Background | The Village of Suffern operates a wastewater treatment plant that treats approximately 1.8 MGD of wastewater per day. The wastewater is collected from 12,000 residents and a fairly significant number of commercial and industrial users. The Village has a pretreatment program that requires Significant Industrial Users to be identified and have their wastewater undergo pretreatment as necessary. Pretreatment measures are necessary to maintain a plant influent standard that is within the design parameters for the facility. This standard is set to ensure the plant is able to function properly, meet permit discharge limits and maintain the toxicity of the sludge that is sent for further processing. Recently, elevated levels of copper and zinc from an unknown source have been identified in the sludge that is leaving the facility.
Challenges | A study is required to identify the users, industries or other sources whose processes or systems could potentially release metal contaminants. This study will involve a volumetric comparison and evaluation of users’ waste stream characteristics to determine each user’s potential contribution of metals. Discrete sampling of wastewater at locations chosen based on the investigation will occur for several months to obtain a comprehensive range of wastewater from users tributary to each sampling location. Both copper and zinc can come from water treatment and heating systems and corrosion and leaching of plumbing, and concentrations of copper in sludge are directly proportional to water hardness since hard water is potentially more aggressive to copper and zinc plumbing. Further complicating the situation, the Suffern water treatment plan utilizes zinc orthophosphate as a corrosion inhibitor in the finished water for corrosion protection.
Solutions | Our team has studied the Village’s water and sewer records and examined case studies and peer-reviewed articles regarding copper and zinc leaching. Using our research and intimate knowledge of the Village’s water and sewer systems, we have identified strategic sampling locations and frequencies to most efficiently evaluate the water treatment facilities’ source contributions of copper and zinc. Once sampling is complete, we will analyze the findings and prepare a lab report summary and evaluation and recommendation report. We will also analyze the Village’s use of zinc orthophosphate in the water system as potential contributor of copper and zinc in the water supply and ultimately in the wastewater sludge.