a b s t r a c tThe performance of a modified anaerobic baffled reactor (MABR) treating synthetic wastewater at different organic loading rates (OLRs) was investigated. The MABR was seeded with anaerobic sludge taken from a local municipal wastewater treatment plant and fed continuously with glucose at OLRs of 0.258, 0.787 and 2.471 kgCOD/m 3 ·d at hydraulic retention time (HRT) of 4 d. Results showed that 99.7% chemical oxygen demand (COD) removal was achieved during the OLR of 0.258 kg COD/m 3 ·d. However, when the OLR was increased to 0.787 kgCOD/m 3 ·d, a minor decrease in the COD removal efficiency (95%) was noted. Further increase of the OLR to 2.471 kgCOD/m 3 ·d 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 the similar decreasing trend (0.542, 0.524 and 0.214 L/g COD removed 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 kgCOD/m 3 ·d). However, during the final OLR (2.471 kg COD/m 3 ·d) the pH profile in MABR significantly dropped as low as 4.01. A similar trend was also observed in the volatile fatty acids (VFAs) profile where higher value (2880 mg/l) was found at the 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.
A B S T R A C TThe biological conversion of biomass into methane during anaerobic digestion has been studied by many researchers in recent years. In this study, optimization of methane composition during chemical oxygen demand removal was observed in a multi-stage Anaerobic Bioreactor. Synthetic glucose was used as a feed substrate, and the reactor was operated at a hydraulic retention time (HRT) of 1-4 d. Complementary experimental and theoretical test procedures were evaluated for methane optimization. The theoretical methane was recorded as 50.13, 50.02, 50.16, and 50.22% for an HRT of 4, 3, 2, and 1 d, respectively. However, the quantity of methane determined experimentally was significantly lower than the theoretical predictions; this was likely due to the microorganism activity in the reactor that may have interfered with the efficiency of the biogas generation. Experimental data showed a decrease in the methane composition (35.4, 21.2, 19.8, and 18.4% for HRT of 4, 3, 2, and 1 d, respectively) in the reactor system. Thus, the theoretical formula and experimental data together provide an alternative method for the evaluation of bioenergy potential in anaerobic digestion.
A B S T R A C TEffluent circulation may affect the phase separation ability of a compartmentalized anaerobic reactor such as anaerobic baffled reactor. In this study, it is proven that this is not always the case. Moreover, the effect of circulation to this type of reactor under different hydraulic retention time (HRT) is still unclear. The present study investigates the start-up performance of a novel modified anaerobic baffled reactor (MABR) at various effluent circulation ratios (R). Results showed that tremendous increase of the treatment efficiency and stable performance was achieved by the MABR system when effluent circulation was employed (e.g. 95.7% COD removal during R of 2 at HRT of 2 d and an OLR of 0.75 kg COD m −3 d −1 ). The pH profiles, volatile acids (HOAc) occurrence and biogas production (L biogas g COD À1 destroyed ) during the start-up period showed favourable conditions in the reactor. In addition, the effect of HRT variations (4, 3, 2 and 1 d) to the MABR with circulation operation R of 2 (optimum circulation) showed the HRT of 2 and 3 caused the MABR to start-up rapidly and efficiently with a chemical oxygen demand removal efficiency of more than 90%. It was concluded that rapid start-up can be achieved by applying effluent circulation to the MABR.
The growth in urbanization, industrialization and irrigated agriculture are imposing growing demands and pressure on water resources. As a case in point, Lunchoo River, Malaysia was considered on of the contributing factor to water quality deterioration with regional consequences on the aquatic ecosystem. Moreover, it also deemed to affect the health of the downstream sub-basin user group. Influenced by tidal, restricted exchange between estuaries and the open sea allows rapid change in salinity, temperature, nutrients and sediment load. Therefore, a balance is vital between development and a good quality of life. In the present study, limitation on point source pollutant and low flow conditions are investigated. An understanding of the existing river and waste stream characteristic is necessary to determine the background level of pollutant. In addition, output generated from this study is an important key towards an optimal management of water resources. Results showed that in making prediction of water quality for Lunchoo River, it is essential to characterize the volume and properties of the river and wastewater stream. Moreover, both hydraulic and constituent flow rate fluctuated greatly in most part of the experimental field.
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