Meeting lower discharge limits for cadmium to prevent fines

Challenge

A U.S. metal finishing facility, that provides repair and manufacturing services to the aerospace and oil industries, generated wastewater from several finishing and electroplating operations.  For many years, their existing conventional wastewater treatment (WWT) system adequately met the local discharge limits. However, when new lower discharge limits were instituted for cadmium, the facility started to experience compliance issues that could lead to violations and fines from the publicly owned treatment works (POTW).

Solution

Evoqua started the evaluation process by reviewing the metal finishing repair and manufacturing processes, including the current WWT system. Composite effluent samples of the facility’s treated wastewater were analyzed, and treatability testing was conducted at Evoqua’s Roseville, MN facility to identify the best media to effectively meet the facility’s permit limit. In addition, a detailed filtration study determined the proper sizing and mix of prefiltration steps needed to remove TSS (total suspended solids) to prevent particulates from fouling the media beds.

After performing the analytical studies, Evoqua recommended our proprietary SCU selective media. The conventional precipitation chemistries used in the customer’s existing system were unable to consistently achieve discharge limits in the parts per billion range, and other commercially available IX resins also were not successful in achieving the permit target.

Evoqua’s SCU product has unique capabilities to remove trace concentrations of regulated heavy metals – even in the presence of highly elevated TSS found in the effluent of a conventional WWT system. Evoqua provided 30-ft³ WWIX SCU media vessels in a worker/polisher configuration, thereby ensuring proper contact to manage the required 50 gpm wastewater flow. 

Results

By conducting a comprehensive and thorough analytical and treatability study of the facility’s wastewater, Evoqua was able to provide the optimal solution to bring the metal finishing facility back into compliance. This eliminated fines and allowed the facility to focus on their core business: producing high quality parts required for civilian and military aerospace platforms and critical oil and gas infrastructure machinery.