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Industrial Wastewater Treatment and Zero Liquid Discharge Centre for Water Research Department of Civil and Environmental Engineering National University.

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Presentation on theme: "Industrial Wastewater Treatment and Zero Liquid Discharge Centre for Water Research Department of Civil and Environmental Engineering National University."— Presentation transcript:

1 Industrial Wastewater Treatment and Zero Liquid Discharge Centre for Water Research Department of Civil and Environmental Engineering National University of Singapore How Yong NG

2 Zero Liquid Discharge (ZLD) – Why?  Environmental compliance regulations get stricter each year  Sometimes the only viable means of meeting discharge restrictions is to eliminate discharge  Public scrutiny of the industry’s impact on the environment is growing  ZLD has a real potential for improving public relations with plant neighbours and government regulatory agencies  Water 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%

3 Zero 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.

4 How to Achieve ZLD? Example: Step 1: Effluent after solvent recovery Step 5: Effluent after clarification Further reduction in TSS by using filters Step 8: High TDS reject from RO Concentration of RO rejects by using evaporators Step 7: Effluent after UF Recovery of low TDS permeate by using RO Step 6: Effluent after filters Reduction in turbidity and SDI by using ultrafiltration Step 2: Raw effluent from industry Removal of organic matter by using anaerobic digestion Step 4: Treated effluent from ETP Clarification by using, tube settler/clariflocculator Step 3: Anaerobically treated effluent Removal of balance organic matter by using aerobic digestion Recovery of solvents by using distillation process Step 9: Solids Extraction & Disposal Separation of salts from mother liquor using centrifuge/ dryer

5 Zero Liquid Discharge - Approaches  Examples of ZLD technologies:  Recycle using Cold Lime Softening  Discharging to the Plant Process  Evaporation Ponds  Evaporation/Crystallization of Discharge Stream  Enhanced ZLD Process  Combination Thermal Process with ZLD  Enhanced Membrane and Thermal ZLD  Wind-Aided Intensified Evaporation (WAIV)  Dewvaporation  Salt Solidification and Sequestration  New Approaches Cold Lime Softening Discharge to the plant process Evaporation pond Evaporation/Crystallization Process


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