Document Type


Publication Date

January 1978


To evaluate the effectiveness of overland flow treatment in upgrading secondary wastewater lagoon effluent, three 15 x 36 m plots on a 2.5 percent slope were constructed and sown for a high density vegetative cover using Reed Canary grass. Wastewater was applied to the upper end of each plot at rates of 7.5, 15, and 22.5 cm/wk. Results from the overland flow system investigation were compared with similar data obtained the preceding year from an existing slow rate land application system on an adjacent site. Secondary effluent from the same lagoon system was applied to the slow rate system study area. After evaluating influent and effluent water quality characteristics from both systems, site specific efficiencies were detailed. Overland flow as a tertiary treatment process may not be suitable to satisfy future discharge standards because of the minimum biochemical oxygen demand and suspended solids effluent concentrations that are attainable. Overland flow could be used as a nitrification-dentrification process if land costs were sufficiently low. The flow rate system can be an excellent tertiary treatment method if the groundwater is protected and no subsurface water collection and discharge is required. If a discharge is required, organic carbon and nutrient concentartions might be unacceptable depending upon initial site soil conditions.