Use of Constructed Wetlands to Treat Domestic Wastewater, City of Arcata, California

Abstract

This paper summarizes 10 years of experience applying oxidation pond effluent to constructed wetlands in Arcata, California. The first five years (1980-1986) was spent experimenting with 6×66 metre constructed wetland mesocosm. The second five years involved fullscale analysis of 2.8 hectares and 12 hectares effluent receiving marshes. Experience to date has verified the capability of constructed wetlands to reliably and effectively meet advanced secondary water quality standards. Effluent BOD and suspended solids concentrations of 30 and 30 mg/l respectively can be met ninety percent of the time with weekly samples; fecal coliform levels of 20 CFU/100 can be met 90 percent of the time. Total inorganic nitrogen levels of 5 can be met in the growing season at 12 mg/l in the non-growing season. Design criteriaaregiven for BOD, SS, coliform, and TIN removal for a temperature range of 6 to 20°C. Experience gained to date on the construction details, vegetation planting, and operational consideration is also summarized in the paper.