Highlights of Research on Overland Flow for Advanced Treatment of Wastewater.

摘要

Overland flow treatment of municipal wastewater was studied in greenhouse grass-soil models. The response of overland flow treatment of nitrogen, phosphorus, and heavy metals to various operating conditions was determined. Nitrogen removal from applied wastewater was exceptionally efficient, with best removal being obtained whenever the applied wastewater was allowed sufficient time to interact with the components of the overland flow system. Sufficient time for adequate treatment of wastewater could be obtained by increasing the application period from 6 to 18 hr, by decreasing the amount of applied wastewater from 1 to 1/2 in./acre, by decreasing the slope of application surface from 8 to 2 percent, or by combinations thereof. Greater than 90 percent nitrogen and heavy metal removal could be obtained during overland flow treatment. Generally, 80 percent of the applied phosphorus was removed with overland flow treatment. Up to 98 percent phosphorus removal could be obtained by addition of stoichiometric amounts of aluminum sulfate to the wastewater prior to land treatment. Nitrogen, phosphorus, and heavy metals were found to accumulate on the soil surface in the organic mat with little movement into lower soil depths. Heavy metals accumulated on the soil surface nearest the point of wastewater application. Elevated levels of heavy metals were correspondingly found in the grass harvested nearest the point of wastewater application. The results of this modeling study indicate that overland flow is a feasible method for treating municipal wastewater to achieve a tertiary level of water quality. (Author)