Time Series Analysis of Coliform Bacterial Density in the River Ganges as a Potential Indicator of Water Contamination and Associated Risks to Human Health

Abstract

In the recent past, increased anthropogenic activities like urbanization and industrialization have caused rapid environmental changes including in river water ecosystems throughout the globe. A special group of microorganisms known as coliform bacteria is routinely used as a bio-indicator of water contamination and the associated risks involved to human health, especially of the rural and urban populace whose lives orient around aquatic ecosystems. In the present study, we carried out a comparative time series analysis of coliform bacterial density at ten stations along the Hooghly River/estuary. The water samples were collected in the month of May (i.e., the premonsoon season) during the period 2015–2020 for analysis of total dissolved solid (TDS) and total coliform (TC) and fecal coliform (FC) load in the selected stations. The spatial variation in the TC and FC matrices (in × 103 most probable number (MPN)/100 ml) exhibited the order Babughat (TC = 18.68; FC = 11.44) > Princep Ghat (TC = 17.22; FC = 10.32) > Ramkrishna Ghat (TC = 15.90; FC = 8.42) > Shibpur Ghat (TC = 14.82; FC = 7.54) > Botanical Garden (TC = 12.74; FC = 6.92) > Second Hooghly Bridge (TC = 10.26; FC = 6.38) > Namkhana (TC = 7.70; FC = 5.84) > Kakdwip (TC = 6.70; FC = 4.82) > Diamond Harbour (TC = 5.58; FC = 4.22) > Bakkhali (TC = 5.56; FC = 3.92). The TDS also exhibited a similar trend, which confirms the regulatory roles of waste materials and dissolved solids on the bacterial counts of the study sites. The increased TC and FC density in some of the stations under study could have direct implications for human health since a subset of these FCs could be pathogenic and might cause enteric diseases in humans.