Study of TSS Reduction in Digested POME Using Coagulation-Flocculation and Sand Filtration for Bioscrubber Pretreatment

The bioscrubber circulation water at the Biogas Power Plant is sourced from overflow digested Palm Oil Mill Effluent (POME) containing very high Total Suspended Solids (TSS), exceeding 500 mg/L. High TSS causes fouling of sprayer nozzles, clogging of packing media, and reduces Thiobacillus bacterial activity in biological H 2 S oxidation. This study aims to evaluate the effectiveness of coagulation-flocculation using Aluminum Sulfate (Alum) and Polyaluminium Chloride (PAC), as well as sand filtration, in reducing TSS levels. Coagulation-flocculation tests were carried out as jar tests with dose variations of 0, 50, 100, 150, and 200 ppm for each coagulant, followed by 30-minute sedimentation. Filtration tests used 300 grams of silica sand (0.5-1.0 mm diameter) in a gravity-driven column (height 30 cm, diameter 5 cm) with three replicates. Furthermore, a novel mixing strategy was developed by combining digested POME with clarified POME from the final sedimentation pond (low TSS) at a 1: 3 ratio. Results show that PAC at optimal dose 150 ppm achieves TSS removal efficiency of 89.36% with final TSS of 150 ppm, outperforming Alum which achieved 82.47% at the same dose. Sand filtration consistently reduced TSS by an average of 80.20% while maintaining TDS at an average reduction of 26.18%, preserving dissolved organics as bacterial nutrients. The 1: 3 mixing strategy successfully reduced TSS to below 50 mg/L, eliminating nozzle and sprinkler clogging, preventing packing media fouling, and achieving H 2 S removal efficiency down to 10 ppm in the bioscrubber outlet. The combination of PAC 150 ppm and sand filtration, along with the 1: 3 mixing strategy, is recommended as a stage.