Effect of organic loading rate (OLR) on modified anaerobic baffled reactor (MABR) performance

The performance of a Modified Anaerobic Baffled Reactor (MABR) treating synthetic wastewater at different Organic Loading Rate (OLR) was investigated. The MABR was seeded with anaerobic sludge taken from a local municipal wastewater treatment plant and fed continuously with glucose at an OLR of 0.258, 0.787 and 2.471 kg COD m-3 d-1 at a Hydraulic Retention Time (HRT) of 4 days. Results showed that 99.7% Chemical Oxygen Demand (COD) removal was achieved during the OLR of 0.258 kg COD m-3 d-1. However, when the OLR was increased to 0.787 kg COD m-3 d- 1, a minor decrease in the COD removal efficiency (95%) was noted. Further increase of the OLR to 2.471 kg COD m-3 d-1 caused the reactor performance to deteriorate dramatically in a COD removal efficiency of 39.5%. Biogas yield was evaluated for the reactor system and followed similar decreasing trend (0.542, 0.524 and 0.214 l g-1CODdestroyed for the different OLRs respectively). There were no significant different in the pH profiles (6.71 – 7.01) during the first two OLRs (0.258 and 0.787 kg COD m-3 d-1). However, during the final OLR (2.471 kg COD m-3 d-1) the pH profile in MABR dropped to significantly as low as 4.01. Similar trend was also observed in the volatile acids (VA) profile where higher values (2880 mg/L) were found at highest OLR. The poor performance of the MABR at high OLR signifies that the microorganisms could not metabolise the organic substance and probably need more time for digestion