IN SITU DENITRIFICATION POTENTIAL FOR SOUTH AFRICAN GROUNDWATER

The occurrence of high nitrate levels in groundwater is a widespread phenomenon. This is ascribed to both natural and anthropogenic causes. High concentrations of ingested nitrate cause methaemoglobinaemia, which can be fatal for infants and livestock. The maximum permissible level of nitrate in drinking water in South Africa is 20 mg/L (as N). This value has been used as a cut-off for the identification of problem areas for water supply in South Africa. In situ nitrate removal is practised by countries in Europe, the United States and Canada. Nitrate removal methods typically use biological denitrification and sometimes ion-exchange. In the USA and Canada, the permeable reactive barrier is widely used, which promotes biological or chemical denitrification. Other techniques use injection of reagents into the aquifer. Examples for in situ biological denitrification, the Nitredox ® method uses a sophisticated arrangement of injection and aeration wells to manipulate oxidation and reduction for control of nitrate, iron and manganese in the aquifer. These treatment plants are specifically designed for nitrate removal and hence achieve optimum results. In South Africa, some conventional treatment methods are used that also remove nitrate, but no known attempts have been made to use in situ technologies aimed specifically at removing nitrate from groundwater. This paper considers the applicability and potential for use of in situ nitrate remediation technologies to South African groundwaters. In view of the Governments standing on safe water for all and the right of each citizen to safe water potable water, it could fulfil its constitutional obligation by providing cleaner i.e. nitrate free water to areas that are solely dependent on these water resource