Treatment of effluent from the upflow anaerobic sludge blanket-hollow centered packed bed fermentor by utilizing Chlorella vulgaris in a fed-batch system

• Published in: Case studies in chemical and environmental engineering 2024-06, Vol.9, p.100756, Article 100756
• Main Authors: Sidabutar, Rivaldi, Trisakti, Bambang, Irvan, Bani, Okta, Nasution, Juan Akmal, Khodijah, Putri, Alexander, Vikram, Daimon, Hiroyuki, Takriff, Mohd Sobri
• Format: Article
• Language: English
• Subjects: Chlorella vulgaris; Cultivation; Effluent UASB-HCPB; Fed-batch
• ISSN: 2666-0164; 2666-0164
• DOI: 10.1016/j.cscee.2024.100756

Palm oil mill effluent (POME) has high levels of contaminants, one of which is Chemical Oxygen Demand (COD) of around 40,000–60,000 mg.L−1. The very high COD levels in POME are harmful in terms of toxicology and aesthetics to the environment. POME treatment by anaerobic digestion can be carried out through the Upflow Anaerobic Sludge Blanket-Hollow Centered Packed Bed (UASB-HCPB) fermentor to produce biogas, while the liquid phase will end up as effluent. However, these effluent not met the quality threshold so further treatment is required. Aerobic process can be address this issue by utilizing microalgae. Chlorella vulgaris is a microalgae that is widely used in wastewater treatment because of its resistance to pollutants and degradation effectiveness. The purpose of this research is to treat the effluent from the UASB-HCPB fermentor by utilizing Chlorella vulgaris in a fed-batch system. The novelty of this research is the utilization of microalgae of Chlorella vulgaris in photobioreactor for treating the effluent from the UASB-HCPB fermentor so that it meets the predetermined quality standards and safe to be discharged into the environment. In this study, the culturing process of Chlorella vulgaris was carried out in photobioreactor with variations of lighting intensity (12:12) and (24:0), with and without aeration. The cultivation process was carried out in the same of the photobioreactor with variation of fed-batch system with effluent addtion of 450 mL.day−1, 900 mL.2 day−1, and 1350 mL.3 day−1 with variation of agitation rate of 10 rpm, 20 rpm, 30 rpm, 50 rpm, and 100 rpm. Based on the experimental results in culturing process, it was found that the aeration and lighting process (24:0) increased the growth of Chlorella vulgaris best with an absorbance of 0.759 with the relationship between optical density and biomass dry weight with a value of (g.mL−1) = 0.008 OD + 0.0017 with R2 = 0.981. The best substrate addition in cultivation process was obtained with the addition of 900 mL.2 day−1 with absorbance 0.758 and specific growth 0.164 day−1. The best COD decomposition efficiency 87.5 % was obtained with the addition of 900 mL.2 day−1. The best agitation of 30 rpm was obtained with absorbance of 0.850 and COD decomposition efficiency of 93.75 % for 12 days cultivation. Total cost estimate offered of 11.1 IDR/L was obtained. This indicates that these conditions are effective for POME effluent treatment applications involving Chlorella vulgaris. The uti