Treatment of potato processing wastewater with engineered natural systems

A full-scale integrated natural system has been used to treat high strength potato processing water for 2 years. The integrated natural system consists of free water surface and vertical flow wetlands, and a facultative storage lagoon. Influent wastewater averages 2800 mg/L COD, 150 mg/L TN and 350 mg/L TSS. Approximately 5300 m3/d of wastewater flows through the treatment system annually. The treatment objective is a 53% reduction in total nitrogen. The wastewater application permit requires an annual nitrogen load of 500 kg/ha yr on 213 hectares of land used to grow alfalfa and other fodder crops. Free water surface wetlands are used for sedimentation, mineralization of organic matter, and denitrification. Vertical flow wetlands oxidize organic matter and nitrogen. A lagoon provides storage during the winter when irrigation is not possible and functions as a facultative lagoon. Free water surface wetlands were planted with Typha latifolia and Scirpus validus in fall 1995. Wastewater application began in July of 1996. In the summer months COD removal has been greater than 95% through the free water surface wetlands and vertical flow wetlands. The removal rate decreased to about 75% in the winter. Average summer water temperatures are 18°C; average winter water temperatures are 3°C. Ammonia removal through the vertical flow wetlands averages 85% during the summer and 30–50% removal during the winter. Addition of exogenous carbon to the free water surface wetlands resulted in 95% removal of N03-N. Use of natural systems have proved to be a cost effective treatment alternative for high strength industrial wastewater.