Profitability and Health Risk Estimation of Rice Cultivation under Wastewater Irrigation from Natural Drainage

The paper reports the results of an empirical study on the profitability of rice cultivation in the rural areas of Allahabad by wastewater irrigation from natural drainage. The results show that plots using wastewater containing organic nutrients earn higher profits than those using groundwater. However, we also find the profitability of plots using wastewater negatively affected by the presence of heavy metals such as Fe, Mn, Cu, Zn, Pb and Ni that are found in the water and soil. Of the two opposing effects of wastewater irrigation, the positive effects of organic nutrients outweigh the negative effects of heavy metal toxicity. The soil along the sides of the wastewater channel shows higher productivity and concentration of heavy metals than the crops away to it but lies within the safe limits of WHO/ FAO. The order of metal contents was found to Fe > Zn > Mn > Ni > Cu > Pb in contaminated irrigation water, and the average abundance order of heavy metal contents in soil are: Fe>Mn>Zn>Cu>Pb>Ni. Very strong positive correlation observed for Cu (r 2 = 0.984; P<0.01) and strong positive correlation for Mn (r 2 = 0.698; P<0.01) while other heavy metals show moderate positive correlation (r 2 , 0.36 to 0.67; P<0.05) between the concentration in wastewater and their availability in the soil of the study area. The Study reveals that there is significant relation between the concentrations of the metals in soil to the concentration of metals in water used for irrigation, but no significant relationship for its transfer to the rice. The low concentration of metals in the soil may be ascribed to its continuous removal by rice grown in the study areas. Daily intake values of heavy metals through consumption of wastewater fed rice are below the recommended oral dose of metal for adult. Consumption of food crops contaminated with heavy metals are a major food chain route for human exposure, but it can safe to state that irrigation of agricultural land of rural areas of Allahabad with wastewater has not led any contamination of food crops with heavy metals. This study regarding DIM (Daily intake of metals) suggest no potential health risk for adults and children with respect to amount of daily intake of heavy metals through ingestion of wastewater irrigated rice crops. However, the concentrations of heavy metals in soil and rice grains were still below the maximal levels, as stipulated by Indian Prevention of Food Adulteration Act (PFA, 1954) and World Health Organization (WHO, 1993) guidelines. IFFCO Phulpur is not discharging its effluent outside the company premises but chances of heavy metals contaminations of crops may occur if the rural drainage system get link to any industrial discharge or any other source of contamination. These results support both efforts to conserve the natural drainage, which will generate a number of ecological benefits, as well as to regulate the discharge of wastewater into the water from households and runoff that are located upstream.