Abstract

Elevated nitrate levels in drinking water by nitrate are an evolving public health concern, since nitrate can undergo endogenous reduction to nitrite, and nitrosation of nitrites can form N-nitroso compounds, which are potent carcinogens. Nitrates are also responsible for a number of health disorders, both in human beings and animals. Thus, nitrate reduction from water has become critical and the need of the hour. Water contaminated with nitrate needs to be treated so that it meets drinking standards. Boiling, softening, or disinfection will not reduce the nitrate content of water, and conventional measures to treat nitrate rich waters such as reverse osmosis, deionization and distillation are extremely cost-prohibitive. In this connection, studies were conducted to explore the avenues for low cost treatment for nitrate reduction in groundwater using selective filter media which are locally available and inexpensive. Media combinations of fly ash with pebbles and charcoal with brickbats were used. To assess their potential as a filter medium, a laboratory scale physical model study was constructed using the above two combinations and from the experimental studies, it was observed that 66% removal efficiency was achieved using flyash and pebbles, while 88% efficiency was achieved using charcoal and brickbats, for a simulated NO₃concentration of 100 mg/L. Also it is seen that this optimum efficiency is achieved with a contact time of 3.5 h. Thus, the use of charcoal and brickbats for a contact period of 3.5 h is seen to produce an optimum degree of nitrate attenuation from groundwater.

Key words: Attenuation, brickbats, charcoal, flyash, groundwater, nitrate, pebbles, removal efficiency.