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Industrial Wastewater Recovery & Reuse: A case History

7 December 2021

Eline Anvik

A large recreational facility in California is treating well water for all premise applications. It must meet the quality requirements of the USEPA Safe Drinking Water Act. The primary treatment technology was electrodialysis reversal (EDR), which generates wastewater during polarity reversal operations and electrode cleaning processes.

In an ongoing effort to conserve water supplies, the State of California strongly recommends the

practice of “zero liquid discharge” (ZLD). As this facility is committed to environmental sustainability, they had attempted to comply by recovering and reusing the wastewater from their EDR system, without success.

The facility employed a consultant who conducted extensive pilot testing to generate design data and effect the construction of a complete treatment system utilizing pressure-driven, crossflow membrane separation technologies to achieve ZLD. The design involves increasing the pH of the EDR wastewater with sodium hydroxide to effect precipitation of calcium, magnesium, and silica salts. The precipitate is concentrated in a tubular microfiltration (MF) system and further dewatered by a belt press with the solids removed to a landfill. Hydrochloric acid is used to lower the MF permeate pH and this stream treated by reverse osmosis (RO) to reduce the TDS to below 300 mg/L, and then directed to the potable water supply. The RO concentrate is pretreated by a crystallizer and fed to a falling film evaporator, followed by a centrifuge and hauled to a landfill. The distillate from these operations is also incorporated into the potable supply. The total volume of wastewater treated is 60,000 gpd (227 m³/day), and approximately 2600 lb/day (1183 kg/day) of solids are produced.

This presentation provides details of the chemistry, technologies utilized and description of the complete system design of this unique ZLD system.

Source: Cartwright, P. 2021. Industrial Wastewater Recovery & Reuse: A case History. Resource recovery and wastewater treatment technologies. AIWW 2021.