Reclamation of wastewater with a soil-turf filter. I. Removal of nitrogen

This study investigated the maximum rate of wastewater that could be applied to two different soils to achieve suitable water quality in the form of leachate, without harming turfgrass and without excess nitrate concentrations. A sand-turf filter removed less nitrogen than a mix-turf filter, but its lower water-holding capacity resulted in higher recharge percentages. The maximum rate of wastewater application that maintained leachate nitrate concentrations below 10 mg/l was also influenced by season. In the summer, the sand-turf filter could accept up to 12.7 cm/wk yielding 9 cm/wk recharge, compared to 18.7 cm/wk yielding 12.5 cm/wk recharge for the mix-turf filter. Corresponding winter values for the sand-turf filter were 13.6 cm/wk applied with 10.8 cm/wk recharge, and 21.9 cm/wk applied to the mix-turf filter yielding 16 cm/wk recharge. The sand-turf removed 52% of wastewater nitrogen (averaging all application rates over the 42-week study). The sand removed 33% of the nitrogen, with 19% removed by the turf. For the mix-turf filter, 64% of wastewater nitrogen was removed - 37% by soil processes and 27% by turf growth.