Presentation on theme: "Industrial Wastewater Treatment and Zero Liquid Discharge"— Presentation transcript:
1Industrial Wastewater Treatment and Zero Liquid Discharge How Yong NGCentre for Water ResearchDepartment of Civil and Environmental EngineeringNational University of Singapore
2Zero Liquid Discharge (ZLD) – Why? Environmental compliance regulations get stricter each yearSometimes the only viable means of meeting discharge restrictions is to eliminate dischargePublic scrutiny of the industry’s impact on the environment is growingZLD has a real potential for improving public relations with plant neighbours and government regulatory agenciesWater use needs to be minimized to allow continued industry growth.ZLD is mainly about discharge, but a very real effect is a reduction of inlet water needs, by as much as 20 – 30%
3Zero Liquid Discharge – Benefits & Costs Benefits (Mickley, 2006):ZLD generally does not require a lengthy or tedious permitting process.It may gain quick community acceptance.It can be located virtually anywhere.It represents a positive extreme in recycling, by efficiently using the water source.Selective salt recovery is a promising consideration in approaching the goal of sustainability.Costs:Capital and operating costs associated with ZLD are higher than any other concentrate disposal method.Significant Energy costs associated with the evaporation process.High chemical costs associated with treatment following a second membrane process.High costs associated with final brine or solids disposal.
4How to Achieve ZLD? Example: Step 1: Effluent after solvent recoveryRecovery of solvents by using distillation processStep 2: Raw effluent from industryRemoval of organic matter by using anaerobic digestionStep 3: Anaerobically treated effluentRemoval of balance organic matter by using aerobic digestionStep 4: Treated effluent from ETPClarification by using, tube settler/clariflocculatorStep 5: Effluent after clarificationFurther reduction in TSS by using filtersStep 6: Effluent after filtersReduction in turbidity and SDI by using ultrafiltrationStep 7: Effluent after UFRecovery of low TDS permeate by using ROStep 8: High TDS reject from ROConcentration of RO rejects by using evaporatorsStep 9: Solids Extraction & DisposalSeparation of salts from mother liquor using centrifuge/ dryer
5Zero Liquid Discharge - Approaches Examples of ZLD technologies:Recycle using Cold Lime SofteningDischarging to the Plant ProcessEvaporation PondsEvaporation/Crystallization of Discharge StreamEnhanced ZLD ProcessCombination Thermal Process with ZLDEnhanced Membrane and Thermal ZLDWind-Aided Intensified Evaporation (WAIV)DewvaporationSalt Solidification and SequestrationNew ApproachesDischarge to the plant processEvaporation/Crystallization ProcessEvaporation pondCold Lime Softening