Publication Summary

A Class II Inspection was conducted August 23-25, 1994 at the City of Loon Lake Wastewater Treatment facility in Spokane County, Washington. The Loon Lake facility operates an aerated lagoon connected in series with two large unaerated detention/polishing lagoons. Effluent is discharged to a sprayfield which is under cultivation. Increases in BOD5 and total solids occurred across the aeration lagoon and these were attributed to algae growth. In contrast, nitrification across the aeration lagoon was pronounced.

A Class II Inspection was conducted August 23-25, 1994 at the City of Loon Lake Wastewater Treatment facility in Spokane County, Washington. The Loon Lake facility operates an aerated lagoon connected in series with two large unaerated detention/polishing lagoons. Effluent is discharged to a sprayfield which is under cultivation. Increases in BOD5 and total solids occurred across the aeration lagoon and these were attributed to algae growth. In contrast, nitrification across the aeration lagoon was pronounced.

Large reductions in BOD5, additional nitrification, and denitrification occurred across the polishing lagoons. It is suggested that further degradation of BOD5 is enhanced by aerobic-anaerobic processes dependent on the growth and impoundment of algae within the lagoons. It is advised that biological treatment is temperature dependent and that the treatment process should be evaluated at different times of the year.

All influent, effluent, and flow results were within State Discharge Permit limits. Agronomic analysis of the effluent discharged to the sprayfield identified sodium ion concentrations and pH as having the potential to adversely impact crop cultivation. A number of metals were detected in the effluent, but a site specific analysis of their impact on ground water was not possible due to a lack of information on specific ground water characteristics.