These slides show sewage characteristics and its design

These slides show sewage characteristics and its design. Look at it , if you need hope this help you.

1. ENVIRONMENTAL ENGINEERING
-
II
SEWAGE CHARACTERISTICS

2. ENVIRONMENTAL ENGINEERING
-
II SEWAGE CHARACTERISTICS
Composition
>99.0% Water
Solids
70% Organic 30% Inorganic
Sewerage characteristics can be divided into three broad
categories:-
1.Physical
2.Chemical
3.Bacteriological

3. ENVIRONMENTAL ENGINEERING
-
II DEFINITIONS OF SOME TERMS IN SEWAGE
CHARACTERIZATION
SOLIDS
TOTALSOLIDS:
Includebothsuspendedanddissolvedsolids.Itismeasured
byevaporatingaknownvolumeofsampleandthe
weightingtheresidue.Resultsareexpressedinmg/l
SUSPENDEDSOLIDS:
Thesearesolidswhicharepertainedonapre-weighedglass
fiberfilterof0.45µ,103-105
0
C

4. ENVIRONMENTAL ENGINEERING
-
II
DISSOLVEDSOLID:
Filtratewhichhaspassedthought0.45µfilteris
evaporatedinchinedish.Theresiduegivesthedissolved
solids.
SETTLEABLESOLIDS:
Itisthefractionofthesolidsthatwillsettleinanimhoff
conein30-60minutes.Theseareexpressedasmg/l.or
ml/l(asperformedinthelab.)

5. ENVIRONMENTAL ENGINEERING
-
II
Theygivearoughmeasureoftheorganiccontentorinsome
instancesoftheconcentrationofBIOLOGICALSOLIDS
suchasbacteria.Thedeterminationismadebyignitionof
residueson0.45µfilterinaMufflefurnaceat550
0
C.The
residuesfollowingtheignitioniscallednon-volatilesolids
orashandisroughmeasureofthemineralcontentofthe
wastewater.
(Note:-Mostoftheinorganicandmineralcontentdonot
volatilizeat550
0
Candarequietresistant)
VOLATILE SUSPENDED SOLIDS

6. ENVIRONMENTAL ENGINEERING
-
II
Bacteriaplacedincontactwithorganicmatterwillutilize
itasfoodsource.Intheutilizationoftheorganicmaterial
itwilleventuallybeoxidizedtostableandproductssuch
asCO
2
andH
2
O.
“Theamountofoxygenrequiredbythebacteriato
oxidizetheorganicmatterpresentinsewagetostableend
productsisknownasbiochemicaloxygendemand.”
BOD

7. ENVIRONMENTAL ENGINEERING
-
II
Itistheamountofoxygenrequiredtooxidizeorganicmatter
chemically(biodegradableandnon-biodegradable)byusing
astrongchemicaloxidizingagent.(K
2
Cr
2
O
7
)inanacidic
medium.ForasinglewastewatersamplethevalueofCOD
willalwaysbegreaterthenBOD.
Theoxidant(K
2
Cr
2
O
7
)remainingisfoundouttofind
K
2
C
r2
O
7
consideredCODandBODcanbeinterrelated.
CHEMICAL OXYGEN DEMAND

8. ENVIRONMENTAL ENGINEERING
-
II DOMESTIC SEWAGE
CHARACTERISTICS
Parameter Range (mg/l)
Total Solids
Dissolved Solids
Suspended Solids
Setteleable Solids
BOD
COD
Total Nitrogen
Alkalinity (as CaCO
3)
350 –1200
250 –850
100 –350
5 –20 (ml / l)
100 –300
250 –1000
20 –85
50 –200

9. ENVIRONMENTAL ENGINEERING
-
II
1personexcrete80gmBOD/day.Populationequivalentof
anindustryisthenumberofpersonswhichmayproducethe
sameamountofBODperday.
Let BOD of tannery is =500 mg/l
Q =10,000 m
3
/ day
Total BOD load by tannery =BOD x Q
=500 x 10000 / 1000
=5000 kg BOD/day
Population equivalent =(5000 / 80) x 1000
=62,500 persons
POPULATION EQUIVALENT

10. ENVIRONMENTAL ENGINEERING
-
II
SEWAGE
TREATMENT

11. ENVIRONMENTAL ENGINEERING
-
II
SEWAGE TREATMENT
Purpose:
1.HealthAspect:Morethan50%diseasesspreadthrough
untreatedsewagepathogens,helminths,wormsetc.
2.DisposalAspect:ifsewageisdisposeduntreatedinwater
bodies,itcanresultinfollowingproblems:-
-DepletionofO
2resourcesofstreams
-Causeturbidity,colourinwaterbodies
-Canbetoxictoaquaticlife
3.Reuseaspect:Sewageistreatedtobereusedfor
-Irrigationpurposes
-Groundwaterrecharge

12. ENVIRONMENTAL ENGINEERING
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II
METHODS OF TREATMENT
1.PrimaryTreatment:
Purpose:
Removesuspended,settleableandfloatingmatters.
MethodUsed:
Screens,GritChambers,PrimarySedimentationtanks
(primaryClarifier)
BODremoval=30–45%
S.Sremoval=40–70%

13. ENVIRONMENTAL ENGINEERING
-
II
PRIMARY TREATMENT
1.Screens:
Purpose&Types:
Thepurposeofscreensistoremovelargeparticlesof
floatingorsuspendedmattersothatthepumpisnotclogged
ordamaged.
Screensconsistofparallelbars,rods,wiremeshor
perforatedplates.Theopeningmaybeofanyshape.
(generallyrectangular)

14. ENVIRONMENTAL ENGINEERING
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II
BAR SCREENS
Mostly,BARSCREENSofRACKSareusedwhichare
eitherhandcleanedormechanicallycleaned.
Openingbetweenbars½”–1½”
Sewage
bars
30 –60
o
SECTION
To Gret
Chamber / P.S
Tank

15. ENVIRONMENTAL ENGINEERING
-
II
PRIMARY SEDIMENTATION TANK
3.PRIMARYSEDIMENTATION TANK
(PrimaryClarifier)
Function
1.TheyremovemostofthesettleablesolidsORabout
40–70%ofthesuspendedsolidsfromsewage.
2.ReduceBODonsecondarytreatmentunitsince80%
ofthetotalBODofmunicipalsewageis
contributedbysuspendedandcolloidalsolids,
between30and45%ofthetotalBODwillbe
removalduringthisprocess.

16. ENVIRONMENTAL ENGINEERING
-
II
Primary Clarifier Design Basis
1.DesignedonAVERAGEFLOWBASIS
2.Surfaceloadingrate:20–60m
3
/m
2
.Day
3.Depth:2–4m
4.DetentionTime:2–4hour
5.SludgeAccumulation:2.5kgofwetsolids/m
3
offlow
6.WeirLoading:≤120m
3
/m
2
.day(topreventhighapproach
velocityatoutlets)
7.Shapes
a.Rectangular: MaxL:W–4:1
Maxlength=30m,
Maxwidth=6–8m
b.Circular: Dia = 10 –30 m

17. ENVIRONMENTAL ENGINEERING
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II
SECONDARY TREATMENT
Aerobic Process
Cell Mass
CHON
(Organic Matter)
CO
2, H
2O, SO
4
-2
, NO
3
Somoresludgeisformedinaerobicprocess.Bacteriathat
workinthepresenceofoxygenareAEROBICBACTERIA.
ThebulkofavailableenergyfindsitswayintoCELLMASS
yieldingastableeffluentwhichwillnotundergofurther
decomposition

18. ENVIRONMENTAL ENGINEERING
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II
AnaerobicProcess
Thesetakeplaceintheabsenceofoxygen
CellMass
CHON
(OrganicMatter)
CO
2,H
2O,H
2S,CH
4,N
2
Lesssludgeisformedinanaerobicprocess.Theend
productsofananaerobicprocessareodorous.Bacteriathat
workintheabsenceofoxygenarecalledANAEROBIC
BACTERIA.

19. ENVIRONMENTAL ENGINEERING
-
II
Suspended Growth Process
Atreatmentprocessinwhichbacteriaarekeptinsuspension
byconstantlyaeratingthewastewatere.g.activatedsludge
process,AeratedLagoonsetc.

20. ENVIRONMENTAL ENGINEERING
-
II
Flocbodyofmicroorganismsgatheredinacrowdoutline.
Aquantityofmicroorganismandnutrientmaterial
supportingthegrowth.
PST
Aeration Tank
SST
Sludge
Digestion
Sludge
Waste
To Sludge
drying beds

21. ENVIRONMENTAL ENGINEERING
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II
Where
Vs =Settleablesolids(measuredbyimhoffcone)
MLSS =Mixedliqueursuspendedsolids(mg/l)
(Ameasurementofmicroorganismsinsewage)SVIfrom
50to150indicategoodsettlingcharacteristics.
SVI =SludgeVolumeIndex

22. ENVIRONMENTAL ENGINEERING
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II
Sludge Bulking
Excessivecarryoverofflocsintheeffluentresultingin
inefficientoperationtofindclarifierinreferredasSLUDGE
BULKING.ItisusuallyduetoFILAMENTOUSMICRO
ORGANISMS.
Reasonsforsludgebulkingmaybe
- insufficientaeration(D.O<1.5mg/l)
- Lackofnutrients(i.eN,P)
- Presenceoftoxicsubstances
- OVERLOADINGi.e.highF/Mratios

23. ENVIRONMENTAL ENGINEERING
-
II
F : M Ratio
F:MratiomeansFOODStoMICROORGANISMSratio.
F:MratioisexpressedintermsofkgBODappliedperday
kgofMLSS.
IfQisthesewageflowinm
3
/dandithasaBOD
expressedinmg/l.
Then FOOD=(QxBOD)/1000kgBOD/day
Also Q
r/Q=V
s/(1000–V
s)(Recirculationratio)
Where
V
s= Volumeofsettledsludge
Q
r= Flowofretainedsludge
Q = Flowofsewage

24. ENVIRONMENTAL ENGINEERING
-
II
If“V”isthevolumeofaerationtankincubicmeterand
hasaMLSSconcentrationexpressedinmg/lthen:
Microorganisms=(VxMLSS)/1000kg.MLSS
Where:MLSS=measureofmicroorganisms=mg/l
F:M=(QxBOD)/(VxMLSS)
=BOD/(txMLSS)
Where“t”isAERATIONTIMEindays.AnF:Mratio
between0.25to0.5perdayisusuallyemployedand
promisesgoodsettlingcharacteristicsofsludge.

25. ENVIRONMENTAL ENGINEERING
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II
Design of the Facility (Design Criteria)
F:M ratio 0.25 to 0.5 per day
MLSS 1500 –3000 mg/l
Air Supply 3 -15 m
3
of air/m
3
of sewage
Return sludge 25 –100 % of sewage flow
Aeration time 4 –8 hours
Dissolve Oxygen (DO) At least 2 mg/l

26. ENVIRONMENTAL ENGINEERING
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II
Nooftanks:Generallymorethenonetankbeprovided.
AerationTankDimensions:Depth3-5m,
L:Wnotbelessthan5:1
Aeration Tank
Diffuses
Plan
Diffuses
0.6 –1m

27. ENVIRONMENTAL ENGINEERING
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II
Aeration Devices
(i)DIFFUSEDAERATION
Airispassedthroughporousdiffusesunderpressure.
Generallyrowsofdiffusesare0.6to1mapart.Thereare
placedatthebottomofaerationtank.
(ii)MECHANICAL AERATION
Inthistypemechanicalsurfaceaerationareemployedthey
agitatethesewagemachinerysoastopromotesolutionof
airfromtheatmosphere.
Impellersaregenerallyusedtoagitatethesewage.

28. ENVIRONMENTAL ENGINEERING
-
II
Problem
Anactivatedsludgeprocessistotreatadomesticsewage
flowof6000m
3
/daywithaBODof240mg/l.TheF:M
rationistobemaintainedat0.4kgBOD/kgMLSS.The
sludgerecirculation0.25anditisdesiredtoachieveanSVI
of100ml/gmcalculatetheMLSSconcentrationinaeration
tankandthesizeoftheaerationtank.

29. ENVIRONMENTAL ENGINEERING
-
II
SOLUTION
Q
r/Q=Vs/(1000-Vs)
0.25= Vs/(1000–Vs)
Vs=200ml
SVI=(Vsx1000)/MLSS
MLSS =(Vsx1000)/SVI
=(200x1000)/100
=2000mg/l
F:M=(Q.BOD)/(V.MLSS)
or V =QxBOD/MLSSxF:M
V =6000x240/2000x0.4=1800m
3

30. ENVIRONMENTAL ENGINEERING
-
II
SOLUTION
Usetwotankshavingvolume900m
3
each.
Let depth=4m
Area=900/4
=225m
2
Usetwoaerationtanks.
.:Areaofeachtank=225m
2
LetL:W=5:1
225=5WxW
W=6.7m
L= 33.5m
Tanksize6.7mx33.5mx4m
Lets(7mx34mx4m)

31. ENVIRONMENTAL ENGINEERING
-
II
Problem
Anactivatedsludgeprocessistobedesignedtotreatsewage
flowof8640m
3
/daywithaBODof200mg/lfromthe
primaryclarifier.UsingF:Mratioof0.4perdayandMLSS
concentrationof3000mg/l,calculatethevolumeofthe
aerationtankofSVIis100,howmuchsludgeshouldbe
returned

32. ENVIRONMENTAL ENGINEERING
-
II
SOLUTION
Q =8640m
3
/day
F:M=QxBOD/VxMLSS
0.4=8640x200/Vx300
V=1440m
3
SVI=Vsx1000/MLSS
Vs=100x3000/1000
=300
Q
r/Q=Vs/1000–Vs
=300/1000–300
=0.42

33. ENVIRONMENTAL ENGINEERING
-
II
SOLUTION
Q
r= 0.42x8640
= 3702m
3
/day

34. ENVIRONMENTAL ENGINEERING
-
II
Problem
Anactivatedsludgeprocesswithaerationtankvolumeof
900m
3
istreatingasewageflow4000m
3
/daywithaBOD
of250mg/l.ItisdesiredtoachieveanSVIof80by
adoptingarecirculationratioof0.25.CalculatetheF:M
rationatwhichtheaerationtankshouldbeoperated.

35. ENVIRONMENTAL ENGINEERING
-
II
Solution
Q
r/Q=Vs/1000–Vs
:.0.25=Vs/1000-Vs
Vs=200mg/l
SVI= Vsx1000/MLSS
MLSS= 200x1000/80
= 2500mg/l
F:M= QxBOD/vxMLSS
= 4000x250/900x2500
= 0.44perday

36. ENVIRONMENTAL ENGINEERING
-
II
Problem
Domesticsewageflowof8000m
3
/dwithaBODof260
mg/listobetreatedbyanactivatedsludgeprocess.Ifa
recirculationrationof0.25andSVIof100isdesired,
calculatethesizeoftheaerationtanktakeF:Mratioas
0.3.

37. ENVIRONMENTAL ENGINEERING
-
II
SOLUTION
Q = 8000m
3
/d
Q
r/Q= 0.25
SVI= 100
Q
r/Q=Vs/1000–Vs
.:0.25=Vs/1000–Vs
Vs=200mg/l
SVI=Vsx1000/MLSS
MLSS=200x1000/100
=2000mg/l

38. ENVIRONMENTAL ENGINEERING
-
II
SOLUTION
Let
F:Mration0.3perday
F:M= QxBOD/VxMLSS
V=3466.6mg/l
Letdepth= 4m
Area = 3466/4
= 866.6m
2

39. ENVIRONMENTAL ENGINEERING
-
II
SOLUTION
Take2unitsofaerationtank:
Each = 433.3m
2
L:W = 5:1
A=LxW
A=5W
2
W=9.3m
L=46.5m
So
size9.3mx46.5mx4m

40. ENVIRONMENTAL ENGINEERING
-
II
TRICKLING FILTER
Tricklingfilterutilizearelativelyporousbacteriagrowth
mediumlikeROCKorFORMEDPLASTICSHAPES.
Bacterialgrowthoccuruponthesurfacewhileoxygenis
providedbyairdiffusionthroughvoidspaces.
Wastewaterisappliedtothesurfaceandpercolates
throughthefilter,flowingoverthebiologicalgrowthina
thinfilm.
Support
Medium
Anaerobic ZoneAerobic Zone
Oxidized
Organics
BOD O
2
CO
2
Fixed water
layer

41. ENVIRONMENTAL ENGINEERING
-
II
TRICKLING FILTER
Nutrients,oxygenandorganicmatteraretransferredtothe
fixedwaterlayerandfromtheretobacteriaandwaste
productsaretransferredtothemovingwaterlayer,primarily
bydiffusion.
Asthebacteriaonfiltermediummetabolizethewastethey
willreproduce,graduallyproducinganincreaseinthedepth
ofSLIMELAYERwiththickeningofbiologicallayer,the
innersidebecomeanaerobicandbacteriastartsdieing
breakingthecontactbetweenslimelayerandcontact
mediumandslimelayerwillsloughoffandbecarriedfrom
thefilterwithwasteflow.Thesesolidsarethenremovedina
secondaryclarifier.

42. ENVIRONMENTAL ENGINEERING
-
II
TRICKLING FILTER
To secondary
sedimentation tank
Under
drain
system
Stone
(60-90 mm dia)
Rotating
Distribution
drain
Dosing
Tank
Primary
Sedimentation
Tank

43. ENVIRONMENTAL ENGINEERING
-
II
TYPES OF TRICKLING FILTER
i.Lowrate
ii.Highrate(mostlyusedthesedays)
Factor LowRate HighRate
1.Medium Stone Plasticballs
2.Hydraulicloading1.9–3.8m
3
/m
2
.d9–27m
3
/m
2
.d
3.Depth 2–3m 1–2.5m
4.Recirculation Nil 1:1to4:1
5.operation Simple Skilled
6.Odour/FlyproblemMore Less
7.Organicloading 0.3–1.5kg/m
3
1.5–18.5
filtervol.day

44. ENVIRONMENTAL ENGINEERING
-
II
ROLE OF RECIRCULATION
Recirculationofeffluenteitherfromtricklingfilterorfinal
clarifierisdoneinmodernTricklingfiltertofollowing
advantages:
i.returnofviableorganismthusimprovingefficiency
ii.Reduceodourandflyproblem
iii.Diluteinfluentandhelpinhandlingshockloads

45. ENVIRONMENTAL ENGINEERING
-
II
Disadvantages
i.Highconstructioncost
ii.Largearearequired
iii.Odourandfly(Psychodafly)problem
Performance
Nationalresearchcouncil(NRC)empiricalformulaisused.
ItisbasedupondatacollectedinUSAduringWorldWar–II
E = (C
i-C
e)/C
i
= 1/(1+0.532(QC
i/VF)
0.5
)

46. ENVIRONMENTAL ENGINEERING
-
II
Problem
Asettledsewageflowof11355m
3
/daycontaining150mg/l
ofBODistobetreatedbyaTrickingfilterwithadepthof2
m.ItisdesiredthateffluentBODshouldbe20mg/l.
Calculatetherequireddiameterofthefilterandhydraulic
loadingonthefilter.Recirculationrationis4.

47. ENVIRONMENTAL ENGINEERING
-
II
Solution
Q = 11355m
3
/d
= 7.88m
3
/min
Q
r= 4x11355
= 45420m
3
/d
r = 4
.:F = 1+4/(1+0.4)
2
= 2.53

48. ENVIRONMENTAL ENGINEERING
-
II
(C
i-C
e)/C
i= (150–20)/150
= 0.8667
E=1/(1+0.532(QC
i/VF)
0.5
)
0.8667= 1/(1+0.532(7.88x150/Vx2.55)
0.5
)
SolvingthisequationwecangetthevalueofV:
V = 5540m
3

49. ENVIRONMENTAL ENGINEERING
-
II
Let
depth= 2m
.:Areaoffilter= 2770m
2
A = /4D
2
D = 59.4m
Totalflowoffilter= Q+Q
r
= 56775m
3
/d
HydraulicLoading= 56775/2770
= 20.4m
3
/m
2
.d

50. ENVIRONMENTAL ENGINEERING
-
II
PROBLEM
22700m3/dofsettledwastewatercontaining300mg/l
ofBODistobetreatedinaTricklingfilter.Itis2min
depthandhydraulicloadingis15m
3
/m
2
.dwitha
recirculationratioof2.calculatefiltersize,%ageBOD
removalandeffluentBOD.

51. ENVIRONMENTAL ENGINEERING
-
II
SOLUTION
Trytosolvebyyourself.
Answer:
Area= 4540m
2
E = 78.97%,
C
e= 63mg/l

52. ENVIRONMENTAL ENGINEERING
-
II
WASTE WATER STABILIZATION PONDS (WSP)
Wastewaterstabilizationpondsprovideausefulmethodof
Wastewatertreatmentanddisposalforgrowingcommunities
wherebothFUNDSandTRAINEDPERSONNELarein
shortsupply.
Intheseponds,“beneficialorganisms”stabilizethe
Wastewaterintoaliquidthatcanbereleasedtothe
environmentadverselyandthatdoesnotplaceanundercost
burdenonadownstreamuser.
WSParebestsolutionwhere:
-Financialresourcesarelimited
-Technicalexpeditearelacking
-Sufficientlandareaisavailableatcheapcost.

53. ENVIRONMENTAL ENGINEERING
-
II
DEFINITION:
Astabilizationpondisarelativelyshallowbodyofwater
containedinaearthen/linedbasinofcontrolledshape
whichisdesignedforthepurposeoftreatingwastewater.

54. ENVIRONMENTAL ENGINEERING
-
II
DRAWBACKS
1. Requirelargearea
2. Anaerobicpondshaveodourproblem.
TYPES
1. Anaerobicponds
2. Facultativeponds
3. Maturationponds
Mostly,theseareusedincombination/series.Atypicalarrangementis
shownbelow:-
F M
An F
An F
M
M M

55. ENVIRONMENTAL ENGINEERING
-
II
ANAEROBIC PONDS
Sludge
CH
4
H
2SCO
2
NH
3
3-5 m
Influent
Effluent
Baffle
Scum

56. ENVIRONMENTAL ENGINEERING
-
II
PROBLEM
Designananaerobicpondtotreatasewageflowof5000
m
3
/dwithaBODof400mg/l.thepondsaretobeloadedat
200gBOD/m
3
.d

57. ENVIRONMENTAL ENGINEERING
-
II
SOLUTION
TotalBODload=5000x400
=2000000gmBOD/l
Volumeofpond= 2000000/200=10000m
3
Taketwoponds.:volumeofonepond=5000m
3
Letdepth=4m
.:Area(MeanDepth)=5000/4=1250m
2
LetL:W= 2.5:1
W = 22.3m~22
L = 55.9m~56
Surface=28x54
Bottom=16x50

58. ENVIRONMENTAL ENGINEERING
-
II
FACULTATIVE PONDS
Applicationmostlyusedfordomesticsewageofordinary
strength
1.5 -2 m
Influent
Effluent
Sunlight
O
2
Algal
Growth
Aerobic
Facultative
Anaerobic

59. ENVIRONMENTAL ENGINEERING
-
II
Threezonesexistinafacultativepond:
I-Thesurfacezonewhereaerobicbacteriaandalgae
exist
II-Anaerobiczonenearbottominwhichaccumulated
solidsaredecomposedbyanaerobicbacteria.
III.Anintermediatezonethatispartiallyaerobicand
partiallyanaerobicinwhichdecompositionisbought
aboutbyFACULTATIVEbacteria.

60. ENVIRONMENTAL ENGINEERING
-
II
DESIGN CRITERIA
TherearedesignonSURFACELOADINGRATES.i.ekgBOD
/ha/day.TheareathuscalculatedisMIDDEPTHSURFACE
AREA(M.D.S.A)
Surfaceloading: 100–400kgBOD/ha/day
Noofponds : Atleasttwo
Detentiontime : 7–20days
SideSlopes : 1V:3H
Depth : 1.5–2m
L:W : 3–2.5:1
De-sludging : 10–15years
Theeffluenthavenosmall,greenishincolourandhasaBODof
around50–75mg/l

61. ENVIRONMENTAL ENGINEERING
-
II
Formula for effluent Quality
Followingformulaisusedtofindouteffluentquality:-
L
e/L
i = 1/(1+Kt)
Where
L
e= effluentBOD,mg/l
L
i= InfluentBOD,mg/l
K= Reactionrateconstant,perday
(normally0.3d
-1
fordomesticsewageat20
0
C)
t= Detentiontime,days
Note:90%ofpondsinworldareFACULTATIVEPONDS.
TemperatureeffectonK
K
2
=K
1
(Ө)T
2
-T
1

62. ENVIRONMENTAL ENGINEERING
-
II
Mara formula far BOD loading
Mara(1988)gavethefollowingformulatofindthesurface
loadingforaspecificregion.Accordingtothisformula
surfaceloadingdependuponaveragetemperatureofthe
coldestmonth
S.L= I5T–50
Where
S.L= SurfaceloadinginkgBOD/ha.day
T = Averagetemperatureofcoldestmonth

63. ENVIRONMENTAL ENGINEERING
-
II Bacteria Algae Symbiosis
(mutually beneficial)
Inaerobiczoneofponds,bacteriaandalgaeexistina
MUTUALLY BENEFICIALorSYMBIOTICrelationship
algaeproduceO
2
duringphotosynthesiswhichisneededby
bacteriatometabolizematter.WhereasbacteriareleaseCO
2
andotherinorganicmatterlikeNandP,whichareneededby
algaetogrowandmeetitsfoodrequirement.Henceunder
normallightconditions,themetabolicactionofthesetwo
microbialgroupscomplementeachother.

64. ENVIRONMENTAL ENGINEERING
-
II
Problem(Facultative Pond)
Designtwofacultativepondstotreataflowof5444m
3
/d
withaBODof150mg/l.takeBODloadingas200kgBOD
/ha.dandassumethedepthofthepondas2m.Findthe
detectiontimeinthepondandefficiencyofthepond.
AssumeK=0.23perday.

65. ENVIRONMENTAL ENGINEERING
-
II
Solution
Qforeachpond= 5444/2
= 2722m
3
/d
Middeptharea= TotalBODload/S.L
= {(2722x150)/1000}/200
= 2.04ha
= 20415m
2

66. ENVIRONMENTAL ENGINEERING
-
II
Let
L:W= 3:1
A = 3W
2
W = 82m
.:L = 249m
SurfaceDimension = 85x252
BottomDimension = 79x246
Volume = 20415x2
= 40830m
3

67. ENVIRONMENTAL ENGINEERING
-
II
.:DetentionTime= V/Q
= 40830/2722
= 15days
L
e= L
i{1/(1+Kt)}
= 150{1/(1+0.23x15)}
= 33.7mg/l
.:E= (L
i–L
e)/L
i
= 150–337/150=77.5%

68. ENVIRONMENTAL ENGINEERING
-
II
MATURATION PONDS
Application:
PrimarilyusedforreductionofPATHOGENS
-Removaloforganicmatter(BOD)
ThesearefullyaerobicandusedafterFACULTATIVE
PONDSwiththepurposeof
i.PolishingofEffluent
ii.RemovalofPathogens
Pathogensdieduetosunlightandlongdetentiontime.
HELMINTHS alsosettleatthebottomwherethey
eventuallydie.

69. ENVIRONMENTAL ENGINEERING
-
II
MATURATION PONDS
1 –1.5 m
Influent
Sunlight
Fully
Aerobic

70. ENVIRONMENTAL ENGINEERING
-
II
DESIGN CRITERIA
Depth = 1–1.5m
DetentionTime = 4–14days
No.ofPonds = Atleasttwo
L:W = 2.5:1
De-sludging = 20years
DesignofmaturationpondsisbasedonCLOIFORM
REMOVALandnoBODreductionconsiderationismade.

71. ENVIRONMENTAL ENGINEERING
-
II
FORMULA
Todesignthematurationpondsonthebasisofcoliform
removal,followingrelationshipisused:-
N
e/N
i = 1/(1+Kt)
Where:
N
i= Noofcoliformininfluent/100ml
N
e= Noofcoliformineff/100ml
K = Bacterialdieawayconstant
(Usuallytakenas2.6perdayat20
0
C)
t = Detentiontimeinpond,days
Effluentfrommaturationpond(Generally)
BOD= 30mg/l
F.C< 1000/100ml

72. ENVIRONMENTAL ENGINEERING
-
II
Problem(Maturation Pond)
Designamaturationpondtotreataflowof2722m
3
/dof
20
0
Cwithcoliformintheinfluentas4x10
5
/100ml.
Assumeadetentiontimeof10days.Findoutthecoliformin
theeffluentofthepondandthepondefficiency.AssumeK=
2.6d
-1
at20
0
C.

73. ENVIRONMENTAL ENGINEERING
-
II
Solution
N
e/N
i=1/(1+Kt)
N
e = 4x10
5
{1/(1+2.5x10)}
= 14814/100ml
VolumeofPond= 2722x10
= 27220m
3
Letdepth= 1.5m
.:Middeptharea= 27220/1.5
= 18146m
2
= 18200m
2

74. ENVIRONMENTAL ENGINEERING
-
II
.:Middepthdimension= 213.3x85.3
SideslopeIV:3H
.:SurfaceDimension= 217.5x89.5
BottomDimension= 2085.5x80.5
PondEfficiency={(4x10
5
–14814)/4x10
5
}x100
=96.2%

75. ENVIRONMENTAL ENGINEERING
-
II
Waste Stabilization Ponds in Pakistan
10 YEARS RESEARCH AT I.E.E.R (UET LAHORE
EVALUATION OF DESIGN PARAMETERS
APPLICATION
Karachi Hyderabad
Lahore Okara
Faisalabad Peshawar
Effluentismostlyusedforirrigation.

76. ENVIRONMENTAL ENGINEERING
-
II
AERATED LAGOONS
AeratedlagoonsoccupyapositioninbetweenWSPand
activatedsludgeprocess.
AnAeratedLagoonisabasininwhichwastewateris
treatedonaFLOWTHROUGHBASIS.Oxygenissupplied
bymeansofsurfaceordiffusedaerations.AeratedLagoon
operateatlowMLSSconcentration.i.e.200–400mg/lbut
withlongretentiontimeascomparedtoactivatedsludge
process.InAeratedLagoonNOSLUDGERECYCLINGis
EMPLOYED.TheeffluentfromanAeratedLagoonis
settledinasedimentationtankbeforedischarge.

77. ENVIRONMENTAL ENGINEERING
-
II
AsamatteroffactAeratedLagoonwereoriginally
developedfromANAEROBICandFACULTATIVEponds.
Screens Aerated
Lagoon
Sludge Drying Beds
PST SST
AERATED LAGOONS
No Sludge recirculation

78. ENVIRONMENTAL ENGINEERING
-
II
DESIGNCRITERIA/CONSIDERATIONS:
Empiricalapproachisused
Detentiontime 4–9days
Depth 3–5m
Powerinput 20watt/m
3
oflagoonvolume
Effluentqualitycanbeestimatedbyusingfollowingformula
Le/Li =1/(1+Kt)
BODremovals 70–90%
F.Col 90%(Poor)
.:ProvideMATUARTIONPONDtofurtherupgradethe
effluentforfurtherREUSE.

79. ENVIRONMENTAL ENGINEERING
-
II
ADVANTAGES:
1.RequiredlessareaascomparedtoWSP
2.LowcapitalcostascomparedtoASP
3.Easytooperate/maintain
4.Highlyskilledplantoperatorsnotrequiredas
comparedtoASP
5.Agoodtreatmentoptionforawiderangeofinduction
e.g.textile,tannery,dairy,fruitsetc.

80. ENVIRONMENTAL ENGINEERING
-
II
LIMITATIONS:
1. Poorcoliformremoval
2. Sludgehandlingproblems
3. Cannotbeusedwherespaceisverylimited.

81. ENVIRONMENTAL ENGINEERING
-
II
TYPES:
1.PartiallyMixed(Facultative):
Limitedaerationdonetosatisfyoxygendemandonly.
SettledsludgeatbottomundergoANAEROBIC
DECOMPOSITION.
1.FullyMixed:
Moreaerationdonetokeepallsuspendedsolidsin
suspension.Morepowerisrequiredinthiscase.
Sludge
Aerator

82. ENVIRONMENTAL ENGINEERING
-
II
SLUDGE DIGESTION
INTRODUCTION
Allconventionalwastewatertreatmentprocessesproduce
largequantitiesofwastematerialintheformofDILUTE
SOLIDMIXTURESknowasSLUDGE.Thecomposition
andsolidcontentareafunctionofrawwastewater.Primarily
andsecondarysludgesaremainlycomposedofwaterwitha
solidcontentofonly0.5to5%.
Hugevolumesofsludgearegenerateddailyinatreatment
plantwhichneedtobetreatedanddisposed.

83. ENVIRONMENTAL ENGINEERING
-
II
PURPOSE OF SLUDGE DIGESTION
1.Toreducethesludgevolumefordisposal
2.Toreducethewatercontentofsludgeforeasy
handling
3.TorecovervaluableGAS
4.TouseitasFERTILIZER.

84. ENVIRONMENTAL ENGINEERING
-
II
PURPOSE OF SLUDGE DIGESTION
Sludgedigestionandsubsequentdisposalfallsamong
importantfunctionscarriedoutatatreatmentplant.
Followingstatisticsrevealthisfact:
Sludge handling
30 –40%Capital cost
50% Operational cost
90% Operational problems in a
treatment plant

85. ENVIRONMENTAL ENGINEERING
-
II AMOUNT AND CHARACTERISTICS OF
SLUDGE:
Sewagesludgeconsistoftheorganicandinorganicsolids
presentinrawsewageandremovalinprimaryclarifierplus
organicsolidsgeneratedinsecondarytreatmentandremoval
insecondaryclarifier.
Specificgravityoforganiccontentofsludgeislightly
greaterthanwaterandnormallylieinarangeof1.01to
1.06.TheSpecificgravityofinorganicfractionissludgecan
beassumedas2.5.

86. ENVIRONMENTAL ENGINEERING
-
II
PROBLEM (Sludge Digestion)
EstimatethesolidsproductionfromTricklingFilterplant
treating1000m
3
/dwithaBODof210mg/landS.Sof260
mg/l.Assumethatprimaryclarificationremove30%of
BODand60%ofinfluentsolids.

87. ENVIRONMENTAL ENGINEERING
-
II
SOLUTION
Removal in primary clarifier = 0.6 x 260
= 156 mg/l
Production in secondary = 0.7(210)(0.5)
= 74 mg/l
Total solids production= 156 + 74
= 230 mg/l
= 230 gm / m
3
= 230/1000 x 1000
Solid production = 230 kg / day

88. ENVIRONMENTAL ENGINEERING
-
II
a.Solids generated in primary clarifier =60% of S.S
b.Solids generated in secondary clarifier
-T.F 0.4 to 0.5 kg/kg of BOD applied
-A.S.P 0.2 to 1.0 kg/kg of BOD applied

89. ENVIRONMENTAL ENGINEERING
-
II
Effect of moisture content upon sludge volume
Theeffectofmoisturecontentuponsludgevolumeis
tremendous.Sludgehandlingtechniquesaredirected
towardsreducing.Themoisturecontentandtherebythe
volumeofsludge.
Throughdigestion,thewatercontentofsludgereduce
significantlyascomparedtorawsludgeasshownbelow:

90. ENVIRONMENTAL ENGINEERING
-
II
Effect of moisture constant upon sludge volume
MoistureContent
Type RawSludgeDigestedSludge
-PrimarySedimentation94–96% 88–94%
TankSludge
-ActivatedSludge 98.5–99.5% 94–96%
-TricklingFilterSludge 96–97% 90–94%

91. ENVIRONMENTAL ENGINEERING
-
II
PROBLEM (Sludge Digestion)
Awastewaterplantproduces1000kgofdrysolidsperday
atamoisturecontentif96%.thesolidsare70%volatile
withaspecificgravityof1.05and30%non-volatilewitha
specificgravityof2.5.Determinethesludgevolume.
a.Asproduced
b.Digestionreducethevolatilesolidscontentby50%
anddecreasesthemoisturecontentto90%

92. ENVIRONMENTAL ENGINEERING
-
II
Solution
a.Mass of Sludge= 1000/0.05
= 20000 KG
95 % = 19000 litre
1000 kg is solid:
70 % volatile= 700 kg
specific gravity= 1.05
Volume = 700/1.05= 667 litre
30% non-volatile= 300 kg
specific gravity= 2.5
Volume = 300/2.5 = 120 litre
Volume of Solids= weight / specific gravity
Totalvolumeofsludge=19000+667+120
= 19787litre(Asproduced)

93. ENVIRONMENTAL ENGINEERING
-
II
b.After digestion Volatile Solids are reduced to 350 kg.
The total solid content is therefore 350 + 300 = 650 kg
Mass of sludge= 650/0.1
= 6500 kg
650 kg is solid:
Water = 5850 litre
Volume of V.S= 350 / 1.05= 333 litre
Volume of Non. V.S= 300/2.5= 120 litre
Total volume of sludge= 6303 litre
% reduction in volume = (19787 –6303 )/ 19787
= 68%

94. ENVIRONMENTAL ENGINEERING
-
II
Formulas
Volume of Solids for organic/inorganic:
Volume of solids = Weight of solids / Specific Gravity
Weight of sludge:
Mass (weight) of sludge = (Weight of solids in Kg)/
Kg (Fraction of solids)

95. ENVIRONMENTAL ENGINEERING
-
II
TYPES OF DIGESTION:
SludgedigestionmaybeANAEROBICofAEROBIC.Both
havetheirmeritsandde-merits.Traditionallyanaerobic
digestersareused.
Comparison
Parameter AerobicAnaerobic
1.VolatileSolidreduction SimilarSimilar
2.BODifsupernatant LOW High
3.CapitalCost LOW HIGH
4.OperatingCost HIGH LOW
5.UsefulbyProduct Nil Yes
6.Dewateringofdigestedsludge DifficultEasy
7.Systemupsets Less Moresusceptible
8.Designapproach EmpiricalEmpirical

96. ENVIRONMENTAL ENGINEERING
-
II
THEORY OF ANAEROBIC DIGESTION
Underanaerobicconditions,sludgedigestionoccurthrough
theactionoftwogroupsofbacteria.
1.AcidFormingBacteria:
Thesebacteriaconvertcomplexorganicsubstances
likefats,carbohydrates,proteinsetc.presentinthe
sludgeintosimpleorganiccompoundsandfattyacids.
CarbohydratesFattyacids(lowpH)
ProteinsAminoAcidsNH
3
+FattyAcids

97. ENVIRONMENTAL ENGINEERING
-
II
2.MethaneFormingBacteria
ThesebacteriaformCH
4
andCO
2
byusingacidandNH
3
andotherproductsofthefirstgroup.Theygetbestinthe
pHrangeof6.5to8andmoreprécisingwithinpHrage
of7.2–7.4.
NH
3
+FattyacidsCH
4
+CO
2
Methaneformingbacteriarequireaninorganicsourceof
nitrogenfortheirnutrition.Theyareinhibitedby
loweringpH.Whereasacidformingbacteriaareabit
resistanttolowpH.Sinceacidformingbacteriamaybe
adverselyaffected.Asaresulttheprocessmayfail.

98. ENVIRONMENTAL ENGINEERING
-
II
MaintenanceofproperpHcanbeobtainedwithlime.
However,thelimeshouldbethoroughlymixedupto
avoidlocalconcentrationbuildup.Usually2to5kgof
limeper1000personsisaddeddailytothedigester.

99. ENVIRONMENTAL ENGINEERING
-
II
MODERN DIGESTERS
Sludgedigestionisaccomplishedinairtightsteeltanks.
Moderndigestersarebothheatedandmixed.
Thefirstdigesterisheatedandmixed.Theseconddigester
isquiescentandservesprimarilyasathickenforthe
digestedsludge.
Digestertanksareusually6mto15mdeep.Hopperbottom
slopeiskeptas1Vertical:3Horizontal.Diameterofthe
digestermayvaryfrom6mto40mdependinguponthe
capacity.

100. ENVIRONMENTAL ENGINEERING
-
II
CoverofthedigestermaybeFLOATINGofFIXED.Fixed
coverarelowcostbutnorpreferable.Floatingcoversare
costlybuttheyminimizethedangerofmixingoxygenwith
thegastoformexplosivemixture.Alsowithfloatingcovers,
theremovalandadditionofsludgeremainsindependentof
eachother.
Themethaneproducedinanaerobicdigestionisnearly
universallyusedtoheatthedigesterandinsomeinstancesto
providemechanicalpowerforotherplantprocesses.
Thedigestedsolidsfromanaerobicprocessesmaybe
dewateredwithoutfurthertreatmentuponopendryingbeds.

101. ENVIRONMENTAL ENGINEERING
-
II
DESIGN CRITERIA
-Detentiontime 10–20days
-Volumeofm
3
/person0.1m
3
/personbiological
(offirstdigester) process,0.05m
3
/personfor
P.S.TSludge

102. ENVIRONMENTAL ENGINEERING
-
II
SLUDGE DRYING BEDS
PURPOSE:
Thepurposeofsludgedryingbedsistodewatereddigested
sludgeandtofurtherreduceitsvolume.Afterdrying,the
volumeofsludgegetsreducedtoaround60%.Drysludge
cakescanbeusedasfertilizer.

103. ENVIRONMENTAL ENGINEERING
-
II
PROBLEM
EstimatethequantityofsolidsproducedinanActivated
SludgeProcesswithflowof5500m
3
/daywithBODandS.S
of250mg/leachassumingthatPSTremove30%ofBOD
and50%ofSSandsludgeproductioninthesecondaryunit
is70%ofBODapplied.
Calculatevolumeofsludgeifitssolidcontentis5%.70%
VolatileSolidswithspecificGravity1.05and30%non-
volatilewithspecificgravity2.5.

104. ENVIRONMENTAL ENGINEERING
-
II
SOLUTION:
Solids removed in P.S.T = 0.5 x 250
= 125 mg/l
BOD applied to secondary unit =0.7 x 250
= 175 mg/l
Solid production in secondary unit = 0.7 x 175
= 122.5 mg/l
Total Solids produced= Primary + Secondary
= 125 + 122.5
= 247.5 mg/l
= 247.5 x 5500/1000
= 1361 kg/day

105. ENVIRONMENTAL ENGINEERING
-
II
SOLUTION
Weight of sludge= Solids / Solid fraction
= 1361 / 0.05
= 27220 kg
Water= 27220 –1361
= 25859 kg
= 25859 litre
Volatile Substances (V.S) = 0.7 x 1361 = 952 . 7 kg
Volume of V.S= 952.7 / 1.05= 907
Volume of Non V.S= 0.3 x 1361 / 2.5 = 163.3 litre
.: Volume of sludge= 25859 + 907 + 163.3
= 26929.3 litre

106. ENVIRONMENTAL ENGINEERING
-
II
DETAILS
Themostcommonmethodofpreparingdigestedsludgefor
finaldisposalisairdryingonsandbeds.Asanddryingbed
isshownbelow:-
5m
300 mm
150 –300 mm
200 –300 mm
Sludge Layer
Coarse Sand
Graded Gravel
Under drain
300 mm
RCC

107. ENVIRONMENTAL ENGINEERING
-
II
Itconsistof150–200mmdepthofcoarsesandunderlain
bylayerofgradedgravelrangingfrom3to6mmdiaattop
to20-40mmdiaatthebottom.Thetotalgravelthicknessis
300mm.
Thebottomofthebedslopetowardsunderdrains.The
underdrainconsistofdraintilesplacesupontrencheswith
openbedsectionsareconcrete.Afreeboardof300mmis
given

108. ENVIRONMENTAL ENGINEERING
-
II
Bedsare6to10mwideandupto40mlong.Atleasttwo
bedsmustbeprovidedineventhesmallestplants.
Dewateringoccurasaresultofdrainageandevaporation
andisheavilydependentuponCLIMATE.Coveringdrying
bedswithglassofplasticsheetsishelpfulinwetclimates.

109. ENVIRONMENTAL ENGINEERING
-
II
Operation of sludge drying bed
Thebedsareoperatedbyfillingwithdigestedsludgetoa
depthof200to300mm.asmallamountofsandmaybelost
witheachdryingcycle.Thetimerequiredfordewatering
mayrangefromseveralmonthstoafewweeksdepending
upontheclimateconditions.
DESIGN
- Arearequirement 0.2m
2
/person
- Commondimensions10mx40m
- Minimumno.ofunits2
- Reductioninsludgevol.60%

110. ENVIRONMENTAL ENGINEERING
-
II
Problem(Sludge Drying Beds)
Estimatethesizeofsludgedryingbedsforasewageflowof
19000m
3
/dwithaBODof200mg/l.

111. ENVIRONMENTAL ENGINEERING
-
II
Solution
BOD contributed/capita/day =80 g BOD/Person/day
.: Population equipment= 19000 x 200 / 80
= 47500 person
Per person area required= 0.2 m
2
.: Total area required= 47500 x 0.2
= 95000 m
2
Let area of one bed= 10 x 40 = 400m
2
.: No of beds required= 9500 / 400
= 23.75
= 24 beds

112. ENVIRONMENTAL ENGINEERING
-
II
Design Parameters for Septic Tank
DetentionTime : 24–48hr
L:W : 3:1
Depth : 1–1.5m
SludgeCapacity : 0.04m
3
/person/year
DesludgingPeriod : 1–2years
Effluentdisposal : Throughsoakagepit

113. ENVIRONMENTAL ENGINEERING
-
II
Diagram:
Manhole
Compartment
Baffle
Vent Pipes
(Gases)
Sludge
Sludge
1
st
Comp (2/3 Length) 2
nd
Comp (1/3 length)
L

114. ENVIRONMENTAL ENGINEERING
-
II
SOAKAGE PIT
Intheabsenceofanysewagecollectionsystem,theeffluent
fromseptictankcanbedisposedinaSOAKAGEPIT.Itisa
circularpitinwhichwaterisabsorbedinthesurrounding
soils.
DesignParameters:
1.Bottomabovewatertable=atleast10’
2.Awayfromwells =atleast50’
3.Diameter =6‘–12’
4.Depth =10’–20’
5.Distancebetweentwopits=3timesdiameteroflarger
pit

115. ENVIRONMENTAL ENGINEERING
-
II
DESIGN OF SOAKAGE PIT
Soil Applicationretentionm
3
/m
3
–day
Coarsetomediumsand 0.049
Finesand,loamysand 0.032
Sandyloamandloam 0.024
Siltloam 0.018
Siltyclay 0.001

116. ENVIRONMENTAL ENGINEERING
-
II
DESIGN OF SEPTIC TANK
CAPACITY:
Detentiontime= 48hrs
Sludge = 0.04m
3
/person/year
1.SludgeCapacity.
A=Pnfs(litre)
Where
P= No.ofperson
n= No.ofyearsbetweendesludging(Normally3years)
f= Factorrelatedtoambienttemp.
(forPakistanf=1.0for3yearsdesludgingperiod)
s= Rateofsludgeandscumaccumulation
take0.04m
3
/person/years(40liter)

117. ENVIRONMENTAL ENGINEERING
-
II
2.Capacityforliquidretention
B = Prq(liters)
Where
P= Persons
q= Averageflowlitre/dayofsewage
r= Minimumretentiontime(indays)forsewagein
tankjustbeforedesludgingiscarriedout(At
least1-day)
3.TotalCapacity= A+B

118. ENVIRONMENTAL ENGINEERING
-
II
SHAPE & DIMENSION
L : W= 3 : 1
Depth= 1.22 –1.83 m

119. ENVIRONMENTAL ENGINEERING
-
II

120. ENVIRONMENTAL ENGINEERING
-
II
INLET&OUTLET
DiameterShouldnotlessthan4”
Slopeshouldnotbelessthan1.5%
GASDEFLECTIONDEVICE

121. ENVIRONMENTAL ENGINEERING
-
II
VENTILATIONARRANGEMENT
Heightaboveground= 10’
ACESS&INSPECTION
Manholesatbothinletandoutlet
CONSTRUCTIONMATERIAL
R.C.Cbeusedinletandoutletshouldbeproperlysealed

122. ENVIRONMENTAL ENGINEERING
-
II
INSTALLATION
Mostimportantismaintenanceofpropergrades.Checkfor
watertightness.
PERIODICMAINTENANCE
Desludgingbedoneaftersomeperiod.Neverclean
completely.Leavesomesludgeinsideaftercleaning.

123. ENVIRONMENTAL ENGINEERING
-
II
DISPOSAL OF WASTEWATER ON LAND
AND WATER BODIES
Liquidwastesmaybedisposedofinanumberofways
(beforegivingatleastsecondaryleveltreatment)
-SurfaceWaters(Rivers,Lakesetc)
-Onland

124. ENVIRONMENTAL ENGINEERING
-
II
DISPOSAL IN SURFACE WATERS
Innaturalstreams,thereisabalancebetweenplantand
animallife,withconsiderableinteractionamongthevarious
lifeforms.Watersofgoodqualityarecharacterizeby
multiplicityofspecieswithnodominance.
Organicmatterwhichentersthestreamisbrokendownby
bacteriatoammonia,nitrates,sulphates,carbondioxideetc,
whichareusedbyplantsandalgaetoproducecarbohydrates
andoxygen.

125. ENVIRONMENTAL ENGINEERING
-
II
Introductionofexcessivequantitiesofwastematerialcan
upsetthecyclebycausingrapidbacterialgrowthand
resultingdepletionofdissolvedoxygeninthestream.
Pollutedwatersarecharacterizedbyverylargenumberof
relativelyfewspecies.
Disposalofwastewaterinastreamshouldbethusregulated
withrespecttobothquantityandconcentrationinorderto
safeguardtheaquaticlifeanddesirablewateruse.Thus
thereisalimitontheamountofliquidwaste.Thatcanbe
disposedofinawaterbody,whichiscalledtheassimilative
capacityofthatwaterbody.

126. ENVIRONMENTAL ENGINEERING
-
II
ASSIMILATIVECAPACITYcanthusbedefinedasthe
amountofwastewaterthatcanbedisposedofinthewater
bodyanditcanbesafelystabilizedwhilemaintainingthe
desiredwaterquality.
Sinceacertainamountofwastewatercanbedischargedinto
areceivingwaterbody,itmaybehighlyun-economicalto
outlawthewastedischarges.However,excessivedischarges
willimpairthestreamwaterquality.

127. ENVIRONMENTAL ENGINEERING
-
II
ON-LAND DISPOSAL WASTEWATER
Atreatment,atleasttosecondarylevelmustbegiven
priortoLANDDISPOSAL.Thisisnecessaryduetothe
followingreasons.
1.ToreducestressuponSOILSYSTEM
2.ToreduceproductionofNUISANCECONDITION

128. ENVIRONMENTAL ENGINEERING
-
II
ON-LAND DISPOSAL WASTEWATER
Followingmethodsmaybeemployedforon-land
disposalofWastewater.
1. SPRAYIRRIGATION
2. RAPIDINFILTERATION
3. OVERLANDRUNOFF
ForGROUNDWATERRECHARGE,wastewateris
dischargedintolargebasinsUNDERLAINBYSAND
andSOILofhighpermeability.Thebottomofbasinis
coveredbyBERMUDA GRASS toabsorb
NUTRIENTS.

129. ENVIRONMENTAL ENGINEERING
-
II
Overland Runoff / Flow
Itisnotatruedisposalsystemsincethewastewatermustbe
collectedafterpassageoversoil.Thisisinfectamethodof
TERTIARYTREATMENTofwastewaterstofurtherreduce
itsBODandnutrientlevels.Thegrassesareplantedonthe
groundoverwhichsewageflow.

130. ENVIRONMENTAL ENGINEERING
-
II
Wastewater Irrigation
Beginning,littleconsiderationwentintohealthhazards
relatedwithrawsewageirrigationcontainingpathogenic
andparasiteorganisms.
After1945,standardsweresetforthefirsttimeforWaste
Watertobeusedforirrigation.TheinteractinWastewater
reuseguidedmomentumandinmaycountriesconcrete
effortsweremadeinthisdirectione.g
- Khartoum:2800hagreenbeltwasirrigated
withtreatedWastewater.

131. ENVIRONMENTAL ENGINEERING
-
II
Wastewater Irrigation
- MexicoCity: 100,000hagrainandfodder
irrigatedwithtreatedWastewater.
- Melbourne:Agriculturefarmswith10,000ha
landirrigatedwithtreatedwastewater,where
50,000sheepand20,000cattlegraze.

132. ENVIRONMENTAL ENGINEERING
-
II
InPakistanrawWastewaterisusedtoirrigate800ha,2000ha
and2500halandinLahore,HyderababdandFaisalabad
respectively.
AlthoughWastewaterreusehasbeenpracticedmorewidelyin
developingcountriesoverthepast30years,muchofitis
UNPLANNED andUNCONTROLLED andposesathreatto
publichealth.Theserisksmustbefullyunderstoodand
appropriatedmeasurestakentoprovideTECHNICALLY
FEASIBLEandECONOMICALLY ATTRACTIVEsolutionso
thatpubliccanreapthefullbenefitofWastewaterreusedwithout
sufferingharmfuleffects.

133. ENVIRONMENTAL ENGINEERING
-
II PUBLIC HEALTH RISK ASSOCIATED WITH
RAW SEWAGE WASTEWATER
Thewastewaterstreamofacommunitycarriesfullspectrum
ofpathogenicmicroorganismsexertedinthefecesandurine
ofinfectedindividuals.Theirconcentrationis:
- Manymillions/litreforbacteria
- Thousands/litreforviruses
- Fewhundred/litreforhelminthseggs
Mostexertedpathogenscansurviveintheenvironmental
longenoughtobetransportedbythewastewatertothe
fields.Theirdieawayrateindescendingorderis
HELMINTHS,BACTERIAandVIRUSES.

134. ENVIRONMENTAL ENGINEERING
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II
Healthriskishighforpeopleusingsaladsandvegetables
EATENUNCOOKED andirrigatedwithRAWSEWAGE.
Suchpeopleareexposedtofollowingdiseasesarrangedin
descendingorderoftheirchanceofoccurrence.
- Helminth(Worm)disease
- Cholera
- Typhoid
SimilarlySEWAGEFARMWORKERSarealsoexposedto
abovediseases.However,evidenceofbacterialandviral
diseasesamongthemislimited.
Thereisnodemonstratedrisktopeopleclosetosewage
irrigatedsites.

135. ENVIRONMENTAL ENGINEERING
-
II
W.H.O Guidelines*
Parameters Value
HelminthEggs ≤ 1/litre
FecalColiform ≤ 1000/100ml
*forirrigationofcorpslikelytobeeatenuncooked,sports
fields,publicparks.

136. ENVIRONMENTAL ENGINEERING
-
II USE OF TREATED SEWAGE
EFFLUENTS FOR IRRIGATION
Allthehumanandanimalmanurewhichtheworldlosesby
dischargeofsewagetoreviewinreturnedtotheland,
insteadofbeingthrownintothesea,shouldsuffertonourish
theworld”(VictorHugo,1868)
Theuseofwastewaterforirrigationarosewiththedesireto
prevent
- Pollutioninriversthusprotectingsurfacewater
quality
- Configure water and nutrientsto
AGRICULTURE
- Inaridandsemiaridareas.

137. ENVIRONMENTAL ENGINEERING
-
II
HISTORY
UseofWastewaterforirrigationpurposecanbetracedbackto
1880s.UK,France,Germany,Australia,Mexicopracticedit.
However,inthebeginninglittleconsiderationwentintothe
healthhazardsrelatedwiththeuseofrawdomesticsewage
usuallycontainingpathogenic&parasiteorganisms.
After1945,Wastewatertreatmentanddisposalthroughland
applicationgainedincreasingalteration.Theusewas
formalizedbysettingstandardsfortheeffluentforirrigation
use.EffortsweremadeatGovtlevelonitisUNPLANNED
andUNCONTROLLED andposesathreattopublichealth.
Theserisksmustbeunderstoodandappropriatemeasures
takentoprovidetechnicallyfeasibleandeconomically
alternatesolutionssothatpubliccanreapthefullbenefitsof
wastewaterwithoutsufferingharmfuleffects.

138. ENVIRONMENTAL ENGINEERING
-
II
Environmental Impact
Assessment (EIA)

139. ENVIRONMENTAL ENGINEERING
-
II
ENVIRONMENTAL ASSESSMENT (EA)
EAhasbecomeestablishedworldwideasanenvironmental
managementtoolusedbygovernmentagencies,companies
andotherorganisationstoidentifypredictandevaluatethe
potentialphysical,biologicalandsocialeffects/impactsof
theprojectsandotherdevelopmentactions.

140. ENVIRONMENTAL ENGINEERING
-
II
TERMINOLOGY
EAorEIA–Environmentalassessmentorenvironmental
impactassessmentarethetermsusedtodescribetheoverall
process.
1.ManycountrieslikePakistanusethetermEIA
2.WorldBankhastheproceduresforEA
3.UKusethetermEA,particularly,toavoidthe
impressiontheprocessisrestricttotheanalysisof
negativeimpacts.
ESorEIS–EnvironmentalstatementorEnvironmental
ImpactStatementdescribethewrittenreportarisingfromthe
studies.

141. ENVIRONMENTAL ENGINEERING
-
II
DEFINITION
“Wheneverthereisaplannedactivity,itwillcausesome
impacts/effectsontheenvironment,theassessmentofthese
impactsiscalledEIA”.
IMPACT:Effectofonethingonanother
ENVIRONMENTAL IMPACT:Thechangeinenvironment
parameter,overaspecifiedperiodandwithinadefinedarea,
resultingfromaparticularactivitycompoundwiththe
situationwhichwouldhaveoccurredhadtheactivitynot
beeninitiated.

142. ENVIRONMENTAL ENGINEERING
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II
PLANNED ACTIVITY
-DAM
-High way
-Air Port
-Building
-Etc
ENVIRONMENT
-Physical
-Land
-Water
-Air
-Biological
-Flora
-Fauna
-Social
-Human
Assessment
Procedures
Methods
IMPACT

143. ENVIRONMENTAL ENGINEERING
-
II
Project Disposal
Is EIA required?
What are key issues?
Baseline data collection
Potential Env Impacts
Analysis Env Alternates
Mitigation Measures
Prepare EIS
Env Monitoring
Screening
Scoping
Identifications & Analysis of
Information
Present Findings
Post Project analysis

144. ENVIRONMENTAL ENGINEERING
-
II
SCREENING
Screeningprocedureincludebothprojectandenvironment
criteria/thresholds.
-thecriteriaisbasedonthescaleandsizeoftheproject
proposal,thenatureoftheactivitiesandsensitivityofthe
environmentalsetting
-Procedureforscreeningarecurrentlyinpracticein
Malaysia,Thailand,othercountriesi..eUKetc.
Forexample:
- Thermalpowerplantofmorethen300MW–
MANDATORY RequiredEIA.

145. ENVIRONMENTAL ENGINEERING
-
II
UKregulations;statesthatnewroadschemesmayrequired
EIAiftheirlengthexceeds1KMandtheirroutepasses
throughaNationalParkofthroughorwithin100mofa
conservationarea.

146. ENVIRONMENTAL ENGINEERING
-
II Two-Stage Screening Procedure
All Projects
No requirement of
EIA
Req of EIA is
uncertain
Mandatory req of
EIA
IEE “Preliminary
Assessment”
IEE is sufficient EIA should be
carried out
Initial Screening
Secondary Screening

147. ENVIRONMENTAL ENGINEERING
-
II
BASELINE CONDITIONS
Baselineconditionsdefinethecharacteristicsoftheexisting
andshapeprojectedfutureconditions,assumingnoproject
isundertaken.
BASELINEDATACOLLECTION
Dataaboutthephysical,biologicalandculturalenvironment
iscollected.
PHYSICALENVIRONMENT
Includesallsuchmajorareasastopography,soil&geology,
hydrology,airquality&Noiselevels

148. ENVIRONMENTAL ENGINEERING
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II
BIOLOGICALENVIRONMENT
Referstofloraandfaunaofthearea,includingaspecifiedof
trees,gasses,fish,birds.Specificreferenceshouldbemade
toendangeredplantsandanimals.
CULTURALENVIRONMENT
Includeshumanpopulation,trendsandpopulation
distribution,historicsite,publicfacilities,i.e.schools,
hospitals,mosques,percapitaincome,commercialactivities
etc.

149. ENVIRONMENTAL ENGINEERING
-
II ANALYSIS OF POTENTIAL
ENVIRONMENTAL IMPACTS
Environmentalimpactanalysisconsistsofcomparingthe
expectedchangesinthephysical,biologicalandcultural
environmentwithandwithouttheproject.
IMPACTCHARACTERISTICS
1. MagnitudeofImpacts
2. DirectionofImpacts