On-site domestic wastewater renovation utilizing a partially saturated recirculating sand filter with lawn irrigation of effluent

A prototype on-site domestic wastewater renovation system was installed in 1988 and monitored during the period of February 1988 to November 1988. The prototype system used a partially saturated recirculating sand filter for renovation and a lawn irrigation sprinkler for distribution of renovated wastewater. The prototype was evaluated on the basis of its ability to remove nitrogen, COD, and coliform bacteria. A lawn plot receiving renovated wastewater, a potable-water irrigated plot and a dry control plot were sampled to evaluate the potential environmental impact of applying renovated wastewater to a lawn.

Water quality samples were collected weekly from various points within the prototype system. Runoff samples were collected from the lawn plots whenever natural precipitation events produced runoff. All water samples were analyzed for the concentration of nitrogen, COD, and coliform bacteria. Seasonal grass samples from the plots were checked for coliform bacterial content in an attempt to assess the potential for human exposure to pathogens by contact with and/or ingestion of lawn grass.

The investigation showed that the prototype had removal efficiencies as high as 82.5% for nitrogen, 96.3% for COD, and log reductions of 2.8 and 2.4 for fecal and total coliforms, respectively. Statistical comparisons of bacterial exposure, runoff water quality and grass yield among each of the plots showed few significant adverse differences when comparing the plot receiving renovated wastewater to the irrigated and dry control plots.