20CE501PE – INDUSTRIAL WASTE MANAGEMENT.ppt

20CE501PE
INDUSTRIAL
WASTE
MANAGEMENT
by
S.MOHANKUMAR
AP/MECH/KNCET

UNIT I INTRODUCTION
Undesirable waste water
characteristics–Characteristicsof
industrialwastewaters–Waste
watercharacteristics–Estimating
theorganiccontent–Measuringthe
efficiencytoxicity–Inplantwaste
controlandwastereuse–Storm
watercontrol.

INTRODUCTION
Industrialwasteisthewasteproducedbyindustrial
activitywhichincludesanymaterialsthatisrendered
uselessduringamanufacturingprocess.
Thewastematerialsgeneratedbyindustriesor
industrialprocesses,iscalledindustrialwaste.It
includeschemicals,trash,oils,solvents,dirtand
gravel,manyharmfulgasesetc.Thesearedumpedin
seas,riversorlandwithoutadequatetreatment.
Thus,becomealargesourceofenvironmental
pollution.

Types or Classification of Industries
•Industries can be classified into the
following four groups,
•(i) Primary Industry
•(ii) Secondary Industry
•(iii) Tertiary Industry
•(iv) Quaternary Industry

PRIMARY INDUSTRY
They are further classified into the following
types, such as
• Genetic Industry
• Extractive Industry
•Manufacturing Industry
• Construction Industry
• Service Industry

Causes of Industrial waste
•a. Lack of policies to control waste
•b. Unplanned industrial waste
•c. Presence of large number of small
scale industries
•d. Inefficient waste disposal
•e. Leaching or resources from out
natural world.

Types of industrial wastes
•Industrial waste can be divided into
following two types –
• Biodegradable industrial waste
• Non –biodegradable industrial waste

Biodegradable wastes
•Those waste materials which can be
decomposed into simpler unharmful
substances by the action of microorganisms
are called biodegradable wastes.
•Some industries such as the paper industry,
food industry, sugar industry, wool industry
etc. mostly produce biodegradable industrial
wastes.
•Management of these wastes can be done at
low cost and easily.

Non-biodegradable wastes
•Non-biodegradablewastecannotbefurther
decomposedviatheactionofthemicroorganisms.
•Suchwasteisthemajorsourceoftoxinsinthe
landfills.Chemicals,metals,plastics,paints,rubber
etc.areexamplesofnon-biodegradablewastes.
•Thesematerialscanremainaslandfillsforthousandsof
yearswithoutanydamage.
•Toxinsfrommetalsandplasticsgetsoakedintothe
earthandpollutethesoilandwatersources.
•Cleaningmaterialssuchdetergent,phenolsetc.
producingindustries,coalindustries,dying
industriesetc.
•producealargeamountofnon-biodegradable
industrialwaste.Thesetypesofwastesaredifficultto
manageandverytoxicinnature.

Effects of Industrial Waste
•Liquid industrial waste which is thrown
into the sea is at an alarmingly dangerous
level for marine ecosystems.
• Industries release many harmful gases
such as carbon dioxide, sulfur dioxide,
nitrogen oxides etc. which cause air
pollution.

•Inindustrialwastewaternitratesand
phosphatesaretherewhichoftencause
eutrophication.
•Generally,airaroundindustriesishighly
pollutedandcausesskin,eyes,throat,nose
andlungsdiseases

•It is one of the main causes of global
warming.
• Industrial wastewater destroys useful
bacteria and other microorganisms present
in soil.
• Some industries cause sound pollution as
well.
• Industrial wastes and industries are
destroying natural habitat of many species
and responsible for wildlife extinction.

INDUSTRIAL WASTEWATER
•Industrialwastewaterisnotjustaby-
productofoilandgasorminingand
chemicalmanufacturingcompanies,
butalsoaby-productoffoodand
beverage processing industries,
essentialinthemakingoftheclothes
onyourback,theshoesonyourfeet,
thecomputeratyourfingertips,and
thecaryourdrive.

•Organicmatter,metals,
andthelikefoundinthe
wastewatermustbe
removedbeforethe
watercanbesafely
dischargedbacktoland,
intobodiesofwater,or

Categories of pollutants
Industrial water contains a large variety of
pollutants which as categorized as follows:
• Organic Pollutants
• Inorganic Pollutants

ORGANIC POLLUTANTS
• Sugars
• Oils and fats
• Proteins
• Hydrocarbons
• Phenols
• Detergents
• Organic acids

INORGANIC POLLUTANTS
• Alkalis
• Mineral acids
• Inorganic Salts
Free Chlorine
• Ammonia
• Hydrogen Sulphide
• Salts of Chromium
• Nickel
Zinc
• Cadmium
• Copper
• Silver
• Phosphates
• Sulphates
• Chlorides
• Nitrates
• Cyanides
• Calcium
• Magnesium
• Sodium
• Potassium
• Iron
• Manganese
• Arsenic etc.

Industries Produce Industrial
Wastewater
a)Metal Finishers
b)Industrial laundries
c)Chemical Manufacturing
d)Mining
e)Steel/Iron Production
f)Oil and Gas Fracking
g)Power Plants
h)Waste water treatment plants
i)Food Processing

UNDESIRABLE WASTE WATER
CHARACTERISTICS

CHARACTERISTICS OF
INDUSTRIAL WASTE WATER
✓A colloidal type of turbidity
✓A typical Colour(Grey –yellowish)
✓A low alkalinity(pH around 7.5)
✓Large amount of Nitrogen,
entirely of organic origin
✓They have an unpleasant odour

EFFECTS OF WASTEWATER
•Oxygendepletiononthebodyofwater
•Presenceofundesirablecolour,odourandtaste
inthewater
•Reducedphotosysnthesis
•Formationofblanketofsuspendedsolidssettling
atthebottomofthereceivingbodyofthewater
•Thedeathoffish
•Toxicityaddedtotheadequatelifeduetothe
formationofmercaptans(mercaptanactsasan
odoranttomakeiteasiertodetect).,
pentachlorophenol,sodiumpentachlorophenate.

Physical Characteristics of
Wastewater
Following are important physical characteristics
of wastewater
(i) Colour
(ii) Odour
(iii) Temperature
(iv) Turbidity
(v) Solid contents (Total solids).

Colour
•Fresh domestic sewage is grey, somewhat
resembling a weak solution of soap.
•The colour of septic sewage is more or less
black or dark in colour.
•The colour of industrial wastewater depends
upon the chemical process used in the
industries.
•Industrial waste water, when mixed with
domestic sewage, may also add colour to it.

Odour
•Normal fresh sewage has a musty odourwhich is
normally not offensive, but as it starts to get
stale, it begins to give offensive odour.
•Within 3 or 4 hours, all the oxygen present in the
sewage gets exhausted and it starts emitting
offensive odourof hydrogen sulphide, gas and
other sulphurcompounds produced by anaerobic
micro-organisms.
•Industrial wastewater may contain either process
of wastewater treatment.

Turbidity
•The turbidity of wastewater depends on the
quantity of solid matters present in the
suspension state.
•Turbidity is a measure of light-emitting
properties of wastewater, and turbidity test is
used to indicate the quality of waste
discharges with respect to colloidal matter.
•The turbidity depends upon the strength of
sewage or waste water. The stronger or more
concentrated the sewage, the higher is its
turbidity. Turbidity can be determined either
by turbidity rod or by Jackson’s turbidimeter.

Total Solids
•Sewage normally contains 99.9 per cent
of water and 0.1 per cent of solids.
Analytically, the total solids content (ST)
of a wastewater is defined as all the
matter that remains as residue upon
evaporation to 103 to 105°C.
•Total solids in wastewater exist in three
different forms (a) suspended solids (b)
colloidal solids and (c) dissolved solids.

CHEMICAL CHARACTERISTICS OF
WASTEWATER AND THEIR
DETERMINATION
(i) pH value
(ii) Chloride content
(iii) Nitrogen content
(iv) Fats, grease and oil content
(v) Sulphides, sulphatesand H2S gas
(vi) Dissolved oxygen (DO)
(vii) Chemical oxygen demand (COD)
(viii) Bio-chemical oxygen demand (BOD)
(ix) Stability and relative stability.

pH VALUE
ThetestforpHvalueofwastewateris
carriedouttodeterminewhetherit-is
acidicoralkalineinnature.
Freshsewageisgenerallyalkalinein
nature,(itspHvaluebetween7.3to7.5).
Ahighconcentrationofeitheranacid(pH
≪7)oralkali(pH≫7)inwastewateris
indicativeofindustrialwastes.

CHLORIDES CONTENT
•Chloridesaremineralsaltsand,therefore,are
notaffectedbybiologicalactionofsewage.
•Chloridesinnaturalwaterresultfromthe
leachingofchloride-containingrocksandsoils
withwhichthewatercomesincontact.
•Watersoftenersalsoaddlargequantitiesof
chlorides.Largeamountsofchloridesmayalso
enterinwastewatersfromindustrieslikeice
creamplants,meatsaltingetc.
•Chloridesfoundindomesticsewagearederived
fromkitchenwastes,humanfaecesandurinary
dischargesetc.
•Humanexcreta,forexample,containabout6gof
chloridesperpersonperday.

NITROGEN CONTENTS
•Thepresenceofnitrogeninwaste-
waterindicatesthepresenceof
organicmatterinit.
•Nitrogenisessentialtothegrowthof
Protistaandplantsandassuchis
knownasnutrientorbio-stimulant.

Nitrogen appears in the following five
different forms in waste-water
Ammonia nitrogen or free ammonia
Organic nitrogen
Albuminoidnitrogen
Nitrites nitrogen and
Nitrates nitrogen.
Fats, Grease and Oils
Surfactants
Phenols, Pesticides and Agricultural Chemicals
Toxic Compounds
Sulphates, Sulphidesand H2S Gas

FATS, GREASE AND OILS
•Fatsandoilsaremainlycontributedfromkitchen
wastes,becausetheyaremajorcomponentsof
foodstuffssuchasbutter,vegetableoilsand
fats.
•Fatsarealsocommonlyfoundinmeats,seeds,
nutsandsomefruits.
•Greaseandoilsarealsodischargedfrom
industrieslikegarages,workshops,factoriesetc.
Fatsandoilsarecompounds(esters)ofalcoholor
glycerol(glycerine)withfattyacids.
•Suchmattersfloatonthetopofsedimentation
tanks,oftenchokepipesinthewinter,andclog
filters.

Surfactants (surface-active agents)
Surfactantscomeprimarilyfromsynthetic
detergents.
Thesearedischargedfrombathrooms,kitchens,
washingmachinesetc.
Surfactants(orsurface-activeagents)arelarge
organicmoleculeswhichcausefoamingin
wastewatertreatment.
Duetothis,aerationofwastewaterishindered.
Alkyl-benzene-sulphonate(ABS),atypeofsurfactant
commonlyusedinsyntheticdetergents,ismore
troublesomesinceitisnotbiodegradable.

Phenols, Pesticides and Agricultural
Chemicals
•Phenolsaremostlyfoundinindustrial
wastewater.
•Ifsuchwastewatersaredirectlydischarged
intoreceivingstreams,theycauseserious
tasteproblemsindrinkingwater,specially
whenwaterisdisinfectedbychlorination.
•However,phenolscanbebiologically
oxidizediftheconcentrationsareupto500
mg/l.

Toxic Compounds
•Copper,lead,silver,chromium,arsenicand
boronaresomeofthecationswhicharetoxicto
micro-organismsresultinginthemalfunctioning
ofthebiologicaltreatmentplants.
•Theseresultsfromindustrialwastewaters.Some
toxicanions,includingcyanidesand
chromates,presentinsomeindustrialwastes
alsohinderthewastewatertreatmentfacilities.
•Hencetheirpresenceshouldbetakeninto
considerationinthedesignofbiologicaltreatment
plants.

Sulphates, Sulphides and H2S Gas
•Sulphatesandsulphidesareformeddueto
decompositionofvarioussulphurcontaining
substancespresentinwastewater.
•Thesulphateions(SO4)occurnaturallyin
mostwatersuppliesandhencetheyarealso
presentinwastewater
•Sulphur,requiredinthesynthesisofproteinsis
releasedinthedegradation.

Following are the gases that are
commonly found in untreated
wastewater
(i) Nitrogen (N2)
(ii) Oxygen (O2)
(iii) Carbon-dioxide (CO2)
(iv) Hydrogen sulphide(H2S)
(v) Ammonia (NH3)
(vi) Methane (CH4).

Oxygen in a sample of wastewater is
reported in the following three ways
(a) Oxygen consumed
(b) Dissolved oxygen and
(c) Oxygen demand.

The demand of oxygen may be
expressed in the following ways
(i) Biochemical oxygen demand (BOD)
(ii) Chemical oxygen demand (COD)
(iii) Total oxygen demand (TOD)
(iv) Theoretical oxygen demand (Th. OD).
In addition to these, the amount of organic
matter present may also be determined by
the total organic carbon (TOC) test.

Biochemical Oxygen Demand (BOD)
•TheBODmaybedefinedastheoxygen
requiredforthemicro-organismstocarry
outbiologicaldecompositionofdissolved
solidsororganicmatterinthe
wastewaterunderaerobicconditionsat
standardtemperature.
•Itisthemostwidelyusedparameterof
organicpollutionappliedtoboth
wastewateraswellassurfacewater

Chemical Oxygen Demand (COD)
•TheBODtesttakesaminimumof5days’
time,andduetothis,itisnotusefulin
thecontroloftreatmentprocesses.
•AnalternativetestistheCODtest,which
canbeusedtomeasurecontentof
organicmatterofbothwastewateras
wellasnaturalwaters.
•CODcanbedeterminedonlyin3hours
incontrastto5daysofBODtest.

Total Oxygen Demand (TOD)
•TheTODmethodisbasedonthe
quantitativemeasurementofthe
amountofoxygenusedtobumthe
organicsubstancesandtoaminorextent,
inorganicsubstances.
•Itisthusadirectmeasureoftheoxygen
demandofthesample.
•Thetestisconductedinaplatinum-catalysed
combustionchamber.

Theoretical Oxygen Demand (ThOD)
•This is a theoretical method of computing the
oxygen demand of various constituents of the
organic matter present in wastewater.
•The organic matter present in the wastewater
may be of animal or vegetable origin,
consisting of principal groups such as
carbohydrates, protein, fats and products of
their decomposition.
•Each one of these is a typical combination of
carbon, hydrogen, oxygen and nitrogen, based
on its chemical formula.

BIOLOGICAL CHARACTERISTICS OF
WASTEWATER
Domesticsewage,byitsnature,contains
enormousquantitiesofmicro-organisms.
Thebiologicalcharacteristicsofsewageare
relatedtothepresenceofthesemicroorganisms.
Thesanitaryengineermusthaveconsiderable
knowledgeof
(i)principalgroupsofmicroorganismsfoundin
waterandwastewater
(ii)pathogenicorganismsinwastewater,and
(iii)organismsusedasindicatorsofpollution.

The various micro-organisms found in water or
wastewater may be broadly classified under
three categories
(i) Aquatic plants
(ii) Aquatic animals
(iii) Aquatic moulds, bacteria and
viruses.

(i) Aquatic Plants:
Under this category, the following are included
(a) Spermophyta–Water weeds.
(b) Bryophyta–Mosses and lever words.
(c) Pteridophyta–Ferns and horsetails.
(d) Thallophyta–Algae.

(ii) Aquatic Animals
They include the following
(a) Vertebrate –Fish and amphibians.
(b) Mollusca –Mussels, snails, slugs,
limplets, cocklets
(c) Arthopoda–Crustacea, insects, spiders,
mites.
(d) Worms –Aquatic earthworms, thread
worms, rotifera.
(e) Metazoa–Hydra, polyzoa.
(f) Protozoa –Endameba histolyticaetc.

(iii) Aquatic Moulds, Bacteria and
Viruses
•Strictlyspeaking,moulds(orfungi),
bacteriaandvirusescomeunderthe
categoryofaquaticplant,butbecauseof
theirspecialimportance,theyare
generallykeptinaseparatecategory.

AEROBIC PROCESSES
Theworkoftheaerobicbacteria,i.e.
combinationwithoxygeniscalledoxidation.
Aerobicbacteriautilisefreeoxygenasan
electronacceptor.
TheendproductsofaerobicactivityareCO2,
H2O,SO4,NO3,NH3andmorebacteria.
Thebulkoftheavailableenergyfindsitsway
intocellmassorheat,yieldingastable
effluentwhichwillnotundergofurther
decomposition

ANAEROBIC PROCESSES
Theworkdonebyanaerobicbacteria,viz.
decompositionoforganicmatteriscalled
putrefactionandtheresultiscalled
liquefaction,asthesolidorganicmatteris
dissolvedbyenzymes.
Anaerobicbacteriaoxidiseorganicmatter
utilisingelectronacceptorsotherthan
oxygen.
Incarryingouttheirmetabolicprocesses,they
produceCO2,H2O,H2S,CH4,NH3,N2,
reducedorganicsandmorebacteria

Theendproductsofananaerobic
fermentationarelikelytobeodourous.
Theproductionofastableeffluentis
unlikelysincewastesdonotusuallycontain
sufficientelectronacceptorstopermit
completeoxidation.
Inthefirststage,theanaerobicbacteria
decomposecomplexorganicmatterinto
simpleorganiccompoundswhileinthe
secondstage,theaerobicbacteriaoxidise
themtoformstablecompounds

ESTIMATING THE ORGANIC
CONTENT
•Theorganicmatterpresentinthewater
bodycanbeanalyzedinlaboratoryby
determiningBiochemicalOxygen
Demand(BOD),ChemicalOxygen
Demand(COD),andbydeterminationof
TotalOrganicCarbon(TOC).

Graph between BOD Vs Time

Biochemical Oxygen Demand (BOD)
•TheBODcanbedefinedastheoxygen
requiredforbiochemicaloxidationoforganic
matterpresentinthewaterunderaerobic
conditions

BOD Test
•Biochemicaloxidationisslowprocessand
theoreticallytakesaninfinitetimetogoto
completioni.e.completeoxidationof
organicmatter.Duringthefirstfewdaysthe
rateofoxygendepletionisrapidbecauseof
thehighconcentrationoforganicmatter
present.
•Astheconcentrationoforganicmatter
decreases,sodoestherateofoxygen
consumption.

Chemical Oxygen Demand (COD)
•DuringCODdeterminationtotalorganic
contentofthewasteisoxidizedbydichromate
inacidsolution.
•Inthistesttodeterminetheoxygen
requirementofthewastewater,strongoxidizing
agent‘potassiumdichromate’isused.
•Acidicenvironmentisprovidedtoaccelerate
thereactionsbyadditionofsulphuricacid.

COD test measures virtually all oxidizableorganic
compounds whether biodegradable or not,
except some aromatic compounds which resists
dichromate oxidation.
The COD is proportional to BOD only for readily
soluble organic matter in dissolved form e.g.
sugars.
No correlation between BOD and COD exists
when:
Organic matter is present in suspended form;
under such situation filtered samples should be
used.
Complex wastewater containing refractory
substances.

Relationship between the organic
carbon fractions in wastewater

MEASURING THE EFFICIENCY
TOXICITY
Acute toxicity
Chronic toxicity

Acute toxicity
Acutetoxicityisthekindofharmwhich
describesclassicalpoisoningeffects.
Peopleoftencomparemeasuresofacute
toxicityexpressedasLD50,whichmeasures
lethaleffectsfromalargeone-timedose,
whentryingtoplacetheseexposuresin
context.Asthefamousquotegoes,“thedose
makesthepoison”characteristicsasshownin
fig

CHRONIC TOXICITY
•Outsideofcasesofacutepoisoning,mostof
thetimeweareinterestedinfindingthe
lowestlevelofdailyexposurethatcauses
harm.
•Asmentionedabove,LD50valuesgiveusvery
littleinformationabouttheselong-term
effects.Instead,chronictoxicitymetricsare
basedonthe“LowestObservableAdverse
EffectsLevel”(LOAEL)andthe“No
ObservableAdverseEffectsLevel”(NOAEL)
characteristicsasshowninfig

IN PLANT WASTE CONTROL
AND WASTE REUSE
Waste Management
•Wastemanagementisaprocessthat
combinesalltheactivitiesnecessaryfor
managingwaste–collectionofgarbage,
transportation,anddisposalofthetrash.
•Itsprimarypurposeistolessenthewasteof
unusablematerialsandavoidpotential
environmentalandhealthrisks.

•The waste can be in any form –liquid,
solid, gas –but with the help of waste
management processes, each state has its
own disposal methods.
•It offers a variety of solutions to recycle
the waste, which ultimately leads down to
finding ways to recycle it as a valuable
resource.

One of the ways to put that plan into action is through
the 3 Rsof waste management —Reduce, Reuse,
Recycle.
1.Reducemeanstocutbackontheamountof
trashwegenerate.
2.Reusemeanstofindnewwaystousethings
thatotherwisewouldhavebeenthrownout.
3.Recyclemeanstoturnsomethingoldand
useless(likeplasticmilkjugs)intosomething
newanduseful(likepicnicbenches,playground
equipmentandrecyclingbins).

WASTE REDUCTION
Wastereductionorsourcereductionisthe
practiceofpreventingwastebydecreasingor
eliminatingtheamountofmaterialsinitiallyused.
Someexamplesofwastereductioninclude
purchasingproductsinbulkquantitiesratherthan
singleservings,likecerealorpotatochips.
Anotherexampleistousereusableserving
utensilsandtraysinsteadofdisposableitems;or
tomanagegrassclippingsbyusingamulching
lawnmowerandleavingclippingsonthelawn.

Effective solid waste disposal
and management methods
1. Preventing or Reducing Waste
Generation
2. Recycling
3. Incineration
4. Composting
5. Sanitary Landfill
6. Disposal in Ocean/Sea
7. Plasma Gasification

Benefits of Waste Management
1. Better Environment
2. Reduced Pollution
3. Energy Conservation
4. Increases Employment Opportunities
5. Helps Create a Change

STORM WATER

STORM WATER CONTROL
Stormwatermanagementmeansto
managesurfacerunoff.
Itcanbeappliedinruralareas(e.g.to
harvestprecipitationwater),butis
essentialinurbanareaswhererun-off
cannotinfiltratebecausethesurfacesare
impermeable

Stormwatermanagementisessentialto
preventerosionofagriculturallandand
floodingofinhabitedurbanorrural
areas.
Bothcasescancauseseveredamagesand
contaminationoftheenvironmentif
sanitationfacilitiesareflooded.
Thisresultsinhighcostsandnotably
massivesufferingforthelocal
communities

UNIT-II
WASTE WATER
TREATMENT PROCESSES

INTRODUCTION
•Wastewatertreatmentistheprocessof
improvingthequalityofwastewaterand
convertingitintoaneffluentthatcanbeeither
returnedtothenatureorincorporatedtothe
watercyclewithminimumenvironmentalissues
orthatcanbereused.
•Theendusermaybedrinking,industrialwater
supply,irrigation,riverflowmaintenance,water
recreationormanyotheruses,includingbeing
safelyreturnedtotheenvironment.

INDUSTRIAL WASTEWATER
PRETREATMENT WORKS
Waste water Pretreatment
Theterm“pretreatment”meansthetreatmentof
wastewaterbycommercialandindustrialfacilities
toremoveharmfulmaterialsbeforebeing
dischargedtoasewersystemunderthecontrol
ofapubliclyownedwastewatertreatmentplant.
Ifyoufailtoproperlytreatyourwateror
improperlymanageyourdischarge,youcould
incurfinesandpossiblelegalaction.

PRIMARY TREATMENT OF INDUSTRIAL
EFFLUENTS
•It is of general nature and is used for removing
suspended solids, odour, colourand to
neutralizethehigh or low pH.
It involves methods of:
(i) Screening
(ii) Neutralization
(iii) Equalization
(iv) Sedimentation
(v) Coagulation

SCREENING
•It is a process through which large materials
like wooden pieces, metal pieces, paper, rags,
pebbles, fibers etc. are removed.
TYPES OF WASTEWATER SCREENS
Coarse screens
fine screens
micro screens

COARSE OF SCREENING IN
WASTEWATER TREATMENT
Coarse screens have clear openings ranging
from 6 to 150 mm (0.25 to 6 in).
Coarse screens consist of parallel bars, rods or
wires, wire mesh or perforated plates with
openings generally of circular or rectangular
shapes.

COARSE OF SCREENING IN
WASTEWATER TREATMENT

Based on the wastewater screening
method used to clean them, coarse
screens are classified into two types
1. Hand cleaned coarse screens
•Used in the screening process in wastewater
treatment at small facilities, hand cleaned coarse
screens are hand raked. They are ideal to use as a
standby during periods of high flow, or when
more modern mechanical screening methods are
under repair or maintenance.
2. Mechanically cleaned screens
•Mechanically cleaned coarse screens increase
efficiency and reduce problems in the wastewater
treatment process.

Mechanically cleaned screens can be
classified into the following four main
categories
1. Chain Driven Screens
•These front and back chain driven screens can
rake from upstream or downstream. An
automatic chain cleans the stream, increasing the
functionality of the entire wastewater treatment
solution.
2. Catenaries Screens
•These front return, front cleaned chain driven
screens use impressive, yet straight forward
internal mechanics to prevent further jamming in
the presence of large or heavy objects.

3. Reciprocating Rakes:
•Also known as a climber screen, these
wastewater treatment screening solutions use
one rake rather than multiple, making them less
efficient when facing heavy loads during the
screening process in water treatment.
4. Continuous belt screen:
•Ultra-high tech, functional and efficient, this type
of screening has many rakes and is continuous
and self-cleaning, whether facing fine or coarse
solid loads.

MICROSCREENS FOR WASTEWATER
SCREENING

MICROSCREENS FOR WASTEWATER
SCREENING
The smallest type of screening in wastewater
treatment is micro screening shown in fig .
These screens are typically low-speed drum
screens
The drums are lined with filtering fabrics with
openings of 10 to 35μm.
Wastewater enters the drum, and the
retained solid waste is collected and disposed
of waste.

FINE SCREENING IN WASTEWATER
TREATMENT PLANTS
Thescreeningprocessinwatertreatment
plantsemploysscreensthathaveclear
openingslessthan6mmcalledfinescreens.
Theyaremadeofwirecloth,wedgewireor
perforatedplates.
Likemicroscreens,theyaretoolsfor
screeninginwastewatertreatmentthatare
usedtoremovefinesolids.

Three common types of fine screening in
wastewater treatment are
•DrumScreens(rotatingcylindersinthe
flowchannel)
•StepScreens(fixedandmovableplates
acrossthewidthofthechannel)
•StaticWedgeWireScreens(usedby
largetreatmentplantswithamplefloor
space)

NEUTRALIZATION
•When pH of the industrial waste is too high or
too low then it should be neutralized by acid
or alkali and only neutral effluent should be
discharged into the public sewer.
(a) Lime stone treatment
•For acidic effluent, lime stone should be used
as it will form calcium compounds [CaCl2,
CaBr2, Ca(NO3) or CaSO4] depending upon
the presence and amount of acid.

(b) Caustic soda treatment
•Althoughitiscostlymethodbutitisalso
utilizedforneutralizingtheacid.
•Herecausticsodaisaddedintheeffluentto
makethepHneutral.Onlysmallamountof
causticsodaisneededforthiswork.

For neutralization of alkaline effluent
the following techniques are used
(a) Carbon dioxide treatment
•If factory is producing carbon dioxide then only this
method should be utilized for neutralizing the pH
otherwise it would be costlier affair. Here CO2 is
passed in alkaline effluent to make its pH almost 7.
(b) Sulphuricacid treatment
•This is a common method of neutralizing alkaline
effluent. Here sulphuricacid is added in the effluent till
pH becomes almost 7.
(c) Utilizing waste boiler –Flue gas
•The stack gas which contains about 12% carbon dioxide
is utilized to react alkaline effluent to make it neutral.

EQUALIZATION
•Wheneffluentisdischargedfromfactorythen
itspHalongwiththequantityofsuspended
solids,dissolvedsolidsetc.varyfromthe
beginningtothelastdependinguponthe
dilution,velocityandtheamountofreactants
etc.

Equalization Tanks
The equalization tanks are provided
(i) to balance fluctuating flows or
concentrations
(ii) to assist self neutralization, or
(iii) to even out the effect of a periodic "slug"
discharge from a batch process.
Types of Equalization Tanks
Equalization tanks are generally of three types:
•Flow through type
•Intermittent flow type
•Variable inflow/constant discharge type

SEDIMENTATION
This treatment is only employed for the
settlement of suspended particles by gravity.
This technique is only used in the beginning to
settle down the solid particles in a high
suspension effluent
When a thick layer of sediment continues to
settle, this is known as consolidation.
When consolidation of sediment, or sludge, is
assisted by mechanical means then this is
known as thickening.

There is a variety of methods for applying
sedimentation and include:
Horizontal flow
Radial flow
Inclined plate
Ballasted flocculation and flocculation blanket
sedimentation.

OIL SEPARATION
Anoilwaterseparatorisapieceof
equipmentusedtotreatwastewater,
makingitsafetodischargeintoan
approveddischargepoint,suchasa
sewer.
Itremovesoils,greaseand
hydrocarbons,leavingonlythenon-
hazardouswater.
Thewastewatercanthendisposeof
safelydrainage.

The four common types of oil water
separators are
Coalescing plate separators -remove oils,
grease, and hydrocarbons from wastewater
Vertical gravity separators -Vertical gravity
separators operate by controlling both fluid
velocity and pressure.
Hydro cyclone separators -Hydro cyclone oil
separators work by sending wastewater through
a 'cyclone chamber', which applies extreme
centrifugal forces.
Petrol and oil interceptor pits -These systems
typically feature two to three compartment gravity
flow systems which work on the premise that
hydrocarbons, petrol, and diesel float above water

Sour water strippers
•Thesourwaterstripperremoves
hydrogensulfideandammoniafromthe
sourwatergeneratedintherefinery.
•Thesourwaterisreceivedfromthe
refineryintheflashdrum,wherelight
hydrocarbonsareflashedoff.
•Thesourwateristhenfedtothefeed
preptank,wherethefeedismixedand
stabilized

Processof Sour water
strippers

•Thesourwateristhenheatedinthe
feed/bottomsexchangerandfedtothestripper
column.
•Steam,generatedinthere-boiler,heatsthe
waterandstripsthehydrogensulfide(H2S)and
ammonia(NH3)fromthewater.
•Thestrippedwaterfromthecolumniscooledin
thefeed/bottomsexchangerandinthestripped
watercooler,andreturnedtotherefinery.
•TheH2SandNH3removedfromthesourwater
iscooledinthepump-aroundcoolersystemor
inanoverheadcondensersystemandsentto
thesulfurrecoveryunitforfurtherprocessing

FLOATATION
•Flotation is a separation technique that
employs the use of gas bubbles as a transport
medium.
•Suspendedparticulatematterthatis
hydrophobicorhasbeenconditionedtobe
hydrophobicattachestothebubblesandflows
intheoppositedirectionofgravitytowardsthe
aqueoussolutionsurface

Removalof micro plastics
•Micro plastics (plastic particles less than 5
mm)are removed from effluent in four municipal
wastewater treatment plants using various
modern final stage treatment technologies,
including flotation.
•For the fast removal of antibiotics from water, a
coagulation-flotation approach (containing an
anionic surfactant and a cationic polyelectrolyte)
can be used.
•A common application for flotation is oily
wastewater (perhaps for density reasons).

Flotation of Metal Ions
•Ion flotation is the act of eliminating surface-
inactive ions from aqueous solutions using
surfactants or collectors, usually an ion with
the same charge as the metal ion to be
eliminated.
•Ion flotation is used to extract metal ions
from solutions containing low concentrations
of heavy metal, which can be produced by
any industrial process, including metal
working, semiconductor, and metal industries,
as well as mine water

Types of flotation
•Flotation can be divided into three categories: natural,
aided and induced flotation.
1. Natural Flotation
•Natural flotation is valid if the density has difference
which is naturally sufficient for separation.
2. Aided Flotation
•Aided flotation takes place when external means are
used to promote the separation of particles that are
naturally floatable
3. Induced Flotation
•Induced Flotation takes place when the density of
particles is artificially reduced to allow particles to
float. This flotation is based on the capacity for certain
solid and

•4. Dissolved Air Flotation (DAF)
It is a method of induced flotation with very fine
air bubble or micro bubbles which are up to 40
to 70 microns.

COAGULATION
•Coagulationisthechemicalwater
treatmentprocessusedtoremovesolids
fromwater,bymanipulatingelectrostatic
chargesofparticlessuspendedinwater.
•Thisprocessintroducessmall,highly
chargedmoleculesintowaterto
destabilizethechargesonparticles,
colloids,oroilymaterialsinsuspension

•Fordealingwaterswithsuchimpuritiesa
chemicalprocesswasevolved.
•Thisprocessremovesalltheseimpurities
withinreasonableperiodof3—4hours.
•Thischemicalprocessiscalledcoagulation
andthechemicalusedintheprocessiscalled
coagulant.

Principle of Coagulation
a.Floe formation
b.Electrical charges
a. Floe formation
When coagulant is added to the water and
thoroughly mixed, it produces a thick insoluble
gelatinous precipitate.
This precipitate is called floe.
The floe has the property of arresting the
suspended impurities in water during its
downward settlement towards the bottom of the
tank.

b) Electrical charges
•The flock ions are electrically charged
(positive) while all the colloidal particles have
negative charge.
•Therefore floes attract the colloidal particles
and cause their removal easily by settlement
at bottom of the vessel in which it is used.

Coagulants
The chemicals given below can be used as coagulants either alone or in combination
1. Sodium aluminates.
2. Sodium aluminates +
Aluminium sulphate.
3. Aluminiumsulphate.
4. Sodium aluminate + Ferric
chloride.
5. Aluminiumchloride (but used
under exceptional circumstances
only).
6. Aluminiumsulphate+ caustic
soda.
7. Ferric chloride alone.
8. Aluminiumsulphate+ hydrated
lime.
9. Polyelectrolyte.
10. Ferrous sulphate.
11. Copper sulphate.
12. Sodium aluminate + Magnesium
chloride.
13. Copper sulphate+ hydrated lime.
14. Ferric sulphate.
15. Aluminium sulphate + Sodium
carbonate.
16. Ferric sulphate+ hydrated lime.
17. Ferrous sulphate+ hydraedlime.
18. Ferrous sulphate+ chlorine.
19. Potassium permanganate +
ferrous sulphate.
20. Magnesium carbonate.

In water treatment plants following are the usual
coagulants most commonly used
1. Ferrous sulphateand lime.
2. Magnesium carbonate.
3. Polyelectrolyte.
4. Aluminiumsulphate.
5. Sodium aluminate.
6. Chlorinated copper

Dry fed Devices

Drypowderofcoagulantisfilledintheconical
hopper.
Thehoppersarefittedwithagitatingplateswhich
preventthechemicalfrombeingstabilized.
Atthebottomofthehopperarevolvinghelical
screworthetoothedwheelisfixed.
Therotationofthehelicalscreworthetoothed
wheelisregulatedthroughaventurideviceinthe
rawwaterpipe.
Whenmoredischargeispassedthroughthe
venturidevice,therotationofthescrewor
toothedwheelgetsincreasedandmore
coagulantisthrowninthewater

Dry fed Devices

Mixing Channel of dry fed device

HEAVY METAL REMOVAL
•The presence of heavy metals in wastewater has
been increasing with the growth of industry and
human activities,
•e.g.,platingandelectroplatingindustry,
batteries,pesticides,miningindustry,rayon
industry,metalrinseprocesses,tanning
industry,fluidizedbedbioreactors,textile
industry,metalsmelting,petrochemicals,
papermanufacturing,andelectrolysis
applications.
•The heavy metal contaminated wastewater finds
its way into the environment, threatening human
health and the ecosystem.

Heavymetalsarenon-biodegradableand
couldbecarcinogenicthus,thepresenceof
thesemetalsinwaterbyimproperamounts
couldresultincriticalhealthissuestoliving
organisms.
Themostpopularheavymetalsarelead(Pb),
zinc(Zn),mercury(Hg),nickel(Ni),cadmium
(Cd),copper(Cu),chromium(Cr),andarsenic
(As).
Althoughtheseheavymetalscanbedetected
intraces;however,theyarestillhazardous.

AERATION
Aeration brings water and air in close contact
in order to remove dissolved gases (such as
carbon dioxide) and oxidizes dissolved metals
such as iron, hydrogen sulfide, and volatile
organic chemicals (VOCs).
Aeration is often the first major process at the
treatment plant.
During aeration, constituents are removed or
modified before they can interfere with the
treatment processes.

•Aeration also helps remove dissolved metals
through oxidation, the chemical combination
of oxygen from the air with certain
undesirable metals in the water
•The efficiency of aeration depends on the
amount of surface contact between air and
water, which is controlled primarily by the size
of the water drop or air bubble

Chemicals Removed or Oxidized by
Aeration
Constituents commonly affected by aeration are
• Volatile organic chemicals, such as benzene (found
in gasoline), or trichloroethylene, dichloroethylene
(used in dry-cleaning or industrial processes)
• Ammonia
• Chlorine
• Carbon dioxide
• Hydrogen sulfide
• Methane
• Iron and Manganese

AERATION EQUIPMENTS
Aerators fall into two categories. They either
introduce air to water, or water to air.
The water-in-airmethod is designed to produce
small drops of water that fall through the air.
The air-in-watermethod creates small bubbles of
air that are injected into the water stream.
All aerators are designed to create a greater
amount of contact between air and water to
enhance the transfer of gases and increase
oxidation.

Water-Into-Air Aerators
Cascade Aerators
Cone Aerators
Slat and Coke Aerators
Draft Aerators
Spray Aerators

Cascade Aerators

Cone Aerators

Slat Aerators

Coke Trays Aerators

Type 1, Draft Aerators

Type 2, Draft Aerators

Spray Aerators

Air-Into-Water Aerators
a.Pressure Aerators
b.Centrifugal Aerators

Centrifugal Aerators

AIR STRIPPING
Airstrippingisaprocessbywhichaliquid,usually
wastewater,isbroughtintointimatecontactwith
agas,usuallyair,sothatsomeundesirable
volatilesubstancespresentintheliquidphase
canbereleasedandcarriedawaybythegas.
Processessuchasmechanicalsurfaceaeration,
diffusedaeration,sprayfountains,sprayortray
towers,andcountercurrentpackedtowersare
encompassedbythetermairstripping.

a. Corrosion

A certain amount of dissolved oxygen is present
in raw and treated waters.
However, dissolved oxygen can cause corrosion.
Corrosion can occur whenever water and oxygen
come into contact with metallic surfaces.
Generally the higher the dissolved oxygen
concentration, the more rapid the corrosion
The solution to this problem is to not over-aerate.
This may be difficult because no definite rule
exists as to what constitutes over-aeration.
The amount of aeration needed will vary from
plant to plant and will also vary with the season.

Air Stripping

False Clogging of Filters (Air Binding)
•Filters in water containing a high amount of
dissolved oxygen will have a tendency to
release the oxygen in the filter as it passes
through.
•The process can continue until the spaces
between the filter media particles begin to fill
with bubbles Called air binding, this causes
the filter to behave as though it is plugged and
in need of backwashing.

Slow Removal of Hydrogen Sulfide
Hydrogen sulfide is most efficiently removed,
not by oxidation, but by the physical scrubbing
action of aeration.
This removal is dependent on the pH of the
water. At a pH of 6 or less, the hydrogen
sulfide is easily removed.
If the water has a high pH, the hydrogen
sulfide will ionize, precluding removal by
aeration.

Three basic control tests are required
for aeration
1. Dissolved oxygen -The concentration of
dissolved oxygen can be used to determine if the
water is over or under-aerated. The pH test will give
an indication of the amount of carbon dioxide
removed.
2. pH -pH increases as carbon dioxide is removed.
pH can also be used to monitor the effective range
for hydrogen sulfide, iron, and manganese removal.
3. Temperature -The saturation point of oxygen
increases as the temperature decreases. As water
temperature drops, the operation.

Unit-III
POLLUTION
FROM MAJOR
INDUSTRIES

SYLLABUS

SOURCES, CHARACTERISTICS, WASTE
TREATMENT FLOW FROM TEXTILES
TEXTILES MILLS WASTE
•The Fibers used in the Textile Industry may be
broadly classified into four groups:
•cotton, wool, regenerated and synthetics.

Cotton textile mill waste
•Carding:-It is a process in the manufacture of
spun yarns whereby the staple is opened,
cleaned, aligned and formed into a continuous
untwisted strand called sliver.
•Drawing:-It is the process of increasing the
length per unit weight of sliver.
•Combing:-A method to remove short fibers,
foreign matter from cotton stock by pressing it
through a series of needles or combs
•Spinning:-It is a process by which a long strand of
fibers is drawn out to a short strand and
converted into a yarn. After drawing out, it is
subjected to twisting and the resulting yarn is
wound into a bobbin.

•Winding:-It is the process of transfer of a yarn
or thread from one type of package to
another.
•Weaving:-It is the process of interlocking two
yarns of similar materials so that they cross
each other at right angles to produce a woven
fabric The entire liquid waste from the textile
mills comes from the following operation of
slashing (or sizing), scouring and resizing,
bleaching, mercerizing, dyeing and finishing.

WOOLEN TEXTILE MILLS WASTE
•Wool wastes originate from scouring,
carbonizing, bleaching, dyeing, oiling, fuelling
and finishing operations.

Effects of the cotton textile and
woolen textile mill wastes on
receiving streams / sewers
•The alkalinity and the toxic substances like
sulphides and chromium affect the aquatic
life; and also interfere with the biological
treatment process; some of the dyes are also
found toxic.

Treatment of Cotton and Woolen
Textile Mill Waste
The pollution load of the waste is dealt with in the
operations like segregation, equalization, neutralization,
chemical precipitation, chemical oxidation and biological
oxidation.
Several chemicals are used to reduce the BOD by chemical
coagulation.
These are alum, ferrous sulfate, ferric sulfate, ferric
chloride etc., lime or sulfuric acid is used to adjust the pH
in this process.
Calcium chloride is found to be effective in treating wool-
scouring waste.
The dye wastes may be treated economically by biological
methods, with prior equalization, neutralization and
chemical oxidation for certain wastes.

Synthetic Textile Mill Waste
•The most prominent man made synthetic fibers
are Rayon, nylon and polyester.
•These fabrics require no processing for the
removal of natural impurities as they are
manmade.
•Manufacture of synthetic fabrics involves two
steps
(i) Manufacture of the synthetic fiber
(ii) Preparation of the cloth

PULP AND PAPER MILL WASTE
•The paper mills use the 'pulp' as the raw
material , which is again produced utilizing
different cellulosic materials like wood ,
bamboo, jute, straw mainly of rice and
wheat, waste paper, bagasseetc. in the pulp
mills.

Manufacturing Process
The Process of manufacturing of paper may
be divided into two phases -Pulp making and
then making of final product of paper.
The major portion of the pollution from
papermaking originates in the pulping
processes.
Raw materials are reduced to a fibrous pulp
by either mechanical or chemical means.
The bark is mechanically or hydraulically
removed from wood before it is reduced to
chips for cooking.

Characteristics of pulp and paper mill
wastes
•Thevolumedependsmainlyonthemanufacturing
procedure,andthewatereconomyadoptedinthe
plant.
•Ithasbeenobservedthatawelloperatedandwell
managedintegratedpulpandpapermill
employingKraftprocessforpulping,producesa
wastevolumeintherangeof225to320m3per
tonofpapermanufactured.
•Themillsmanufacturingspecialqualityofpaper
producelargeramountofwaterforwashingand
bleaching.

The effect of wastes on receiving
water courses or sewers
Crudepulpandpapermillwastes,orinsufficiently
treatedwastescauseveryseriouspollutionproblems,
whendischargedintothestreams
Thefinefibersoftenclogthewaterintakescreensin
thedownstreamside.
Atoxiceffectmayalsobeinducedupontheflora(all
plantlife)andfauna(allanimallife)ofthestream
duetosulfitesandphenolsinthewaste.
ThebottomdepositofLignin-Cellulosicmaterials
nearthepointofthedischargeofthewasteinastream
undergoslowdecompositionandmayleadtothe
dissolvedoxygendepletionfollowedbythecreationof
anaerobicconditionanddestructionoftheaquatic
life.

The treatment of the waste may consist of all or a
combination of some of the following processes
1.Chemical treatment for color removal
2.Activated carbon for color removal
3.Physical treatment for clarification
4.Biological treatment of the waste

The treatment of the pulp and paper
mill waste

Flow Chart of Lagooning

FERMENTATION
•TheFermentationindustriesincludebreweries
anddistillerymanufacturesofalcoholand
certainorganicchemicalsandsomepartsof
thepharmaceuticalindustrysuchasproducers
ofantibiotics.
•Thetransformationofgrapejuiceintowine,
themanufactureofalcoholfrommolasses,
andtheuseofyeastindoughtomakebread
arefamiliarexamplesoffermentation.

TANNING INDUSTRY
Tanning Process
The tanning process consists of three basic
stages
1. Preparation of the hides for tanning.
2. Tanning proper.
3. Finishing.

Tannery wastes originate from the beam
house and the tan yard.
In the beam house curing, fleshing, washing,
soaking, remove haring, lime splitting,
bating, picklingand degreasing operations are
carried out.
In the tan yard, the final leatheris prepared
by several processes.
These include vegetable or chrome tanning,
shaving and finishing.
The finishing operation includes bleaching,
stiffing and fat liquoring and coloring.

PHARMACEUTICAL INDUSTRY
•Pharmaceuticalwastecanresultfrommany
activitiesandlocationsinahealthcare
facility.
•Ifyouhaveacompoundingpharmacyon
site,itgeneratesdrugwaste.
•Anywheremedicinesareemployedcanbe
thesiteofspills,half-usedbottles,andIV
equipmentwithresidualmedicineonit.

Sources of Pharmaceutical Waste
• Wastewater Treatment Plants (WWTPs)
These WWTPs focus on stopping waste from
reaching the water or sources of water.
• Humans and Animals
• Pharmaceutical Waste Treatment Plants
• Unused Drugs
• Healthcare Institutions.
• Homes and Farms Where Food is Grown
• Personal Care Products.

Characteristics of pharmaceutical
waste
In general, the composition of
pharmaceutical wastewater is complex,
which has
• High concentration of organic matter,
• Microbial toxicity,
• High salt, and
• It's hard to biodegrade

DAIRY WASTES
Units Operation in a Dairy
•Receiving Stations
The receiving station serves as a collection point for
raw milk from the farmers. When milk is delivered
to the dairy in cans and these cans are emptied,
rinsed and washed and in some cases sterilized
before returning.
•Bottling
Raw milk received is weighed and classified
(generally based on the fat content), it is preheated,
pasteurized, cooled and then filled into bottles,
polythene bags, cardboard packets etc.

Product Making
•Dry milk, milk powder, cheese, butter and other
products as ice cream, condensed milk are
prepared out of milk.
Sources of wastes
•Wasteproducingoperationsarewashingof
bottles,cases,cans,tanks,coolingequipment,
Processingequipmentandfloors
•Dripping,leaks,spillagesandoverflowsdueto
improperequipmentorinefficientoperation.
•Dischargesfromevaporators
•Wastedbuttermilkandwhey(wateryliquidleft
whenmilkformscurds).
•Spoiledrawortreatedproducts

Characteristics of diary wastes

Treatment of Waste
•As evident from the high BOD/COD ratio, the
dairy wastes can be treated efficiently by
biological processes.
Reduction of volume and strength of the
wastes by
a.Prevention of spills, leakages and dropping of
milk from cans.
b.By reducing the amount of water for
washes
c.By segregating the uncontaminated cooling
water and recycling the same.

SUGAR MILL WASTES
CHARACTERISTICS AND
COMPOSITION OF WASTE WATER
MANUFACTURING PROCESS SUGAR
MILL WASTES

Introduction
•In Countries like India, Cuba and Jamaica, the
sugar is produced from sugar canes, while in
many other places beetrootsare used as the
raw materials for the sugar production.
•In India most of the sugar mills operate for
about 4 to 8 months just after the harvesting
of the sugar canes

Manufacturing Process
Thesugarcanesarecutintopiecesand
crushedinaseriesofrollerstoextractthe
juice,inthemillhouse.
Juiceisextractedfromthesugarcane,leaving
afibrousresiduecalledbagasse,whichcanbe
usedasafuelfortheboilersorcanbe
disposedofassolidwaste.

1.The milk of lime is then added to the juice
and heated, when all the colloidal and
suspended impurities are coagulated; much
of the color is also removed during this lime
treatment.
2.Lime is added to the extracted juice to raise
its pH and to prevent the inversion of the
sucrose molecule to glucose and fructose.
3.The coagulated juice is then clarified to
remove the sludge.

•The clarifier is further filtered through filter
presses, and then disposed off as solid waste.
•The filterate is recycled to the process, and
the entire quantity of clarified juice is treated
by passing sulphur dioxide gas through it.
•The process is known as “sulphitation
process"; color of the juice is completely
bleached out due to this process.

•The clarified juice is then preheated and
concentrated in evaporators and vacuum pans.
The partially crystallized syrup from the vacuum
pan, known as "massecuite“(massecuite
(countable and uncountable, plural
massecuites)A suspension of sugar crystals in a
mother liquor, after boiling of syrup; produced in
a sugar factory.)is then transferred to the
crystallizers, where complete crystallization of
sugar occurs.

Characteristics of Sugar Mill Waste

STEEL PLANT WASTES
•Integrated steel plants usually consist of five
main units, Viz; Coal washer, Coke oven blast
furnace, steel melting shop and rolling mills.
•In addition to the above the plants may have
auxiliary units like oxygen plant and power
plant for their own uses.

Characteristics of Coal Washeries

METAL PLATING WASTE
Platingistheapplicationofaplate,orcoat,of
metaltoasurfacefordecoration,reflectionof
light,protectionagainstcorrosion,or
increasedwearingquality.
Electroplatingisthemostcommonmethod
becauseitpermitsthecontrolofthethickness
oftheplating.Weoffer:Gold,Nickel,Copper,
andChromeplating.

OIL REFINERIES WASTE
Sources of Waste Water & Manufacturing Process
Crude oils are complex mixtures of hydrocarbons
of varying molecular weight and structure.
These hydrocarbons range from simply highly
volatile substances to complex waxes and
asphaltic compounds.
The final petroleum products are obtained from
the crude oil through a series of operations viz.
topping, thermal cracking, catalytic cracking,
catalytic reforming etc.

Ingeneral,thecrudeoilisfirstsubjectedto
fractionaldistillationintheprocessknownas
“topping“.
Theproductsobtainedarecalledrawproducts
andincluderawgasoline,rawnaphtha,raw
kerosene,gasoil,fueloiletc.
Nowtheseintermediaterefineryproductsare
againtreatedtoyieldvariousfinishedmarket
productsaspertherequirements.
Theoperationspracticedinclude"catalytic
cracking"or"thermalcracking"andfurther
purificationprocesseslike"acidtreatment”,
"sweetening treatment”,
"hydrodesulphurization"etc.

FERTILIZER PLANT WASTE
Fertilizer industry can be divided into three main
categories depending upon
1. Fertilizer raw materials
2. Fertilizer intermediates
3. Fertilizer products

Fertilizer Intermediates
•1. Sulphuricacid
•2. Phosphoric acid
•3. Nitric acid
Fertilizer products:
SOLID
N -Fertilizers
•1. Ammonium nitrate
•2. Urea
•3. Ammonium sulfate P -Fertilizers
•4. Super phosphates NPK fertilizers

PETROCHEMICAL COMPLEX
WASTE
Petroleum,knownas"industrialblood",isimportantenergy
andindustrialrawmaterial,aswellasanimportant
productionanddailynecessitiesofhumanbeings.
Withtherapiddevelopmentofeconomyandsociety,oiland
itsproductshavebeenwidelyusedinvariousfieldsofthe
nationaleconomyandpeople'sdailylife,andtheiruseand
demandaregraduallyincreasing.
Intherefiningprocess,petroleumwillproduceby-products
thathaveanimpactontheenvironment,including
petrochemicalwastewater.
Asoneofthemainsourcesofpetroleumpollution,
petrochemicalwastewaterhasaseriousnegativeimpacton
economicdevelopmentandtheecologicalenvironment.

The treatment process of oily
wastewater

CORN STARCH INDUSTRY
•Corn starch industry contributes almost 12%
of starch production.
•Maizestarch,producedworldwide,
contributeshugeamountofacidiceffluent
(pH3-5)containinghighChemicaloxygen
demand(COD)(10000-30000mg/L),
biologicaloxygendemand(BOD)(4000-8000
mg/L),nitrogenouspollutant(400-900mg/L)
andotherpollutants.

•Conventionalmethodsofanaerobicdigestion
andnitrification-denitrificationprocessare
widelybeingusedtotreatstarchindustry
effluent.
•TheanaerobicdigestionrequiresneutralpH
operationthusincreasesoperationalcost.
•Similarly,nitrificationanddenitrification
processesarelengthyprocessesconsuming
highoperationalcostandrequiresecondary
treatmentforgeneratedexcesssludge.

•Starch is widely used in food,
pharmaceutical, paper & textile industry in
large quantities. Maize is used as a bulk
source of starch production in various
countries.
•It is the highest produced cereal crop and
widely cultivated throughout the world,
counts among major contributors of raw
material in bulk industrial scale.

•Themaingoalofallavailabletechnologiesareto
removemaximalremovalofcarbonaceousand
nitrogenouscontaminantfromwaterandto
makethewaterreusableforirrigationpurpose
ortomakeitpotablebyapplyingfurther
advancedtechnologieslikereverseosmosisafter
biologicaltreatment
•Thetechnologiesdevelopedovertimeforaerobic
andanaerobictreatmentareinconsiderationto
neutralpHwastetreatment,whilestarch
effluentsarehighlyacidicinnature.
•Thusthereisacompulsoryrequirementto
neutralizetheeffluentbydilutionorchemical
additionbeforeintroducingittotreatment
system

OdourRemoval
•Wastewatertreatment,istheprocessofremoving
contaminantsfromwastewaterandhouseholdsewage.
•Itincludesphysical,chemical,andbiological
processestoremovephysical,chemicalandbiological
contaminants.
•Odorsemittedbywastewatertreatmentaretypically
anindicationofanaerobicconditions.
•Earlystagesofprocessingwilltendtoproducetoxic
gases,likeHydrogenSulphide(HS),SulphurDioxide
(SO),BromineandOxidesofNitrogen,Chlorineetc
•whichcanbeevencorrosiveinhigherconcentrations,
whichmakesodorremovalanecessarycriteria.

Chemical Oxidation System
•Chemicaloxidationprocessinvolvesoxidizing
agentsreactingwithorganicpollutantsinthe
airandoxidizingthem.
•Essentially,thesepollutantsundergoa
chemicalreactionthattransformstheminto
non-toxicsubstancesandtrapsodor
efficiently.
•Theseadvancedtechnologyfiltersnotonly
removeodorsbutalsodestroysotherharmful
organicmatters.

•Chemicaloxidationeffectivelyoxidizes
99%organicpollutantstolessdangerous
orharmlesssubstances
•Removesothertypesofodorcausing
substanceslikeaminescompounds.
•Helpstoachieveimmediateodorcontrol.

Biological Oxidation System
•TheknowledgeandexperienceofAqozahas
madeitpossibletoadapttothemosteco-
friendlytechnologiesforthechangingtimes
andchangingneeds.
•Ouremergingodourcontrolunitsuse
biologicaloxidationforthedestructionand
removalofVOCs,organicmatters,odorsand
hydrocarbons.

WASTE MINIMIZATION AND
RESOURCE CONSERVATION
•Waste is also the inefficient use of utilities such as electricity, water,
and fuel, which are often considered unavoidable overheads.
•The costs of these wastes are generally underestimated by
managers.
•It is important to realize that the cost of waste is not only the cost
of waste disposal, but also other costs such as:
▪Disposal cost
▪Inefficient energy use cost
▪Purchase cost of wasted raw material
▪Production cost for the waste material
▪Management time spent on waste material
▪Lost revenue for what could have been a product instead of
waste
▪Potential liabilities due to waste.

Classification of Waste Minimization
(WM) Techniques

Source Reduction
Under this category, four techniques of WM are
briefly discussed below:
a) Good Housekeeping
b) Process Change
(i) Input Material Change
(ii) Better Process Control
(iii) Equipment Modification
(iv) Technology change
c) Recycling
i) On-site Recovery and Reuse
ii) Production of Useful by-product
d) Product Modification

Unit-Iv
BIOLOGICAL
WASTE WATER
TREATMENT
PROCESS

SYLLABUS

LAGOONS
A lagoon is a shallow body of water separated
from a larger body of water by barrier islands,
reefs (ridge of material or near the surface of the
ocean), isthmuses(An isthmus isa narrow strip of
land that connects two larger landmasses and
separates two bodies of water) or peninsulas(an
area of land that is almost surrounded by water)..
When barrier bars and spits form at the mouth of
a bay and block it, a lagoon forms.
The lagoons would gradually get filled up by
sediments from the land giving rise to a coastal
plain.

Lagoon –Types
• Coral lagoons, and
• Barrier Island or coastal lagoons
• River Mouth Lagoons
• Artificial Lagoons

Coral Lagoons –Locations
Coral lagoons have the conditions necessary for coral growth.
For many island communities in the Pacific, the coral lagoons
are of great importance.
Coral lagoons are restricted to tropical open seas.
Coral lagoons are mainly found within 25°latitude of the
Equator.
Coral lagoons are found in the isolated places of the
Caribbean, parts of the Indian Ocean, and found widely in
the western Pacific.
• The atolls of the Pacific Ocean are the most spectacular
examples of coral reefs.
• The Great Barrier Reef of Australia is another example
where coral lagoons are found.
• These are the most common type of lagoon that find in the
coastal regions.

Coastal or Barrier Island Lagoons –
Locations
Coastal or Barrier Island lagoons are formed only
where there is abundant sediment for construction of
the protective barrier islands.
Coastal or Barrier Island lagoons rarely occur where
high cliffs form the coast.
These lagoons are usually associated with low coasts.
They occur where the swells are usually less violent.
Coastal or Barrier Island lagoons are characterized by
brackish marshes, fine-grained sedimentation, and
quiet water conditions.

Barrier Island Lagoons

River Mouth Lagoons
They form at the mouths of the coastal rivers.
These can also be considered coastal lagoons.
They have brackish water which means partly
fresh water and partly saltwater.
These can be seen most commonly in
Newzealand and South Pacific islands.

Artificial Lagoons
These are man-made and not natural.
These are increasing and becoming popular.
These can be used for recreation or residential or
other purposes.
They are more controlled and safe as they can be
made anywhere with suitable conditions and
requirements.
The only freshwater can also be found here
rather than brackish water.

STABILIZATION BASINS

STABILIZATION BASINS
•WasteorWastewaterStabilizationPonds
(WSPs)arelarge,man-madewaterbodiesin
whichblackwater,greywaterorfaecalsludge
aretreatedbynaturaloccurringprocessesand
theinfluenceofsolarlight,wind,
microorganismsandalgae.
•Thepondscanbeusedindividually,orlinked
inaseriesforimprovedtreatment

There are three types of ponds,
(1) anaerobic,
(2) facultative and
(3) aerobic (maturation), each with different
treatment and design characteristics.
WSPs are low-cost for O&M and BOD and
pathogen removal is high.
However, large surface areas and expert design
are required.

•WSPsshouldbelinkedinaseriesofthreeormorewith
effluentbeingtransferredfromtheanaerobicpondto
thefacultativepondand,finally,totheaerobic
pond.
•Theanaerobicpondistheprimarytreatmentstage
andreducestheorganicloadinthewastewater.
•Theentiredepthofthisfairlydeepman-madelakeis
anaerobic.
•SolidsandBODremovaloccursbysedimentationand
throughsubsequentanaerobicdigestioninsidethe
accumulatedsludge.
•Anaerobicbacteriaconvertorganiccarboninto
methaneandthroughthisprocess,removeupto60%
oftheBOD.

•InaseriesofWSPs,theeffluentfromthe
anaerobicpondistransferredtothefacultative
pond,wherefurtherBODisremoved.
•Thetoplayerofthepondreceivesoxygenfrom
naturaldiffusion,windmixingandalgae-
drivenphotosynthesis.
•Thelowerlayerisdeprivedofoxygenand
becomesanoxicoranaerobic.
•Settleablesolidsaccumulateandaredigestedon
thebottomofthepond.
•Theaerobicandanaerobicorganismswork
togethertoachieveBODreductionsofupto
75%.

Anaerobic and facultative ponds are designed
for BOD removal, while aerobic ponds are
designed for pathogen removal.
An aerobic pond is commonly referred to as a
maturation, polishing, or finishing pond
because it is usually the last step in a series of
ponds and provides the final level of treatment.

Anaerobic Treatment Ponds (APs)
•The main function of anaerobic ponds is BOD
removal, which can be reduced 40 to 85 %
(WSP 2007).
As a complete process, the anaerobic pond
serves to:
Settleundigestedmaterialandnon-degradable
solidsasbottomsludge
Dissolveorganicmaterial
Breakdownbiodegradableorganicmaterial

Facultative Treatment Ponds (FPs)
•FacultativeTreatmentPondsarethesimplest
ofallWSPsandconsistofanaerobiczone
closetothesurfaceandadeeper,anaerobic
zone.
•TheyaredesignedforBODremovalandcan
treatwaterintheBODrangeof100to400
kg/ha/daycorrespondingto10to40g/m2/day
attemperaturesabove20°C.

The facultative pond serves to:
• Further treat wastewater through sedimentation
and aerobic oxidation of organic material
• Reduce odour
• Reduce some disease-causing microorganisms
if pH raises
• Store residues as bottom sludge

Advantages of Stabilization basins
• Lower operating cost in terms of operators and
chemicals
• Large settling zone –less susceptible to poor
settling or sludge bulking
• Minimal operator attention
• Takes up less area –Smaller footprint
• Faster process
• Higher BOD reduction efficiency
• More concentrated bacterial population
• Can treat higher loaded waste streams

Disadvantages of Stabilization basins
• Harder to remove accumulated biological solids
• Poorer removal efficiencies , particularly in
cold weather
• Takes up more area –larger footprint
• More initial capital
• Higher operational cost –dewatering chemicals &
solids disposal
• Must be properly managed to better handle
upsets
• Susceptible to sludge settling Issues (bulking)
• Need for highly trained operators –more
testing to control & requires more attention.

AERATED LAGOONS
•Anaeratedlagoon(oraeratedpond)isa
simplewastewatertreatmentsystemconsisting
ofapondwithartificialaerationtopromote
thebiologicaloxidationofwastewaters.
•Therearemanyotheraerobicbiological
processesfortreatmentofwastewaters,they
allhaveincommontheuseofoxygen(orair)
andmicrobialactiontoreducethepollutants
inwastewaters.

Types of Aerated Lagoons
Aerated lagoons are deep waste stabilization ponds in
which sewage is aerated by mechanical aerators to
stabilize the organic matter present in the sewage,
rather than relying only on photosynthetic oxygen
produced by algae.
Thus aerated lagoons represent a system of sewage
treatment that is intermediate between oxidation
ponds and activated sludge systems.
•Depending on how the microbial mass of solids is
handled in the aerated lagoons the same are classified
as:
(i) Facultative aerated lagoons and
(ii) Aerobic aerated lagoons.

Characteristics of Aerated Lagoons

Advantages of Aerated Lagoons
(i)Theaeratedlagoonsaresimpleandruggedin
operation,theonlymovingpieceofequipment
beingtheaerator.
(ii)Theremovalefficienciesintermsofpower
inputarecomparabletosomeoftheother
aerobictreatmentmethods.
(iii)Civilconstructionmainlyentailsearthwork,and
landrequirementisnotexcessive.Aeratedlagoons
requireonly5to10percentasmuchlandas
stabilizationponds.
(iv)Theaeratedlagoonsareusedfrequentlyfor
thetreatmentofindustrialwastes.

ACTIVATED SLUDGE PROCESSES
Activated sludge treatment can define as a
conventional method, which can separate the
solid wastes, suspended organic matter, soluble
matter and parasites.
Activated sludge treatment involves a series of
stages, which firstly separates the raw or
primary sludge, then separates the waste
activated sludge and finally involves disinfection
and clarification of the effluent.
Therefore, it contributes a significant role in the
control of water pollution by eliminating the
undesired chemicals, particulate matter and
parasites from the sewage and industrial waste.

Activatedsludgetreatmentcandefineasthe
wastewatertreatmentplant,whicheliminates
theparticulatematterlikesand,unwanted
inorganicandorganicwastesandharmful
microorganismsfromthesewagewaste.
Theprocessisfollowedbytheprimary,
secondaryandtertiarytreatmentmethods.

•Primarytreatmentisaphysicalmethod,which
involvestheseparationoflargesolidmatterlike
leaves,sand,gravelparticlesetc.
•Secondarytreatmentisabiologicalmethod,
whichseparatesthesuspendedandsoluble
organicmatterbymakingtheuseofbacterial
flocs.
•Tertiarytreatmentisachemicalmethod,which
isafinalstagetodisinfectthesecondaryeffluent
bymakingtheuseofchlorinegas.

Flow Diagram of Activated Sludge Process

Advantages
•Theprocessofactivatedsludgetreatmentreleaseshigh-
qualityeffluent(wastewaterreleasedfromthesewage).
•ItensuresthemaximumreductionofBODand
parasitesupto99%duringthesecondarytreatmentof
wastewater.
•Activatedsludgeprocesscanresistdifferentorganicand
hydraulicshockload.
•Theactivatedsludgetreatmentplantcanbe
establishedintheminimallandareacomparedtothe
waterstabilizationpond.
•ItalsoensuresmaximumremovalofnutrientslikeN2,
K,Phfromtheorganicmatter.

Disadvantages
•Theactivatedsludgeprocessrequireshighcapital.
•Italsorequiresacontinuouselectricitysupply.
•Itsoperationandmaintenancerequireskilled
labour-power.
•Theprocesscannotbeestablishedatthe
communitylevel.
•Theconstructionofanactivatedsludgeplant
requiresexpertdesign,andgenerally,allare
equipment’sarenotlocallyavailable.
•Effluentfromthewastewaterrequiresproper
disinfectionandappropriatedischarge.

Trickling filtration
•Tricklingfilterprocessisoneofthetypesof
aerobicwastewatertreatment.
•Itisafixed-bedbioreactorthatisthepartof
secondarywastewatertreatment,which
eliminatesthecoarseparticles,suspended
organicandinorganicwaste,smallcolloidsetc.
•outoftheprimaryeffluent.Atricklingfilteris
alsocalledbiologicalfilter,asitmakestheuseof
activemicrobialmassasabioweapontodegrade
thewasteoutofprimarysewage.

•Tricklingfilterprocesscandefineasthe
biologicalsystem,whichtendstoseparateor
degradethemaximumorganicandinorganic
waste(upto85%)outoftheprimaryorraw
sludgeviatheslimelayer.
•Thedesigningofatricklingfilterunitincludes
asupportstructure,pebbleorplasticfilled
mediaandrotarydistributor.

Trickling Filter Process

Trickling Filter Unit

Layout of Trickling Filter

•Dependinguponthehydraulicandorganic
shockload,tricklingfilterscanbecategorized
intotwotypes,namely
–highrateandlowratetricklingfilter.
Thehydraulicloadingratecandefineasthe
sewageflow(Q)perunitvolume(V)offilterbed
inaday,whiletheorganicloadingratecandefine
asthekilogramsofBOD(Y5)introducedintothe
perunitvolume(V)inaday.

Advantages
• It is a simple and reliable secondary treatment unit of the
wastewater.
• It can be used to degrade a variety of organic waste.
• Trickling filter can resist shock loadings.
• It efficiently oxidizes the ammonia or efficient in
ammonium oxidation.
• Trickling filter aids to produce effluent free of BOD,
COD, nutrients, suspended colloids etc.
• Its construction requires a small land area, unlike
constructed wetlands.

Disadvantages
Its designing requires high capital costs.
The designing of a trickling filter requires expert skills
Its operation and maintenance require regular
attention by the skilled labourpersonnel.
The trickling filter process is a continuous process,
which needs an uninterrupted supply of electricity and
wastewater distribution.
It sometimes causes flies breeding and odourproblem.
The effluent produced by the trickling filter needs to
treated further by the chemical disinfectants.
Accumulation of excessive biomass may cause clogging
of the TF-unit.
Not all parts and materials may be locally available.

ROTATING BIOLOGICAL CONTACTORS

•A rotating biological contactor (or RBC) is a type
of fixed media filter which removes both organic
matter and ammonia from water.
•It can be added to a packaged plant for more
efficient ammonia removal, replacing the aerator
in both location and function.
•Although RBC's are less prevalent than trickling
filters or oxidation ditches, they produce a high
quality effluent and wastewater operators should
be familiar with them.

Advantages
• High contact time and high effluent quality (both
BOD and nutrients)
• High process stability, resistant to shock hydraulic or
organic loading
• Short contact periods are required because of the
large active surface
• Low space requirement
•Well drainable excess sludge collected in clarifier
• Process is relatively silent compared to dosing
pumps for aeration
• No risk of channelling
• Low sludge production

Disadvantages
• Continuous electricity supply required (but uses
less energy than trickling filters or activated sludge
processes for comparable degradation rates)
• Contact media not available at local market
• High investment as well as operation and
maintenance costs
• Must be protected against sunlight, wind and rain
(especially against freezing in cold climates)
• Odourproblems may occur
• Requires permanent skilled technical labourfor
operation and maintenance

ANAEROBIC DECOMPOSITION
•Anaerobicdigestioncanbedescribedasbiologicaloxidation
ofbiodegradablewastebymicrobesunderanaerobic
conditionsorinsimplertermsitistheprocessofconverting
complexorganicmoleculesintosimplermoleculeswiththe
helpofmicroorganismsinabsenceofoxygen.
•Theendproductofthisproducthasahighconcentrationof
carbondioxideandmethane.
•Anaerobicdigestionisabiochemicalprocess,itmainlyutilizes
substrateswithhighorganicmatter,suchassludge,domestic
waste,sewage,andwastefromafeedstockofcattle.
•Itismainlyusedinfermentationtechnologyandthe
managementofwaste.

Anaerobic Digestion Process
•Anaerobicdecompositionisperformedinanaerobic
digestersmainlybyagroupofanaerobicbacteriacalled
methanogensandacetogens,thegroupofbacteriado
notuseoxygenastheirsourceofelectrondonorrather
theyacceptelectronsfromacetateandmethanefortheir
ener
1. Hydrolysis
2. Acidolysisor Acidogenesis
3. Acetogenesis
4. Methanogenesis

Hydrolysis

Hydrolysis
Itisalsoknownastheliquefactionofcomplex
molecules.
Theprocessofbreakingthechainswiththehelpof
hydrolyzingenzymesisknownashydrolysis.
Highmolecularweightpolymericcomponentsare
brokendownintosimplesugarsandmonomerswhich
canbereadilyaccessibletobacteria.
Acetate,hydrogen,andsomeVFAs(VolatileFattyAcid)
producedduringthesesteps.
VFAscannotbedirectlyusedbythemicroorganismsso
theyarefirstcatabolizedintosmallmoleculesthatcan
beutilizedbythebacteria.

Acidolysis or Acidogenesis
•Itistheprocessofacidicbreakdownofoligo
polymersandcompoundsintosimpler
molecules.
•Acidogenesisperformedbyacidogenic
bacteria,duringthisreactionammonia,
carbondioxide,andhydrogensulfide,aswell
asotherbyproducts,areformed.

Acetogenesis
Acetogenesis is the process of formation of
acetic acid with the help of acetogens.
This reaction produces carbon dioxide and
hydrogen as the main byproduct.

Methanogenesis
•Thisisthefinalstepofanaerobic
decomposition.
•ItisapHsensitivereactionthatoccurs
betweentherangeofpH6.5topH8.During
thisstep,theintermediateproductfromother
stepsisusedtoproducemethane,carbon
dioxide,andhydrogen.

The Breakdown of Three Major Food
Groups are as Follows
Carbohydrates→simplesugars→alcohol
andaldehydes→organicacids
Protein→aminoacids→organicacid+
NH3
Fatsandoils→organicacid

The Genera of Microbes Responsible for
Anaerobic Digestion are:
1. Pseudomonas
2. Flavobacterium
3. Escherichia
4. Aerobacter

•The Genera of Bacteria Responsible for
Methanogenesis:
1. Methanococcus
2. Methanobacteria
3. Methanosarcina

Advantages of Anaerobic Decomposition
1.The lower operating cost of the digester makes it
commercially viable.
2. Sludge occupies less volume and is easier to dry.
3. Reduce production of landfill gas, which when
damaged leads to an outburst of methane (major
greenhouse gas)
4. Methane produced in the digestorcan be used as
biogas, an alternative source of energy.
5. It reduces the energy footprint of conventional
wastewater treatment technology.
6. It has reduced the use of chemical fertilizer as the
digestive (the content of the reactor after completion
of digestion) can be used as fertilizer.

LABORATORY EVALUATION OF
ANAEROBIC TREATMENT
Conventionaldigestersaremainlyusedforthe
stabilizationofprimaryandsecondarysludge,originating
fromsewagetreatment,andforthetreatmentofindustrial
effluentswithahighconcentrationofsuspendedsolids.
Theyusuallyconsistofcoveredcircularoregg-shapedtanks
ofreinforcedconcrete.
Thebottomwallsareusuallyinclined,soastofavourthe
sedimentationandremovalofthemostconcentratedsolids.
Thecoveringofthereactorcanbefixedorfloating(mobile).
Sinceconventionaldigestersarepreferablyusedforthe
stabilizationofwasteswithahighconcentrationofparticulate
material,thehydrolysisofthesesolidscanbecomethelimiting
stageoftheanaerobicdigestionprocess.

Depending on the existence of mixing devices
and on the number of stages,
Three main digester configurations have been
applied
• low-rate anaerobic sludge digester
• one-stage high-rate anaerobic sludge
digester
• two-stage high-rate anaerobic sludge
digester

Schematic Representation of A Low
Rate Anaerobic Sludge Digester

Schematic representation of a one
stage high rate anaerobic sludge
digester

Schematic Representation of a Two
Stage High-Rate Anaerobic Sludge
Digester

ADSORPTION
•Adsorption may be defined as the process of
accumulation of any substance giving higher
concentration of molecular species on the surface of
another substance as compared to that in the bulk.
•When a solid surface is exposed to a gas or a liquid
molecules from the gas or the solution phase
accumulate or concentrate at the surface.
•The phenomenon of concentration of
molecules of a gas or liquid at a solid surface
is called adsorption.
•"Adsorption" is a well established and powerfull
technique for treating domestic and industrial effluents.
•In water treatment, the most widely method is
"adsorption" once the surface of activated carbon.

Types of Adsorbents
1.Oxygen-containing compounds are typically
hydrophilic and polar, including materials such
as:
•Silica gel
•Zeolites

Treatment of Waste Water by
Adsorption

Mostly two common carbon
adsorption process such as
(1) Granular Activated Carbon (GAC)
(2) Powdered Activated Carbon
(PAC)

2.Carbon-based compounds are typically
hydrophobic and non-polar, including materials
such as:
✓Activated carbon
✓Graphite
3.Polymer-based compounds are polar or non-
polar function groups in a porous polymer
matrix.

Classification of Adsorbents
1. Engineered adsorbents
»(a) Activated carbon
»(b) Polymeric adsorbents
»(c) Oxidicadsorbents
»(d) Synthetic zeolites
2. Natural and low cost absorbents:
»(a) Mineral absorbents
»(b) Agricultural waste/by products
»(c) Industrial waste/ by products

Types of Adsorption
Depending on the type of attractions between
adsorbateand adsorbent, the adsorption can be
divided into two types:
•Physical Adsorption or Physisorption
•Chemical Adsorption Chemisorptions

Physical Adsorption (or) Physisorption
•Whentheforceofattraction
existingbetweenadsorbateand
adsorbentareweakundercoal
forceofattraction,theprocessis
calledphysicaladsorptionor
physisorption.

Characteristics of Physisorption
o Energetic and kinetics.
o Effect of temperature.
o Effect of pressure.
o Specificity.
o Nature of adsorbate
o Surface area of adsorbent.

Chemical Adsorption (or)
Chemisorption
•Whentheforceofattractionexisting
betweenadsorbateandadsorbent
arechemicalforcesofattractionor
chemicalbond,theprocessiscalled
chemical adsorption or
chemisorption.

Characteristics of Chemisorption
•✓Energetic and kinetics.
•✓Effect of temperature.
•✓High of pressure. High specificity.
•✓Surface area.

Factors Influencing Adsorption
Adsorption on a solid is influenced by a number of
factors such as
✓Surface area.
✓Nature of adsorbate.
✓Hydrogen ion concentration (pH) of the solution.
✓Temperature.
✓Mixed solutes.
✓Nature of adsorbate.

Modes of Operation
•✓Batch flow system
•✓Column flow system.

Types of Adsorption Isotherm
•✓Type I Adsorption Isotherm
•✓Type II Adsorption Isotherm
•✓Type III Adsorption Isotherm
•✓Type IV Adsorption Isotherm
•✓Type V Adsorption Isotherm

Theory of activated carbon
Activatedcarbon,alsoknownasactivatedcharcoal,
isaformofcarbonprocessedtohavesmall,low-
volumeporesthatincreasethesurfaceareaavailable
foradsorptionorchemicalreactions.
Ithashighdegreeofmicroporosity.
Theword'active'isalsosometimesusedfor'activated'.
Thesurfaceareamayvarygreatlydependingupon
precusor(rawmaterial)andtheconditionof
carbonizationformakingactivecarbon
Anactivationlevelsufficientforusefulapplication
maybeobtainedsolelyfromhighsurfacearea.
Chemicaltreatmenthasbeenfoundtoenhancethe
adsorptionpropertiesofactivatedcarbon.

•ACisusuallyderivedfromcharcoal.
•Whenderivedfromcoal,itisreferredtoasactivatedcoal.
•Activatedcokeisderivedfromcoke.
•Thereforeactivatedcarbon,activatedcharcoal,activated
coke,activecarbonmaybesaidtoperformthesame
function.
•Chemicalorphysicalactivationmethodsandmicrowave
radiationmethodsarethecommonlyusedtechniques
adoptedforpreparationofactivatedcarbon.
•Theyareusedasanadsorbentbytheseparationand
purificationindustries.
•Theyarecomposedofamicroporous,homogenous
structurewithhighsurfaceareaandshowradiation
stability.
•Theiradsorptioncapacitydependsonporosityandits
surfacechemistry.

Activated Carbon Powder
Granules Pellets

TYPES OF ACTIVATED CARBON
(1) Powdered Activated Carbon (PAC)
(2) Granular Activated Carbon (GAC)
(3) Extruded Activated Carbon (EAC)

Powdered Activated Carbon (PAC)
•Powderedactivatedcarbonsgenerallyfallin
theparticlesizerangeof5to150Å,withsome
outlyingsizesavailable.
•PAC’saretypicallyusedinliquid-phase
adsorptionapplicationsandofferreduced
processingcostsandflexibilityinoperation.

Granular Activated Carbon (GAC)
Granularactivatedcarbonsgenerallyrangein
particlesizesof0.2mmto5mmandcanbe
usedinbothgasandliquidphaseapplications.
GACsarepopularbecausetheyofferclean
handlingandtendtolastlongerthanPACs.
Additionally,theyofferimprovedstrength
(hardness)andcanberegeneratedandreused.

Extruded Activated Carbon (EAC)
Extrudedactivatedcarbonsareacylindrical
pelletproductranginginsizefrom1mmto5
mm.
Typicallyusedingasphasereactions,EACs
areaheavy-dutyactivatedcarbonasaresultof
theextrusionprocess.

Applications of Activated Carbon (AC)

Applications of Activated Carbon (AC)
•Activatedcarbonisanincrediblydiversematerialthatlends
itselftothousandsofapplicationsthroughitssuperior
adsorbentcapabilitiesvariousapplicationofactivatedcarbon
•Theavailabilityofhighsurfaceareaofparticlespossessed
byACaswellitsadsorptiveabilitymakesitasignificant
constituentinmanyindustries.
•Industrieslike;petroleum,fertilizerplants,nuclear,
pharmaceuticals,cosmetics,textilesautomobile,and
vacuummanufacturingallusesAC.
•AChasfoundtobegoodporousmaterials,whichmakeit
veryeffectiveinadsorptionofsolutesfromaqueoussolutions.
•Thiswassuggestedtobeduetothepossessionoflarge
specificsurfacearea.

Applications of Activated Carbon (AC)
•Metal recovery
• Food & Beverage
• Medical
• Air Emission purification
• BiogassPurification
• Remediation
• Waste water purification

SLUDGE QUALITY
CONSIDERATIONS
To determining sewage sludge quality it depends
on three following parameters:-
The presence of pollutants (arsenic,
cadmium, chromium, copper, lead, mercury,
molybdenum, nickel, selenium, and zinc)
The presence of pathogens (e.g., bacteria,
viruses, parasites)
The sewage sludge’s attractiveness to
vectors (e.g., rodents, flies, mosquitoes)

STRIPPING OF VOLATILE
ORGANICS
AirStrippingandVOCRemoval-Movingair
throughcontaminatedgroundwaterorsurface
waterinanabove-groundtreatmentsystem.
Airstrippingremoveschemicalscalled
"volatileorganiccompounds"or"VOCs.“
VOCsarechemicalsthateasilyevaporate
whichmeanstheycanchangefromaliquidto
avapor(agas).

Sources of volatile organic
compounds
•Man made
•Anthropogenic

Man made volatile organic
compounds emissions
• Transportation
• Petroleum and petrochemical industry
• Electrical power generation
• Chemical process industries

Effects of VOC’s
• Photochemical smog
• Health effects
• Global warming
•Odour
• Carcinogenicity

Harmful chemical of VOC’s
• Benzene
• Toluene
• Xylene
• Phenol
• Pyridine
• Chloroform
• Methyl Ethyl Ketone

Flowchart of VOC Removal Technology

VOC Organic Component Removal

NITRIFICATION AND
DENITRIFICATION
•Nitrificationis the
conversionofammonia
(NH3+)tonitrate(NO3-).
•Denitrificationis the
conversionofnitrate(NO3-)
tonitrogengas(N2).

NITRIFICATION AND
DENITRIFICATION
Theconversionofammonia
intonitritesisknownas
nitrification.
Theconversionofnitratesinto
nitrogen isknown as
denitrification

NITRIFICATION AND
DENITRIFICATION

Nitrification
The process of conversion of ammonia or reduced
nitrogen compounds into the easily absorbable form
of nitrogen that is nitrates and nitrites.
It is an aerobic process.
Chemoautotrophic bacteria play a major role in this
process.
First, the ammonia is converted into nitrite by the
process of oxidation.
NitrococcusandNitrosomonastake part in this
process.
Nitrite is oxidisedto nitrate with the help
ofNitrobacter.
Then, nitrate is taken up by the root of the plant.

Nitrification
Nitrificationisatwo-stepprocess.
BacteriaknownasNitrosomonasconvert
ammoniaandammoniumtonitrite.
Next,bacteriacalledNitrobacterfinishthe
conversionofnitritetonitrate.
Biologicalnitrificationistheprocessinwhich
Nitrosomonasbacteriaoxidizeammoniatonitrite
andNitrobacterbacteriaoxidizenitritetonitrate.
Thisprocessresultsintheoverallconversionof
ammoniatonitrate.

•Nitrificationistemperaturesensitive.The
optimumtemperaturefornitrificationis
generallyconsideredtobe30°C.
•NitrificationconsumesalkalinityandlowerspH
intheactivatedsludgemixedliquor.
•pHbelow6.5orabove8.0cansignificantly
inhibitnitrification.
•OptimumpHvaluesfordenitrificationare
between7.0and8.5.Denitrificationisan
alkalinityproducingprocess.

Denitrification
The process of conversion of nitrates and
nitrites into the gaseous form of nitrogen is
called denitrification.
It is mostly converted to nitrogen and nitrous
oxide.
Bacteria participating in this reaction
arePseudomonasandThiobacillus.

UNIT -V
SLUDGE
TREATMENT
AND
DISPOSAL

INTRODUCTION
•Sludge is an odious, semisolid residual that resembles
thick soft mud produced from the solid–liquid
separation processes in wastewater treatment.
•It is usually very inconsistent in its composition and
most often unmanageable.
•The final destination of treated sewage sludge usually
is the land.
•Dewatered sludge can be buried underground in a
sanitary landfill.
•It also may be spread on agricultural land in order to
make use of its value as a soil conditioner and fertilizer.

SLUDGE IS CATEGORIZED INTO THE
FOLLOWING GROUPS
a. Primary sludge
•Primary sludge is generated by the separation
of settleablesolids from the raw wastewater
during the primary sedimentation treatment
process.
•The total solids concentration in raw primary
sludge ranges between 5% and 9%, and is
typically 6%.

b. Secondary sludge
•Secondary sludge is the activated waste biomass
resulting from biological treatments.
•Some sewage plants also receive septic tank
solids from household on-site wastewater
treatment systems.
c. Sludge produced in advanced treatment
process
•It may contain viruses, heavy metals,
phosphorous, or nitrogen.

THE OBJECTIVES OF THE SLUDGE TREATMENT
• To decrease moisture content in the
sludge (Volume reduction)
• To remove organic matters
• To destroy microorganisms
• To eliminate toxic materials.

SLUDGE DISPOSAL METHOD
•Sludgefromconventionalwastewater
treatmentplants(WWTP)isderivedfrom
primary,secondaryandtertiarytreatment
processes.
•Mostoften,thesludgeproducedhasa
concentrationofafewgramsperliter,andis
highlybiodegradable.
•Eachprocesshasadifferentimpactonthe
waterpollutionload.

SLUDGE DISPOSAL METHOD
•Pre-treatment
•

Pre-treatment
•Pre-treatment consists of various physical and
mechanical operations, such as screening,
sieving, blast cleaning, oil separation and fat
extraction.
•Pre-treatment allows the removal of
voluminous items sands and grease.
•The residues from pretreatments are not
considered to be sludge.
•They are disposed of in landfills.

Primary sludge
Primary sludge is produced following primary
treatment.
This step consists of physical or chemical
treatments to remove matter in suspension
(e.g. solids, grease and scum).
The most common physical treatment is
sedimentation.
Sedimentation is the removal of suspended
solids from liquids by gravitational settling.

•Chemicaltreatmentsarecoagulationand
flocculation.
•Coagulationandflocculationareusedto
separatesuspendedsolidswhentheirnormal
sedimentationratesaretooslowtoprovide
effectiveclarification.

Secondary
sludge
•Secondarysludgeisgeneratedfromtheuseof
speciallyprovideddecomposerstobreakdown
remainingorganicmaterialsinwastewaterafter
primarytreatment.
•Theactiveagentsinthesesystemsaremicro-
organisms,mostlybacteria,whichneedthe
availableorganicmattertogrow.
•Therearevarioustechniquessuchaslagooning,
bacterialbeds,activatedsludgeaswellas
filtrationorbiofiltrationprocesses.

Tertiary sludge
Tertiarysludgeisgeneratedwhencarryingout
tertiarytreatment.
Itisanadditionalprocesstosecondarytreatment
andisdesignedtoremoveremainingunwanted
nutrients(mainlynitrogenandphosphorus)
throughhighperformancebacterialorchemical
processes.
Thesetreatmentsarenecessarywhenahighlevel
ofdepollutionisrequired,forexamplein
sensitiveareasidentifiedintheMemberStates.

SLUDGE
CHARACTERISTICS
•Wastewatersludgetypeissolid,semi-
solid,ormuddyliquidwhereeachof
thoseconsistsofthevariousorganicor
non-organicmaterials,heavymetals,
pesticides,polycyclicaromatic,phenols,
andmanyothermaterials.

Screening
•Screeninggrindersarebeneficialformedium-size
plants.Reduced-sizesolidsarereturnedtoraw
sewageormixedwithsewagesludgedepending
ongrinderlocationrelatedtothetreatmentunits
Itcontainsbothorganicandinorganicmatter.
Grit
•Finalgritdisposalisbyburial.Itmaybeineither
asanitarylandfillorotheracceptedlandfill
operation.Thegritmustbehavingaminimumof
6inches(15cm)ofsoilcovering.Thisisto
preventvectorattractionandodorsItinvolves
organicandinorganicmatter,especiallyfatsand
grease.

Characteristics of Primary and
Secondary Sludge

ANAEROBICAND AEROBIC
DIGESTION
Anaerobicdigestionisacommonmethodofreadying
sludgesolidsforfinaldisposal.
Allsolidssettledoutinprimary,secondaryorother
basinsarepumpedtoanenclosedairtightdigester,
wheretheydecomposeinananaerobicenvironment.
Therateoftheirdecompositiondependsprimarilyon
properseeding,ph,characterofthesolids,temperature
etc.digestionservesthedualpurposeofrenderingthe
sludgesolidsreadilydrainableandconvertingaportion
oftheorganicmattertogaseousendproducts.
Itmayreducethevolumeofsludgebyasmuchas50%
organicmatterreduction.Afterdigestion,thesludgeis
driedand/orburnedorusedforfertilizerorlandfill.

The following factors are measures of the
effectiveness of digestive action
• Gas production,
• Solids balance,
• B.O.D,
• Acidity and ph,
• Sludge characteristics and odors.

Aerobic sludge treatment
process in waste water

Aerobic Digestion
Works
Aerobicdigestionisthedegradationofthe
organicsludgesolidsinthepresenceofoxygen.
Theoxygenisintroducedasfinebubblesofair
intothereactor.
Themicro-organismsinthesludgeconvertthe
organicmaterialtocarbondioxideandwater,and
theammoniaandaminospeciestonitrate.
Aerobicdigestionisgenerallylowerincapitalcost
thananaerobicdigestion(AD)forplantsbelow
20,000m3/dwastewatercapacity.

In addition, aerobic digestion
• It is simple in construction, requiring no tank
covering
• More easily operated and controlled than AD
• It does not generate nuisance odors
• It can process sludge with a high nutrient
content
• Generates supernatant streams having low in
BOD and nutrient concentrations
• Removes ammoniacalcompounds, and
• Achieves a similar VSS removal (40−50%) as
that for AD.

THICKENING
•Thickening is a first step to reduce
sludge water content.
•Sludge reaches 10 to 30 % dryness,
and can still be pumped.

Gravity thickening

Gravity thickening
Gravitythickeningistheprocessbywhichbio-
solidsarecondensedtoproduceaconcentrated
solidsproductandarelativelysolids-free
supernatant.
Wateriscollectedatthetop.
Theprocessiscapableofthickeningthesludgeby
2to8times,bringingitfromafewgrams/litreto
afewtensofgrams/litre.
Performingcostsarerelativelylow,asonlyan
electricitysupplyisneededtooperatetheharrow
andthepumps.

•Gravitythickenersgenerallyretain80−90%of
thesolidsinthethickenedproductstream,
dependingonthesludgecharacteristicsand
theefficiencyoftheprecedingconditioning
stage.
•Gravitythickenersarewidelyusedforprimary
andmixedsludge,butarelesseffectivefor
wasteactivatedsludge(WAS).

Advantages
• Gravity thickening equipment is simple to
operate and maintain.
• Gravity thickening has lower operating costs
than other thickening methods such as DAF,
gravity belt or centrifuge thickening.
Truck traffic at the plant and the farm site can be
reduced;
• Trucking costs can be reduced;
• Existing storage facilities can hold more days of
biosolidsproduction

Disadvantages
•Scumbuild-upcancauseodors.Thisbuildup,whichcan
occurbecauseoflongretentiontimes,canalsoincrease
thetorquerequiredinthethickener.Finally,scumbuild-
upisunsightly.
•Greasemaybuildupinthelinesandcauseablockage.
Thiscanbepreventedbyquickdisposalorabackflush.
•Septicconditionswillgeneratesulfur-basedodors.This
canbemitigatedbyminimizingdetentiontimesinthe
collectionsystemandattheplant,orbyusingoxidizing
agents.
•Supernatantdoesnothavesolidsconcentrationsaslow
asthoseproducedbyaDAForcentrifugethickener.Belt
thickenersmayproducesupernatantwithlowersolids
concentrationsdependingontheequipmentandsolids
characteristics.

Dissolved Air Floatation
Thickener

Dissolved Air Floatation
Thickener
•Thetechniqueofairflotationcanbeusedwhen
thesolidparticleshavealowrateofsettlement,
andinsewagesludgetreatmenttheprocessis
usedtothickensurplusactivatedsludge.
•Dissolvedairflotationisawatertreatment
processthatclarifieswastewaterbyremovalof
suspendedsolids,oils,greases,BOD,COD,and
metals.
•Thisisachievedbydissolvingairinthe
wastewaterunderpressureandthenreleasing
theairatatmosphericpressureinaflotation
tank.

Rotary drum
filtering

Rotary drum filtering
Rotarydrumthickeningincreasesthesludgesolids
concentration(i.e.thickensthesludge)byagitating
thesolidsinaslowly-rotatingvesselwithporous
wallsthoughwhichthewater(orfiltrate)drainsthe
sampleofrotarydrumfilteringforsludgedisposal.
Arotarydrumthickener(RDT)isbasedonthesame
principleasagravitybeltthickener(GBT),inthat
waterdrainsfromthesludgethrougharetaining
porousmedium.
ForanRDTtheporousmediumisthecylindricalwall
ofa0.5−1.5mdiameterdrumwhichrotatesat
speedsbetween5and20RPMwhilethesludge
continuallypassesthroughit.

Applications
• The rotary filter is most suitable for continuous
operation on large quantities of slurry.
• If the slurry contains considerable amount of
solids, that is, in the range of 15-30%.
• Examples of pharmaceutical applications include
the collection of calcium carbonate, magnesium
carbonate and starch.
• The separation of the mycelia from the
fermentation liquor in the manufacture of
antibiotics.
• Block and instant yeast production.

Gravity Belt
Thickening
Gravitybeltthickening(GBT)increasesthesludge
solidsconcentration(i.e.thickensthesludge)by
allowingthewater(orfiltrate)todrainfromthesludge
undergravitythroughapermeablemedium(amoving
belt)onwhichthesludgesits.
Gravitythickeningistheprocessbywhichbiosolidsare
condensedtoproduceaconcentratedsolidsproductand
arelativelysolids-freesupernatant.
Thebiosolidstechnologyfactsheetforgravity
thickeningprovidesadescriptionofgravitythickening
applicabilitytowastewatertreatmentplants.

Gravity Belt Thickening
•GBTisalow-pressureprocesswhichoperates
byallowingthewatertodrainfromthesludge
undergravity.
•Abeltfilterpress,ontheotherhand,operates
bysqueezingwaterfromthesludgeunder
pressure,andachievesahigherdrysolids
concentrationasaresult.

Gravity Belt Thickening

Centrifugation
Centrifugalthickeningincreasesthesludge
concentration(i.e.thickensthesludge)by
encouragingtheparticlestomigratetothe
wallsofarapidlyrotatingcylindricalvessel
undertheinfluenceofacentrifugalforce.
Thereareanumberofconfigurationsof
centrifugeusedforreducingthewater
contentofsludge.
Theycanbeusedforboththickeningand
dewatering.

Centrifuges are available in a number of
configurations, including
• Solid bowl
• Basket, and
• Disc-nozzle.

VACUUM FILTER

Operation of a Vacuum Filter Cycle
Thefiltercycle,whichisonefullrevolutionof
thedrum,consistsofthreeparts;theformtime,
thedryingtime,andthedischargetimethefirst
partofthecycle,whenthedrumissubmerged,is
thecakeformationorformtime.
Itisduringthispartofthecyclethatsludgesolids
arebeingdrawntothemediabytheeffectofthe
vacuumandarereceivingtheinitialcompression
necessarytoformacohesivecake.
Initially,thewaterandfineparticlesaredrawn
throughthemedia,leavingonlythecoarser
particlesontheface.

However,asthedrumcontinuestorotate,andthe
thicknessofthesludgecakeisincreased,thefiner
particlesaretrappedaswellasthecoarsesolids.
Thereisanindicationthattherateofcakeformationis
proportionaltothesquarerootofthetimeelapsedsince
thestartofcakeformation,butthisismodifiedbyan
upperlimitofcakethicknessbeyondwhichthecake
formationfallsrapidly.
Thisupperlimitoccursastheflowresistanceofthe
cakeapproachestheavailablepressuredifferential
suppliedbythevacuum.
Thisconsequentlyplacesanupperlimit,whichisthe
minimumtimenecessarytoformacakeofsufficient
thicknesstobesuccessfullydischarged.
Withintheselimits,theformtimecanbevariedby
changingthetotalcycletime,orbychangingthe
submergence

Thesecondportionofthecycleisthedryingtime.
Duringthispartofthecycle,moistureisremoved
fromthecakeandascertainsamountof
compressiontakesplace.
Theamountofmoistureremovedisdependent
upontwocontrollingfactors.
First,thecakemaybecompressedtoalevel
beyondwhichresistancetoairflowprevents
additionaldewateringatthepressuredifferential
available.
Secondly,dryingmaybecarriedtoapointwhere
thecakebeginstocrackandthepressure
differentialacrossthecakedropsduetoleakage
ofairthroughthecracks.

The moisture content of the cake may be
altered by making adjustments in the total
cycle time, or by changing the submergence.
The third and final portion of the total cycle
time is the discharge time.
In the case of-a belt type filter, the media with
the cake is separated from the drum, the cake
is discharged, and the media is washed and
returned to the drum.

PRESSURE FILTERS
Pressurefilterpressdewateringisabatchprocess
inwhichdewateringisachievedbyforcingthe
waterfromthesludgeunderhighpressure.
Itproducesacakethatisdrierthanthat
producedbyanyotherdewateringalternative.
Anotheradvantageisthatthehighsolidscapture
resultsingoodfiltratequality.
Disadvantagesincludehighcapitalcost,relatively
highoperationandmaintenancecosts,high
chemicalcosts,andalargearearequirementfor
theequipmentinsmallwastewatertreatment
plants.

Amongthevarioustypesofpressurefilter
pressesthathavebeenusedfordewatering
sludge,thetwomostcommonlyusedarethe
fixed-volumerecessedplatefilterpressand
thevariable-volumerecessedplatefilter
press.
Fixed-VolumeRecessedPlateFilterPress
Thefixed-volumepressconsistsofaseriesof
recessedplatesheldinaframeandpressed
togethereitherhydraulicallyor
electromechanicallybetweenafixedendand
amovingend

Solidscapturesolidsinfeed-solidsin
filtratesolidsinfeedx100
CakeunderCompression
Shapeoffilterchamberduringfiltration
Shapeoffilterchamberduringcake
compressionbydiaphragm

Pressure Filters

BELT PRESSURE FILTER
Thebeltfilter(sometimescalledabeltpressfilter,or
beltfilterpress)isanindustrialmachine,usedfor
solid/liquidseparationprocesses,particularlythe
dewateringofsludgeinthechemicalindustry,mining
andwatertreatment.
Abeltfilterpress(BFP)providessludgedewatering
bypressingthesludgetoforcethewaterthrougha
permeablemedium.
Theprocessproducesacake(thedewateredproduct)
havingadrysolids(DS)contentof30%ormoreinthe
caseofprimarysludge.
Thisistobedistinguishedfromthelower-energy
gravitybeltthickenerprocesswhichachievesa
maximumDScontentof~10%.

ABFPcombinesdrainageandmechanical
pressuresequentiallytoremovewater.
Theequipmentnormallycomprises2−3
recirculatingbelts,withtwobeltscombining
atsomepointtocompressthesludgeand
squeezewaterfromit.
Theconditionedsludgefeedisfirstconveyed
alongagravitydrainagesectionofoneofthe
porousbelts,aswithagravitybeltthickener.
Itisthensubjecttopressureasitispassed
betweentworecirculationbelts,forminga
wedgezoneattheinlet,whichtravelovera
roller.

Incommonwiththegravitybeltthickener,the
beltsaresubjecttocleaningwithwaterspray
tolimitthepluggingofthefilterbeltpores.
Thewastewashwateriscombinedwiththe
filtrate.
TheoverallperformanceoftheBFPis
dependentonthefeedsludgesourceand
characteristicsandthedosingconditions.
Aswithallotherthickeninganddewatering
technologies,primarysludge–bothrawand
anaerobicallydigested–aremorereadily
filteredthanwasteactivatedsludge(WAS).

SLUDGE SAND DRYING BED FILTER

SLUDGE SAND DRYING BED FILTER
Sludgedryingbedsprovidesludgedewateringby
allowingtheliquidtobothdrainundergravitythrough
apermeablemediumonwhichthesludgesits,andto
evaporateunderambientconditions.
Lagoonsprovidedewateringthroughevaporationalone.
Dryingbedsareuncomplicatedindesignandoperation,
sincetheyinvolvesimplyspreadingthesludgeasathin
(upto300mm)layeroveraporousbedofsandand
gravel.
Thewateristhenallowedtodrainthroughthebedand
intoanetworkofembeddeddrainagepipestoallowit
tobecollected.
Furtherwaterremovalisprovidedbyevaporationfrom
thesludgesurface.

•Thedegreeofdewateringattainabledependson
thedryingdurationand,ifthebedisuncovered,
theweatherconditions.
•Oncesufficientlydewatered,whichtakes10−15
daysandisevidentfromtheappearanceofcracks
andadarkbrownsurface,thesolids(30−40%DS
ordrysolids)aremechanicallyremoved.
•Removalisnormallyusingafrontendloaderor
specialistmechanicalsludgeremovalequipment

FACTOR AFFECTING DEWATERING
PERFORMANCE
Under land disposal the following methods may
be included
• Burial
• Fill
• Application as fertilizer or soil conditioner

Burial Sludge Disposal

Burial Sludge Disposal
This method is used principally for raw sludge,
where, unless covered by earth, serious odor
nuisances are created.
The sludge is run into trenches two to three
feet wide and about two feet deep.
The raw sludge in the trenches should be
covered by at least 12 inches of earth

Fill
•Useofsludgeforfillisconfinedalmostentirely
todigestedsludgewhichcanbeexposedtothe
atmospherewithoutcreatingseriousor
widespreadodornuisances.
•Thesludgeshouldbewelldigestedwithoutany
appreciableamountofraworundigestedmixed
withit.
•Eitherwetorpartiallydewateredsludge,suchas
obtainedfromdryingbedsorvacuumfilterscan
beusedtofilllowareas

Fill
Lagoonsusedfordisposalareusuallyfairly
deep.Sludgeisaddedinsuccessivelayers
untilthelagooniscompletelyfilled.
Finaldisposalofdigestedsludgebylagoonsis
economicalasiteliminatesalldewatering
treatments.
Itisapplicable,however,onlywherelow
wasteareasareavailableontheplantsiteor
withinreasonablepipingdistance.
Theyarefrequentlyusedtosupplement
inadequatedryingbedfacilities.

Soil Conditioning or Fertilizer
•Sewage sludge contains many elements
essential to plant life, such as nitrogen,
phosphorous, potassium, and in addition, at
least traces of minor nutrients which are
considered more or less indispensable for
plant growth, such as boron, calcium, copper,
iron, magnesium, manganese, sulfur, and
zinc.

Soil Conditioning or Fertilizer
In fact, sometimes these trace elements are
found in concentrations, perhaps from
industrial wastes, which may be detrimental.
The sludge humus, besides furnishing plant
food, benefits the soil by increasing the water
holding capacity and improving the tilts, thus
making possible the working of heavy soils
into satisfactory seed beds.
It also reduces soil erosion.

Nitrogen is required by all plants, particularly where
leaf development is required.
Thus, it is of great value in fertilizing grass, radishes,
lettuce, spinach, and celery.
It stimulates growth of leaf and stem.
Phosphorous is essential in many phases of plant
growth.
It hastens ripening, encourages root growth and
increases resistance to disease.
Potassium is an important factor in vigorous growth.
It develops the woody parts of stems and pulps of
fruits.
It increases resistance to disease, but delays ripening
and is needed in the formation of chlorophyll.

INCINERATION
Incineration−orcombustionofsewagesludge
isthemostwidely-acceptedalternativeend
disposalmethodafterlandspreading.
Itisanoxidativemethod,convertingthe
organiccarbon,nitrogen,sulphur,nitrogen
andphosphorusintogaseousand
predominantlymineral(i.e.inorganic)solid
products.

Theincinerationofsludgewaste,derivedfrom
wastewater,usesthermaltreatmenttooxidizeorganic
mattercontainedinthesludge.
Incinerationiscarriedoutinafurnaceusingoxygen
andhightemperatures(over850degreesCelsius)
resultingintotal,ornear-total,oxidizationofthe
organicmaterial.
Incinerationisthemostestablishedandwidely
implementedofthesludgethermochemicaltreatment
processes,withtheoriginalsewagesludgeincinerators
installedinthemid-1930s.
Therearecurrentlyhundredsoflargesewagesludge
incineratorsinoperationacrosstheworld,mostof
whichgeneratepoweraswellasconvertingthesludge
toash.

Sludge sand drying bed filter

Incineration of Sewage Sludge in Coal-
Fired Power Plants

Incineration of Sewage Sludge in Coal-
Fired Power Plants
Toavoidthehighcostsofastand-alone
incinerationplantforsludgeandtoimprovethe
energyrecoveryefficiency,possibilitieshavebeen
investigatedtoincineratedriedsludgeinacoal-
firedpowerplant.
Inthiscase,beneficialusecanbemadefrom
existingcoalcombustioninstallationsandexisting
exhaustgastreatmentsystems.
Becausetheamountofincineratedsludgeis
smallcomparedtotheamountofcoal,theeffect
oftheincinerationofthesludgeontheairand
ashqualitiescanbeneglected.

THANK
YOU

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