Harun Ar Rashid, Mozibur Rahman, Mijanur Rahman, MD Abu Talha

The study deals with assessing water quality parameters including pH, total dissolved solids (TDS), dissolved oxygen (DO), biological oxygen demand (BOD), chemical oxygen demand (COD), temperature, transparency, and turbidity of the Turag River in Gazipur, Bangladesh based on the standards of the Department of Environment (DoE) in Bangladesh and the Environmental Quantity Standard (EQS). The chemical parameters of water were investigated for eight stations (S1 to S8) in the Turag River through laboratory experiments considering three different sources, i.e., discharge point (DP), contamination point (CP), and midpoint (MP). The average pH values ranged between 7.12 and 8.34, indicating that all values were within the standard limits (pH=6.5 to 8.5). The average values of TDS were 488 to 905 ppm, which discloses a low TDS condition. The average values of DO were 4.05 to 5.71 mg/l, indicating a low DO value from the standard level (4.0 to 6.0 ppm for domestic and 5.0 ppm for fish culture). The values of BOD were between 16.24 and 26.54 mg/l, indicating a higher condition than the expected value of BOD (6.0 ppm for fish culture and 10.0 ppm for irrigation). The average values of COD were between 30 and 51 mg/l which is higher than the permissible limit. The temperatures of water varied from 27 to 32.53ºC, indicating standard temperatures (20 to 30ºC) for aquatic creatures. The average transparency values maintained the standard limits (≤15.75 inches) for aquatic organisms. Finally, the turbidity values indicate a higher condition than the standard limit (10 NTU, Nephelometric turbidity units). According to the investigation, the water quality of the Turag River mostly exceeds acceptable limits. Therefore, urging advising the government to do constant monitoring to reduce the level of pollution of the Turag River.