Publication Summary

An announced Class II inspection was conducted at the Eastsound Sewer and Water District Orcas Village Wastewater Treatment Plant (Orcas Village WWTP) on October 21-23, 1996. The plant was producing a good quality effluent. The 24-hour effluent sample results were within limits in the Orcas Village National Pollutant Discharge Elimination System (NPDES) permit for 5-day biochemical oxygen demand (BOD5), total suspended solids (TSS), fecal coliform, and pH. One total residual chlorine measurement (0.6 mg/L) exceeded the permitted monthly average (0.5 mg/L) but was within the permitted weekly average (0.75 mg/L). Effective control of chlorine dosing is recommended.

An announced Class II inspection was conducted at the Eastsound Sewer and Water District Orcas Village Wastewater Treatment Plant (Orcas Village WWTP) on October 21-23, 1996. The plant was producing a good quality effluent. The 24-hour effluent sample results were within limits in the Orcas Village National Pollutant Discharge Elimination System (NPDES) permit for 5-day biochemical oxygen demand (BOD5), total suspended solids (TSS), fecal coliform, and pH. One total residual chlorine measurement (0.6 mg/L) exceeded the permitted monthly average (0.5 mg/L) but was within the permitted weekly average (0.75 mg/L). Effective control of chlorine dosing is recommended.

Influent ammonia, nitrite-nitrate, and phosphorus concentrations were considerably higher than those associated with typical municipal wastewater influent, but the concentrations were typical for septic tank effluent. Septic tank effluent comprises the influent for the Orcas Village WWTP. Complete nitrification occurred through the plant, with all measurable ammonia converted to nitrite-nitrate.

Split samples showed good agreement for all BOD5 analyses and for effluent TSS analyses. There was variability in influent TSS results between the Ecology and Eastsound laboratories, and the cause was unclear. Hydraulic and organic loading to the plant were very low during the inspection. Influent BOD5 and TSS loads were both below 4% of the monthly average design loading for the plant. The BOD5 influent load during a 1990 Class II inspection was 60% of monthly average design load, but removal efficiencies were high during both inspections.

Two recirculation lines are designed to operate at equal flow rates. The plant′s recirculation flow meters indicated that the flow in one line was more than ten times that of the other. Fouled flow sensors are suspected, but properly functioning meters are needed to evaluate actual flow through the lines. Regular maintenance of the flow sensors is recommended.