Impact of Industrial Effluents on The Water Quality and Aquatic Biota in Rajshahi

Abstract

The physico-chemical conditions of industrial effluents and their effocts on the water quality, aquatic biota and macrovegetation at three different sampling spots in Rajshahi have been studied during the month of Novcmber'96 to Octobcr'97. Sampling spot one was a canal receiving effluent fro111 the Rajshahi Sugar Mills at Harian. sampling spot two was two K.M away from spot one in the same canal receiving effluent from Rajshahi power house at Katakhali, where the two effluents mix and sampling spot three was in the river Padma two kilometer from spot two where the mixed effluent is discharged. Sampling was performed weekly. Multiple regression analysis have been made to establish the interrelationships between the physico-chemical and biological conditions. Spot-I In the effluent mixed black water at this spot, the monthly mean ranges of various physicochemical variables and plankton were: air temperature 19.75 to 33°C; water temperature 25 to 37.3°C: transparency 6.5 to 20 cm.: TSS 120 to 430 mg/I: TDS 640 to 6 I 60 mg/I : pH 6.1 to 7.2: DO anoxia to I. 15 mg/I: Eh 0.092 to 0.228 111 Volt: rH2 8. IO to I 0.21: BOD 5.2 to 16.36 mg/I: COD 892 to 24 71 mg/I: electric conductivity 261.89 to 1558. 17 μ ohms/c111.: chloride 26.98 to 142.06 mg/I: co~ 9 to 109 mg/I: CO., alkalinity Zero: HCO3 alkalinity 76 to 556 mg/I: total hardness 230 to 604 mg/I: calcium hardness 72 to 478 mg/I: magnesium hardness 1.55 to 65.39 mg/I: NI-Li 0.212 to 0.74 mg/I: NH., 0.20 to 0.70 mg/I: NH4.N 0.165 to 0.58 mg/I: PO4 0.008 to 0.0 14 mg/I; silicate zero: total sulphide 0.92 to 5.03 M mol 1'1 : oil-grease 1.04 to 7.13 mg/I: phytoplankton abundance 27354 to 64982 units/I and zooplankton abundance 29169 to 75935 units/I. The phytoplankton were represented by 29 genera of which IO genera belonged to Chlorphyccac, 6 genera to Cyanophyceac, 5 genera to Euglcnophyceae. 4 genera to Xanthophyceae and 4 genera to Bacillariophyceac. The 30 genera of zooplankton recorded. were represented by Protozoa ( 19 genera), Porifera ( I genera), Rotifcra (6 genera), Nematoda and Crustacea both with 2 genera. A total of 11 genera of macrophytcs were recorded from this spot. The dominant genera was Eichhornia sp.----