Problem: When the wastewater treatment plant for the city of Madison, Indiana, received a new phosphorus limit of 1.0 ppm, the staff of 12 assessed the plant’s treatment processes and determined that biological reduction alone wouldn’t be enough to meet the new limit. 

Solution: The decision was made to add a chemical-feed program to the process. Since frequent rain events increase flow but dilute the concentration of phosphorus entering the plant, plant leadership ruled out flow-based feeds. They instead selected a ChemScan mini oP Analyzer from In-Situ for its large, blockage-resistant sample tubing, internal self-cleaning features and low cost of ownership. Installed at the point of effluent, it measures phosphorus levels leaving the plant in 15-minute increments and adjusts the chemical feed accordingly.  

Result: The analyzer allows the plant to confirm compliance in real time. Its low-maintenance operation also enables the plant’s small staff to use their resources efficiently and direct labor where needed. The plant uses polyaluminum chloride to precipitate influent phosphorus, which binds to phosphorus and adds to the sludge layer. Better chemical control also helps reduce cost by minimizing sludge production. 800-446-7488; www.in-situ.com