Study on Water Quality of Bhairab River in Khulna Region

Abstract

Water is an important element for all living beings on this planet. All life forms of the earth depend upon water. No life can exist without water since water is as essential for life as air is. Generally water contains many physical, chemical and biological impurities. Surface water sources may be mainly in the form of rivers, lakes, pond, glaciers and rainwater. Modem urbanization, increasing population, household wastes and industrialization day by day are deteriorating these sources. Bhairab River is not further than the ill concern. It receives huge quantities of pollutants and thus degrading its water quality gradually. This paper deals with assessment of water quality of Bhairab River and also its trends. To fulfill the present aim of the study, a total length of 36.98 Km along the river from Rupsha ghat to Noapara Bazar ghat was divided into ten sampling stations. Water samples were collected every month from each of the sampling stations through the year 2014 for laboratory testing. Twenty water quality parameters such as temperature, pH, turbidity, conductivity, color, alkalinity, hardness, TS, TDS, SS, phosphate, nitrite, nitrate, chloride, DO. BOD, COD, manganese, fecal coliform and total coliform were examined by standard method. Among those twelve were found out of Bangladesh drinking standard. Water quality assessment was performed by determining water quality index (WQI) following National Sanitary Foundation (NSF) method. The study analyzed trend of water quality index. Present research is conducted based on field and secondary data. In the correlation study it is found that major parameters are more or less correlated with each other. Three important parameters like chloride, TDS and conductivity each are significantly correlated with each other. It helps water quality management and monitoring. Average water quality index obtained for the year 2014 in both temporal (twelve months) and spatial (ten stations) are 64 and 65. respectively which is close to each other. As per NSF water quality index range Bhairab River is medium in quality, and this water is not suitable for drinking without treatment. The study also reveals that water quality index is progressively decreasing with course of time. In 2005 water quality index was observed 71 while in 2014 it reduced to 64. During last ten years WQI is decreased by 7 points, so yearly average decreasing presumed 0.70 point per year. Following this rate projected water quality index of studied river assumed to be 51.39 and 35.65 for the year 2030 and 3050 respectively. After that water quality turns medium to bad. This is an alarming for the local environment. Bottom line is that water quality of Khulna region expressly Bhairab River is being deteriorated day by day.