Physio-chemical, Bacteriological and Adenoviral Parameters of Sewage in Punjab, India

Abstract

The primary point source of surface water pollution, particularly in developing countries, is sewage. To describe the causes of microbial contamination, researchers have developed several microbial source tracking (MST) tools. Adenovirus is one of these tools that is producing encouraging results. Therefore, the purpose of this study is to examine adenoviral load and its comparison to bacterial load at various stages of sewage treatment plants (STP). For this study, two STPs in Punjab, India, one in Balloke Ludhiana and one in Pholriwal Jallandhar, were chosen. The sewage samples were analyzed at different sewage treatment steps. Untreated sewage samples were collected after the primary treatment (physical separation methods), the second sample after secondary and tertiary treatment (polishing pond) and the last sample after final clarification (chlorination/disinfection). Using the quantitative RT-PCR, the maximum concentrations of human adenovirus (HAdV) were 2.8×10⁶ copy no. L^-1 and 1.63×10⁶ copy no. L^-1  in Pholriwal STP, Jallandhar and Balloke STP, Ludhiana respectively. All samples tested positive for HAdV, except one at the Balloke STP outflow, which had an overall positive detection rate of 87.5% after final clarification/chlorination. The samples after secondary/tertiary treatment and the samples after final clarification did not differ significantly from one another, but they did differ significantly from the samples of untreated sewage. Adenovirus load was reduced by 2.7±0.65 log₁₀, overall, throughout the STP, the coliform count was reduced by 4.12±0.66 log₁₀, and enterococci were reduced by 3.75±0.37 log₁₀. Thus, the STPs demonstrated their ability to reduce microbial load, but a decrease in viral load was significantly less by 2 log₁₀ than a decrease in bacterial load.