Deuel Vocational Institution (DVI) ZLD Driking Water Treatment System - Tracy, California

A study was conducted by an environmental engineering firm to design a suitable treatment system for the groundwater currently used as the potable water supply for DVI. Reverse Osmosis (RO) was determined to be an effective technology in meeting the applicable standards for water quality. The RO system would remove total dissolved solids (TDS), iron, and manganese from the brackish groundwater originating from wells that supply DVI.

However, the quantity of concentrate from the RO system posed a challenge to minimize the impact of this stream. It was determined that a Zero Liquid Discharge (ZLD) system was the only acceptable option to successfully meet the mandates regarding the elimination of system wastewater effluents.

The solution to reduce the volume of the RO concentrate was utilization of evaporation technology to minimize waste of this wastewater effluent stream and recover additional treated water. The reduction in wastewater volume allows for effective management of the material in four, small evaporation ponds to comply with the State of California's Zero Liquid Discharge (ZLD) mandates.

HPD was selected to provide the brine concentrator system (BCS) for this project. This technology is a key component in maximizing water recovery from the primary treatment waste stream.

The entire treatment system is designed to treat 800,000 gallons of water per day of brackish groundwater from four wells on the facility grounds. A three-step filtration process is used prior to the primary treatment in the RO system. The filtered and pretreated raw water enters the RO system where dissolved salts are rejected and permeate is sent to post treatment for final distribution to DVI as potable water.

The resulting concentrated reject from the RO system is then sent to the BCS where up to 250 gallons per minute of concentrate is processed in a single-stage, falling film evaporator. The BCS reduces the volume of this wastewater effluent stream by ~98% and returns high-quality distillate to post treatment where it is blended with the RO permeate.

The brine concentrator uses seeded-slurry, falling film evaporation technology. It is driven by mechanical vapor recompression (MVR), which optimizes energy efficiency.