From July through mid-October, wastewater from vegetable and cheese processing facilities caused phosphorus spikes at the Beaver Dam (Wis.) Wastewater Treatment Plant. Operators sampled phosphorus just before the effluent outfall three times per week and adjusted the liquid ferric chloride feed accordingly.
"We were chasing our tail a little because the adjustment was always after the fact," says utility foreman Rob Minnema. "If we were high one week, we overfed ferric to make sure the average for the month was below our 1.0 mg/L total phosphorus limit." The average dose was 300 gpd at 12.5 gph.
An upgrade completed in spring 2011
