Chitosan as biocoagulant for coal mining wastewater treatment

Chin, Chee Leong (2024) Chitosan as biocoagulant for coal mining wastewater treatment. Final Year Project, UTAR.

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Abstract

Coal mining produces massive amounts of mine water. Coagulation and flocculation are the most commonly used methods to treat coal mining wastewater. A conventional wastewater treatment plant in the mining industry normally uses chemicals such as alum as the coagulants to treat the wastewater. However, these coagulants produce a large volume of sludge which is non-biodegradable and consists of alum residue which is hazardous. Hence, this study proposes the use of chitosan, a biopolymer material that is a more environmentally friendly coagulant to treat coal mining wastewater. The chitosan properties, such as its degree of deacetylation, various molecular weights, and different functional groups were varied to investigate the effect of their properties on the coagulation performance. Jar tests were conducted to study the effect of operating parameters such as chitosan dosage and wastewater pH on the treated wastewater quality. The wastewater was mixed at a higher speed of 100 rpm for 3 minutes, followed by slow stirring at 20 rpm for 20 minutes, and finally left for settling for 30 minutes. The chitosan with the lowest molecular weight and degree of deacetylation of equal or more than 85 % (MW50000 Chitosan) was determined as the best chitosan, providing the highest removal of COD, turbidity, suspended solids, and apparent colour of 97.67 %, 99.98 %, 99.99 %, and 99.99 %, respectively at a low dosage of 30 mg/L at pH 6. Supernatant from alum-treated water shows 100.4 mg/L of alum, while no alum was detected in chitosan-treated water. Hence, it shows that wastewater treated using chitosan is relatively non-hazardous. Considering the superior performance of alum and the low alum residual of wastewater treatment using chitosan, it is deduced that chitosan shows potential to replace the conventional coagulant as an alternative biocoagulant in treating mining water.

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