Nitrification in Overland Flow and Wetland System Following a Waste Stabilization Pond

A study was conducted to evaluate the nitrification capability of an existing and successfully operated overland flow and wetland wastewater treatment system following a waste stabilization pond for a small town. Seasonal temperature effects on performance were also investigated. The treatment system studied consists of a two-cell waste stabilization pond followed by an overland flow system and a wetland system. The overland flow system consists of two parallel fields (425' x 185' each) (130m x 56m each) where reed canary grass is well established. The wetland system consists of four cells (120' x 105' each) (37m x 33m each), two of which are surface flow type and the other two are sub-surface flow type. The influent and effluent samples were analyzed for BOD₅, suspended solids (SS), pH, temperature, ammonia nitrogen, and nitrate nitrogen. The results of the study indicate that the combined overland flow and wetland system provided excellent treatment of municipal wastewater. The overall average BOD₅ removal by the entire treatment system was about 90.7%. The highest removal was 96.0% and the lowest was 85%. The overall suspended solids removal varied from 41.7 to 99.2% with an average of 88.2%. The ammonia nitrogen removal efficiency of the entire treatment system was 88% which indicates significant ammonia nitrification.