Influence of Semi-arid Climate on Characterization of Domestic Wastewater

Abstract

Rapid urbanization causes increase in urban population. Over half of the world’s population lives in cities. By 2050, seven out of every 10 people will be city dwellers. India is a part of this global trend. Nearly 28% of India’s population lives in cities and this is expected to increase to 41% by the year 2020. Urban population will generate huge amount of domestic wastewater (WW). The promising alternative for disposal of wastewater is its utilization for irrigation after treatment. To utilize domestic wastewater, it is vital to generate the information about of different quality parameters and their variations due to seasonal weather conditions. Physiochemical water quality parameters (EC, pH, turbidity, total solids, NH4–N, NO3–N, P, K, Na, Ca, Mg, CO3, HCO3 and heavy metals (Cu, Zn, Mn, Fe, Cr, Mo) of domestic wastewater were determined for the period of one year. The data set is used to present spatial and temporal variations of the domestic wastewater quality. Identification of wastewater quality parameters responsible for temporal variations due to effect of semi-arid climate was done through multivariate cluster analysis. Correlation study between the identified parameters was also conducted. Wastewater was slightly acidic in nature with mean value of pH 6.87. Highest concentration was observed for total solids. Concentration of ammoniacal nitrogen was higher than nitrate nitrogen; similarly bicarbonate concentration was higher in comparison to carbonate concentration. In the category of heavy metals highest concentration with mean value 0.98 mg l−1 was observed with iron and least with molybdenum with mean value 0.01 mg l−1. Most of the water quality parameters concentration was higher during summer season, moderate during winter season and least during rainy season. Correlation study between quality parameters shows the presence of bicarbonate with calcium and magnesium. Presence of calcium, magnesium and bicarbonate play important role for the quantum of total solids in domestic wastewater. Wastewater quality was under safe limit throughout the year in terms of irrigation water quality indices SAR and Mg/Ca ratio. But it was under safe to moderate limit in terms of residual sodium carbonate (RSC) index. Cluster analysis divides the months of a complete year in three clusters. First cluster have six months (July, August, September, October, November and December), second cluster have four months (January, February, March and April) and third cluster have two months (May and June).