Effect of inoculum source and effluent recycle on the start-up performance of a modified anaerobic inclining-baffled reactor treating recycled paper mill effluent

In this study, three start-up techniques of modified anaerobic inclining-baffled reactor (MAI-BR) were performance to understand the effect of inoculum source and effluent recycle on the treatment of recycled paper mill effluent (RPME). Flocculant anaerobic sludge from a palm oil mill pond and digested anaerobic sludge from a sewage treatment plant were inoculated in the first and second start-up/phase1, respectively. Results show that high chemical oxygen demand (COD) removals of 93 and 88% were achieved in the first and second start-up/phase1, respectively. The amount of methane produced in the second start-up/phase1 within 15 d was doubled as compared to the amount produced in the first start-up, with a higher methane content of 79% (as compared to 62% in the first start-up). This result indicated that the inoculum source has a significant effect on the reactor performance. The results in the second start-up/phase2 also showed that COD removal and methane production increased up to 94% and 0.52 L CH4/d, respectively. This finding can conclude that the use of effluent recycle has a favorable effect on the performance of MAI-BR. During the first start-up, second start-up/phase1, and second start-up/phase2, the volatile fatty acid/alkalinity compartmental ratios were varied at 0.01–0.06, 0.03–0.43, and 0.02–0.14, respectively, and the overall effluent pH levels were higher than 6.5. The findings indicate the stability of the MAI-BR system in treating RPME.