INNOVATIVE COAGULATION FLOCCULATION STRATEGIES USING CHITOSAN-BASED HYBRIDS FOR HEAVY METAL AND ORGANIC POLLUTANT REMOVAL

In Pakistan, freshwater resources are highly threatened by municipal and industrial effluents that are characterized by high contents of organic pollution and heavy metals, including lead (Pb) and cadmium (Cd). This experiment measured the performance of chitosan, polyacrylamide (PAM) and sodium alginate used as an individual and in combination of these at 25 and 50 mg L-1, in removing BOD, COD, turbidity, total dissolved solids (TSS), electrical conductivity (EC) and heavy metals present in the sewage wastewater in Quetta. The experiments with the jar were carried out under the controlled conditions (pH 5, 30 °C, rapid mixing at 250 rpm, slow mixing at 50 rpm and then 1 h settling). The individual polymer of chitosan was most efficient in removal and recorded the following removals 86% BOD, 78.9% COD, 66% Cd, 73.5% Pb and 44.75 TDS at 50 mg L-1. The removal was further increased by combined polymer treatments, whereby the PAM50 + Chit50 mixture gave a 98.13% BOD, 91.1% COD, 98.4% turbidity, and 91% heavy metal removal. This is explained by the fact that the complementary mechanisms are in the higher performance of combined treatments, chitosan neutralizes the charges, binds the metals and stabilizes the flocs, whereas PAM enhances the aggregation of particles by bridging. The removal of Pb was always greater than that of Cd because of the affinity of chitosan to Pb2+. The addition of extra polymer enhanced removal without floc destabilization, which showed the best treatment conditions. These findings indicate that biopolymer-based hybrid systems, especially chitosan-PAM and chitosan-alginate systems, represent long-term, cost-effective and biodegradable methods of municipal wastewater treatment and that it is a viable measure to improve the quality of water in the fast-developing cities.