Publication Summary

An announced Class II Inspection was conducted at the City of Chehalis Wastewater Treatment Plant on June 2 - 4, 1997. The plant was performing well during the inspection. The conventional parameters of BOD5, TSS and fecal coliform indicate a well-treated, high quality effluent. Effective nitrification was being achieved by the plant.

An announced Class II Inspection was conducted at the City of Chehalis Wastewater Treatment Plant on June 2 - 4, 1997. The plant was performing well during the inspection. The conventional parameters of BOD5, TSS and fecal coliform indicate a well-treated, high quality effluent. Effective nitrification was being achieved by the plant.

All unit processes were operating within or close to design parameters typical of their type with the exception of the south aeration basin. The south aeration basin has a volume of 128,000 ft3, and its four aerators provide only 0.47 hp/1000ft3 of power as compared with 0.75 to 1.50 hp/1000ft3 necessary for complete mixing. If aeration basin performance is inadequate under conditions more demanding than those of this inspection, increased mixing horsepower in the aeration basin might resolve the problem.

The fecal coliform count in the sludge sample was well within the maximum limit for Class A sewage sludge in accordance with EPA regulations. Twelve priority pollutant metals were detected in the sludge sample. All metals were found in concentrations lower than EPA sludge application limits and ceiling concentrations for land application of municipal sludge.