Treatment of Primary Sewage Effluent by Rapid Infiltration,

Treatment of unchlorinated primary sewage effluent by using rapid infiltration basins resulted in a high degree of wastewater renovation in a humid, cool northern climate. Inundating 9 treatment basins for 7 days followed by 14 days of rest, from 4 January to 21 June 1974, resulted in effluent additions totaling about 27 m. Analysis of the groundwater from the treatment site and from the peripheral area showed that total coliform bacteria, 5-day biochemical oxygen demand, and chemical oxygen demand were essentially removed, while phosphorus concentrations were only one-third of the applied effluent concentrations. Total nitrogen additions to the treatment basins during the 7-day inundation period were about 54 greater than the nitrogen additions in the 1973 investigations. This study showed that proper management is needed if rapid infiltration basins are used for nitrogen removal by maintaining effluent infiltration in northern climates.