Publication Summary

An announced Class II inspection was conducted March 3-6, 1996 at the City of Marysville Wastewater Treatment Plant (Marysville) in Snohomish County, Washington. Included were analyses of three industrial contributors to the Marysville collection system: National Foods Corporation, Pacific Coast Feathers Company, and Quil Ceda Tanning Company.

An announced Class II inspection was conducted March 3-6, 1996 at the City of Marysville Wastewater Treatment Plant (Marysville) in Snohomish County, Washington. Included were analyses of three industrial contributors to the Marysville collection system: National Foods Corporation, Pacific Coast Feathers Company, and Quil Ceda Tanning Company.

Moderate reductions in BOD5, CBOD5, TOC, and TSS occurred across the treatment plant, but calculations suggest that more robust removal efficiencies are theoretically possible. Effluent ammonia concentration was relatively high, but was not expected to exceed water quality criteria at the edge of the acute mixing zone. Analysis of the facility′s complete mix aeration cells determined that aeration met minimum oxygenation requirements, but was inadequate for mixing. Marysville should investigate the impact of mixing on treatment effectiveness. Calculations suggest that the current recirculation rate to the first and second oxidation ponds from the fourth lagoon may not be highly effective in reducing BOD5. Detention time across the two oxidation ponds appears to be adequate and sludge buildup was minimal. BOD5 and TSS concentrations increased across the third and fourth stabilization ponds, and this is likely due to algae growth. The in-plant sand filter appeared to be operating effectively.

The 24-hour effluent composite CBOD5 concentration exceeded the NPDES permit weekly and monthly average limits. Although the comparison is based upon a single sample, Marysville should ensure that the plant does not on average exceed these limits. TSS was 80% of the weekly limit and Marysville should ensure that the limit is not exceeded during seasons when greater algae growth may occur. The Pacific Coast Feathers BOD5 grab sample and Quil Ceda Tanning BOD5 24-hour composite sample concentrations exceeded state waste discharge permit daily maximum limits. National Foods 24-hour composite pH measurement also exceeded the state waste discharge permit limit. The dischargers should ensure that effluents concentrations are within permit limits. Contributions of toxic loads to the Marysville treatment plant influent were generally low.

The Marysville whole effluent copper concentration exceeded water quality criteria, but is expected to be reduced to below criteria within the dilution zone. The Marysville effluent chronic fathead minnow bioassay indicated toxicity at low concentrations, and a reasonable potential exists for chronic conditions in the receiving water. Additional bioassays, including bioassays for marine organisms, are recommended. Effluent CBOD5 and BOD5 results differed substantially for Ecology and Marysville split samples and it is recommended that Marysville review holding procedures. Marysville sludge concentrations do not exceed limits for land application or hazardous waste designation.