Publication Summary

An announced Class II inspection was conducted at the Aberdeen Wastewater Treatment Plant on March 17-19, 1997. Extreme wet-weather conditions prevailed during the inspection and the plant was hydraulically overloaded, exceeding design peak loading. The plant was being operated at maximum capacity during the inspection, with flow rate limited by discharge pump capacity. The conventional parameters of 5-day biochemical oxygen demand (BOD5 ) and total suspended solids (TSS) showed that there was little or no removal through the plant during the inspection.

An announced Class II inspection was conducted at the Aberdeen Wastewater Treatment Plant on March 17-19, 1997. Extreme wet-weather conditions prevailed during the inspection and the plant was hydraulically overloaded, exceeding design peak loading. The plant was being operated at maximum capacity during the inspection, with flow rate limited by discharge pump capacity. The conventional parameters of 5-day biochemical oxygen demand (BOD5 ) and total suspended solids (TSS) showed that there was little or no removal through the plant during the inspection.

The effluent met National Pollutant Discharge Elimination System (NPDES) permit limits for BOD5 and TSS concentrations, and pH. As a result of dilution from infiltration and inflow, the influent also met these limits. Weekly average loading limits for BOD5 and TSS in the 24-hour composite effluent sample were each exceeded by a factor of greater than 2. Removal of BOD5 and TSS during the 24-hour inspection was 4.2% and -12.5% respectively, as compared with monthly average permitted minimum removals of 85%. Fecal coliform counts exceeded the permitted monthly average but were within the weekly permitted average. This indicates that despite hydraulic overloading during maximum flow conditions, effective disinfection was achieved. Aberdeen′s reported results for the entire month of March show compliance with BOD5, TSS, and flow monthly and weekly permit limits.

Copper, lead, silver, and zinc were detected in the effluent sample. A reasonable potential was found for copper to violate water quality standards. All metals in the sludge sample were found in concentrations lower than EPA sludge application limits and ceiling concentrations for land application of municipal sludge.