Feed-Forward Automation for Cost Effective Chemical Treatment of Food Manufacturing Wastewater

A food manufacturing plant in the western United States pre-treated its wastewater with pH neutralization followed by dissolved air flotation (DAF), prior to discharge to a municipal water reclamation plant. Due to manpower limitations, chemical treatment of the DAF was automated based on flow-paced feed with manual dosage set points. It was discovered that the wastewater varied in both quantity and quality, independently, which led to significant overdosing to ensure adequate final effluent quality. Chemical coagulant demand was found to be proportional to wastewater turbidity (suspended matter). A relationship was developed and converted into a control algorithm for automation of coagulant and flocculant dosages. This feed-forward control loop was implemented on top of the flow-paced control. Chemical costs were reduced by more than 40% following implementation, with little change in effluent quality. The plant continued to meet its discharge limits.