Assessment of water quality of Adi Ganga at Bansdroni and Kalighat points using WAWQI and CCMEWQI methods

Abstract

In this study, the water quality of Adi Ganga (Tolly Nullah) was assessed for two sampling points at Kalighat and Bansdroni located in South Kolkata, West Bengal, India.The West Bengal Pollution Control Board (WBPCB) collected raw water samples from the above stations and in the months of June, July, September, October in 2014 and February, May, August, November every year from the year 2015 to 2020 and subsequently tested different water quality monitoring parameters. These results have been studied in the present study to determine the Water Quality Index (WQI). The WQI is a standard tool that is internationally accepted for assessing water quality. It includes the concentration of several constituents present in it. WQI reduces a large number of water quality indicators into helpful for the selection of appropriate treatment techniques to meet the concerned issues. The objective of this study is to evaluate the water quality of raw water of Kalighat and Bansdroni in terms of WQI under the influence of several physical, chemical and biological parameters by using the Weighted Arithmetic Water Quality Index (WA WQI) and the Canadian Council of Ministers of Environment Water Quality Index (CCME WQI) methods. No radioactive substances were considered. This study also partly reflects the water quality of the Hooghly river at the sampling points as tidal ingression occurs here. The evaluation is done as per data available for seven physico-chemical and biological parameters i.e. pH, biochemical oxygen demand (BOD), Dissolved Oxygen (DO), total coliform, Chemical Oxygen Demand (COD), Total Suspended Solids (TSS), fecal coliform for consecutive seven years from 2014 to 2020. The results were compared with the standards set by the Bureau of Indian Standards (BIS).A total of 441test reports of water were collected andevaluated by comparing their values with the BIS. The obtained CCME WQI values for Bansdroni (out of 31 values, 24 are poor, 6 are marginal and only one is fair) and for Kalighat (out of 32 values, 25 are poor and 7 are marginal) indicate the “poor” and not suitable for drinking without treatment. WA WQI values for both the above stations (all values of WA WQI >100) also indicate the raw water quality is “unfit for consumption” by humans without proper treatment. CCME WQI values of Bansdroni and Kalighat are observed the highest in August 2019 and the lowest in August 2015 for Bansdroni and November 2014 for Kalighat, respectively. It specifies that BOD was one of the main parameters affecting water quality for this study during this period.