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.