Dr. Md. Abdul Karim

Abstract: A wide variety of organic or inorganic compounds can cause the pollution of aquatic bodies and microorganisms often play a major role in determining the extent of this pollution. The river Buriganga is found to be Dhaka’s main outlet of sewage waste. The residential and commercial establishments along the river cause discharge of wastewater either directly into the river or into drains and canals which subsequently find their way into the river. So, investigation of water quality of river to mitigate the problems is an utmost need. The present project has been undertaken for determination of seasonal changes in the water quality parameters and application of bioremediation for improvement the quality of water through enhancing the decomposition rate of pollutants using indigenous bacteria.<br/><br/>To get a fair idea about the microbial load as well as physicochemical properties of the river water samples were collected from 2 selected sites at 5 different seasons (summer, rainy, autumn, late autumn and winter). Temperature and pH of water varied 22 to 32ºC and 6.61 to 7.14, respectively, while air temperature varied between 16 and 33.5ºC. Aerobic heterotrophic plate count (HPC) showed a range of 1.0 × 105 to 20 × 105 cfu/ml in water, while, enteric and related bacterial count in 3 different media (SS agar, MacConkey agar and Cetrimide agar) showed 12 × 102 cfu/ml to uncountable, 3 × 102 to 19 × 102 cfu/ml, and 0-14 cfu/ml in water, respectively. Chemical content like NH4+-N, NO3--N, NO2--N, and PO4- values were showed the water is polluted. Furthermore, the load of aerobic HPC and the presence and abundance of Escherichia, Proteus morganii, Plesiomonas sp., Hafnia sp. and Alcaligenes sp. in the water clearly showed significant level of microbial pollution in the river.<br/><br/>To enhance heterotrophic activities after decomposing organic matter in the polluted river water, three promising bacterial strains isolated from the study site were introduced into the experimental system. Addition of strains Chryseobacterium arthroshpaerae strain: FDAARGOS 519, Bacillus subtilis strain: E20, and Bacillus subtilis subsp. subtilis strain: 168 stimulated net regeneration of dissolved inorganic nitrogen (DIN) and dissolved inorganic phosphorus (DIP) in the sample water collected in June 2019 by approximately 50%. Same exponential trends were also seen with the samples collected in October 2019. These results suggest that the application of such effective bacteria as described here would be promising for the stimulation of heterotrophic activities in the field of polluted environments.