Assessment of chemical and microbial contamination in groundwater through leaching of sewage waste in Delhi, India

Abstract

The identification of proxy indicator for groundwater infiltration and bacterial contamination is an important step in managing groundwater resources and hazard assessment. The objective of the present study was to estimate the hydro-chemical data of Khyberpass, Delhi, location to explore the preliminary, chemical and microbial contamination of groundwater samples through setup lysimetric experiments which were mimicking natural field conditions. The calculated mean values of physico-chemical and microbial parameters in control leachate, drain leachate and drain samples exceeded permissible limits of World Health Organization (WHO). All the groundwater samples for preliminary test were found within WHO permissible limits, whereas drain, drain leachate and control leachate exceeded from WHO permissible limits. Physico-chemical contaminations in drain leachate were significantly higher in groundwater samples as electrical conductivity (272 %), total dissolved solid (230 %), total hardness (420 %), alkalinity (166 %), biological oxygen demand (265 %) and chemical oxygen demand (651 %) and dissolved oxygen (87 %). Significantly different values of spread plate count, pour plate count, total coliform and fecal coliform in drain leachate of Khyberpass were recorded as 3.97 × 104, 1.87 × 104, 1.13 × 103 and 6.74 × 103 CFU/ml, respectively, in the groundwater samples. Lysimetric experiments have shown that while passing the water from soil profile, the maximum population of microbial flora as well as the chemical pollutants which would have been adsorbed to the soil (holding capacity) indicating the compact nature of soil structure, nevertheless some fraction of chemical and microbial pollutants leached down to the aquifer from a point source and diluted entire ecosystem. The unlined drains (non concrete) and unsanitary environmental conditions could be additional risk factors for groundwater contamination.