Publication Summary

A Class II Inspection was conducted September 20-22, 1993, at the city of Medical Lake Wastewater Treatment facility in Spokane County, Washington. Most effluent results are within the Ecology compliance order load and concentration limits, but several exceed NPDES permit limits.

A Class II Inspection was conducted September 20-22, 1993, at the city of Medical Lake Wastewater Treatment facility in Spokane County, Washington. The Medical Lake facility operates an aerated lagoon connected in series with two large unaerated treatment/settling lagoons. Effluent flow meter calibration was checked and the meter was found to be accurate. Recalibration of pump flow measurements or, if necessary, the addition of an influent flow measurement device is recommended. A higher than typical BOD5/TOC ratio was found for influent samples. TSS removal efficiency was moderate likely due to algae growth in the settling ponds. NH3-N removal occurred in the system.

Most effluent results are within the Ecology compliance order load and concentration limits, but several exceed NPDES permit limits. Effluent pH exceeded both NPDES permit and compliance order limits. Effluent TSS concentration exceeded the percent of influent concentration stipulated by the monthly NPDES permit limit. Wastewater metal concentrations were all within EPA and state water quality criteria for receiving waters. Concentrations of sludge metals did not exceed EPA criteria for the land application of municipal sludge, although fecal coliform densities exceeded Class A land application standards.