The hydrochemistry and pollution status of tannery effluent as well as the Buriganga River were studied. The water quality parameters namely temperature, pH, salinity, TDS, EC, DO, COD, Cr, Cd, Ni, Cu and Zn of tannery effluent were 22.8-31.5 o C, 7.4-10.6, 3920-6280 mg/l, 4680-7220 mg/l, 7070-10810 µs, 0.3-1.1 mg/l, 1020-3800 mg/l, 7.7656 mg/l, 0.0198 mg/l, 0.2070 mg/l, 0.0304 mg/l and 0.3021 mg/l, respectively whereas in water of the Buriganga River were 22.0-31.6 o C, 6.2-7.8, 69-642 mg/l, 97-871 mg/l, 146-1309 µs, 1.1-4.1 mg/l, 140-800 mg/l, 0.0306-0.2163 mg/l, 0.0018-0.0162 mg/l, 0.0663-0.2486 mg/l, 0.0112-0.0238 mg/l and 0.0878-0.2948 mg/l, respectively. According to the statistical analysis Salinity, EC, TDS, COD, Cr, Cd, Cu and Zn show positive correlations with each other and negative correlations with Temp. and DO. Ecological risk factor shows that Cr is the highest risk metal for ecosystem. The hydrochemistry has been revealed that the water is not safe for aquatic lives.

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Assessment on the level of pollution of Turag river water was performed by measuring various physico-chemical parameters.

Nanosized titanium dioxide (TiO2) nanoparticles were used for the photocatalytic reduction of hexavalent chromium in the presence of formic acid. The photoreduction of Cr(VI) in the absence of formic acid was quite slow. When formic acid was added in the chromium solution as the hole scavenger, a rapid photocatalytic reduction of Cr(VI) was observed, owing to the consumption of hole and the acceleration of the oxidation reaction. Furthermore, three commercial TiO2 nanoparticles (AEROXIDE® P25; Ishihara Sangyo ST-01; FUJIFILM Wako Pure Chemical Corp.) were evaluated for the photoactivity of reduction of Cr(VI).

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Environmental analysis does not become properly meaningful unless follow the standard procedure in sampling, preserving and also in analysis. This study investigates different studies on surface and groundwater pollution and discusses their findings along with impacts on environment, human health and aquatic ecosystem demolition. Fresh water is a vital need for drinking, household, agricultural and industrial use. Fresh water availability is shrinking worldwide due to imprudent use. Abound availability of fresh water in Bangladesh is now polluting due to unwise dumping of industrial, household, agricultural and municipal wastes. Water body in urban arena is severely polluted rather than rural part. The over concentration of DO, BOD, COD, EC, TDS, Cr, Cd, Pb was observed in Dhaka region. The highest arsenic concentration was found in the ground water of Lakshimpur. The main sources of pollution in industrial cities are anthropogenic sources like untreated industrial effluent and municipal wastes whereas in rural part the main sources of pollution are agricultural and naturogenic. Transboundary impact also intensifies some river water pollution. Government approved the policies, ordinance, acts and laws however, due to lack of proper implementation and monitoring water pollution problem increasing day by day.

The pollution due to minerals and anions in surface water and their settlement tendency on sediment of the Turag river has been studied. Higher concentration of potassium and phosphate ion in surface water and similar deposition on sediment has been recorded. The observed average concentration of Na, K, Cl-, PO4 3- in surface water and in surface sediment was 22.10, 13.20, 108.50, 17.80 mg/L and 1359.07, 2526.10, 37.50, 31.76 mg/kg, respectively. This high concentration of minerals and anions in surface water and sediments indicates that hidro-environment of the Turag river is badly affected.The minerals and ions are strongly correlated (r = 0.99) which implies that they come from similar sources and forcefully added to the river in a regular basis. Principal component analysis reveals that only one principal component is covering more than 99 % of cumulative variance. There are very few variations of parameters in the principal component to indicate that all parameters exert similar effect on hydro-environment and are contributing to deteriorate the ecological balance.These are supported by dendrogram analysis.Bangladesh J. Sci. Ind. Res.53(3), 161-168, 2018

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