SCOURGE OF NITRATE TOXICITY: ITS CLINICAL MANIFESTATIONS AND REMEDIATION EMPLOYING RO TECHNOLOGY

摘要

Groundwater pollution has become a drastic problem principally because of nature and wide spread use of modern chemicals viz. pesticides and fertilizers. Excessive application of fertilizers as well as organic wastes and sewage has been implicated in the nitrogen pollution of groundwater. Therefore, the issue of rising nitrate concentration in groundwater has become a subject of extensive research in India and Rajasthan in particular. In natural water, nitrate ((NO_3~-) N is usually ＜5mg/L. In fact, additional amount of excess nitrate in groundwater arise due to the biological oxidation of organic nitrogenous substances of sewage, industrial and agricultural origin. Water containing excess nitrate, when is ingested, enters GIT, where by the microbial action in non-oxidizing conditions, get reduced to nitrite (NO_2~-). In accordance with the UPSH drinking water standards, a limit of 10mg/L for NO_3~- and 0.1mg/ L for NO_2~- must be regularly monitored in water supplies as they are deemed to be potentially hazardous to infants ＜5months old (methamoglobinemia: BBS) the long-term hazard in adults relates to the reaction in the digestive system between NO_3~- (＞100ppm) and in organic matters (amine and /or amides) resulting in the production of nitrosamines (carcinogens). Number of cases (human and livestock), suffering from gastric cancer have been observed. Reverse osmosis (RO) process has great potential in the purification of nitrate ion containing waters. Generally, the presence of particular substances may affect the removal of specific ions. The presence of di-hydrogen phosphate ions (DHP-ions) in the feed solution enhances the nitrate removal efficiency of the polyamide RO membrane. In this work, a Flmtec TW30, polyamide thin-film composite, RO membrane was used for nitrate removal through RO set up. The rejection of individual nitrate was found to be around 76per cent. After addition of KH_2PO_4 to the feed containing nitrate ions the rejection was improved up to 84per cent. This high level of increment in rejection of nitrate ion indicates the possible usage of KH_2PO_4 in RO for nitrate removal. This fact of removal is due to the potassium ions binding to the electronic lone-pairs of polyamide membrane holds di-hydrogen phosphate ions. This establishes a negative layer on the surface of the membrane. The diffusion of nitrate through the membrane is diminished by the formed layer. Present manuscript delineates clinical manifestations of nitrate toxicity and mitigation of nitrate ion by means of state-of-the-art reverse osmosis technology.