Benefits of ZLW
- Recovers resources such as high quality water and salts for potential use for road application
- Protects water quality in rivers and streams by limiting chlorides, sulfates and other dissolved solids
- Creates clean water discharge while generating zero liquid waste
- Residuals are limited to a non-hazardous solid waste suitable for landfill disposal
The ZLW Process:
The process consists of three primary treatment components.
1. Raw-Water Pretreatment System:
A raw-feed water tank with jet mixing prevents solids from settling. From there, the water is treated for metals removal followed by chemical softening to reduce alkalinity and hardness. Veolia's proprietary MULTIFLO™ system combines softening and clarification with Turbomix™ technology to minimize chemical use and promote formation of a crystalline sludge that is easily dewatered in a filter press.
Chemical Softening System consists of two aeration tanks, a crystallization tank, and a clarifier.
The water is then conveyed to an aluminum precipitation step followed by multimedia filtration (MMF) to remove residual suspended solids.
2. Reverse Osmosis (RO) System:
The RO system is the heart of the water treatment process that generates clean water for discharge.It consists of parallel skids designed to achieve chloride and TDS specifications while operating at a high recovery rate. Before entering the single-pass, three-stage RO system, water from the MMFs goes through cartridge filters to remove any fine colloidal particles. The clean permeate from the RO system goes into a product water tank where it combines with distillate from the evaporator and crystallizer in the brine management system. Minerals are then added to protect aquatic life before it is discharged.
3. Brine Management System:
Effective brine management enables the overall system to achieve zero liquid waste.Reject from the RO membranes is sent to a second MULTIFLO™ softening system followed by Veolia's HPD® evaporation and crystallization technology. The HPD evaporator recycles hot vapors, minimizing the energy needed to concentrate the brine.
The concentrated brine then enters an HPD crystallizer, from which a side stream flows to a centrifuge that separates crystalline salts from the water. The water recovered from the evaporator and crystallizer is combined with the water recovered from the RO system to achieve the overall goal of zero liquid waste. Salts recovered from the system can be further treated for use as road salt, or managed as a non-hazardous solid waste for landfill disposal.