Cutting Edge Treatment Process Paves the Way for Permit Compliance at California Wastewater Treatment Plant
Situation
Discharge permit limitations, governed by the National Pollutant Discharge Elimination System (NPDES) or other local control boards, are often updated to expand protection for downstream ecosystems and users. As a result, a municipal wastewater treatment plant (WWTP) in Southern California was in violation of their Regional Water Quality Control Board’s recently tightened discharge limits. Chloride (Cl-) concentrations now consistently exceeded a maximum threshold of 100.0 milligrams per liter (mg/L) in their secondary effluent.
The rural, inland location for this facility offered limited options for wastewater disposal and conventional treatment, including membrane filtration and ion exchange. These alternative solutions would not only be expensive to buy and operate, but would be unable to meet the new restrictions without generating significant volumes of waste.
Target
Return the WWTP to compliance, meeting multiple NPDES contaminant limits with minimal brine volume generation and low operating costs.
Activity
MI Systems conducted an on-site pilot of its END® Technology prior to a full-scale buildout to demonstrate effective chloride removal. The pilot provided a high-performance solution to meet updated permit restrictions. The process was designed to recover at least 95% of the client’s wastewater volume with minimal noise, energy consumption, and maintenance, and will enable on-site brine management using a small evaporation pond – an option not possible with conventional desalination methods.
END® Technology transforms EDR via advanced electrode, membrane, and spacer materials and improved membrane and cell geometry. These breakthroughs improve salt rejection, reduce energy consumption, and lower the maintenance requirements of an already well-proven process. Automated polarity reversal provides a ‘Self-Cleaning’ flush of scale-forming ions and other foulants for robust, high-performance operation.
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Results
Piloting END Technology validated effective chloride removal to below the 100.0 mg/L permit limitation while operating at 96% overall recovery and consuming only 0.5 kWh per cubic meter of product water, surpassing the performance of other competitive high-recovery processes. The next best process was expected to only provide 90% recovery, requiring off-site disposal of the waste brine – an unsustainable opex expense for the WWTP at almost two tanker trucks per day for the full-scale operation.
A planned 200 GPM full-scale system will expand on the successful pilot demonstration of the WWTP’s secondary effluent. Upon start-up, the WWTP will be in compliance with their chloride discharge limit, having done so without sacrificing water recovery or significant energy.