Effectively treating cadmium cyanide rinse waters for regulatory compliance

Challenge

A prominent Midsouth aerospace manufacturer decided to bring the manufacturing of aircraft landing gear and other components in-house to reduce costs and improve profitability.  The manufacturer planned to install a new cadmium cyanide (CdCN) electroplating process for these high-stress parts to provide the necessary durability and corrosion inhibition.  However, the existing wastewater treatment system was not capable of treating the wastewaters from this new CdCN process. The aerospace manufacturer reached out to Evoqua for a new treatment solution with speed of installation being a critical factor.

Solution

The customer initially requested a proposal for a conventional capital system. Evoqua evaluated the chemistries in the new manufacturing process and provided a proposal for a capital CN-destruct system, using alkaline chlorination, to meet the discharge requirements of the treated process wastewaters. While CN-destruct systems are effective at treating cyanide-bearing wastewaters, hazardous chemicals are used during operation, such as sodium hypochlorite, and a large up-front capital expense is required.

Due to the manufacturer’s limited budget, short project lead-time and desire to reduce employee exposure to conventional treatment chemicals, Evoqua provided an alternative solution. Wastewater ion exchange (WWIX) services were recommended for the removal of cadmium cyanide via ion exchange instead of chemical oxidation and Cd precipitation. This eliminated the risk of employee exposure to chemicals and was a more effective solution for the project timing and budget.

Evoqua’s WWIX services utilize ion exchange resin canisters for the removal of dissolved heavy metals from a variety of rinse water and wastewater streams. Once the capacity of the lead WWIX resin vessel is exhausted, the entire tank (with the resin in place) is shipped to Evoqua’s Roseville, MN RCRA Part-B processing facility, using a DOT-licensed transporter, for removal and environmentally-compliant management of the spent resin.

Results

By installing 30-ft³ WWIX anion resin system in a lead-lag configuration, the aerospace manufacturer was soon treating up to 75 gpm of their CdCN wastewater. Evoqua’s WWIX services met the facility discharge compliance goals for both cadmium and cyanide without the addition of any hazardous chemicals, such as those used in CN-destruct systems. This protects the health and safety of the manufacturer’s employees and allows them to focus on manufacturing while knowing their process wastewater treatment needs are met.