Protacted recharge of treatd eswage into sand part I: quality changes in vertical transport through the sand

Abstract

When the Lake George sewage treatment plant was put into operation in 1939, it was described as a “complete treatment” plant. This was because the treated effluent is discharged onto natural delta sand seepage beds which are “at least 25 feet deep.” Studies were made to determine the removal efficiency in the sand beds of coliforms, BOD, chlorides, and the nitrogen and phosphorus compounds. It was found that when beds were dosed, they were no longer saturated with water at 15 feet. Ten feet of sand were found to remove coliforms by 99% and BOD by 96%. However, nitrates, phosphates, and chlorides remained in significant concentrations after filtration through 10 feet of sand. Phosphate removal in an infrequently used sand bed was greater than in a continuously used bed.

Cuando se puso en marcha la depuradora del lago George en 1939, se describió como una planta de "tratamiento completo". Esto se debía a que el efluente tratado se vierte en lechos de filtración de arena naturales del delta que tienen "al menos 25 pies de profundidad." Se realizaron estudios para determinar la eficacia de eliminación en los lechos de arena de coliformes, DBO, cloruros y compuestos de nitrógeno y fósforo. Se comprobó que cuando se dosificaban los lechos, dejaban de estar saturados de agua a 15 pies. Se comprobó que tres metros de arena eliminaban los coliformes en un 99% y la DBO en un 96%. Sin embargo, los nitratos, fosfatos y cloruros permanecieron en concentraciones significativas después de la filtración a través de 10 pies de arena. La eliminación de fosfatos en un lecho de arena de uso infrecuente fue mayor que en un lecho de uso continuo.