pct pollution control technology ( m rehan tahir) - waste water treatment

8/3/2019 PCT Pollution control Technology ( M REHAN TAHIR) - Waste Water Treatment

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Pollution ControlPollution ControlTechnologyTechnology

BY :BY :

Muhammad Rehan TahirMuhammad Rehan Tahir

MphilMphil Environmental policy & ManagementEnvironmental policy & ManagementMscMsc PhysicsPhysics

[email protected]@gmail.com


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Wastewater ManagementWastewater Management

Source: www.oconomowocusa.com/ wastewater.gif


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Clean Water ActClean Water Act

The Clean Water Act governs the discharge ofThe Clean Water Act governs the discharge ofwastewater. The Federal Water Pollution Control Act ofwastewater. The Federal Water Pollution Control Act of1972, as amended by the Clean Water Act of 1977 and1972, as amended by the Clean Water Act of 1977 andthe Water Quality Act of 1987, gave the EPA broadthe Water Quality Act of 1987, gave the EPA broadauthority to establish theauthority to establish the National Pollutant DischargeNational Pollutant DischargeElimination System (NPDES).Elimination System (NPDES).

The NPDES program regulates the discharge ofThe NPDES program regulates the discharge ofpollutants frompollutants from point sourcespoint sources, such, such municipalmunicipaltreatment plantstreatment plants, industries, animal feedlots, aquatic, industries, animal feedlots, aquaticanimal production facilities, and mining operations.animal production facilities, and mining operations.


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PartPart--1: Characteristicsand1: Characteristicsandtreatment Systemstreatment Systems


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Significance ofWastewaterSignificance ofWastewater

ContaminantsContaminants

Suspended solidsSuspended solids can cause sludge depositscan cause sludge depositsand anaerobic conditions in the environmentand anaerobic conditions in the environment

Biodegradable organicsBiodegradable organics can cause anaerobiccan cause anaerobic

conditions in the environmentconditions in the environmentPathogensPathogens transmit diseasetransmit disease

NutrientsNutrients can cause eutrophicationcan cause eutrophication

Heavy metalsHeavy metals

toxicity to biota and humanstoxicity to biota and humansRefractory organicsRefractory organics toxicity to biota andtoxicity to biota and

humanshumans

Dissolved solidsDissolved solids interfere with reuseinterfere with reuse


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Characteristics of DomesticCharacteristics of Domestic

WastewaterWastewater


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OnOn--Site Disposal SystemsSite Disposal Systems

In locations where sewers and a centralizedIn locations where sewers and a centralized

wastewater treatment system are not available,wastewater treatment system are not available,

on site disposal must be usedon site disposal must be used

Septic systems most common for individual

Septic systems most common for individualresidencesresidences

Engineered systemsEngineered systems used for unfavorable site used for unfavorable site

conditionsconditions

Larger systems required for housing clusters,Larger systems required for housing clusters,rest areas, commercial and industrial facilitiesrest areas, commercial and industrial facilities


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Septic SystemsSeptic Systems

Septic Tank: settling,

flotation and anaerobic

degradation


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Septic Systemscontd.Septic Systemscontd.

Drain field (cross-section) aerobic degradation


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Septic Systemscontd.Septic Systemscontd.

Soil must passSoil must pass percolation testpercolation test soil typesoil type

rate of water infiltrationrate of water infiltration

depth to water tabledepth to water table

Design specificationsDesign specifications Tank volume and number of chambersTank volume and number of chambers

Drain field sizeDrain field size

Drain field materialsDrain field materials

Basis for design is empiricalBasis for design is empiricalTank must be pumped to remove solids everyTank must be pumped to remove solids every

11--3 years3 years

Drain field replacement may be requiredDrain field replacement may be required


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Engineered Systems..Mound systemEngineered Systems..Mound system

Mound systems are both treatment and disposal systems

Design overcomes certain site restrictions, e.g., slowly permeable

soils, low WT etc.


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Engineered SystemsIntermittentEngineered SystemsIntermittent

sand filterssand filtersSand filter is also anSand filter is also an

aerobicaerobic treatment systemtreatment system

Surface of the bed isSurface of the bed is

intermittently dosed withintermittently dosed with

waste waterwaste waterSize of doseSize of dose should notshould not

saturate sandsaturate sand

Water is collected in theWater is collected in the

under drain and passed onunder drain and passed on

to absorption field.to absorption field.


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Municipal WastewaterMunicipal WastewaterTreatment SystemsTreatment Systems


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Municipal WastewaterMunicipal Wastewater

Treatment SystemsTreatment Systems

PretreatmentPretreatment removes materials thatremoves materials that

can cause operational problems,can cause operational problems,

equalization optionalequalization optional

Primary treatmentPrimary treatment remove ~60% ofremove ~60% ofsuspended solids and ~35% of BODsuspended solids and ~35% of BOD

Secondary treatmentSecondary treatment remove ~85%remove ~85%

of BOD and suspended solidsof BOD and suspended solids

Advanced treatmentAdvanced treatment varies: 95+ % ofvaries: 95+ % ofBOD and solids, N, PBOD and solids, N, P


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Pretreatment ofIndustrialPretreatment ofIndustrial

WastewatersWastewaters

Industrial wastewaters must be pretreatedIndustrial wastewaters must be pretreatedprior to being discharged to municipalprior to being discharged to municipalsewer systemsewer system

Approach is to remove materials that willApproach is to remove materials that willnot be treated by municipal systemnot be treated by municipal system

Local authority must monitor and regulateLocal authority must monitor and regulateindustrial dischargesindustrial discharges

Pretreatment requirements set by U.S.Pretreatment requirements set by U.S.EPAEPA


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Prohibitions for industriesProhibitions for industries

Pollutants that create aPollutants that create a fire hazard or explosionfire hazard or explosion

Pollutants that can causePollutants that can cause corrosivecorrosive structural damage tostructural damage toWWTPWWTP

Solid or viscous pollutants in amounts that will causeSolid or viscous pollutants in amounts that will causeobstruction to flowobstruction to flow

Any pollutant, incl. Oxygen demanding wastes releasedAny pollutant, incl. Oxygen demanding wastes releasedat a flow rate that will causeat a flow rate that will cause interference with WWTPinterference with WWTP

HeatHeat in amount that willin amount that will inhibit biological activityinhibit biological activity

Petroleum oil, nonPetroleum oil, non--biodegradable oil or products ofbiodegradable oil or products ofmineral oil in amounts that will cause interference ormineral oil in amounts that will cause interference or

pass through untreatedpass through untreatedPollutants that result inPollutants that result in toxic gasestoxic gases, vapors or fumes, vapors or fumes

within WWTP in a quantity that may cause acute workerwithin WWTP in a quantity that may cause acute workerhealth and safety problemshealth and safety problems


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Bar racksBar racksPurpose:Purpose: remove larger objects thatremove larger objects that

would damage or foul the pumps,would damage or foul the pumps,valves or other mechanical equipmentvalves or other mechanical equipment

Solid material stored in hopper andSolid material stored in hopper and

sent to landfillsent to landfill

Mechanically or manually cleanedMechanically or manually cleaned


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Grit ChambersGrit ChambersPurposePurpose: remove inert dense material,: remove inert dense material,

such as sand, broken glass, silt andsuch as sand, broken glass, silt andpebblespebbles

All these material combined are calledAll these material combined are calledgritgrit

Avoid abrasion of pumps and otherAvoid abrasion of pumps and othermechanical devicesmechanical devices

Three basic types:Three basic types: VelocityVelocity--controlledcontrolled (also called horizontal(also called horizontal

flow grit chambers)flow grit chambers)

AeratedAerated

Constant level shortConstant level short--termterm

VelocityVelocity--controlled only can becontrolled only can beanalyzed by Typeanalyzed by Type--1 settling (Stokes1 settling (Stokeslaw)law)


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Grit Chambers: Velocity ControlledGrit Chambers: Velocity Controlled


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Type I SettlingType I Settling -- Stokes LawStokes Law

2( )

18

ss

g dv

V V

Q

!

wherewheress == settling velocitysettling velocity

ss = density of particle (kg/m= density of particle (kg/m33))

= density of fluid (kg/m= density of fluid (kg/m33))

gg = gravitational constant (m/s= gravitational constant (m/s2)2)

dd = particle diameter (m)= particle diameter (m)

= dynamic viscosity (Pas)= dynamic viscosity (Pas)


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Example: Grit Chamber DesignExample: Grit Chamber Design

DesignDesign a grit chamber to remove sanda grit chamber to remove sand

particles (particles (VVss = 2650 kg/m= 2650 kg/m33) with a mean) with a meandiameter of 0.21 mm. Assume the sand isdiameter of 0.21 mm. Assume the sand is

spherical and the temperature of thespherical and the temperature of the

wastewater is 20wastewater is 20 ooC. The wastewater flow isC. The wastewater flow is

10,000 m10,000 m33/d. A velocity of 0.3 m/s will be/d. A velocity of 0.3 m/s will be

automatically maintained, and the depth mustautomatically maintained, and the depth must

be 1.5 times the width at maximum flow.be 1.5 times the width at maximum flow.NoteNote: Design means the size (length, width: Design means the size (length, width

and height)and height)


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SolutionSolution

24

2 2 3 3

3

3

Calculate the settling velocity:

m kg kg9.8 2650 998 2.1 10 m

( ) ms m m 0.039kg18 s

18 1.00 10 m s

Calculate the cross-sectional area:

m s d10,000

d 0.3 m 1440 min

-

s

s

s

g dv

QA

v

V VQ

v ! ! !

v

! !

2

0.5 0.5

2

min0.39 m

60 s

Calculate depth and width

0.391.5 1.5 0.51 m

1.5 1.5

1.5 0.51 1.5 0.76 m

Determine the detention time required for a particle to fall the entire t

s

s

A A W W W W

D W

!

! v ! ! ! !

! v ! v !

ank depth

0.76 m19.4 s

0.039 m/s

Determine the length to achieve this detention time

19.4 s 0 3 m/s 5 8 m

Thus, the tank must have dimensions

W = 0.51 m, D = 0.76 m, L = 5.8 m

d

s

d

Dt

v

L t v . .

! ! !

! v ! v !


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Equalization BasinEqualization Basin

Flow equalization isFlow equalization is not a treatment processnot a treatment process

Technique to improve the effectiveness ofTechnique to improve the effectiveness ofprimary and secondary treatmentprimary and secondary treatment

Accounts forAccounts fordiurnal variationsdiurnal variations in wastewaterin wastewaterflowflow

Usually achieved by large basins to collectUsually achieved by large basins to collectwastewater and pumped to treatment plant at awastewater and pumped to treatment plant at aconstant rateconstant rate

AdequateAdequate aeration and mixingaeration and mixing need to beneed to beprovided to prevent odors and deposition ofprovided to prevent odors and deposition ofsolidssolids


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Primary TreatmentPrimary Treatment

Separates suspended solids andSeparates suspended solids and

grease from wastewater.grease from wastewater.

Wastewater is held in a tank forWastewater is held in a tank for

several hours allowing theseveral hours allowing the particles toparticles to

settle to the bottom and the greasessettle to the bottom and the greasesto float to the top.to float to the top.

The solids drawn off the bottomThe solids drawn off the bottom

and skimmed off the top receiveand skimmed off the top receive

further treatment as sludgefurther treatment as sludge..The clarified wastewater flows onThe clarified wastewater flows on

to the next stage of wastewaterto the next stage of wastewater

treatment.treatment.


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Primary Settling BasinsPrimary Settling Basins


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Primary Settling Tank DesignPrimary Settling Tank Design

Characterized byCharacterized by TypeType--II settlingII settling, therefore no, therefore nomathematical relationship is used for designmathematical relationship is used for design

Design data are developed fromDesign data are developed from lab tests withlab tests withsettling columnssettling columns

SizeSize rectangular: 3rectangular: 3--24 m wide x 1524 m wide x 15--100 m long100 m long

circular: 3circular: 3--90 m diameter90 m diameter

Detention time: 1.5Detention time: 1.5 --2.5 hours2.5 hours

Overflow rate: 25Overflow rate: 25--60 m60 m33

/m/m22

daydayTypical removal efficienciesTypical removal efficiencies

Suspended solids: 50Suspended solids: 50--60%60%

BODBOD55: 30: 30--35%35%


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Secondary TreatmentSecondary Treatment

Provide BOD and suspended solidsProvide BOD and suspended solidsremovalremoval beyond what is achieved inbeyond what is achieved inprimary treatmentprimary treatment

Basic approach is to use Basic approach is to use aerobicaerobic

biological degradationbiological degradation::

organic carbon + Oorganic carbon + O22 CO CO22

Objective is achieved by allowingObjective is achieved by allowingthe BOD to be exerted in thethe BOD to be exerted in thetreatment plant rather than in thetreatment plant rather than in thestreamstream


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Create a very rich environmentCreate a very rich environment

for growth of a diverse microbialfor growth of a diverse microbialcommunity by keeping acommunity by keeping a highhighdensity of microorganismsdensity of microorganisms ininthe systemthe system

Maintain good contact betweenMaintain good contact betweenorganisms and wastes (organisms and wastes (provideprovidemixingmixing))

Provide high levels of oxygenProvide high levels of oxygen

((aerationaeration))Favorable temperature, pH,Favorable temperature, pH,

nutrients (design and operation)nutrients (design and operation)

No toxic chemicals presentNo toxic chemicals present

((control industrial inputscontrol industrial inputs))

How is thisaccomplished?How is thisaccomplished?


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Unit Processes of SecondaryUnit Processes of Secondary

TreatmentTreatment

Dispersed/suspended GrowthDispersed/suspended Growth

Activated sludgeActivated sludge

Oxidation ditches/pondsOxidation ditches/ponds

Aerated lagoons, stabilization pondsAerated lagoons, stabilization ponds

Fixed/attached GrowthFixed/attached Growth

Trickling filtersTrickling filters Rotating Biological Contactors (RBCs)Rotating Biological Contactors (RBCs)


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Activated SludgeActivated Sludge

Process in which a mixture ofProcess in which a mixture of

wastewater and microorganismswastewater and microorganisms(biological sludge) is(biological sludge) is agitated andagitated andaeratedaerated

Leads toLeads to oxidation of dissolvedoxidation of dissolvedorganicsorganics

After oxidation, sludge isAfter oxidation, sludge isseparated from wastewaterseparated from wastewater

To induce microbial growth, weTo induce microbial growth, weneed:need:

Food, oxygenFood, oxygen Mixed LiquorSuspended SolidsMixed LiquorSuspended Solids

(MLSS) of 3,000 to 6,000 mg/L(MLSS) of 3,000 to 6,000 mg/L

East Lansing WWTP


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Activated SludgeActivated Sludge

WasteActivated

Sludge(WAS)

ReturnSludge Mixed

Liquor Air

Secondaryclarifier

w/w

Treated

w/wDischarge toRiver or Land

Application


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Activated Sludge DesignActivated Sludge Design

ttdd = approximately 6= approximately 6 -- 8 hr8 hr8 m8 m33 of air per mof air per m33 of wastewater treatedof wastewater treated

Long rectangular aeration basinsLong rectangular aeration basins

Air is injected near bottom of aerationAir is injected near bottom of aerationtanks through system of diffuserstanks through system of diffusers

Aeration system used to provide mixingAeration system used to provide mixing

MLVSS and F/MMLVSS and F/M controlled by wasting acontrolled by wasting aportion of microorganismsportion of microorganisms


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F/M ratioF/M ratio-- Major design parameterMajor design parameter

0

0

where:

flow rateinitial soluble BOD

volume

mixed liquor volatile

suspended solids (MLVSS)

F QS

M VX

QS

V

X

!

!!

!

!

Low F/M (low rate of wasting)Low F/M (low rate of wasting)

starved organismsstarved organisms

more complete degradationmore complete degradation

larger, more costly aerationlarger, more costly aeration

tankstanks

more Omore O22 requiredrequired

higher power costs (to supplyhigher power costs (to supply

OO22))

less sludge to handleless sludge to handle

High F/M (high rate of wasting)High F/M (high rate of wasting) organisms saturated with foodorganisms saturated with food

low treatment efficiencylow treatment efficiency


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Trickling FiltersTrickling FiltersNot a true filtering orsieving process.Not a true filtering orsieving process. The filter media (fist sizeThe filter media (fist size

rocks) only provides surface for bacteria to grow.rocks) only provides surface for bacteria to grow.

Rotating distribution arm sprays primary effluent over circular bed ofRotating distribution arm sprays primary effluent over circular bed ofrock or other coarse mediarock or other coarse media

Air circulates in pores between rocksAir circulates in pores between rocks

BiofilmBiofilm develops on rocks and micro develops on rocks and micro--organisms degrades wasteorganisms degrades wastematerials as they flow pastmaterials as they flow past

Organisms slough off in clumps when film gets too thickOrganisms slough off in clumps when film gets too thick


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Trickling FiltersTrickling Filters

Can useCan use plastic mediaplastic media

lighterlighter -- can get deepercan get deeperbeds (up to 12 m)beds (up to 12 m)

reduced space requirementreduced space requirement

larger surface area forlarger surface area forgrowthgrowth

greater void ratios (bettergreater void ratios (betterair flow)air flow)

less prone to plugging byless prone to plugging byaccumulating slimeaccumulating slime


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Trickling Filter Plant LayoutTrickling Filter Plant Layout


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Rotating Biological Contactors (RBCs)Rotating Biological Contactors (RBCs)

Consists of series of closely spaced discsConsists of series of closely spaced discsmounted on a horizontal shaft and rotated whilemounted on a horizontal shaft and rotated while~40% of each disc is submerged in wastewater~40% of each disc is submerged in wastewater

Discs: lightDiscs: light--weight plasticweight plastic

Slime is 1Slime is 1--3 mm in thickness on disc3 mm in thickness on disc


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RBCscontd.RBCscontd.

Aeration

Shearing of excessmicroorganisms

Attached microorganismspick up organics

Filmmixes withwastewater

PrimarySettling

SludgeTreatment

SecondarySettling

Sludge Treatment


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LowLow--Tech solutionsTech solutions

Oxidation Ponds/DitchesOxidation Ponds/Ditches

Treatment ponds used for many years

Oxidation Pond was used to indicate a pond with partially

treated waste water whereas the term lagoon was used to indicate a

pond that received raw wastewater

Waste stabilization pond has been used as an all-inclusive term

that refers to a pond or a lagoon used to treat organic waste by

physical and biological processes

Mainly three divisions i.e., aerobic, facultative and anaerobic


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Aerobic/Facultative/Anaerobic PondsAerobic/Facultative/Anaerobic Ponds

Aerobic PondsAerobic Ponds-- Shallow (


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Secondary ClarifierSecondary Clarifier

East Lansing WWTP


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Land ApplicationsLand ApplicationsS

pray irrigation and infiltrationS

pray irrigation and infiltrationOverland flowOverland flow

WetlandsWetlands

Source: Environmental Science, 4th ed., B.J. Nebel

and R.T. Wright, Prentice- Hall, N.J., c. 1981


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Source: Environmental Science, 4th ed., B.J. Nebeland R.T. Wright, Prentice-Hall, N.J., c. 1981

Spray irrigationSpray irrigation

Usually follows oxidation ponds,Usually follows oxidation ponds,aerated lagoonsaerated lagoons

Application leads to filtering,Application leads to filtering,

biological degradation, ionbiological degradation, ionexchange, sorption, photoexchange, sorption, photo--degradationdegradation

Need about 1 acre/100 peopleNeed about 1 acre/100 people

ProblemsProblems climateclimate

pathogenspathogens

need buffer zoneneed buffer zone

SecondaryTreatment

Flooding,channeling

spray irrigation


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Overland flowOverland flow

Water irrigated onto long narrow fieldsWater irrigated onto long narrow fields

Use grasses that take up large amounts of nitrogenUse grasses that take up large amounts of nitrogen

Underlying soil should be fairly imperviousUnderlying soil should be fairly impervious

ExampleExample:: Emmitsburg, MDEmmitsburg, MD Treats 1 MGD on 200 acresTreats 1 MGD on 200 acres

Fields planted withFields planted with reedcanarygrassreedcanarygrass

Below ~1 ft topsoil is compacted clayBelow ~1 ft topsoil is compacted clay

W/W applied to one side of field, percolates throughW/W applied to one side of field, percolates throughtopsoil to a collecting guttertopsoil to a collecting gutter

Water in gutter (clear and nutrientWater in gutter (clear and nutrient--free)free)

Collected in another reservoir and sprayCollected in another reservoir and spray--irrigated ontoirrigated ontoforage cropsforage crops

SecondaryTreatment

Application to landslopped at 2-8%


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Overland Flowcontd.Overland Flowcontd.

AdvantagesAdvantages free waterfree water

free nutrientsfree nutrients

plants can be fed toplants can be fed to

animalsanimals lowlow--costcost

lowlow--maintenancemaintenance

water meets dischargewater meets discharge

regulations (NPDES)regulations (NPDES)

DisadvantagesDisadvantages will not work in coldwill not work in cold

climatesclimates

pathogen dispersion inpathogen dispersion in

airair need buffer zonesneed buffer zones

need large amount ofneed large amount of

landland


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WetlandsWetlandsUse of natural or artificial wetlandsUse of natural or artificial wetlands

Floating plants act as filters and supportFloating plants act as filters and support

bacterial growthbacterial growth

(From: Environmental Science, 4th ed., B.J. Nebeland R.T. Wright, Prentice-Hall, N.J., 1981)


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Disinfection andDisinfection andSludge ManagementSludge Management


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ObjectivesObjectives

Part I: Advanced Wastewater TreatmentPart I: Advanced Wastewater Treatment

to understand the most common types ofto understand the most common types ofadvanced wastewater treatment usedadvanced wastewater treatment used

to understand the contaminants removed byto understand the contaminants removed byeacheach

Part II: Sludge Treatment and DisposalPart II: Sludge Treatment and Disposal

to understand the origins of sludgeto understand the origins of sludge

to understand the issues dealing with theto understand the issues dealing with thedisposal of sludgedisposal of sludge


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Part I:Part I:

Advanced Wastewater TreatmentAdvanced Wastewater Treatment

Numerous pollutants are present (or canNumerous pollutants are present (or canbe present) in untreated wastewaterbe present) in untreated wastewater

Some are not removed by conventionalSome are not removed by conventionalsecondary wastewater treatment.secondary wastewater treatment.

There may be a need, or pressure, toThere may be a need, or pressure, to

remove these pollutants based on theremove these pollutants based on theuses of the receiving wateruses of the receiving water


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Secondary W/W TreatmentSecondary W/W Treatment

High treatmentHigh treatment

efficiencyefficiency BOD to ~ 20BOD to ~ 20 -- 50 mg/L50 mg/L

SS to ~ 20 mg/LSS to ~ 20 mg/L

Low treatmentLow treatment

efficiencyefficiency

NitrogenNitrogen

PhosphorusPhosphorus

Heavy MetalsHeavy Metals

PoorlyPoorly--biodegradablebiodegradable

organic chemicalsorganic chemicals

Small particlesSmall particles

Resistant organismsResistant organisms

ProblemsProblemsPresence of smallPresence of small

particles that are tooparticles that are toosmall to be removed bysmall to be removed bysettling.settling.

Attached to theseAttached to theseparticles can be organicparticles can be organicchemicals and metals.chemicals and metals.

Particles may eventuallyParticles may eventuallysettle in river or streamsettle in river or stream

(longer detention time).(longer detention time).Particles can also beParticles can also be

bacteria, protozoa, etc.bacteria, protozoa, etc.


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FiltrationFiltrationProcess similar to that used in waterProcess similar to that used in water

treatmenttreatment

Commonly uses dualCommonly uses dual-- or multimedia filtersor multimedia filtersbecause single media filters (sand filters)because single media filters (sand filters)clog too easilyclog too easily

Removes:Removes:

residual suspended solidsresidual suspended solids microorganismsmicroorganisms

Achieves:Achieves: 80% reduction in suspended solids for activated80% reduction in suspended solids for activated

sludge (~ 10sludge (~ 10 -- 25 mg/L SS)25 mg/L SS)

70% reduction in suspended solids for trickling70% reduction in suspended solids for tricklingfilter sludgefilter sludge

No removal of:No removal of: soluble BOD or CODsoluble BOD or COD

soluble phosphate, nitrate, heavy metals, etc.soluble phosphate, nitrate, heavy metals, etc.


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Activated Carbon AdsorptionActivated Carbon Adsorption

Refractory (nonRefractory (non--biodegradable) organicbiodegradable) organic

chemicals are present as soluble CODchemicals are present as soluble CODSecondary effluent COD values of ~ 30 toSecondary effluent COD values of ~ 30 to

60 mg/L60 mg/L

The same process as pollutant retardationThe same process as pollutant retardationis soils (from groundwater hydrology)is soils (from groundwater hydrology)

More efficient than process on soilsMore efficient than process on soils

A ti t d C b Ad tiA ti t d C b Ad ti


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Activated Carbon AdsorptionActivated Carbon Adsorption

Carbon is heated to about 1500Carbon is heated to about 1500 ooC toC to

activateactivate surfaces surfacesHigh surface area of particles with vast poreHigh surface area of particles with vast pore

spacesspaces Capable of absorbing high quantity of organicsCapable of absorbing high quantity of organics

Surface area > 1,000 mSurface area > 1,000 m22/g/g

Wastewater effluent is passedWastewater effluent is passed

through filter (under pressure)through filter (under pressure)

Carbon becomes exhaustedCarbon becomes exhausted IndicationsIndications

removal of material ceasesremoval of material ceases effluent pollutant level too higheffluent pollutant level too high

Replace carbon in systemReplace carbon in system

Regenerate carbon onRegenerate carbon on--site or offsite or off--sitesite


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Membrane ProcessesMembrane Processes

A phase that acts as a barrier toA phase that acts as a barrier to

the flow of molecular or ionicthe flow of molecular or ionic

species between other phasesspecies between other phases

Driven by pressuresDriven by pressures

Should achieve 100% removalShould achieve 100% removal

based on molecular weight cutoffbased on molecular weight cutoff

Actual removal observed lessActual removal observed less --

may be shortmay be short--circuitingcircuiting

Ph hPh h R lR l


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PhosphorusPhosphorusRemovalRemoval

By now, we know theBy now, we know the problemsassociatedproblemsassociated

with excessphosphorouswith excessphosphorousMost phosphate in the form of (HPOMost phosphate in the form of (HPO44

22--))

Usually accomplished withUsually accomplished with chemicalchemicalprecipitationprecipitation (salts)(salts)

Ferric chloride: FeClFerric chloride: FeCl33 Alum: AlAlum: Al22(SO(SO44))33

yy14H14H22OO

Lime: CaO or Ca(OH)Lime: CaO or Ca(OH)22FeClFeCl33 + HPO+ HPO44

22-- = FePO= FePO4 (s)4 (s) + HCl+ HCl

AlAl22(S

O(S

O44))3314H14H22O + 2 HPOO + 2 HPO4422-- =

2AlPO=

2AlPO4 (s)4 (s) + 2H+ 2H

+ ++ +

3S

O3S

O4422--

Effective pH range for alum or ferric chloride isEffective pH range for alum or ferric chloride is5.5 to 7.05.5 to 7.0

If insufficient alkalinityIf insufficient alkalinity -- must add lime tomust add lime to

neutralize Hneutralize H++


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PhosphorusRemovalPhosphorusRemoval

SecondaryEffluent

RapidMix

ReactionBasin

SettlingBasin

PrimaryEffluent

Activated Sludge

FeCl3SecondaryClarifier

FeCl3

Nit R lNit R l


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Nitrogen RemovalNitrogen Removal

Problem: nitrogenous BODProblem: nitrogenous BOD

Anaerobic conditions in streamAnaerobic conditions in stream

Forms: NHForms: NH33, NH, NH44++, NO, NO22

--, NO, NO33--

Nitrification/ DeNitrification/ De--nitrificationnitrification

OccursOccurs in activated sludge processin activated sludge process -- by increasing theby increasing the

detention time in activated sludge basindetention time in activated sludge basin

in separate reactorin separate reactor

Nitrification:Nitrification:NHNH44

++ + 2O+ 2O22 = NO= NO33-- + H+ H22O + 2HO + 2H

++ (2 steps)(2 steps)

DeDe--nitrification:nitrification:

2NO2NO33-- + organic matter= N+ organic matter= N22+ CO+ CO22 + H+ H22OO

Nit R l tdNit R l td


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Nitrogen Removal..contd.Nitrogen Removal..contd.AmmoniastrippingAmmoniastripping

Raise pH to convert ammonium ionsRaise pH to convert ammonium ionsto ammoniato ammonia

NHNH44++ + OH+ OH-- = NH= NH33 + H+ H22OO

Ammonia purged from water inAmmonia purged from water inprocess similar to aerationprocess similar to aeration

TrayTray--type Air Strippertype Air Stripper

(From: http://www.mittelhauser.com/airstrip.html)

Packed Column Air Stripper

(From: http://www.carbonair.com/OS.htm)


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Part II: Sludge TreatmentPart II: Sludge Treatment

Sl d TSl d T


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Sludge TypesSludge Types

Bar screensBar screens

Grit chambersGrit chambersPrimary sludgePrimary sludge

3 to 8% solids3 to 8% solids

About 70% organic materialAbout 70% organic material

Secondary sludgeSecondary sludge Consists of wasted microorganisms and inert materialsConsists of wasted microorganisms and inert materials

About 90% organic materialAbout 90% organic material

WAS: 0.5 to 2% solidsWAS: 0.5 to 2% solids

Trickling filter sludge: 2Trickling filter sludge: 2--5% solids5% solids

Tertiary sludgeTertiary sludge If secondary clarifier is used to remove phosphate, thisIf secondary clarifier is used to remove phosphate, this

sludge will also contain chemical precipitates (more difficultsludge will also contain chemical precipitates (more difficultto treat)to treat)

Denitrification sludgesDenitrification sludges -- similar to WAS sludgesimilar to WAS sludge

Not true sludge, not a fluid. Since it can bedrained easily and is relatively stable, itcan be disposed of directly in a municipallandfill.


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Sludge TreatmentSludge Treatment

Ash

Sludge Thicken Condition Dewater SanitaryLandfill

Stabilize Condition Dewater SoilIncorporation

Reduction


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Sludge Treatment: ThickeningSludge Treatment: Thickening

FlotationFlotation Especially effectiveEspecially effective

on activated sludgeon activated sludge

Increases solidsIncreases solids

content from 0.5content from 0.5 -- 1%1%to 3to 3--6%6%

Gravity thickeningGravity thickening Best with primaryBest with primary

sludgesludge

Increases solidsIncreases solids

content from 1content from 1--3% to3% to10%10%

PrimarySludge

Gravity Thickening

SecondarySludge

Flotation

Further processing


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ThickeningThickening

Gravity Thickener(From: http://www.thomasregister.com/

olc/dorroliver/sedi.htm)

Flotation


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Sludge Treatment: StabilizationSludge Treatment: Stabilization

Aerobic DigestionAerobic Digestion Extension of activated sludgeExtension of activated sludge

Accomplished by aeration ofAccomplished by aeration of

sludge then followed bysludge then followed by

sedimentationsedimentation

Supernatant goes back to head ofSupernatant goes back to head of

plant (high in BOD, TKN, totalplant (high in BOD, TKN, total--P)P)

Treated sludge is 3% solidsTreated sludge is 3% solids

Anaerobic DigestionAnaerobic Digestion

2 stage: acid fermentation2 stage: acid fermentationfollowed by methanefollowed by methane

productionproduction

Advantages:Advantages:

produce methaneproduce methane

do not add oxygendo not add oxygen

As with aerobic digestion,As with aerobic digestion,

supernatant goes to headworkssupernatant goes to headworks

Sl d T t t C diti iSl d T t t C diti i


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Sludge Treatment: ConditioningSludge Treatment: Conditioning

Chemical ConditioningChemical Conditioning Add lime, ferric chloride,Add lime, ferric chloride,

or alumor alum

Can also add polymersCan also add polymers

Chemicals are addedChemicals are addedjust prior to dejust prior to de--wateringwatering

stagestage

Heat TreatmentHeat Treatment High temperatures (175High temperatures (175--230230

ooC)C)

High pressures (10 to 20High pressures (10 to 20

atmospheres)atmospheres)

AdvantagesAdvantages bound water is released andbound water is released and

sludge is easily dewateredsludge is easily dewatered

DisadvantagesDisadvantages

complex processcomplex process

highly concentrated liquidhighly concentrated liquidstreamstream

Sl d T t t DSl d T t t D t it i


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Sludge Treatment: DeSludge Treatment: De--wateringwatering

Sludge Drying BedsSludge Drying Beds

Most popular methodMost popular method

SimpleSimple

Low maintenanceLow maintenance

Effected by climateEffected by climate

FiltrationFiltration

Apply vacuum to pullApply vacuum to pull

out waterout water

Force out water byForce out water by

essentially squeezingessentially squeezing

water between twowater between twomoving filter beltsmoving filter belts

Sludge Drying Beds

(From: http://www.infilcodegremont.com/)

VacuumFiltration

(From: http://www.thomasregister.com/

olc/dorroliver)


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DeDe--watering:watering:

Belt Filter PressBelt Filter Press

East Lansing, MIFairhaven, MA

(From: http://www.environline.com/fhwpcf.htm)

Sl dge Treatment Vol me Red ctionSl dge Treatment Vol me Red ction


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Sludge Treatment: Volume ReductionSludge Treatment: Volume Reduction

IncinerationIncineration

Complete evaporation ofComplete evaporation ofwater from sludgewater from sludge

Requires fuelRequires fuel

Solid material is inertSolid material is inert

Exhaust air must beExhaust air must betreated prior to dischargetreated prior to discharge

Wet OxidationWet Oxidation

Treated sludge is wetTreated sludge is wet Requires energyRequires energy

Solid material is inertSolid material is inert

Exhaust air must beExhaust air must be

treated prior totreated prior todischargedischarge

(From: http://www.unep.or.jp/CTT_DATA/WATER/

WATER_4/html/Water-173.html

(From: http://www.

infilcodegremont.com/)

High Temperature Fluidized Bed IncinerationHigh Temperature Fluidized Bed Incineration


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Sludge Disposal RegulationsSludge Disposal Regulations

The regulations that govern the use or disposalThe regulations that govern the use or disposalof sewage sludge are codified as 40 CFR partof sewage sludge are codified as 40 CFR part

503 and have become known as 503503 and have become known as 503

regulationsregulations

The regulations apply to sewage sludge that is:The regulations apply to sewage sludge that is: Land appliedLand applied

Placed on a surface disposal sitePlaced on a surface disposal site

Incinerated in an incinerator that accepts only sewageIncinerated in an incinerator that accepts only sewage

sludgesludge

F ilit O tiF ilit O ti


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Facility OptionsFacility Options

Considerations for wastewater treatmentConsiderations for wastewater treatment

facility options include:facility options include: costscosts

capitalcapital

operation and maintenance (including energy)operation and maintenance (including energy)

availability of spaceavailability of space

degree of treatment required by NPDES permitdegree of treatment required by NPDES permit

municipal or municipal plus industrialmunicipal or municipal plus industrial

Flow rateFlow rate

distance from residential propertiesdistance from residential properties

problems with: odors, flies, other nuisancesproblems with: odors, flies, other nuisances

agricultural usage or land application optionsagricultural usage or land application options

presence of pathogenspresence of pathogens

experience of design engineersexperience of design engineers

pct pollution control technology ( m rehan tahir) - waste water treatment

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