Evaluation of Compliance Strategies to Meet Stringent Effluent Copper Limits

The objective of this evaluation was to determine the optimal means for the City of Puyallup, Washington to comply with stringent wastewater treatment plant effluent copper limits through bench and pilot testing of possible approaches. A source evaluation determined that corrosion of domestic and commercial plumbing was the primary source of copper in wastewater entering Puyallup's Water Pollution Control Plant (WPCP).Testing conducted to evaluate compliance strategies with effluent copper limits included:Conducting a “pipe loop pilot study” to evaluate the efficacy of two potential drinking water corrosion control technologies to reduce copper and zinc concentrations discharged to the treatment plant via domestic sewage and to evaluate the impact of the different technologies on overall drinking water system quality.Evaluating the potential for enhanced metals removal within the treatment plant through bench testing using conventional, readily available chemicals such as ferric chloride and through the use of specialized polymers.Based on the pipe loop pilot study, corrosion control in the drinking water system was projected to reduce, on average, WPCP influent copper by approximately 20%. Use of specialized polymers was found to reduce WPCP effluent dissolved copper by 75 – 95% at optimal doses. The City selected the use of specialized polymers as the mean of achieving compliance with their effluent copper limits.