water treatment.pdf

7/22/2019 Water Treatment.pdf

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STATE OF THE ART WASTE WATERSTATE OF THE ART WASTE WATER

TREATMENT PLANT WITHTREATMENT PLANT WITH

INNOVATIVE SOLUTIONS FORINNOVATIVE SOLUTIONS FOR

BAPCO REFINERY BAHRAINBAPCO REFINERY BAHRAIN

Authors:Authors:

GlenGlen DaiggerDaigger, Si Givens, Mauro Marinetti, Carlo, Si Givens, Mauro Marinetti, Carlo ZaffaroniZaffaroni(CH2M Hill)(CH2M Hill)

Savas Soydaner, David Smith, ManoSavas Soydaner, David Smith, Mano VenkatVenkat, Ali, Ali RedhaRedhaAwadhAwadh,, EbrahimEbrahim MahdiMahdi (BAPCO).(BAPCO).


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IntroductionIntroduction

BapcoBapco identified a need to install secondary treatment to improveidentified a need to install secondary treatment to improvethe quality of the waste water being discharged from the Refinerthe quality of the waste water being discharged from the Refinery toy tothe Gulf.the Gulf.

At present the waste water undergoes primary treatment in a systAt present the waste water undergoes primary treatment in a systememwhich consists of American Petroleum Institute (API) oil separatwhich consists of American Petroleum Institute (API) oil separatorsorsfollowed by Induced Air Flotation (IAF) units.followed by Induced Air Flotation (IAF) units.

BapcoBapcoss waste water was considered a challenge to treat becausewaste water was considered a challenge to treat because

of:of: high temperaturehigh temperature

high and variable salinityhigh and variable salinity

stringent water quality regulations.stringent water quality regulations.

Initially the use of a process based on physicalInitially the use of a process based on physical--chemical treatmentschemical treatmentswas considered a possibility because there was no definitivewas considered a possibility because there was no definitivereference in the literature to indicate that the waste water witreference in the literature to indicate that the waste water with theseh thesecharacteristics was treatable biologically.characteristics was treatable biologically.


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Introduction (ContIntroduction (Contd)d)Biological secondary treatment was favored because of its lowerBiological secondary treatment was favored because of its lowercost.cost.

Biological secondary treatment has been common practice for aBiological secondary treatment has been common practice for along time in Oil Refineries because of the high flow rates and tlong time in Oil Refineries because of the high flow rates and thehenature and concentration of the contaminants.nature and concentration of the contaminants.

This presentation describes how and why the biological processThis presentation describes how and why the biological processtechnology that will be used in the new plant was selected.technology that will be used in the new plant was selected.


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Application of Waste Water TreatmentTechnologies Based on Flow and COD

Concentration

The range of different wastewater treatment methods

1

10

100

1000

0.1 1 10 100Chemical Oxygen Demand (COD), g/l

Wastewater,m3/h

Wet oxidation

AdsorptionCombustion

Biology

Ozone technology

BAPCO


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Discharge SpecificationsDischarge Specifications

1 Discharge specification: severe specifications on 4

different nitrogen forms (TKN,N-NH4, N-NO3, N-NO2);

combined with specificationson organic carbon (COD, TOC,BOD);

2 Waste water (WW)composition out of

existing units: high salinity

carbon nitrogen combination

proper for a biological system

3 - Large hydraulic flow:27,300 m3/d(9,950,000 m3/y)

Effluent specifications as required by EWP

Pa ram eter Un its

Final Effluent

Specification

Mo nthly Average (a )

Final Effluent

Specification

Maximum (b )

General Properties

pH - 6 to 9 N ot sp ecified

F

(C)

Total Suspended So l ids mg/ l 20 3 5

Turbidity NTU 25 7 5

BO D mg/ l 25 5 0

C OD mg/ l 150 350

Total Kjeldahl Nitrogen mg/ l 5 10 Oil and Grease mg/ l 8 1 5

Phenols mg/ l 0.5 1

Total Coliform s MPN /100m l 1000 10000

T OC mg/ l 50 -MBAS mg/ l 0.1 0.1

Inorganic

Oxygen mg/ l N ot specified N ot sp ecified

Am monia n i trogen a s N mg/ l 1 3

Sulfide as H 2S mg/ l 0.5 1

Residual Chlorine mg/ l 0.5 2

Cyanide as CN mg/ l 0 .0 5 0.1

Chloride as NaC l mg/ l N ot specified N ot sp ecified

Nitrate [NO 3] N mg/ l N ot specified 1 0

Nitrite [NO 2] N mg/ l N ot specified 1

T otal phosphorus mg/ l 1 2

M etals

Aluminum mg/ l 15 25

Arsenic mg/ l 0.1 0.5

Cadmium mg/ l 0 .0 1 0 .05

Total Chromium mg/ l 0.1 1

Copper mg/ l 0.2 0.5

Iron mg/ l 5 10

Lead mg/ l 0.2 1Mercury mg/ l 0 .001 0.005

Nickel mg/ l 0.2 0.5

Z inc mg/ l 2 5

Tem perature

T + 3C for

receiving w ater

T + 3C for

receiving water


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First StepsFirst StepsIt was necessary to use a fundamental approach since there wereIt was necessary to use a fundamental approach since there wereno plants working under similar conditions.no plants working under similar conditions. BapcoBapco decided to startdecided to startwith the basics.with the basics.

Samples of waste water were sent fromSamples of waste water were sent from BapcoBapco to two independentto two independent

consultants in the UK. These consultants performed bench scaleconsultants in the UK. These consultants performed bench scaletreatability tests on the waste water using live activated sludgtreatability tests on the waste water using live activated sludge.e.

The bench scale tests gave a good positive indication that the wThe bench scale tests gave a good positive indication that the wasteastewater from the existing primary treatment is biologically treatawater from the existing primary treatment is biologically treatable.ble.

The bench scale tests did not provide any firm indication regardThe bench scale tests did not provide any firm indication regardinging

which biological process would be best suited.which biological process would be best suited.The bench scale tests did not provide enough information to deveThe bench scale tests did not provide enough information to developlopa plant design and what information there was, was unlikely toa plant design and what information there was, was unlikely toremain valid through scaleremain valid through scale--up.up.

Following the bench scale testsFollowing the bench scale tests BapcoBapco concluded that the next stepconcluded that the next step

would be to conduct pilot scale tests on site in order to increawould be to conduct pilot scale tests on site in order to increase these thelevel of confidence and provide further insight to the solution.level of confidence and provide further insight to the solution.


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Pilot PlantPilot PlantA pilot plant with anoxic and aerobic biological treatment zonesA pilot plant with anoxic and aerobic biological treatment zonesfollowed by a membrane separation stage was established on site.followed by a membrane separation stage was established on site. ItIt

was fed with water from the primary treatment.was fed with water from the primary treatment.

The pilot plant was operated on a continuous basis byThe pilot plant was operated on a continuous basis by BapcoBapco forforseveral months and then for 7 months together with CH2M Hill.several months and then for 7 months together with CH2M Hill.

Pilot plant operation provided a range of fundamental processPilot plant operation provided a range of fundamental processinformation. These parameters were used as inputs into processinformation. These parameters were used as inputs into processsimulationsimulation programmesprogrammes in order to:in order to:

select the most appropriate treatment technologyselect the most appropriate treatment technology

prove that the selected technology is effective, applicable andprove that the selected technology is effective, applicable and

viable.viable.

In parallel to the pilot plant operation, onIn parallel to the pilot plant operation, on--site tests, analyses andsite tests, analyses andinvestigations were carried out to characterize the waste waterinvestigations were carried out to characterize the waste water andandthe composite streams.the composite streams.


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Pilot PlantPilot Plant FlowsheetFlowsheet

WasteActivated

Sludge

A

noxi

c

PhosphoricAcid

Aerobi

c

Final Effluent(permeate)

MembraneUnit

Spent

Caustic

FeedTank

2

FeedTank

1

SeaWater in

Sea

Water out

Effluentfrom IAF

MembraneTank Feed

HeatExchanger

Caustic

Soda

Acetic

Acid


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Pilot Plant ResultsPilot Plant Results

The Pilot Plant demonstrated that an MBR can be used to treatThe Pilot Plant demonstrated that an MBR can be used to treatBapcoBapcoss waste water and provide as complete a biological treatmentwaste water and provide as complete a biological treatment

as possible, leaving only hard/ nonas possible, leaving only hard/ non

--biodegradable/ recalcitrant CODbiodegradable/ recalcitrant COD

and TKN unand TKN un--oxidized.oxidized.

Additional bench scale tests were performed in a onAdditional bench scale tests were performed in a on--site laboratory,site laboratory,using sludge from the pilot plant, to verify the biousing sludge from the pilot plant, to verify the bio--kinetic constants.kinetic constants.

Fundamental process information was used as input to processFundamental process information was used as input to processsimulations used to optimize the design.simulations used to optimize the design.

Reference sites in Italy were visited. These sites were using siReference sites in Italy were visited. These sites were using similarmilar

technology in a tightly controlled discharge environment.technology in a tightly controlled discharge environment.

All of this was translated into a practical design.All of this was translated into a practical design.


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Reasons for Selecting MBRReasons for Selecting MBR

TechnologyTechnologyAn MBR process, as BAT, was considered becauseAn MBR process, as BAT, was considered because

the low TSS limitthe low TSS limit

the low TKN limitthe low TKN limit low sludge growth ratelow sludge growth rate

low contaminant loadinglow contaminant loading

Poor floc settling properties resulting from the high salinity.Poor floc settling properties resulting from the high salinity.

It was considered unlikely to meet the specs with anything otherIt was considered unlikely to meet the specs with anything otherthan an MBRthan an MBR..

Despite rapid growth in the number of MBR installations, they haDespite rapid growth in the number of MBR installations, they haveve

not been used in refinery applications because of the perceivednot been used in refinery applications because of the perceived riskriskof membrane fouling by oil. The pilot plant demonstrated theof membrane fouling by oil. The pilot plant demonstrated themanageability of this risk.manageability of this risk.


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What the WWTP will achieve forWhat the WWTP will achieve for

BapcoBapcoThe WWT project will enableThe WWT project will enable BapcoBapco to significantly improve theto significantly improve thequality of the discharged process water and comply with thequality of the discharged process water and comply with theenvironmental regulations as specified by the Bahrain Governmentenvironmental regulations as specified by the Bahrain Government..

Currently the Best Available Technology (BAT) for the secondaryCurrently the Best Available Technology (BAT) for the secondarybiological treatment of refinery waste water would be an MBR; abiological treatment of refinery waste water would be an MBR; abiological plant (anoxic and anoxic zones) followed by a membranbiological plant (anoxic and anoxic zones) followed by a membraneeseparation stage.separation stage.

This process offers the most complete biological treatment possiThis process offers the most complete biological treatment possibleble

including nitrogen removal. The specification from the EWP isincluding nitrogen removal. The specification from the EWP isstringent on all forms of nitrogen.stringent on all forms of nitrogen.

Further biological treatment is not possible and as a result ofFurther biological treatment is not possible and as a result of this thethis thepolluting nature of the treated water is at an absolute minimum.polluting nature of the treated water is at an absolute minimum. ThisThiswas supported by toxicity testing.was supported by toxicity testing.

No problems with oil on the membrane or other issues concerningNo problems with oil on the membrane or other issues concerningthe membrane material have been encountered.the membrane material have been encountered.


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Process ConfigurationProcess Configuration

Currently the Best Available Technology (BAT) for the secondaryCurrently the Best Available Technology (BAT) for the secondarybiological treatment of refinery waste water would be an MBR; abiological treatment of refinery waste water would be an MBR; abiological plant (anoxic and anoxic zones) followed by a membranbiological plant (anoxic and anoxic zones) followed by a membranee

separation stage.separation stage.

This process offers the most complete biological treatment possiThis process offers the most complete biological treatment possiblebleincluding nitrogen removal. The specification from the EWP isincluding nitrogen removal. The specification from the EWP isstringent on all forms of nitrogen.stringent on all forms of nitrogen.

4 biological stages (anoxic/ aerobic/ anoxic/ aerobic) are neces4 biological stages (anoxic/ aerobic/ anoxic/ aerobic) are necessarysaryto meet the stringent specifications.to meet the stringent specifications.

Further biological treatment is not possible and as a result ofFurther biological treatment is not possible and as a result of this thethis the

polluting nature of the treated water is at an absolute minimum.polluting nature of the treated water is at an absolute minimum. ThisThiswas also supported by toxicity testing.was also supported by toxicity testing.

No problems with oil on the membrane or other issues concerningNo problems with oil on the membrane or other issues concerningthe membrane material were encountered.the membrane material were encountered.


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Final Process ConfigurationFinal Process ConfigurationThe final process configuration is:The final process configuration is:

Max capacity 5000Max capacity 5000 USgpmUSgpm

Unit feed pitUnit feed pit

Equalization systemEqualization system

Cooling systemCooling system

Integrated 4Integrated 4--stage flexible biological system (organics removal,stage flexible biological system (organics removal,nitrification and denitrification)nitrification and denitrification)

Membrane tanks for liquid/solid separation systemMembrane tanks for liquid/solid separation system

Sludge treatment (storage and dewatering system)Sludge treatment (storage and dewatering system)

Chemical storage and dosing systemsChemical storage and dosing systems..


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Spent CausticSpent CausticBapcoBapco has a waste stream of spent caustic, and ways of handling ithas a waste stream of spent caustic, and ways of handling itin an environmentally acceptable way were being investigated.in an environmentally acceptable way were being investigated.

During the waste stream characterization it was confirmed that tDuring the waste stream characterization it was confirmed that thehespent caustic from the refinery was problematical because of itsspent caustic from the refinery was problematical because of its veryvery

odorous and toxic nature.odorous and toxic nature.

Following experiments on the pilot plant it was demonstrated thaFollowing experiments on the pilot plant it was demonstrated thattthe spent caustic, when added in a controlled manner could bethe spent caustic, when added in a controlled manner could beprocessed by without a problem.processed by without a problem.

The Pilot Plant mass balance showed a COD shortfall as requiredThe Pilot Plant mass balance showed a COD shortfall as requiredby the deby the de--nitrification reaction. As an additional benefit, the spentnitrification reaction. As an additional benefit, the spentcaustic could help reduce the shortage by providing COD. Thiscaustic could help reduce the shortage by providing COD. Thissaves acetic acid addition as COD source.saves acetic acid addition as COD source.

As another benefit, the alkalinity provided by the spent causticAs another benefit, the alkalinity provided by the spent causticreduces the alkalinity required for nitrification. This saves frreduces the alkalinity required for nitrification. This saves fresheshcaustic addition.caustic addition.


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ProcessProcess FlowsheetFlowsheet

Acetic acid or othercarbon source

Return

ActivatedSludge Waste

ActivatedSludge

Aerob

icAnoxi

c

Ano

xic

Equalised Effluentfrom IAF

Nitrate Recycle

Final Effluent(permeate)

MembraneUnit

SpentCaustic

Aerob

ic


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Project StatusProject StatusThe EDP has been completed.The EDP has been completed.

FlowsheetFlowsheet,, P&IDsP&IDs have been developed.have been developed.Front End Engineering Design (FEED) has started.Front End Engineering Design (FEED) has started.

Engineering Procurement and Construction (EPC) willEngineering Procurement and Construction (EPC) will

follow.follow.Options for further treatment to allow water reuse areOptions for further treatment to allow water reuse are

being examined.being examined.


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SummarySummary

From a position of no one knowingFrom a position of no one knowing

anything about the best process, if any atanything about the best process, if any atall, to treat its problematic waste water andall, to treat its problematic waste water and

spent caustic,spent caustic, BapcoBapco first established afirst established a

knowledge base and then developed thatknowledge base and then developed that

further to a practical design based on anfurther to a practical design based on an

MBR, a state of the art technology.MBR, a state of the art technology.

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