A feasibility study of municipal wastewater desalination using electrodialysis reversal to provide recycled water for horticultural irrigation

A membrane desalination system based on electrodialysis reversal (EDR) has been evaluated for its capacity to remove salt from treated municipal wastewater to provide a source of recycled water for horticultural applications. Economic and technical feasibility was determined using data collected from a pilot scale plant, from which the following parameters were calculated: salt removal, water recovery and overall process economics. The pilot plant consisted of a pre-treatment multimedia filtration unit (MMF) and an EDR system with a capacity of approximately 144 kL/day. Treated effluent from a wastewater treatment plant (WWTP) was used as feed water for the desalination pilot plant. Water quality guidelines for horticulture specify an upper limit for total dissolved solids (TDS) of 375 mg/L. The EDR process reduced the TDS from 1104 mg/L to 328 mg/L. Additionally, the process reduced the conductivity of recycled water by 72%, including the removal of 84% calcium, 76% chloride, 59% fluoride, 64% alkalinity and 60% phosphate, demonstrating that the EDR treated water is a viable alternative supply. The power consumption of the EDR plant was found to be 0.6 kW h/kL and the media filtration 0.4 kW/kL. The total operating cost was estimated to be 18 cents/kL to deliver 82% water recovery.

► Salt reduction of tertiary effluent evaluated by electrodialysis reversal (EDR)
► The pilot plant consisted of multimedia filtration (MMF) and EDR systems.
► MMF reduced turbidity of tertiary effluent from approximately 2 NTU to < 0.5 NTU.
► EDR reduced the conductivity of tertiary effluent from 1924 μS/cm to 526 μS/cm.
► Pilot plant capacity of 144 kL per day running at 82% recovery cost 18 cents/kL.