Publication Summary

A Class II Inspection was conducted at the Stanwood Wastewater Treatment Plant on September 8-9, 1992. Stanwood operates a lagoon-type secondary wastewater treatment system discharging to the Stillaguamish River. An algal bloom occurred in the lagoon during the inspection resulting in degraded effluent quality. Comparison of inspection data with NPDES permit limits found BOD5, TSS, and fecal coliforms in excess of weekly and/or monthly permit limits. Few priority pollutant scan compounds were detected in the Stanwood influent, effluent, and sludge samples. Several of the bioassay organisms tested were sensitive to the Stanwood effluent. Microcystis, the organism comprising the algal bloom, may have contributed to the observed toxicity.