| Summary: | The present study investigates the removal efficiency of chemical oxygen demand (COD) and total suspended solids (TSS) of anaerobically digested palm oil mill effluent in batch studies through the following 4 strategies: coagulation by chitosan, addition of ferrous sulphate (FeSO4), chitosan with hydrogen peroxide (H2O2) and chitosan with Fenton oxidation. The parameters tested were chitosan dosage (500–12,500 mg/L), FeSO4 dosage (500–12,500 mg/L), mixing time (15–60 min), sedimentation time (1–4 h) and initial pH (2–9) and H2O2 (500–7500 mg/L). Coagulation only by using chitosan (2500 mg/L) achieved the maximum COD and TSS removal of 70.22 ± 0.23 and 85.59 ± 0.13 %, respectively. An increase in the TSS removal (98.7 ± 0.06 %) but with a reduction in the COD removal (62.61 ± 2.41 %) was observed when FeSO4 (2500 mg/L) was added along with chitosan (2500 mg/L). Alternatively, an improvement in the COD (82.82 ± 1.71 %) and TSS (89.92 ± 0.48 %) removal efficiencies was observed when chitosan was coupled with H2O2 (500 mg/L). Finally, chitosan (2500 mg/L) integrated with Fenton oxidation (FeSO4 of 2500 mg/L and H2O2 of 500 mg/L) resulted in 100 % TSS and 73.08 ± 4.11 % COD removals. Overall chitosan with H2O2 proved to be the most promising alternative for POME treatment compared to chitosan with Fenton oxidation.
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