Publication Summary

A Class II Inspection was conducted at the City of Chewelah Wastewater Treatment Plant on October 3-6, 1994. The conventional parameters of BOD5, TSS, and pH indicate an effluent of good quality. The effluent met all permit limits with the exception of fecal coliform. Fecal coliform counts for samples collected on two days exceeded the permit limits for monthly average and weekly average. No chlorine was detected in the effluent.

A Class II Inspection was conducted at the City of Chewelah Wastewater Treatment Plant on October 3-6, 1994. The conventional parameters of BOD5, TSS, and pH indicate an effluent of good quality. The effluent met all permit limits with the exception of fecal coliform. Fecal coliform counts for samples collected on two days exceeded the permit limits for monthly average and weekly average. No chlorine was detected in the effluent.

NH3-N concentrations in the influent (11.0 mg/L) remained essentially unchanged in the effluent (10.2 mg/L), indicating the absence of significant nitrification in the lagoons. For river and effluent conditions at the time of the inspection, it was found that the chronic water quality criterion for ammonia was exceeded assuming maximum mixing of 25% of the river flow.

The need for chlorination at higher concentrations followed by dechlorination, or an alternate method of disinfection, was determined.

Chewelah BOD5 analyses results were considerably lower than Ecology's, and as reported in Discharge Monitoring Reports (DMRs), have been low for several years, suggesting a persistent cause of low BOD5 results. The cause is believed to be the failure to keep samples cool prior to analysis at the Colville laboratory.

Bis(2-ethylhexyl)pthalate in the effluent exceeded the State fresh water chronic criterion by a factor of ten. All other organic compounds and metals found in the effluent were in concentrations lower than State water quality criteria. Mercury effluent concentrations were 88% of the State fresh water criterion.