Effects of Hydrologic Regime on Nutrient Removal from Wastewater Using Grass Filtration for Final Treatment,

摘要

Grass filtration has been proposed as a method for final treatment of secondary treated sewage effluent. The effectiveness of grass filtration or overland flow wastewater systems,however,has not been tested adequately. Thus, a field study was conducted to determine the effects of wastewater application rate,flow distance,application frequency,and season of the year on nitrate and phosphate removal. The removal of phosphate and nitrate,however,increased as the application frequency was decreased. However,in all the field tests,the reduction in phosphate and nitrate was very small,zero to approximately 20%. Laboratory tests,undertaken because of the small nitrogen removals in the field,were conducted. Five to six hours were required in the laboratory to achieve a 90% reduction in nitrate concentration from an effluent with an initial NO3-N concentration of 12mg/l. The field and laboratory studies indicate that obtaining a sufficiently long contact time is the most important consideration in designing a grass filtration system.