Abstract:
This study focused on the identification of some water quality parameters of Buriganga river adjacent to Dhaka City. In this study, a portion of Buriganga river from Showary ghat to Pagla has been selected as the study reach to assess the existing water quality during the wet season of the year 2022 and dry season of the year 2023. Water samples were collected from twelve monitoring locations along this reach during that period. Different water quality parameters have been assessed in this study including pH, DO, EC, Color, COD, BOD5, NH3-N, H2S and Cl-. Heavy metals (Chromium, Lead) have been measured during the month of March, 2023. In-situ test was performed for some parameters like pH, DO and EC. Spatial and temporal variation of Buriganga river water quality have been assessed in this study through graphical analysis and comparing with previous studies.
DO concentration was higher in the rainy season than in dry season. Maximum dissolve oxygen in rainy season was found 4.24 mg/L at Posta in October 2022. Minimum DO was found in Showary ghat in March 2023. EC was observed 169 to 185 μS /cm in wet season and 542 to 852 μS /cm in dry season. BOD5 in the rainy season is lower than dry season. Maximum BOD5 was found 128 mg/l in March 2023 at Pagla and minimum BOD5 was found 1.0 mg/l in October 2022 at Showary ghat. COD value was found 8.0 to 42.0 mg/L in the rainy season; whereas in dry season it was much higher from 51.0 to 316.0 mg/L. Average BOD5 to COD ratio was found less than 0.30, which indicates that the amount of non-biodegradable organic matter is higher than biodegradable organic matter in Buriganga river. Chloride concentration was found lower (9.0 to 17.0 mg/L) in wet season and during dry season the value rises 30.0 to 67.0 mg/L. Other parameters like NH3-N, H2S are higher in dry season than rainy season. Pollution load in Buriganga river increases during dry season and washed out during monsoon. Pollution trend from previous data indicates that pollution load has increased during the last 50 years. Minimum DO concentration decreased almost six times during 1968 to 2023 in Buriganga river, Maximum Chloride concentration has increased around 12 times during that period and change of maximum BOD5 concentration was Observed almost 14 times during last 23 years(2000-2023).
