Soil Absorption Systems and Nitrogen Removal

Abstract

The mass of nitrogen wasted from conventional soil absorption systems used as waste water drainage and treatment facilities sometimes contributes to pollution of vulnerable groundwater tables. The scope of nitrogen compounds transformation along the different stages of treatment shows that nitrate is quite often the nitrogen end product of efficient aerobic soil treatment for septic tank effluent. Results are reported from long term on-site compact sand filter study, showing that nitrate production depends on hydraulic conditions, but can be very efficient when filtering media is kept unsaturated, for an experimental hydraulic load of 15cm/day When clogging of the system is induced by increasing hydraulic load, nitrate production decreases drastically while removal for other parameters such as organic matter is also affected. A synthetic effluent study gives results on nitrification and denitrification operating conditions applied to sand columns and shows that denitrification can be efficient as a second step of treatment when an extra carbon source is added at the head of a second anaerobic sand column.