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Environmental engg
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Wastewater Disposal
Natural MethodsDilutionLandArtificial MethodsPrimary TreatmentSecondary TreatmentTertiary Treatment
Disposal by DilutionDilution as treatmentDilution after treatmentSelf purifying capacity of water body
Dilution without treatmentWhen wastewater is fresh When no floating or settleable matter are presentWater body has a large volume in comparison to waste waterDiluting water has sufficient DOGood mixing conditionsSwift forward currents availableWaste water has no toxic substancesReceiving water is not a source of drinking water
Dilution after TreatmentWastewater discharge is detrimental to aquatic lifeWastewater contains toxic substancesInsufficient volume in receiving watersReceiving waters used for navigationReceiving waters source of drinkingWastewater is staleReceiving waters has no favourable currents
STANDARDS OF DILUTION
DILUTION FACTORRequired PurificationAbove 500No Treatment required300 to 500Primary treatment sedimentation SS > 150 ppm150 to 300Sedimentation, screening and chemical precipitation, - SS > 50 ppm< 150Thorough treatment. SS > 30 ppm; BOD > 20 ppm
RECEIVING WATERSRiversLakesSeaEstuaries
SELF PURIFICATION OF RIVERSActions Dilution SettlingOxidation & reductionTemperatureSunlight
ZONES OF POLLUTIONZONE OF DEGRADATIONZONE OF ACTIVE DECOMPOSITIONZONE OF RECOVERYZONE OF CLEAR WATER
OXYGEN SAGDO DeficitDO SagDO recoveryDeficit = Saturation DO Actual DOSaturation DO temperature dependent also on dissolved solids like Chlorides.14.6 mg/L at 00 C and linearly decreases to 7.6 at 300 CRe-aeration due to DO Deficit, turbulence, photosynthesis etc.
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