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The public concern over sediment contamination brought on by mining operations, excessive use of chemical fertilisers or pesticides, industrial, agricultural, and municipal effluent, is increasing. Dredging is a more expensive treatment option than in situ capping of polluted sediment for immobilising pollutants in sediments on site. In order to stop the release of Cr and Cu from chemically contaminated sediments, this study aimed to evaluate the efficiency of utilising active capping materials such as bentonite (B), kaolin (K), and a 1:1 combination of bentonite and kaolin (BK) as capping materials. In a 90-day laboratory experiment carried out in glass tanks with a 1 cm thickness cover of capped material plus sand spread over the polluted sediment, the efficacy of B, K, and BK in inhibiting trace metal leachability was examined. The findings demonstrated that B and BK decreased the ability of sediments to leach Cr and Cu. The results suggest that BK and B should be considered as a suitable active material for capping treatment of polluted sediment sites because of their high Cu and Cr trapping. According to an analysis of adsorption kinetics, chemisorption was the adsorption process. The outcomes of this study demonstrated the potential for using kaolin, a bentonite-kaolin clay mixture covered with sand, and bentonite as capping materials for the in-situ treatment of Cr and Cu polluted coastal sediments. [ABSTRACT FROM AUTHOR]

Cultivation of microalgae has been suggested as a green approach for a sustainable wastewater treatment especially heavy metal bioremediation. This study investigated the bio-removal of zinc (Zn), iron (Fe), cadmium (Cd) and manganese (Mn) from domestic wastewater (DW) and food processing wastewater (FW) using green microalgae, Botryococcus sp.. The total of five treatments represented by five different cell concentrations (1×103, 1×104, 1×105, 1×106 and 1×107 cells/mL) of Botryococcus sp. in the wastewaters medium. The results revealed high removal efficiency of Zn, Fe, Cd and Mn after 18 days of the culture compared to control (wastewaters without algae). In DW , Zn, Fe, Cd and Mn were successfully removed at the highest efficiencies up to 71.5%, 51.2%, 83.5% and 97.2%, respectively while in FW, the same metal concentrations were reduced by up to 64.4%, 53.3%, 52.9% and 26.7%, respectively. Overall, most of the algae cell concentrations tested were successfully reducing the metals contaminant presence in both wastewaters and provides a baseline for further phycoremediation coupled with biomass production.

The adsorption of lead ion from palm oil mill effluent produced directly from the mill was investigated using mixed adsorbents that were used to prepare the composite. Experiments were carried out under predetermined conditions of pH, shaking speed, contact time and particle size. Equilibrium study was carried out to determine the adsorption capacity of the mixed media. The reduction of the lead ion was effective on the adsorbent materials. The Temkin and Freundlich models were applied to describe the adsorption pattern on the mixed media. The experimental data fitted well to the Temkin isotherm with a correlation coefficient of 1, this was used to indicate the level of interaction of the adsorbent-adsorbate and also the energy utilized in the adsorption process. The hydrophobic behaviour of the activated coconutshell and cow bone carbons was observed for average contact angle of 105° and 95° for the coconut shell and cow bone respectively. The influence of the hydrophobic materials in the mixed media and the zeolite assisted in the ion exchange and in the adsorption of the heavy metal.

In this study, initially 11 different bacterial strains were tested for the degradation capabilities against Basic Orange 2 dye. In initial screening with 78.90% degradation activity, Escherichia coli emerged as the most promising strain to degrade the selected dye, and was then employed in subsequent experiments. For further enhancing the degradation capability of selected bacteria, the effects of various physicochemical parameters were also evaluated. Among the tested parameters, 20 ppm dye concentration, 1666 mg/L glucose concentration, a temperature of 40 °C, 666 mg/L sodium chloride concentration, pH 7, 1000 mg/L urea concentration, a 3-day incubation period and the use of sodium benzoate as a redox mediator (666 mg/L) were found to be ideal conditions to get the highest decolorization/degradation activities. Finally, all the mentioned parameters were combined in a single set of experiments, and the decolorization capacity of the bacteria was enhanced to 89.88%. The effect of pH, dye concentration, incubation time and temperature were found to be responsible for the optimum degradation of dye (p < 0.05), as predicted from the ANOVA (analysis of variance) of the response surface methodology. The metabolites were collected after completion of the process and characterized through Fourier transform irradiation (FTIR) and gas chromatography mass spectrometry (GC-MS). From the data obtained, a proposed mechanism was deduced where it was assumed that the azo bond of the dye was broken by the azoreductase enzyme of the bacteria, resulting in the formation of aniline and 3, 4-diaminobezeminium chloride. The aniline was then further converted to benzene by deamination by the action of the bacterial deaminase enzyme. The benzene ring, after subsequent methylation, was transformed into o-xylene, while 3, 4-diaminobezeminium chloride was converted to p-xylene by enzymatic action. These findings suggest that Escherichia coli is a capable strain to be used in the bioremediation of textile effluents containing azo dyes. However, the selected bacterial strain may need to be further investigated for other dyes as well. [ABSTRACT FROM AUTHOR]

The effectiveness of replacing cement with rice husk ash (RHA) on the leachability of copper from stabilized sediment was studied. RHA was added at 5, 10 15 and 20% and also cement was added at 10% throughout to the total dry weight of mixture, after which curing was undertaken at room atmosphere for 7, 14 and 28 days. The immobilization efficiency of amendments was evaluated using TCLP and SPLP. The high percentage efficiency of treatment was observed for the TCLP as 97.82 and 99.92% at 28 days for the SPLP. Characterization study was carried out using X‐ray diffraction (XRD) analysis to study the reaction products and crystalline phases of the treated sediment after 28 days to observe the possible mechanisms responsible for the immobilization of the investigated heavy metal. Results have indicated that partial replacement of cement with RHA in binder system has increased the strength and reduced leachability of copper of the treated sediment compared to untreated sediment. [ABSTRACT FROM AUTHOR]