A Comprehensive Assessment of Water Quality and Mass Balance of the Bhairab River, Khulna
Authors: Hashan Md. Mahadi 
Published: January 2024

Abstract: Water is a vital component for all organisms on Earth. Water is essential for the survival of all living organisms on Earth. Water is vital for life, much like oxygen, since no kind of life can survive without it. Water often includes several physical, chemical, and biological contaminants. Surface water sources mostly consist of rivers, lakes, ponds, glaciers, and precipitation. The sources are becoming degraded due to contemporary urbanization, escalating population, domestic trash, and industry. The Bhairab River is not far from the sick worry. The water quality of the area is rapidly deteriorating due to the significant influx of contaminants it gets. This research focuses on evaluating the water quality and mass balance of the Bhairab River. In order to achieve the current objective of the research, a stretch of 22.9 kilometers from Jailkhana Ferighat to Shuvorada Kheya Ghat, Fultola, was split into 10 sample sites. The water samples were collected monthly from each monitoring site during the year of 2021 for laboratory analysis. A total of nine water quality indicators, including Fecal Coliform, Temperature, Biochemical Oxygen Demand (BOD), pH, Turbidity, Total Solids (TS), Phosphate, Dissolved Oxygen (DO), Nitrate, and Chloride, were analyzed using standardized methods. The water quality evaluation was conducted by calculating the WQI using the National Sanitary Foundation (NSF) technique. The mass balance has been determined by means of analysis. The current study is being undertaken using both primary and secondary data sources. The investigation reveals that the primary parameters exhibit varying degrees of correlation with each other. In December, the temperature reached a minimum of 16.8 °C, while in May, it peaked at 37.5°C. The pH reached its peak at 8.80 in August, while it had its lowest point at 7.94 in January. The pH variation is minimal and similar throughout the board. The measured turbidity level was 564 NTU, which is the average value. The maximum total solids (TS) concentration recorded was 3346 mg/L, while the minimum concentration was 2460 mg/L. The phosphate content reached its peak at 8.12 mg/L in S5, while it was at its lowest at 4.26 mg/L in S4. The maximum nitrate concentration measured was 26.4 mg/L, while the minimum concentration was 12.80 mg/L. The maximum biochemical oxygen demand (BOD) recorded was 1.80 mg/L at location S6, whereas the minimum BOD was 0.60 mg/L at location S3. The concentration of BOD was consistently low during each month. The highest fecal coliform (FC) concentration observed in November was 1024 N/100ml, while the lowest concentration was 572 N/100ml. The drinking water quality standard for fecal coliform (FC) in Bangladesh is zero per 100 milliliters. The greatest, average, and lowest values surpass the allowable limit set by BDS. The water quality index determined for the year 2021 for Ten Stations has an average value of 43, indicating a similar level of water quality throughout the stations. According to the range of NSF water quality index, the Bhairab River has a poor quality rating. Therefore, this water is not safe for drinking without undergoing treatment. The Bhairab River has a Mass Balance value of 362349.09 gallons per day