Seasonal Variation of Nitrate Level in Ground and Surface Waters of Lucknow and its Remediation using Certain Aquatic Macrophytes

The nitrate level was monitored in drinking water and surface water in the vicinity of Lucknow (a city with over 28 lakhs population) during winter, summer and rainy season of the year - 2007, and 2008. The drinking water samples were collected from 22 sites, out of which 11 sites were from urban vicinity, 6 were from peri-urban areas, and 5 sites were located in rural areas. The nitrate level in drinking water sources of 6 urban vicinities was found over the permissible level (45 mg L⁻¹), which ranged from 47 to 114 mg L⁻¹. In peri-urban region only one site carried nitrate in drinking water over the permissible level. Out of 5 sites tested in rural vicinities, 2 carried nitrate level (53 to 62 mg L⁻¹) over the permissible level. On the other hand, all the 11 sites located in urban, peri-urban and rural localities showed more than 3 fold higher level of nitrate over the permissible level (13 mg L⁻¹) in the surface water bodies. Though, there was a little seasonal variation in the nitrate level during summer, rainy and winter, the level was often higher in rainy and winter seasons than that in the summer season. The increase in nitrate level in rainy season was however, more pronounced in the surface water as compared to that in drinking water. Eight macrophytes e.g. Peltandra virginica, Utricularia vulgaris, Eichhornia crassipes, Trapa natans, Mimulus glabratus, Marsilea quadrifolia, Pistia stratiotes and Polygonum persicaria were grown in nitrate contaminated water in the pot condition, which variably removed nitrate from the water. The various macrophytes grown in nitrate contaminated water, removed 58 to 74% nitrate within 15 days. Maximum removal of nitrate was observed by Pistia stratiotes followed by Trapa natans, Polygonum persicaria and Mimulus glabratus within close vicinity. Our experiment indicates that surface water bodies and drinking water sources can be treated effectively for the remediation of nitrate contamination using selected macrophytes.