Industrial-Metal Precipitation Filtration

Plant History: The Bodine Aluminum Wastewater Treatment Facility is an existing facility that was to undergo an upgrade to enhance treatment as well as increase capacity. The facilities major purpose is to treatment and remove heavy metals from the foundry process waste stream before discharge to the sanitary sewer in Troy, MO. Bodine Aluminum manufactures engine blocks and components for Toyota.

Plant Description: The Bodine WWTF is designed for an peak daily flow 60 USgpm. The treatment system consists of chemical addition, flocculation, clarification, pH adjustment, and filtration. Treated effluent is either discharged into the sanitary sewer or reused as gray water in the manufacturing facility.

Tertiary Filters: After pH adjustment the influent is pumped to the Centra-flo Model CF-25 continuous backwash, moving bed sand filter. The Centra-flo unit has been continuously operated since startup.

Filter Startup: This facility was on a fast tract construction schedule managed by Black & Veatch Construction. The filter was put into operation less than 8 weeks after order. The filter replaced a pressure filter device that had historically been plagued with problems and required a lot of operator attention and time. The goal of the installation Centra-flo was to produce a high quality filtrate, reduce operator attention and maintenance requirements, and to operate continuously without backwash shutdowns.

The Centra-flo did all these things very well after initial startup. After approximately 8 weeks operation, the Centra-flo began to experience headlosses in excess of design. After a quick evaluation of the operation and process, APT, Black & Veatch, and Bodine Aluminum all concluded that the problem with the Centra-flo headloss was not a filter problem at all. It was the result of the pH level in the filter being too high. The pH in the filter influent was above 9.5. At that level, calcium carbonate was precipitating within the filter and causing elevated headloss. A simple solution was designed, installed and once operational eliminated the problem completely.