# NEW TECHNOLOGIES FOR
CONTROLLING
OILY BILGE WATER DISCHARGES

Presented at the Marine Environmental Engineers Technology Symposium (MEETS) May/June 2001

Author: Hal Alper

1

### Hal Alper



# New Technologies for Controlling Oily Bilge Water Discharges

ABSTRACT

US m ilitary vessels are lim ited to oily bilge water discharge concentration of 15 ppm under 40 CFR part 1700, uniform national discharge standards (UNDS). International com m e rcial discharge standards appear to be stabilizing at 5

ppm . In order for these regulations to have the desired effect of reducing oily bilge water discharge, im provem e nts in treatm e nt technology and enforcem ent m u st take place. This paper reviews developm ents in treatm e nt of oily bilge water and detection of oily discharge
from ships. New technologies developed to bridge the gap between oil/water separator (OWS) capability of approxim a tely 250 ppm and discharge standard of at m o st 15 ppm are covered, with em phasis on cross flow m e m b rane filtration technologies and oleophilic poly m eric surfactant (PS) infused filtration devices. Developm ents in detection of oily discharge utilizing sy nthetic aperture radar (SAR) and enhanced tracking procedures are also reviewed.



## INTRODUCTION

Of the oil released by vessels, 25% is reported to

com e from spills and 75% from operational discharges. Oily bilge discharge is second only to oily ballast tank discharge in its contribution. Historically , oily bilge water has been treated using oil/water separator (OWS) technology or discharged with m i nim a l treatm e nt. OWS technology alone is not capable of m eeting current oily bilge water discharge standards. Discharge standard for vessels of the United
States arm e d forces under 40 CFR part 1700, is 15 ppm . International com m e rcial discharge standards are as low as 5 ppm . A variety of technologies have risen to fill the gap between OWS capability and discharge standards.
Am ong these are sy stem s based on gravity separation, size separation, chem ical affinity separation and flocculation. There has also been a gap between regulation and enforcem ent. Unregulated discharges have been problem atic. There have been significant advances in the ability to detect such di scharges in the past few

y ears; the m o st significant of which is sy nthetic aperture radar (SAR). We will review OWS technology and developm ents in oily bilge water

treatm e nt and detection. For purposes of this paper we will consider engine wet exhaust

treatm e nt as sim ilar to bilge water.



## REGULATION

Section 312 of the CWA requires the Secretary
of Defense and the adm i nistrator of the U.S.
Environm ental Protection Agency (USEPA) to develop uniform national standards to control certain discharges from vessels of the arm e d
forces. These m easures are im plem ented in 40 CFR. Chapter VII and Part 1700, entitled
Uniform National Discharge Standards (UNDS).

The following discharges require Marine Pollution Control Devices (MPCD):

Aqueous Film -Form i ng Foam Catapult Water Brake Tank and Post-Launch
Retraction Exhaust
Chain Locker Effluent
Clean Ballast
Com p ensated Fuel Ballast Controllable Pitch Propeller Hy draulic Fluid
Deck Runoff Dirty Ballast
Distillation and Reverse Osm o sis Brine
Elevator Pit Effluent
Firem a in Sy stem s Gas Turbine Water Wash Gray water Hull coating Leachate



### 2Motor Gasoline Com p ensating Discharge Non-oily Machinery Wastewater Photographic Laboratory drains Seawater Cooling Overboard Discharge Seawater Piping Biofouling Prevention
Sm all Boat Engine Wet Exhaust
Sonar Dom e Discharge
Subm arine Bilgewater Surface Vessel Bilgewater/Oil-Water Separator Discharge Underwater Ship Husbandry Welldeck Discharges

We will address oily bilge water discharge with

som e discussion of sm all boat engine wet exhaust discharge. Discharge lim it for oily bilge water under UNDS is 15 ppm but the need to
have environm entally sound ships extends bey ond U.S. coastal waters. European countries and other countries with large coastlines (i.e. Japan, New Zealand) have been very active in the pursuit of elim inating operational discharges in conjunction with International Maritim e Organization (IMO) and independently in som e

areas.



### Nature of Discharge (NOD)

Bilge water arises from a variety of sources, which are allowed to drain to the lowest part of the ships' hull, known as the bilge. Sourcesinclude valve and piping leaks, boiler blowdown, and condensed steam . On surface vessels, bilge water is usually transferred to a holding tank where it is stored for disposal or treated in an OWS before being discharged. Oily bilge
water contains bio-accum u lative persistent organic pollutants (POP' s ) such as poly a rom a tic hy drocarbons and chlorinated arom atic hy drocarbons, arom atic hy drocarbons (BTEX) and oil, copper, iron, m e rcury , zinc and nickel,
in addition to em ulsify ing agents such as detergents and solvents.



## TREATMENT

Gravity Separation-OWS Technology

In the past, OWS have been used exclusively for

treatm e nt of oily bilge water (OBW) however this technology is unable to m eet the 15 ppm requirem e nt. Many OWS sy stem s on cruise and naval ships produce an effluent in the average range of 100-250 ppm . Ships equipped with oil

content m onitors (OCM' s ) have the ability to return bilge water, not m eeting discharge standards to the OWS for reprocessing.

The effluent concentration after OWS is m o re a

m easure of the degree of em ulsification of the influent than of the efficiency of the OWS. With 100% non-aqueous phase pollutants, OWS are capable of achieving quite low effluent
concentrations. All OWS’ s work based on gravity separation driven by density differences. If the suspended particles or droplets have effectively neutral buoy ancy , OWS ceases to be effective. Additionally OWS’ s are ineffective in

rem oving colloidal m e tals and soluble

com pounds. By definition, these are close to or at neutral buoy ancy . We m u st look for other properties to exploit in order to achieve the desired reduction of pollutants in bilge water. The technologies discussed below can all be considered post OWS polishers, as OWS technology is optim al as a first step for bulk

rem oval of non-aqueous phase com ponents.



### Siz e Separation – Membrane Technology

Cross Current Flow Mem b rane technologies essentially work as m o lecular sieves and have been used to produce pure water in m unicipal and industrial applications. Cross flow operations ty pically fall into three categories:

Ultrafiltration (UF), Nanofiltration (NF), Hy perfiltration, m o re com m only known as
Reverse Osm o sis (RO) with the following particle size and m o lecular weight ranges.

RO – 5 to 15 angstrom s 100 to 300 MW

Com ponents Retained: 99% of m o st ions,

m o st organics over 150 MW

Process Applications: Brackish sea water, Desalting, boiler feed purification,



### 3blowdown reclam ation, pretreatm e nt to ion exchange, ultrapure water production.

NF – 10 to 80 angstrom s 200 – 10,000 MW

Com ponents Retained: 95% divalent ions,
40% m onovalent ions, organics greater than
150-300 MW

Process Applications: Hardness rem oval, organic and m i crobiological rem oval, dy e desalting, color rem oval

UF – 100 to 1000 angstrom s 1,000 – 100,000 MW

Com ponents Retained: Most organics over
1000 MW

Process Applications: Pre- and posttreatm e nt ion exchange, beverage clarification, concentration of industrial organics and dilute suspended oils, rem oval of py rogens, bacteria, viruses, and colloids.

The m o st com m only used of these is Reverse
Osm o sis due to its highest capability for rem oval
of dissolved im purities. There are four m a jor configurations for m e m b rane m odules: plate and
fram e units, hollow fiber, tubular and spiral
wound. Mem b ranes are available in a variety of

m a terials. Som e com m on ones are cellulosic and poly a m i de for RO and NF and poly s ulfone,

ceram ic and fluorinated for UF. UF has

m o lecular weight cutoff of 1,000 to 100,000. Pressure ranges are UF – 25 to 400 psi, RO and NF operate in the 500 to 1000 psi range. Crossflow is necessary in m e m b rane sy stem s due to the necessity of running continuously in a self-cleaning m ode. This is due to the fact that even a tiny fraction of foulant m ass can have a
severe effect on m e m b rane perform ance. Backwashing is not possible because the poly m eric m e m b rane is coated onto a support lay e r. Flow reversal causes separation of

m e m b rane from support lay e r. All cross flow

sy stem s separate the influent wastestream into
two effluent stream s. These are the perm eate (purified water which has passed through the

m e m b rane) and concentrate (pollutants rejected by m e m b rane) which m u st be continuously flushed away

.

The inherent tendency of m e m b ranes to catch all
but the sm allest particle sizes renders them susceptible to fouling by organic, inorganic and biological m a terials. Cross current flow does not suffice in keeping the m e m b ranes clean and so they m u st be periodically cleaned. This can be tricky business, as m e m b rane chem ical

com p atibility m a y be sim ilar to those of the fouling agent, in which case, the cleaner will
also dissolve the m e m b rane. Short of dissolution, m e m b ranes can be denatured by solvents, high or low pH' s and tem p erature

extrem es. At the very least, m e m b rane / cleaner

com p atibility m u st be tested. It is unlikely that

m e m b rane cleaning will ever be totally
elim inated even with the use of low
concentrations of chem ical cleaning agents in the process stream (Ning). Effective pre-filtration of particulate and
chem ical fouling agents should be considered when designing a m e m b rane filtration sy stem

.

Currently , Ultrafiltration (UF) has been the prim ary m e m b rane technology utilized in post OWS bilge water polishing. RO and UF

m e m b ranes are susceptible to organic and inorganic fouling. UF sy stem s are not fine enough to capture ionic pollutants and therefore inorganic fouling has not been an issue. UF

sy stem s are able to capture m o st organic

com pounds over 1000 m w and are consequently susceptible to organic fouling.

Ceram i c m odule ultrafiltration sy stem s have been tested and used on naval ships for

treatm e nt of OBW with generally good results. The sy stem s are able to achieve a reduction from approxim a tely 232 ppm to < 5 ppm at flow of about 5 gallons per m i nute (GPM). Ceram i c UF

sy stem s require periodic cleaning and

m a intenance and can be overwhelm ed by concentrated slugs of influent, however they are

m o re robust than m o st poly m eric m e m b ranes and can withstand wider pH and tem p erature ranges therefore m a king cleaning easier. Better pre-filtration of organics (especially concentrated slugs) would probably m a ke the

sy stem m o re efficient and m o re cost effective.



### 4

### Chemical Affinity Separation-PS Technology

Chem ical Affinity Separation involves the use of
standard filter m a terials infused with curable poly m eric surfactant (PS). Once cured into a substrate, the oleophilic properties of PS are transferred into a substrate, thereby greatly enhancing its' ability to attach organic

com pounds to its' m a trix. Once attached, these

com pounds becom e hy drophobic and tend not to
re-release.

Regular 5-m i cron m e lt-blown poly p ropy lene (MBPP) filters treated with curable viscoelastic
PS results in a filter sim ilar in capability to cross flow UF m e m b ranes for rem oval of organic

com pounds and colloidal m e tals. PS infused filters exhibit less than 1 psi pressure drop
across the filter to saturation. (See Figure 1 and Table 1)

Ta ble 1

Removal of Col l o i d al Metal s

MYCELX

Cadm ium

, I C P <0. 020
Chr o m i um , I C P 0. 026 Copper

, I C P 0. 351 Lead, ICP <0.10 Nickel, I C P <0. 050
Silver

, I C P <0. 020

Z i nc, I C P <0. 020

After Floccu lation

Cadm ium

, I C P <0. 020
Chr o m i um , I C P 0. 070 Copper

, I C P 0. 452 Lead, ICP <0.10 Nickel, I C P 0. 052
Silver

, I C P <0. 020

Z i nc, I C P 0. 884

Holding Tanks

Cadm ium

, I C P <0. 020
Chr o m i um , I C P 0. 062 Copper

, I C P 1. 0

L ead, I C P 0. 12 Nickel, I C P 0. 060
Silver

, I C P <0. 020

Z i nc, I C P 3. 1

All Test s EP A Met h od 200. 7 Pressure Drop Anal ysi s Fi gure 1

∆ P vs. % Saturation

This is a critical property that enables PS to capture concentrated slugs of oil without clogging the sy stem , therefore m a king themuseful as prefilters for m o re sensitive and therefore easily
fouled filtration m e thods.

PS technology works by chem ically im m obilizing the pollutants into the filter m a trix. The filters can be regenerated and the o il recovered water free by centrifugation up to 100 tim es. This technology
has been utilized in m u ltiple oily bilge applications in different way s , two of which are highlighted below.



### PRIMARY POLISHING TREATMENT

The pictured unit in figures 2, 3 and 4 is a MX-22 PS Technology device. It contains (22) 30-inch length, 5-m i cron MBPP filters infused with PS. This unit sees an average of 250 ppm post OWS effluent and discharges less than 1 ppm effluent in a single pass, even when periodically exposed to slugs as concentrated as 10,000 ppm . This

sy stem has been used for one y ear and has required only 1 filter set changeover. Spent filters are regenerated by centrifugation. Discarded filters are incinerated. (See Figures 2-4) It is an interesting property of PS technology that high oil loading im proves its' ability to capture highly

em ulsified oils and colloidal m e tals. PS filters are not capable of capturing m e tals that are not organically bound.



### 5Figure 2

Figure 3

Fi gure 4

Trea tment o f Oily Bilg e Wa ter o n Oil Drilling Ship Fi gure 5

Cruise Ship Oily Bilge Water



### SECONDARY POLISHING

This trial was conducted in conjunction with a

m a jor cruise line on its' fl agship vessel. The ship is equipped with a clay filter followed by two OWS in series and an oil content m onitor.
Effluent is re-circulated until a concentration of 15 ppm is achieved.

A PS MX-12 unit (twelve 30” 5 m i cron filters) was installed post OWS to assure a m a rgin of safety before discharge. To date, this sy stem has processed 99,000K gallons of 15 ppm bilge water in 3 weeks (~ 4000K gal/day ) and discharge
concentration has rem a ined below 1 ppm . One filter set replacem ent has been required. Approxim a te quantity of oil rem oved was 15 lbs.



### PRETREATMENT TO ENHANCE
MEMBRANE PERFORMANCE

A third ty pe of use for PS MX units which is being field tested for industrial applications but is also applicable to oily bilge applications is in pre-filtration to enhance the robustness and perform ance of m e m b rane filtration sy stem s. As stated earlier these sy stem s are susceptible to organic and m e tallic colloid fouling. The ability of PS units to absorb concentrated slugs without breakthrough or pressure drop m a kes them ideal
chem ical prefilters to work in conjunction with

m e m b rane sy stem s. Most of the tim e the

m e m b rane will see clean water greatly reducing fouling and preserving capacity . The m e m b rane



### 6capacity is conserved for NF or RO range pollutants. Prelim inary results indicate that

m e m b rane life is extended about 20 fold while operating costs are reduced by 50%.

Fi gure 6

Composite Unit

We feel that sim ilar im provem e nts would be
realized in UF m e m b rane bilge sy stem s currently in use. It is interesting to note, contrary to our expectations, that OBW we have encountered has not been sufficiently em ulsified to require NF or RO polishing post PS MX
filters. In m o st cases post PS effluent is BDL (below detectable lim its). It appears that

m easures taken to segregate em ulsifiers from OBW are having an effect.



### OTHER METHODS

Various other m e thods ha ve been developed for bilge water treatm e nt. I will briefly m e ntion
these.

- OWS / flocculation – these sy stem s follow
OWS with flocculate in treatm e nt tanks followed by additional filtration of effluent

to rem ove the flocculating agent. Flocculating agent is then dewatered.

- Biological – m echanical separator followed by a biological cham ber consisting of oil eating m i crobes supported in m a trix. Microbe sy stem s have lacked “robustness” in the past.

- Em ulsify ing agents, which render oil digestible to m i crobes.

- Burning after heating and vapor separation. 

### EXHAUST METHODS

Exhaust gas discharge can contain m a ny of the pollutants present in bilge water including BTEX, m e tals, diesel and oils. Exhaust discharge directly into the water has becom e a significant waste m i nim i zation initiative. PS infused filters have been used to polish wet exhaust processed through water separation devices resulting in effluent less than 1 ppm concentration. Figure 7 is a schem atic of process flow for this sy stem . When treated this way

, wet exhaust polluted water can essentially be looked at as another source of bilge water. 1- 5ppm < 1ppm 250ppm

OWS PS RO

Fi gure 7

Wet Exhaust Treatment System



## DETECTION OF DISCHARGES

The need to have environm entally sound ships extends bey ond US coastal waters as European countries and other countries with large coastlines (i.e. Japan, New Zealand) have been

very active in the pursuit of elim inating operational discharges in conjunction with
International Maritim e Organization (IMO) and independently in som e areas.

One of the areas in which European and other foreign countries have been very active in is
detection and enforcem ent. The developm ent of Sy nthetic Aperture Radar (SAR) has m a de it possible to detect surface or dissolved oil day or night under a variety of weather conditions discharged above or under the surface. Sy nthetic aperture radar as the nam e im plies does not



### 7actually use a lens like conventional sy stem s. The aperture is actually the arc described by an orbiting satellite in a given period of tim e. Sensors m onitor scattered electrom a gnetic
reflections in this tim e period and a com puter im age is generated. One of the interesting properties of the SAR is that higher resolutions can be achieved at greater distances due to larger lens (arc) radius.

The European space agen cy has been working on oil detection at sea using its SAR, ERS1 and ERS2 (European Rem o te Earth Sensing Satellites). These satellites have successfully been able to detect test and real spills and have been used for observing discharge trends.

A study of 660 SAR im ages acquired over the southern Baltic, the North Sea and the Gulf of Ly on in the Mediterranean Sea by ERS2 taken
since 1996 indicates that seas are m o st polluted along the m a in shipping routes. SAR im ages acquired during descending (m orning) and ascending (evening) satellite passes show different percentages of oil pollution, because

m o st of the pollution occurs during night tim e and is still visible on the SAR im ages acquired
in the m o rning tim e. The fact that m o st discharges occur at night is a strong indicator of
the need for effective m onitoring.

Japan has deploy ed a SAR sy stem since 1991 consisting of x-band (9.55 GHz) and L-Band (1.27 GHz) resulting in high-resolution im ages. The purpose of CRL/NASDA is to m onitor
earth’ s environm ent and disasters. The United States hy perspectral NEMO satellite will also have the ability to detect oily discharges. In the past, other m e thods have been tested such as the use of an infrared line scanner coupled with side looking airborne radar (SLAR) to detect oil discharges from ships (ISOWAKE experim e nts),
with m i xed results.

Much work has been done up to now to detect illegal ocean discharges. It appears that SAR

sy stem s will be able to provide a higher level of
detection and enforcem ent than was possible until recently . Besides satellite observation, other ty pes of m easures are also being
considered. One idea would be to use a black box operating on the basis of probes to indicate the level and nature of the liquids ejected. The
International Maritim e Organization (IMO) is study ing the possibility of equipping passenger ships with a black box to record safety -related

param e ters so as to determ ine the cause of accidents, as is the case onboard aircraft. The
aim is to supplem ent this ty pe of equipm ent with
“environm ental indicators”. A second idea
would be to m a rk cargoes, or the fuel, with a coloring to ensure traceability and to be able to work back to the polluting vessel. A com puter

sy stem for keeping tabs on shipping traffic is being put through its paces at the regional safety
and em ergency center (CROSS) in Jobourg (Manche). This sy stem could be used to identify polluting vessels by spotting the whereabouts of oil slicks in relation to the route followed by ships. This approach could be used to

com p lem e nt the two other solutions.



## DISCUSSION

Both enforcem ent and technology capable of

m eeting discharge standards are necessary to reduce oil pollution caused by ships. It appears that detection and tracking technology and the political desire to enforce regulations will m a ke
it m u ch m o re difficult in the near future to discharge oily bilge water that is not in

com p liance with local standards. Although we prim arily discussed the results of SAR im aging,
there are m u ltiple local efforts under way ranging from aerial surveillance utilizing
infrared line scanners to utilization of m o re conventional satellite detection sy stem s.

Regarding treatm e nt technologies, the ultim ate oily bilge water treatm e nt technology has probably not y e t been built. All the technologies

m e ntioned in this article have their good points and weaknesses. Processes sensitive enough to capture highly em ulsified or dissolved organic

com pounds are susceptible to fouling, requiring

m a intenance and expense. Conversely

, processes that are not susceptible to clogging are not capable of alway s capturing the m o st highly

em ulsified or dissolved organic com pounds.



### 8The optim al sy stem m u st be sensitive y e t robust. This probably im plies a 2 to 3 stage sy stem , as adequate protection of sensitive com ponents is probably a critical elem ent in overall sy stem robustness. It is also possible that OWS could be

m a de m o re efficient by rendering collecting
surfaces m o re oleophilic thereby reducing the need for pre-filtration.

The author does not believe that em ulsify ing agents which carboxy late paraffins thus rendering them digestible to m o st m i crobes is a prudent way to go, although probably the m o st facile. Use of these m a terials will ultim ately alter nutrient balance especially in fresh water, thus leading to m u ch faster eutropification.



## CONCLUSION

The im portance of treating OBW is illustrated by the num ber of technologies that have developed to treat this waste stream

. The ultim ate oily bilge water treatm e nt sy stem probably has not been built y e t and will m o st likely be a com posite utilizing m u ltiple technologies. Detection of oily discharges and the ability to track to specific ships will probably
becom e a reality regarding enforcem ent within the next 5 y ears.



## REFERENCES

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Tom pkins, K. T., L. P. Murphy , B. L. Owsenek, R. P. Pignataro, A. T. Rodriguez, “Ultrafiltration
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### 9Instrum e nts”, Conference Paper: EUSAR 1998, European Conference on Sy nthetic Aperture Radar, Friedrichshafen, Germ any , May 1998.



## ACKNOWLEDGMENTS

Jackie Pardue, Cortney Hoagland, Dave Hilbig, Fikret Kipcakli Hal Alper is the author and is President of MYCELX Technologies Corporation in Gainesville, GA. Mr. Alper received his training
in chem istry at Cornell University and has
authored num erous patents in a variety of
chem istry related fields.



### 10