl et al., 2005).

Ammonia concentrations in washwater increase d between the inlet and discharge in 4 of 10 samples; the average discharge concentration was 60 μg NH 3 -N/L, 5 percent higher than the average inlet concentration. Dissolved inorgani c nitrogen (combined n itrite, nitrate, and ammonia) concentrations increased between the inlet and discharge in 8 of 10 samples; the average discharge concentration was 215 μg N/ L, 21 percent higher th an the average inlet concentration (Hufna gl et al., 2005).

Metals

The washwater samples collected onboard the Pride of Kent were analyzed for total concentrations of barium, lithium, strontium, calcium, potassium and magnesium, vanadium, chromium, manganese, iron, cobalt, nickel, lead, copper, zinc and mol ybdenum. Copper, lead, nickel and zinc exceeded EPA’s NRWQC for sa ltwater aquatic organisms in the washwater discharge. When exceedances were detected in the di scharge, they were often also detected in the intake in similar or even higher concentrations, indicating that the ambien t seawater was a likely source of the metals. In addition, the sampling c onducted at several points within the washwater system onboard the Pride of Kent provided further identification of likely sources of the metals that were detected (H ufnagl et al., 2005).

Sampling conducted throughout the seawater/washwater treatmen t system revealed that the seawater scrubbing process itsel f did not influence the concentra tions of metals in washwater. No metals, except for iron, were detected directly downs tream of the scrubbers. Metals present in the washwater in particulate form, including ir on and vanadium, were removed by the treatment system and retained in the sludge settling tank (Hufnagl et al., 2005).Exhaust Gas Scrubber Washwater Effluent Section 5 – Characterization of Pollutants in EGCS Washwater Discharges

21 The reduced pH of the washwater leaving th e scrubber affected the solubility of metal ions. The highest metals concentrations downs tream of the scrubber were measured for iron, which may be contributed by contac t with the ship’s st eel components. Elevat ed copper, nickel and zinc concentrations were also detected. Th e copper may originate from ship coatings that contain copper as antifouling biocide while ni ckel, like iron, is a compound of ship steel.

Details of the exceedances of water quality criteria for metals are provided below (Hufnagl et al., 2005):

 Copper was detected in intake and disc harge samples at Dover in March and November, and in November at Calais. C opper was also detected in the discharge samples collected on the channel crossing in November. All intake and discharge samples exceeded acute and chronic saltwater criteria. Intake copper concentrations ranged from 37 to 129 μg/L, while concentrations in discharges ranged from 32 to 129 μg/L.

 Lead was detected during November in di scharge samples from the channel crossing and Calais, and both intake and discharge sa mples from Dover. Lead concentrations in these samples ranged from 18 to 34 μg/L, all of which exceeded the chronic saltwater criterion for lead.

 Nickel was detected in a single discharge sample, from Calais in November, but was not detected in the corre sponding intake sample. The measured concentration, 34 μg/L, exceeded the saltwater chronic criterion.

 Zinc was detected in each of the discharg e samples collected in Dover, but in only one intake sample (at one-fifth of the disc harge concentration). At Calais, zinc was detected in one discharge sample. Of the samples collected during the channel crossings, zinc was detected in one intake and one discharge sample from different sampling events. All of the discharge sample s exceeded the acute and chronic criteria; however, the occurrence and increase in zinc concentrations was suspected to be an artifact introduced by sample contamination.

PAHs

Samples were analyzed for dissolved and pa rticulate concentrati ons of the 16 PAHs defined to be environmentally relevant by the EPA 7 , including both small (4-6 rings) and large (>6 rings) PAHs. Total PAH concentrations (i .e., the sum of disso lved and particulate concentrations for the 16 PAHs) increased signifi cantly from intake to discharge in all samples.

7 EPA’s priority pollutant list of 16 PAHs includes: naphthalene, acenaphthylene, acenaphthene, fluorene, phenanthrene, anthracene, fluoranthene, pyrene, be nzo[a]anthracene, chrysene , benzo[b]fluoranthene, benzo[k]flouranthene, benzo[a]pyrene, dibenz(ah)anthr acene, benzo[ghi]perylene, and indeno(1,2,3-cd)pyrene.Exhaust Gas Scrubber Washwater Effluent Section 5 – Characterization of Pollutants in EGCS Washwater Discharges

22 The average total PAH discharge concentration was 3,080 ng/L, twelve times the average intake concentration of 250 ng/L. The PAH composition was dominated by phenanthrene, fluorene and pyrene in all samples (Hufnagl et al., 2005).

For individual PAHs, concentrations in th e washwater discharge samples were higher than concentrations measured in the seawater inle t by factors of one to tw o orders of magnitude.

EPA has classified seven PAH compounds as probable human carcinogens, and NRWQC have been established for nine PAHs to protect human health. A summary of the concentrations measured for these PAH compounds and for phena nthrene, the most abundant PAH in these samples, in intake seawater and washwater discha rge samples is presented in Table 3. Five of the PAH compounds (benz[ a ]anthracene, benzo[ a ]pyrene, benzo[ b ]+ benzo[ b ]fluoranthene and chrysene) exceed the human health criterion in al l or nearly all discharge samples. Two others (dibenz[ a,h ]anthracene and indeno[1,2,3, c,d ]pyrene) exceeded the criteri on in about half of the samples (Hufnagl et al., 2005).

Table 3. Concentrations of PAHs in the Seawater Intake and Was hwater Discharge from the Pride of Kent Scrubber Trial

PAH Median Total Influent Concentration (ng/L) (n=13) Median Total Discharge Concentration (ng/L) (n=13) Dissolved Fraction, f d Human
Health Criterion (Organism Consump. Only, ng/L, Except As

Noted) Number of Discharge Concentrations Exceeding Criterion

Benz[ a ]anthracene 6 262 0.36 18 12
Benzo[ a ]pyrene 5 136 0.12 18 12
Benzo[ b ]fluoranthene + benzo[ k ]fluoranthene 4 49 0.10 18 12

Chrysene 12 373 0.40 18 13
Dibenz[ a,h ]anthracene 8 9 0.15 18 6
Fluorene 14 137 0.97 5.3 mg/L 0
Indeno[1,2,3, c,d ]pyrene 5 18 0.13 18 8
Phenanthrene 54 1,230 0.88
Pyrene 23 408 0.53 4 mg/L 0 Source: Hufnagl et al., 2005

Even higher PAH concentrations were measured inside the seawater scrubber washwater treatment system. The total PAH concentrations in samples collected prior to seawater dilutionExhaust Gas Scrubber Washwater Effluent Section 5 – Characterization of Pollutants in EGCS Washwater Discharges

23 ranged from 11,900 to 20,400 ng/L. Phenanthrene concen trations prior to seawater dilution were 5,100 to 8,200 ng/L, six to ten times lower than th e 50 μg/L IMO Guideline. Most of the total PAHs were bound to soot particles, and concentr ations were reduced by multicyclone treatment. Note, however, that improving the treatment effi ciency would further reduce particulate PAH concentrations in the washwater discharge. Th e relatively high PAH concentrations in the discharge samples were predominantly the low molecular weight PAHs (such as the two and three benzene ring compounds: fluorene and phenanthr ene) that are more soluble in water and not effectively removed by particle separation. Ba sed on the average total PAH concentrations in intake and discharge samples, and a ssuming a washwater flow rate of 216 m 3 /hr and 2.25x dilution by reaction water, the EGCS on the Pride of Kent discharged about 33 grams of total PAH per day (Hufnagl et al., 2005).

No increase in PAH concentrations was observe d in ambient harbor samples collected in front of the seawater scrubber discharge. Princi pal component analyses indicated that the PAH compounds measured in the seawater scrubber sa mples originated from a petroleum source rather than a combustion source, as would be e xpected from the funnel. Incomplete combustion of the fuel was suspecte d (Hufnagl et al., 2005).

5.3 T HE S UULA F RESHWATER S CRUBBER T RIAL

In 2008 a Finnish maritime consortium installe d and tested an EGCS aboard the tanker
MT Suula (Wärtsilä, 2010). This scrubber trial offers a contrast to th e other studies of seawater scrubbers because the Suula was outfitted with a closed fres hwater scrubber. A medium speed 680 kW auxiliary engine fed exhaust gas to the sc rubber, which was smaller than what would be used in a full scale EGCS. In the freshwater scrubber, sulfur oxides in the exhaust gas are transferred to washwater containing sodium hydr oxide and sulfates are formed. The washwater leaving the scrubber was dosed with sodium hydroxi de, cooled by a seawater heat exchanger to limit evaporative loss, and then re-circulated back to the scrubber. A fraction of the washwater was bled off for treatment and discharge, at a rate of about 0.1 m3/MWh or 0.07 m 3 /hr (430 gallons per day, GPD), based upon the auxiliar y engine size (persona l communication with Wärtsilä; see Attachment A). The bleed-off washwater was treated prior to discharge to remove pollutants in a high efficiency treatment plan t that combined coagulation and flocculation, dissolved air flotation, oil a nd sludge skimming, and granular activated carbon adsorption (Wärtsilä, 2007). Pollutants removed from the bleed-off washwater were retained as sludge, which was collected into a residual sludge tank and held for disposal at a shore-side waste reception facility. The rate of sludge generati on was approximately 0.1 to 0.4 kg/MWh (Wärtsilä, 2010).

As a part of certification test s that were conducted during the scrubber trial, water quality for the bleed-off washwater was demonstrated to the classification societies Germanischer Lloyd and Det Norske Veritas (DNV). The freshwater scrubber fulfilled all the IMO GuidelineExhaust Gas Scrubber Washwater Effluent Section 5 – Characterization of Pollutants in EGCS Washwater Discharges

24 discharge quality criteria for pH, turbidity, PAHphe, and nitrate due to the efficiency of the water treatment unit (Wärtsilä, 2010). The bleed-off tr eatment unit was found to have a very high cleaning efficiency regardless of the fuel sulfur content (both low- and hi gh-sulfur content fuels were tested). Results from the project re port are summarized below (Wärtsilä, 2010):

pH

Sodium hydroxide (NaOH) was added to the scrubbing water circulation to maintain the process pH and the efficiency of SOx removal. Due to efficient NaOH dosing and monitoring in this system, the pH of the discharge was ma intained at a value of 7.65 (Wärtsilä, 2010).

Nitrate

Certification tests demonstrated that the nitr ate concentration in the bleed-off discharge was less than 2,000 mg/L. When normalized fo r a washwater discharge rate of 45 t/MHw 8 , this concentration is reduced to 9 mg/L, which is below the IMO limit of 60 mg/L (Wärtsilä, 2010).

Turbidity

The turbidity of the discha rge bleed-off following water treatment was 0.5 FNU, also under the IMO limit of 25 (Wärtsilä, 2010).

PAHs and Organic Compounds

The PAHphe concentration of the discharged bleed-off water was 14 μg/L. This is considerably lower than the flow-normalized IMO limit of 2,250 μg/L. The bleed-off treatment unit achieved PAHphe reductions of 97 to 98 percen t when the scrubber was tested with fuels of different sulfur contents. Hydro carbon (C10-C40) concentrations were also reduced by nearly 100 percent, to discharge concentrations of less than 1 mg/L (Wärtsilä, 2010).

The authors of this study noted that conti nuous measurement of the PAHphe equivalence in a reliable way is challenging using existi ng technology. Traditional sampling and laboratory analyses onshore are a more reliable approach to monitoring PAH content in discharge. Additional research and development work was suggested to find the be st methodology for PAH monitoring in the discharge (Wärtsilä, 2010).

Metals

Metals were also removed from the bleed-off washwater by the treatment unit prior to discharge. The sum of metals 9 specified by IMO Resolution MEPC.184(59) was reduced by 66

8 See Section 4 for an explanation of the IMO Guideline discharge limit flow normalization.Exhaust Gas Scrubber Washwater Effluent Section 5 – Characterization of Pollutants in EGCS Washwater Discharges

25 to 83 percent, to a concentration less than 60 mg /L (total metals concentration). The discharge concentrations for individual metals were not re ported. The IMO Guidelines indirectly limit the permissible amount of metals in the washwater discharge by its the turb idity criterion. As this case illustrates, a considerable concentration of metals can be discharged even though the discharge turbidity is well under the limits established by the IMO Guidelines (Wärtsilä, 2010).

5.4 S UMMARY OF M ARINE EGCS S CRUBBER T RIALS

The trials conducted with wet scrubbers onboard marine vessels have demonstrated the capabilities of this technology to remove sulfur emissions from exhaust gas. They have also provided limited data characterizing constituen t concentrations in washwater discharges. The trials aboard the Zaandam
, Pride of Kent and Suula provided measurements of several washwater constituents including pH and pollutants removed from the exhaust gas (SOx and NOx, and the products of their transformation: acidity, SO 4 , NO 3 and COD) and PM (PAHs, hydrocarbons and metals). Neutralization of wash water was achieved by blending with sufficient seawater “reaction water”. Washwa ter was also treated to remove the suspended solids that were attributed to PM removed by the scrubbers . Treatment was accomplished using multicylones alone or in combination with filt ration, or, more effectively, using an advanced treatment system incorporating coagulation and f iltration, flotation and adsorption.

Issues with the technology for continuous monitoring of PAHs, as required by the IMO Guidelines, were noted in two of the trials. One trial also reported diffi culties with continuous monitoring of turbidity. Washwater monitoring re sults also suggested that some constituents warrant further consideration, in cluding pH, metals, PAHs and n itrate (see Section 6). Although all of the constituents are addressed in the IMO scrubber washwater guidelines, the guideline limits may be inadequate for metals and PAHs.

It should also be noted th at the trials aboard the Zaandam
, Pride of Kent and Suula were limited, because the scrubbers were installed on auxi liary engines that were not always operating at full power when washwater was sampled. When exhaust is scrubbed at higher power output levels, or when larger propulsion engine exhaust is scrubbed, more washwa ter will be generated and discharged. Due to this and the fact that constituent concentrations in exhaust and/or washwater may be different at higher power outpu ts, the representativeness of the trial results may be uncertain. In addition, the performance and effects of seawater scrubbers may be different in areas with brackish water or freshwater (H ufnagl et al., 2005). Freshwater may have, for example, less pH buffering capacity, unless the water drains a carbonaceous area; therefore, the ability of such a water body to assimilate acidic washwater discharge may be limited.

9 These metals include cadmium, copper, nickel, lead, zinc, arsenic, chromium and vanadium.Exhaust Gas Scrubber Washwater Effluent Section 6 -Assessment of Pollutants Discharged in Scrubber Washwater and Protectiveness of IMO Guidelines

26 

## SECTION 6
ASSESSMENT OF POLLUTANTS DISCHARGED IN SCRUBBER

WASHWATER AND PROTECTIVENESS OF IMO GUIDELINES

In Section 5, data were presented that charac terize the constituent concentrations that can be expected in scrubber washwater discharges. These concentrations were compared to EPA NRWQC as a preliminary screen for all discharge da ta with the potential to cause or contribute to the nonattainment of a wate r quality standard in a given receiving water body. The pollutant concentrations were also compared to IMO Gu ideline limits, when available. In addition, an analysis of the protectiveness of the IMO Guideline washwater limits offered in an impact assessment prepared for the European Comm ission on the revision of Directive 1999/32/EC 10 was considered and incorporated in this discussion where appropriate (AEA, 2009).

EPA’s NRWQC are recommended concentrations of analytes for a water body that are intended to protect human healt h, aquatic organisms and the water body uses from unacceptable effects from exposures to thes e pollutants. The NRWQC are not directly related to analyte discharge concentrations for a number of reas ons (USEPA, 2010a). Firs t, NRWQC are based not only on concentration, but also on duration and fr equency. Second, it is not always necessary to meet all water quality criteria within the discha rge pipe to protect the integrity of a water body (USEPA, 1991). Under EPA’s regulations at 40 CFR 122.44(d)(1)(ii), when determining whether a discharge causes, has the reasonable potent ial to cause, or contributes to an in-stream excursion above a narrative or numeric criteria within a state water quality standard, the permitting authority will use procedures that account for, where appropriate, the dilution of the discharge in the receiving water. A mixing zone allows for ambient c oncentrations above the criteria in small areas near outfalls while dilu tion occurs. To ensure mixing zones do not impair the integrity of the water body, th e permitting authority will determine the mixing zone such that it does not cause lethality to pa ssing organisms and, considering likely pathways of exposure, significant human health risks.

Nevertheless, comparing analyte concentr ations in vessel discharges to NRWQC provides a conservative screen of whether these discharges cause, have the reasonable potential to cause, or contribute to nonatta inment of the water quality st andards in a water body. If the concentration of a given analyte in vessel discharge is less than th e applicable screening criterion values, the discharge would likely not cause, have the reasonable pot ential to cause, or contribute to nonattainment of a water qualit y standard based on that value, particularly after considering assimilation and/or dilution by th e receiving water. On the other hand, if the concentration of a given analyte in vessel discharge is greater than the applicable screening criterion value, then there is the possibility of ecol ogical or human health risk.

10 Sulfur Content of Certain Liquid FuelsExhaust Gas Scrubber Washwater Effluent Section 6 -Assessment of Pollutants Discharged in Scrubber Washwater and Protectiveness of IMO Guidelines

27 Because the washwater discharges were meas ured at the “end of pipe” before being released into a harbor where they are subsequen tly diluted, discharge con centrations greater than the applicable criterion do not necessarily indicat e that a discharge poses a significant risk or would be likely to cause or contribute to a water quality standard exceedance. However, exceedance of a screening benchmark indicates that the discharge warrants further consideration regarding the potential to cause or contribute to nonattainment of water quality standards.

Mobile sources such as vessels complicate th e analysis because they discharge into many different water bodies. In general, greater mixi ng and dilution would be expected for discharges from vessels that are in motion while discharging than from stat ionary sources. Vessel discharges to areas with high vessel traffic, areas with a low degree of flushing, or impaired water bodies could reduce mixing and dilution. With these f actors in mind and assuming the discharge data presented in this document are representative of scrubber washwater disc harges in general, a discharge concentration marginally above the applicable screening criterion value is most likely not of significant concern. On the other hand, a di scharge concentration s ubstantially above the applicable screening criterion va lue (e.g., by a factor of 10 or 100) may be more likely to be of concern, particularly if the discharge is of signifi cant volume, is in an area of low flushing, is in an area where there is a high degree of vessel traffi c, or is in a waterbody th at is already impaired or under other stress.

The dispersion (mixing) of pollutants discharg ed from a ship has been evaluated using numerical hydrodynamic models. The overall di spersion has been modeled for different scenarios regarding ship size, washwater di scharge point and speed (MARINTEK, 2006). The dispersion in the wake behind a moving vessel ha s been identified as the dominant dilution process (MARINTEK, 2006). For a 163 m length vessel moving at a constant speed of 14.5 knots with a washwater discharge of 440 m 3 /hour at 8 m depth and 20 m ahead of the stern, the washwater was diluted by a factor of 1:30 before the discharge passed the stern of the ship and by a factor 1:2,000 at a distance 50 m behind the st ern. At slower vessel speeds, such as while maneuvering in a confined harbor , less dilution is e xpected. The power output of the propulsion engines is also expected to be lower at slower vessel speeds, whic h would also reduce the rate of washwater discharge (assuming the vessel is scrubbing propulsion engine exhaust).

Dilution in port may be influenced by local conditions, but much less mixing is expected in comparison to the discharge from a moving ve ssel. One study assumed a speed of 0 knots, a washwater temperature of 7.5°C, and an ambien t current speed of 5 centimeters per second (cm/s) (MARINTEK, 2006). A dilution factor of 1:100 in the center of the plume was predicted less than 20 m downstream from the discharge, co rresponding to an averag e dilution factor of approximately 1:150. The dilution factor will probab ly be smaller than this if the washwater discharge is warmer than 7.5°C (for co mparison, the maximum washwater discharge temperatures measured during the Pride of Kent trials were 37°C), because heated effluent will be buoyant and may tend to “float” on top of the ambient water instead of mixing.Exhaust Gas Scrubber Washwater Effluent Section 6 -Assessment of Pollutants Discharged in Scrubber Washwater and Protectiveness of IMO Guidelines

28 The pollutant concentrations were also compared to IMO Guideline limits, when available. The IMO washwater criteria are sti pulated in Section 10 of Annex 9 of Resolution MEPC.184(59) and regard pH, PAH content, turbid ity and nitrate content. These concentration limits do consider the dilution of washwater disc harges in the ambient water in a mixing zone surrounding the vessel. The IMO Guideline limits al so reflect the results of monitoring, which generally did not detect increase s in pollutant concentrations in the discharge plume, even in close proximity to the point of discharge. The current IMO Guidelines imply that the washwater criteria apply everywhere; however, in earlier versions the criteria were only applied to harbors, estuaries and ports (AEA, 2009). It is uncertain, at present, if se parate limits will be developed for operation at open sea.

6.1 P H

There is some concern that sending seawaterback into the ocean with acidic sulphurcontaining wastewater is harmfu l enough to the marine ecosystem that it “renders the technology impractical” (Kehoe et al., 2010). The washwater from a seawater scrubber unit can have a pH as low as 3; therefore, to avoid a negative impact on ecosystems a nd potential corrosion issues, the washwater must be further neutralized and dilute d with additional seawater to increase the pH level to greater than 6.5, as required under the IMO EGCS Guidelines. Alternatively, the IMO Guidelines allow the pH limit for the discha rge to be determined during commissioning by measuring pH in the plume at a distance of 4 m from the discharge point, and determining the discharge pH that corresponds to a plume pH equa l or exceeding a value of 6.5. This alternative compliance method of measuring the pH is consis tent with EPA CORMIX principles where 4 m is considered the boundary of th e initial mixing zone between wa ter discharged overboard and water surrounding the vessel (Jirka,1996 and EGCSA, 2010).

Low pH water can adversely impact marine organisms such as shellfish and, as many organisms are only able to survive when environm ental conditions are stable, a decrease in pH may be a risk for those organisms. The IMO indicat es that, in general, no environmental harm is considered to arise from short-term exposure of seawater with pH values as low as 6.5 (Hassellöv and Turner, 2007). A different pH disc harge criteria is appl ied for moving vessels: during maneuvering and transit, a maximum differe nce of 2 pH units is allowed between the ship’s inlet and overboard disc harge. As previously noted, fo r vessels underway, the mixing of discharged washwater with fres h seawater by the turbulence of the ship’s wake is highly effective, so that recovery of the pH to that of the su rrounding water is rapidly achieved (EGCSA, 2010).

Most studies of the pH reduc tion associated with scrubber washwater discharges have focused on local receiving water impacts. As seawater scrubbing cuts short the cycle of SO 2 directly deposited in the ocean, this technology may also accelerate the pH decrease in surface waters of the oceans. However, this effect is minor compared to ocean acidification due toExhaust Gas Scrubber Washwater Effluent Section 6 -Assessment of Pollutants Discharged in Scrubber Washwater and Protectiveness of IMO Guidelines

29 increased carbon dioxide concentrations in th e atmosphere (Kehoe et al., 2010). One study estimated that the pH of the ocean would d ecrease by 0.02 within the next 100 years, assuming that sulfur is evenly distributed in the 100 m deep surface layer (Kehoe, 2010). In comparison, another study predicted that average pH of the surface ocean may decline by 0.255 by year 2100 (Kehoe, 2010).

EPA’s NRWQC criteria for marine aquatic life is expressed as a pH in the range of 6.5 to 8.5, but not more than 0.2 standard units outsi de of normally occurring range (USEPA, 1976). EPA guidelines concerning the introd uction of acids state that, with in the initial mixing zone, the pH change is not allowed to be higher than 0.2 (EGCSA, 2010). In co mparison to the EPA pH criteria, the IMO Guidelines have the same lower limit, but lack the limit on pH change.

Problems were encountered during two of the seawater scrubber trials with neutralization of the acidic washwater resulting in the discha rge of washwater with pH values below 6.5. On the Zaandam , the discharge washwater pH was more than 2 standard units lower than the intake values. The mean pH of the discharged wash water was 5.8 while in the coastal waters of California and Hawaii and 6.3 in Alaska. The di scharge of low pH washwater effluent was associated with low washwater and/or reaction water flow rates. On the Pride of Kent , the average decrease in washwater pH was only 1.39. However, all of the discharged washwater pH values were below 6.5 during one sampling event; tw o-thirds of the pH values were below this limit in another.

A 2007 study calculated the amount of water needed for scrubbing SO 2 and dilution to first obtain pH of 6.5 and then a pH change with in the initial mixing zone of 0.2 (Hassellöv and Turner, 2007). The nominal flow rate of sc rubbing water used by MEPC is around 45 t/MWh giving about 540 t/hr for a ship with a 12 MW engi ne. The estimated quantities of water needed for scrubbing are presented in Table 4. With the present criteria for pH, the dilution in the sea and natural buffering may rapidly achieve acce ptable levels, even in confined areas. Furthermore, vessels use substantially less propu lsion power when traveling at low speeds and maneuvering in harbors and othe r confined areas. Vessels usi ng EGCS for propulsion engines should therefore discharge less washwater in har bors, further limiting the impact of seawater scrubbers on receiving water pH. As previously stated, operati on of a seawater scrubber in brackish or freshwater may have different effects (e.g., fresh waters with less pH buffering capacity). Almost 7 times more water for dilu tion is needed when scrubbing takes place in freshwater, compared to the open sea.Exhaust Gas Scrubber Washwater Effluent Section 6 -Assessment of Pollutants Discharged in Scrubber Washwater and Protectiveness of IMO Guidelines

30 Table 4. Approximate Amount of Water (t /hr) Affected by a Scrubber for a 12 MW Engine

Quantity of Water

Open Ocean Baltic Sea Freshwater River

Water for scrubbing 700 900 2,500
Water for dilution to pH = 6.5 1,400 1,700 15,000

Factor for dilution to ∆ pH of 0.2 3 3.5 2.5
Total amount of water 6,300 9,100 44,000
Source: Hassellöv and Turner, 2007

In an environmental impact assessment of the Pride of Kent seawater scrubber trials, samples were taken directly in front of the washwa ter discharge from a stationary vessel in each harbor at distances of 1 to 5 m, 50 m, 350 m and 700 m. While washwater samples taken from inside the ship had pH values of 6.2 to 6.5, in no sample taken within the discharge plume was the pH below that of the surrounding water (EGCSA, 2010).

The IMO criterion for pH limits the amount of water that may be affected by low pH during scrubber operation to a reasonable amount. This is dependent on the dilution, volume of water and the specific area of concern. As noted, specific attention may be needed for waters with low alkalinity. Increasing the volume of react ion water used to neutralize washwater in open seawater systems, or operating closed fr eshwater systems in zero-discharge mode as needed, may be practical solutions to limit pH change in vulnerable (i.e., low alkalinity) receiving waters.

6.2 PAH

PAHs are the largest known group of car cinogenic substances and include many individual chemical substances containing two or more condens ed aromatic rings. PAHs occur naturally in petroleum and are also produced as by-products of fuel combustion. PAHs are an important class of environmental contaminants that are known to accumulate in ecosystems. The EPA has identified 16 PAH compounds as priority pollutants. Some of these compounds are carcinogenic and/or mutagenic to mammals; in a ddition, they have both acute toxicity and sublethal effects on some aquatic organisms. PAHs may also bioaccumulate in edible shellfish, which gives them a pathway to humans (Hartmann and Quinn, 1999).

The IMO has set limits for the online monito ring of phenanthrene, based on studies to date which have shown no negative influences of EGCS washwater on port environments. Phenanthrene is the most prevalent of the 16 EPA PAHs found in the vessel washwater systems (Behrends et al., 2005). Furthermore, the IMO asse rts that, as PAHs are also found naturally inExhaust Gas Scrubber Washwater Effluent Section 6 -Assessment of Pollutants Discharged in Scrubber Washwater and Protectiveness of IMO Guidelines

31 petroleum, their monitoring ensures that unbur ned oil or hydrocarbons do not enter the sea (EGCSA, 2010). The IMO also requests ship ow ners to sample inlet and untreated and discharged washwater, and to employ gas ch romatography-mass spectrometry analysis for PAHs.

Sediments can be disturbed during the maneuveri ng of a ship in shallow water, and as a result may enter the washwater system. Since ha rbor sediments are often contaminated with PAHs, PAHs can enter the washwater system along with the sediment. The IMO therefore requires the background concentratio n of PAH at the washwater inle t be taken into account when measuring the PAH concentration at system disc harge. It is also required that washwater monitoring take place following water treatment, but before any dilution for correction of the washwater pH.

While a set of 16 PAHs is customarily analy zed and measured as individual chemicals, the IMO Guidelines set the washwater criteri a for PAH in phenanthrene equivalents. The rationale for this is unclear but may be that measuring PAH is a surrogate for hydrocarbons and phenanthrene was found to be the most abundant P AH in the analysis of washwater during trials on the Pride of Kent . However, the concept of phenanthrene equivalents is not well established and needs to be explained or replaced (AEA, 2009). Assuming that it simply means that the phenanthrene concentration is measured, the 50 μ g/L criteria correspond to about 2.2 g/MWh of PAHphe. Thus, the washwater criterion may be high, especially considering that the scrubber washwater should be treated before monitoring for PAHphe. A 12 MW engine could, with the suggested limit, emit around 27 g/hr phenanthr ene in addition to unknown amounts of other PAHs. This emission limit may be unacceptably high, and widespread use of scrubbers emitting washwater with PAH concentrations close to th is limit could pose a risk to the environment (AEA, 2009).

The Oslo and Paris Conventions for the prot ection of the marine environment of the northeast Atlantic (OSPAR) have developed Ecot oxicological Assessment Criteria (EAC) for a large range of chemicals, including PAHs. The EAC can be applied as Predicted No Effect Concentration (PNEC) values (MARENTEK, 2 006). The EAC for phenanthrene in water is proposed as a range: 0.5 to 5 μ g/L (provisional value). The PNEC value is the maximum permissible concentration that can be sustai ned over time. The Pr edicted Environmental Concentration (PEC) equals the proposed washwa ter criteria multiplied by the dilution (if inlet concentration is assumed to be zero). Since the washwater criterion is set to 50 μ g/L PAHphe (for a scrubber washwater flow of 45 t/MWh), the washwater must be diluted by a factor of 10 to 100 to reach this PNEC concentration (AEA, 20 09). Furthermore, the background concentration should also be considered, which may l ead to further limits on the emissions.

The median concentration of phenanthren e measured in the washwater following treatment but before mixing with reaction water on the Pride of Kent was 6.1 μ g/L, well belowExhaust Gas Scrubber Washwater Effluent Section 6 -Assessment of Pollutants Discharged in Scrubber Washwater and Protectiveness of IMO Guidelines

32 the 50 μ g/L PAHphe IMO Guideline limit. Compar ison of the other PAHs measured in washwater discharged by the Pride of Kent during scrubber trials to the EPA NRWQCs suggests that scrubbers may emit washwater with concentrations of other P AHs that could pose a risk to the environment. The EGCS on the Pride of Kent was discharging about 33 grams of total PAH per day. Dividing the median discharge concentra tions by the applicable human health criteria (values tabulated in Section 5), th e dilution required to reach the crit eria is calculated to be as high as 21 for chrysene, 15 for benz(a)anthracen e, and 7 for benzo(a)pyrene. Phenanthrene concentrations measured in the washwater discharge on the Zaandam and Suula were <1.3 μ g/L and 14 μ g/L; concentrations for the ot her PAHs were not reported.

The PAH criterion appears to have been sele cted to allow continuous monitoring of the washwater discharge. While it may be appropriate to use phenanthrene for monitoring purposes, the criteria should, nevertheless, ensure that all of the environmentally relevant PAHs are controlled. How the measured phe nanthrene equivalents relates to the 16 EPA PAHs, for example, or its correlation to total hydrocarbons needs to be establis hed during certification. Furthermore, it remains to be established that the PAH IMO Guideline lim it will ensure that the levels of total hydrocarbon compound emi ssions are at safe levels (AEA, 2009).

6.3 T URBIDITY
Turbidity is a measure of the amount of su spended solids in the water, based upon the loss of optical transparency (i.e., cloudiness) of the water. When combined with PAH, the measurement of turbidity is in tended to demonstrate that the scrubber and washwater treatment system is operating correctly (EGCSA, 2010). Ho wever, this method of continuous monitoring has not been demonstrated to be a reliable measur e of the concentration of PM (including metals) emitted with the washwater (AEA, 2009). Turbidity can be a useful indicator of the status of the scrubber (i.e., that suspended part icles are not being formed in th e scrubbing process and/or the washwater treatment process is functioning properly). Turbidity, however, is not a direct method of determining the amount of exhaust particles that end up in the washwater because there is no direct correlation between turbid ity and particle concentration. Further, turbidity values are strongly dependent on the size of pa rticles in the water; smaller particles are likely to have significantly less influence on the measured turbidity than larger ones. Studies are required to correlate the turbidity measurements with concentrations of PM, ash, metals, etc. in the washwater before turbidity can be considered as a reliable indicator of pa rticulate levels in the washwater (AEA, 2009). These uncertainties make it difficult to make an environmental assessment of the turbidity criteria.

Turbidity was measured in the scrubber trials onboard the Zaandam and the Suula

. During the Zaandam trials, the maximum turbidity was 8 NTUs, well below the 50 NTU IMO Guideline limit. Turbidity levels actually declin ed between the inlet and discharge in the firstExhaust Gas Scrubber Washwater Effluent Section 6 -Assessment of Pollutants Discharged in Scrubber Washwater and Protectiveness of IMO Guidelines

33 year of that trial (i.e., the sc rubber system removed turbidity fro m the seawater used as scrubber washwater). On the Suula , the turbidity was 0.5 FNU, also well below the guideline limit.

6.4 N ITRATE
Nitrate is the most highly oxidized form of n itrogen, and excess nitrate concentrations in aquatic systems can result in a rapid increase or accumulation in the population of algae, possibly leading to algae blooms and eutr ophication. This can di srupt functioning of an aquatic system, causing a variety of problems such as a lack of ox ygen in the water needed for fish and shellfish to survive (Behrends and Liebeze it, 2003). In near-shore or har bor situations, where phosphorous is available (e.g. from river inputs, runoff from ag riculture or direct inpu t of domestic sewage), addition of nitrates may lead to enhanced biomass production.

The IMO Guidelines include two criteria for nitrate concentration in the washwater: 60 mg/L or a limit based on removing 12 percent of the NOx from the exhaust stream, based on a hypothetical scrubber design capable of re moving more NOx than the soluble NO 2 fraction. A scrubber unit on a ship operating close to this 12 percent limit may, de pending on the sea area, increase the ship’s contribution to the nitrat e load in the sea (AEA, 2009). In principle, washwater discharges from numerous ships ope rating EGCS could lead to large additional loadings of nitrates to sensitive aquatic ecosystems.

A 2009 report analyzed the impact of the 12 pe rcent exhaust NOx remo val criteria in the Baltic Sea (AEA, 2009). The Baltic is heavily tra fficked by vessels, is a SECA, and is highly impacted by eutrophication. Serious e fforts have been made to decrea se the flow of nutrients into the Baltic and the total emissi on of NOx from shipping in th e Baltic is currently around 400 kilotons per year. Modeling was used to estimate that about 13 percent of the NOx emitted from shipping in the Baltic Sea is also deposited in th at water body; the rest is deposited over land or (to a smaller extent) in other sea regions. C onsequently, approximately 107 kilotons per year (calculated as nitrates) is depos ited in the Baltic Sea from Ba ltic shipping. If all of these ships were to use scrubbers, and all of these scrubbers captured 12 percent of the NOx in the exhaust and released it as nitrates in the scrubber washwa ter, the total nitrate lo ading from vessels would increase to 193 kilotons (an increase of about 86 kilotons per year). Notwithstanding several unrealistic assumptions, this estimate does give a maximum possible increase in nitrate loading. Twenty-five percent of the total load of nitr ogen to the Baltic Sea comes from atmospheric deposition; the rest comes from rivers and direct wa terborne discharges. Thus, the hypothetical maximum increase in the load of nitrates to a water body of the si ze of the Baltic Sea would be a nearly-negligible, 2 percent, if all ships were to use scrubbers.

A 2009 report estimated the potential for additional biomass production due to the discharge of nitrate from the washwater of an EGCS, using the nitrate levels monitored over the ten-month period of the Pride of Kent trials (Hufnagl, 2005). Addi ng 9.59 μM of nitrate to the 10-60 μM ambient concentrations measured in ha rbors, when converted by stoichiometry, equalsExhaust Gas Scrubber Washwater Effluent Section 6 -Assessment of Pollutants Discharged in Scrubber Washwater and Protectiveness of IMO Guidelines

34 an increase in plankton biomass of 2.13 mg /L over the 2.2-13.3 mg/L biomass produced by ambient nutrients. The potential for increase in annual production was equa ted to less than the actual production during one s unny day (Hufnagl, 2005). Thus, these calculations also demonstrate that the impact of the nitrates disc harged in washwater from seawater scrubbers is likely to be minimal (EGCSA, 2010).

Nitrate concentrations were measured in all three of the scrubber trials. Low nitrate concentrations (>146 μ g/L and 638 μ g/L) were measured in the Zaandam and the Pride of Kent washwater discharge. Onboard the Suula, a significantly higher con centration (<2,000 mg/L) was detected. However, since the IMO Guideline lim it of 60 mg/L for nitrate is normalized by the washwater discharge rate, the normalized nitrat e concentration of 9 mg/L is below the IMO Guideline (the Suula , using a closed scrubber system, disc harges bleed-off washwater at about 1/500 th of the customary rate for an open seawater scrubber).

Nitrate loadings from washwater disc harges can be calculated from the Pride of Kent and Suula EGCS trial data. Based on the average co ncentration increases between intake and discharge samples, the nitrate washwater loadi ng from the seawater scrubber EGCS on the Pride of Kent was 0.35kg NO 3 -N per day. The dissolved inorgani c nitrogen washwater loading was 0.53 kg N/d. The freshwater scrubber aboard the Suula generated a nitrate loading of less than 3.4 kg NO 3 -N per day.

6.5 S ULFATE , COD AND D ISSOLVED O XYGEN

Sulfate is an abundant and cons ervative component of seawat er; therefore, the discharge of this parameter does not repr esent a limiting factor for seawat er scrubbing. Studies and field testing confirm that the sulfate increase from exhaust gas scrubbing would be insignificant when compared with the quantity already in the oceans (Hassellöv and Turner, 2007 and Hufnagl, 2005). For example, washwater sampling aboard the Pride of Kent demonstrated that scrubbers added a negligible amount of sulfate.

When SO 2 is dissolved in water, a reaction occurs whereby the sulfur dioxide is ionized to bisulfite and sulfite, which is then readily oxidized to sulfate in seawater containing oxygen (Hassellöv and Turner, 2007). This process increa ses the COD, which could potentially have an adverse impact on aquatic systems. COD is a m easure of the theoretical oxygen consumption of a water sample (i.e., the amount of oxygen require d for degradation of the organic matter). There are no environmental standards for COD (MARINTEK, 2006).

Tolerance to reduced dissolved oxygen vari es between organisms, life stages and environmental conditions. The Norwegian Marine Technology Resrach Institute concluded that COD was not a matter of concern under the ci rcumstances of their study (MARINTEK, 2006). Using worse case scenarios, a study evaluated how much dilution of washwater would be required to return oxygen levels to within 1 perc ent of those of the ambient water. They foundExhaust Gas Scrubber Washwater Effluent Section 6 -Assessment of Pollutants Discharged in Scrubber Washwater and Protectiveness of IMO Guidelines

35 that if the pH of the washwater had already b een corrected to within 0.2 standard units of ambient values, then no further dilution would generally be required to maintain DO levels (Hassellöv and Turner, 2007)

It is known from various in-field tests and m odeling of discharge plumes that the pH and oxygen of discharged water very rapidly returns to that of the surrounding water, especially when the vessels is underway; t hus, the IMO does not require disso lved oxygen to be monitored (EGCSA, 2010).

6.6 M ETALS
Metals are a diverse group of pollutants, many of which are toxic to aquatic life and humans. While some metals, including copper, ni ckel, and zinc, are known to be essential to organism function, many others, including thallium and arsenic, are nonessentia l and/or are known to have only adverse impacts. Even essen tial metals can do serious damage to organism function in sufficiently elevated concentrations . Adverse impacts can include impaired organ function, impaired reproduction, birth defects, an d at extreme concentrations, acute mortality.

There are a number of sources for metals to enter the washwater in wet scrubber systems:

 System materials, typically iron, copper and zinc may be a source of metals. The reduced pH of washwater, which can be as low as pH 3 within the system, will increase the solubility of metal ions and th erefore the choice of materials is very carefully considered by exhaust gas cleaning system designers.

 System inlet water may contain metals f ound in seawater or from electrochemical protection to prevent fouling of seawater pipes and from antifouling paints (typically copper). Electrochemical protection is often installed at the inle t to seawater pumping systems to prevent the parasitic growth of organisms that may foul pipework, filters and coolers of ship’s machinery. An EGCS may take a washwater supply from a point with electrochemical protection, but will not ha ve a direct influence on it (EGCSA, 2010).

 The combustion of fuel and lubricant is an other source of metals , typically vanadium, nickel, calcium and zinc. Although it makes up a relatively small amount of the overall PM, ash represents the incombustible residu e of burning fuel oil and lubricant. The majority of fuel oil ash content consists of metal compounds that occur naturally in petroleum; principally vanadi um and nickel, which are oil soluble and so cannot be removed by onboard pre-treatment such as filtration and centr ifugal purification (EGCSA, 2010). These metals can also enter ecosystems from unscrubbed exhaust emissions into the atmosphere.

The IMO Guidelines do not contain any limits for the concentrations of metals in washwater discharge, although the IMO requests sh ip owners to sample and analyze washwater for a suite of metals. Turbidity is monitored as a surrogate for suspended solids. Presumably,Exhaust Gas Scrubber Washwater Effluent Section 6 -Assessment of Pollutants Discharged in Scrubber Washwater and Protectiveness of IMO Guidelines

36 turbidity values below the limit of 5 FTU/NTU indicate that the washwater treatment system is effectively removing particulates from the washwa ter, as well as particulate metals. Washwater samples taken from various points w ithin the scrubber system during the Pride of Kent trials showed that that the majority of metals were bou nd to particles or were particulates themselves and were effectively removed by the washwater treatment plant.

Monitoring conducted during scrubb er trials demonstrates th at metals are present at concentrations above EPA NRWQC for several metals, even though the washwater treatment plants were functioning and turbidity limits we re being met. The monitoring during scrubber trials also considered the contribution of metals detected in the washwater intake. Comparison of the metals measured in washwater discharged by the Zaandam during scrubber tr ials to the EPA acute and chronic NRWQCs suggest s that scrubbers may emit wash water with arsenic, copper, lead, nickel and selenium con centrations that could pose a ri sk to the environment. During scrubber trials aboard the Pride of Kent , copper, lead, nickel and zinc 11 were measured in washwater discharge at concentrations exceed ing NRWQCs. Washwater discharged by the Suula was reported to contain less than 60 mg /

L of total metals (the sum of cadmium, copper, nickel, lead, zinc, arsenic, chromium and vanadium). This concentration greatly exceeds the NRWQCs for any of these metals (or even the approximate ly 1 mg/L sum of the NRWQCs for all of these metals except vanadium); therefore, exceedances of NRWQCs for the several metals parameters, in each of the scrubber trials, suggest that scr ubbers may emit washwater with concentrations of metals that could pose a risk to the environment.

6.7 S UMMARY

A number of constituents found in EGCS wash water discharges have been evaluated to determine whether these discharges could cause an exceedance of any NRWQC. The protectiveness of the IMO Guideline washwater limits were also evaluated in terms of whether they adequately mitigate the potential for washwate r discharges to result in ecological or human health risk.

Based on this evaluation, several metals (inc luding arsenic, copper, lead, nickel and selenium) and PAHs (chrysene, benz(a)anthrace ne and benzo(a)pyrene) were measured in washwater discharges at end-of-pipe concentr ations that exceeded the NRWQC for that chemical. Accordingly, these parameters have th e potential to contribute to an exceedance of water quality standards on a localized scale. The IMO Guideline washwater limits intended to address turbidity and PAH-phenant hrene equivalents may not be sufficiently protective, based upon the available monitoring data (EGCSA, 2010).

The pH of EGCS washwater discharges ma y also be a concern, because wet scrubbing involves the transfer of SOx fr om exhaust gasses to washwater, which is accompanied by a

11 Zinc concentrations were suspected to be an artifact introduced by sample contamination.Exhaust Gas Scrubber Washwater Effluent Section 6 -Assessment of Pollutants Discharged in Scrubber Washwater and Protectiveness of IMO Guidelines

37 significant increase in acidity. The increased acidity must be neutralized, either by the natural alkalinity in seawater or by addi ng an alkaline chemical to freshwater. The monitoring data from scrubber trials onboard ships demonstrate that wa shwater neutralization is generally effective, although large volumes of reaction water may be required in open systems depending on the alkalinity of the water body. The IMO Guideline washwater limits for pH may be protective, both at sea and in confin ed harbors (EGCSA, 2010).

The IMO Guidelines require continuous measur ement of washwater tu rbidity to monitor the operation of the scrubber and the washwate r treatment system. For example, washwater turbidity declined from inlet to discharg e onboard one vessel conducting scrubber trials; however, it is not clear that m onitoring turbidity serves as a surrogate for other washwater constituents of concern (HA & H-K, 2010).

Total hydrocarbon concentrations in washwater discharges we re low or below detection in the scrubber trials, despite the observation of a visible sheen accompanied by sooty deposits in the washwater discharge plume in one of these tr ials. Two other washwater parameters, nitrate and sulfate, appear unlikely to cause a concern because the quantities of these parameters that have been measured in EGCS washwater discharg es should be readily assimilated in marine and estuarine receiving waters. In the case of nitrat e, most of the EGCS washwater loading (1 to 3 kg/d/vessel, based on monitoring dur ing trials) would be deposited to the receiving water via the atmosphere if scrubbers were not used 12

.

12 The nitrate in scrubber washwater is derived from the oxida tion of atmospheric nitrogen as well as nitrogen in fuel that occurs during combustion. As such, NOx and nitrate emissions are unaffected by the sulfur content of the fuel and switching to low-sulfur fuels will not reduce these emissions. Consequently, compliance with MARPOL Annex VI via the two SOx control strategies (fuel switching and EGCS) result in roughly comparable loadings of nitrate to receiving waters (see calculation and discussion of Baltic Sea nitrate load ing in Section 6.4).Exhaust Gas Scrubber Washwater Effluent Section 7 - Acronyms

38 

## SECTION 7
ACRONYMS

Organizations and Associated Initiatives

AEA AEA Energy & Environment Consulting Group
DNV Det Norske Veritas EGCSA Exhaust Gas Cleaning Systems Association
EPA Environmental Protection Agency MEPC Marine Environment Protection Committee MARPOL International Convention for the Pr evention of Pollution From Ships SECA Sulfur Oxide Emission Control Area EU European Union IMO International Maritime Organization NRWQC National recommende d water quality criteria GESAMP Group of Experts on the Scientif ic Aspects of Marine Environmental Protection VGP Vessel General Permit ETM EGCS Technical Manual CORMIX Cornell Mixing Zone Expert System OSPAR Administrator of the Oslo and Paris Conventions for the protection of the marine environment of the northeast Atlantic

Chemical abbreviations
SOx Sulfur oxides (SO 2 and SO 3 ) NOx Nitrogen oxides (NO and NO 2 ) PAH Polycyclic aromatic hydrocarbon BETX Benzene, toluene, ethylbenzene and xylene PAHphe Polycyclic aromatic hydrocarbon ph enanthrene equivalence concentration TPH-D/G Total petroleum hydrocarbon –diesel and gasoline components DIN Dissolved inorganic nitrogen THC Total hydrocarbon TKN Total Kjeldahl nitrogen HEM Hexane extractable material COD Chemical oxygen demand TSS Total suspended solids

Units of measure
MGD Million gallons per day MW MegawattExhaust Gas Scrubber Washwater Effluent Section 7 - Acronyms

39 MWh Megawatt-hour PPB Parts per billion t Metric ton FNUkt Formazin nephlometric units Kilotons NTUFNU Nephlometric turbidity un its Formazin nephlometric units NTU Nephlometric turbidity units EGCS Exhaust gas cleaning system PMEGCS Particulate matter Exhaust gas cleaning system PECPM Predicted environmental c oncentration Particulate matter PNECPEC Predicted no effect concentration Predicted environmental concentration EACPNEC Ecotoxicological assessment crite ria Predicted no effect concentration GC-MSEAC Gas chromatography-mass spectrometry Ecotoxicological assessment criteria AWPGC-MS Advanced wastewater purifica tion Gas chromatography-mass spectrometry MSAWP Motor ship Advanced wastewater purification MS Motor shipExhaust Gas Scrubber Washwater Effluent Section 8 - References

40 

## SECTION 8
REFERENCES

AEA. 2009. Cost Benefit Analysis to support th e impact assessment accompanying the revision of Directive 1999/32/EC on the sulfur content of certain liquid fuels . Report to European Commission by AEA, Association ASPEN and Swedish Environmental Research Institute. (http://ec.europa.eu/envi ronment/air/transport/pdf/CBA_of_S.pdf)

Aalborg. 2010. EGCS SMM Workshop 2010 presentation (http://www.aalborgindustries.com/scrubber/docum ents/ExhaustGasCleaning_000.pdf)

Behrends, B. and G. Liebezeit. 2003. A Theoreti cal Environmental Impact Assessment of the Use of a Seawater Scrubber to Reduce SOx and NOx Emissions from Ships. Research Centre Terramare. Wilhelmshaven, Germany.

Couple Systems. 2010. Dry EGCS Proce ss Dry Exhaust Gas Cleaning System (http://www.egcsa.com/pdfs/Couple- Systems-EGCS-SMM-Workshop-2010.pdf).

DNV. 2009. Exhaust Gas Cleaning System (EGCS) (http://www.dnv.lt/binaries/Exhaust%20G as%20Cleaning%20System%20%28EGCS%2 9_tcm173-392685.pdf)

EGCSA. 2010. Exhaust Gas Cleaning Systems Asso ciation web site (http://www.egcsa.com/thescience.php), accessed September 3, 2010.

Entec. 2005. European Commission Directorate General Environmen t, Service Contract on Ship Emissions: Assignment, Abatement and Mark et-based Instruments, Task 2c – SO 2 Abatement Final Report. August 2005. Entec UK Limited.

Filancia, A. 2009. Reducing Emissions from Sh ipping, Wärtsilä’s Solutions. Presented at Sustainable Shipping Conference 2009. San Francisco, California. (http://www.sustainableshippi ng.com/events/2009/sanfrancisc o/Presentations/Filancia/fil ancia.pdf).

Gregory, D. 2010. SMM 2010. Hamburg, Germany. September 8-9, 2010 (http://www.egcsa.com/pdfs/EGCSA-Ov erview-EGCS-SMM-Workshop-2010.pdf).

Hartmann, P.C. and J.G. Quinn. 1999. Partitioning of Pyrogenic and Petrogenic Polycyclic Aromatic Hydrocarbons in Narragansett Bay Sediments, Ninth Annual V. M. Goldschmidt Conference, 1999.

HA & H-K. 2010. Holland America Line Sea Wa ter Scrubber Technology Demonstration Project. Final Report by Holland Americ a and Hamworthy-Krystallon to U.S. Environmental Protection Agency. March 31, 2010. (http://www.hollandamerica.com/assets//about -best-cruise-lines/F inal_report.pdf).Exhaust Gas Scrubber Washwater Effluent Section 8 - References

41 Hassellöv, I.M. and D. Turner. 2007. Seawater scr ubbing - reduction of SOx emissions from ship exhausts. The Alliance For Global Sustainability. Gothenburg, 2007.

Hatley, J.F. 2010. SOx Regulations and Principles/Economics of Scrubbers. Presented at the 74th Annual International Joint Conference of the Canadian Shipowners Association and the Lake Carriers’ Association. Niagar a on the Lake, Ontario. June 20-21, 2010. (http://www.shipowners.ca/uploads/I NTENATIONAL%20JOINT%20CONFERENCE% 20-JUNE%202010/7%20John%20Hatley.pdf).

Henriksson, T. 2007. SOx scrubbing of marine exhaust gases. WÄRTSILÄ Technical Journal. February 2007.

Hufnagl, M., Liebezeit, G. and B. Behrends. 2005. Effects of Sea Wate r Scrubbing, Final Report to BP Marine. Research Ce ntre Terramare, Wilhelmshaven, Germany and School of Marine Science and Technology, University of Newcastle, Newcastle upon Tyne, UK. March 2005.

Jirka, G.H., Doneker, R.L. and S.W. Hinton.1996. User's Manual for CORMIX: A Hydrodynamic Mixing Zone Model and Deci sion Support System for Pollutant Discharges into Surface Waters. Office of Science and Technology, U.S. Environmental Protection Agency. September 1996.

Kehoe, J., Nikopoulou, Z. and M. Liddane. 2010. Imp act Study of the Future Requirements of Annex VI of the MARPOL Convention on S hort Sea Shipping. SK EMA consortium, a project supported by the European Commi ssion Directorate-General for Energy and Transport. (http://www.eskema.eu/de faultinfo.aspx?topicid=189&index=1).

MARINTEK. 2006. MARULS WP3: Washwater Cr iteria for Sea Water Exhaust Gas SOx Scrubbers. Prepared by the Norwegian Marine Technology Research Institute (MARINTEK) for the Norwegian Shipowners’ Association/Research Council of Norway. November 2006. (http://prosjekt.marintek.s intef.no/maruls/documents/R eport%20Scrubber%20washwater %20WP3.pdf).

MEPC. 2008. 58/23 Annex 16, Report of the Mari ne Environment Protection Committee on its fifty-eighth session. Internati onal Maritime Organization, 2008.

Motorship Newsletter. 2010. Breakthrough orde r for Krystallon scrubbers. June 11, 2010 (http://www.motorship.com/n ews101/breakthrough-order-fo r-krystallon-scrubbers).

Orr, J.C. et al. 2005. Anthropogenic ocean acidif ication over the twenty-f irst century and its impact on calcifying organisms. Nature. 437, 681-686.

SINTEF. 2006. Marine Use of Low Sulfur Heavy Fuel Oil, WP3 Wastewater Criteria, Dispersion Modeling. SINTEF Materials and Chemistry. Brattørkaia, Norway. May 29, 2006.Exhaust Gas Scrubber Washwater Effluent Section 8 - References

42 SSG. 2007. SOx scrubbing of marine exhaust gases. Scandinavian Shipping Gazette. 18/2007. (http://www.shipgaz.com/old/magazi ne/issues/2007/18/1807_article1.php)

USEPA. 1976. Quality Criteria for Water (Red Book). US Environmental Protection Agency. July 1976. Pb-263 943.

USEPA. 1991. Technical Support Document fo r Water Quality-Based Toxics Control. EPA/505/2-90-001. U.S. Environmental Pr otection Agency. Washington, D.C.

USEPA. 2005. National Recommended Wa ter Quality Criteria (Table). (http://water.epa.gov/ scitech/swguidance/standard s/current/index.cfm).

USEPA. 2008 Final Issuance of National Pollut ant Discharge Elimination System (NPDES) Vessel General Permit (VGP) for Discharges Incidental to the Normal Operation of Vessels: Fact Sheet. U.S. Environmental Protection Agency.

USEPA. 2009a. Regulatory Impact Analysis: C ontrol of Emissions of Air Pollution from Category 3 Marine Diesel Engines. Asse ssment and Standards Division, Office of Transportation and Air Quality, U.S. Envir onmental Protection Agency. December, 2009. EPA-420-R-09-019.

USEPA. 2009b. Vessel General Permit (VGP). U.S. Environmental Protection Agency. Version 2/5/2009. (http://www.epa.gov/npde s/pubs/vessel_vgp_permit.pdf).

USEPA. 2010a. Study of Discharges Incidental to Normal Oper ation of Commercial Fishing Vessels and Other Non Recreational Vessels less than 79 feet. Report to Congress. (http://cfpub.epa.gov/npdes/ve ssels/reportcongress.cfm).

USEPA. 2010b. Designation of North American Emission Control Area to Reduce Emissions from Ships: Regulatory Announc ement. EPA-420-F-10-015, March 2010 (http://www.epa.gov/oms/regs/ nonroad/marine/ci/420f10015.htm).

Wärtsilä. 2007. Reference sheet for Se nitec M-Series. Accessed August 1, 2010. (http://www.wartsila.com/Wartsila/sweden/doc s/locals/sweden/solut ions/Finnclipper.pdf)

Wärtsilä. 2010. Public test repo rt, exhaust gas scrubber installe d onboard MT “Suula”. Wärtsilä Finland Ecotech Scrubber Project Team. June 20, 2010. (http://www.ciserv.com/Wart sila/global/docs/en/servi ce/Leaflets/enviro/Scrubber Test_Report_onboard_Suula.pdf)

Waterco. 2010. MultiCyclone for Cooling Towers (http://www.waterco.eu/installations/watertreatment-installations?ptitle=multicyclone -for-cooling-towers_39) , accessed November 10, 2010.