Performance of an up-flow anaerobic sludge bed (UASB) reactor treating landfill leachate containing heavy metals and formaldehyde

Municipal Solid Waste (MSW) landfill leachate is a serious environmental issue and treated using various methods, mostly involving biological treatment. In the present study, an up-flow anaerobic sludge bed (UASB) was used for the treatment of matured landfill leachate that contains heavy metals (As, Fe, Ni, and Cd) and Formaldehyde (FA). Accordingly, the OLR to the UASB reactor was gradually increased from 0.125 to 2.5 kg CODm-3d-1, to observe the process performance. The process performance of the reactor was characterized in terms of pH, Chemical Oxygen Demand (COD) removal, Total Volatile Acid (TVA) production, Mixed Liquor Suspended Solids (MLSS), Mixed Liquor Volatile Suspended Solids (MLVSS) washout, and Methane composition. Results showed that at a Hydraulic Retention Time (HRT) of 4 days and an OLR of 0.125 kg CODm-3d-1, up to 79.04% COD removal efficiency was observed. However, when the OLR was increased gradually from 0.375 to 2.5 kg CODm-3d-1, the COD removal efficiency decreased to 9.5%, suggesting that the high accumulation of heavy metals may have inhibited the methanogens. During this period, the heavy metal and formaldehyde concentration were 9.40, 0.43, 0.50, 12.80 and 8.60 mgL-1 respectively

Methane optimization in multi-stage anaerobic reactor (Ms-Ar)

The biological conversion of biomass in Anaerobic Digestion (AD) into methane was studied by many researchers in recent years. In the present study, optimization of methane production during chemical oxygen demand (COD) removal was observed in a novel Multi-Stage Anaerobic Reactor (MS-AR). A synthetic glucose was used as a feed substrate and the reactor was operated at a hydraulic retention time (HRT) of 1 to 4 d. Two complementary test procedures for methane optimization were evaluated; the theoretical and experimental. The theoretical methane gas was recorded as 50.13, 50.02, 50.16, and 50.22 % for HRT of 4, 3, 2 and 1 day, respectively. The results signify well with the empirical formula at each HRTs studied in the reactor. However, the quantity of methane gas present in the real application is significantly lower than the theoretical. This is due to the microorganism activity in the reactor that may have interfere with the efficiency of the biogas production. Actual data showed a decrease in the methane gas production (35.4, 21.2, 19.8, and 18.4 %) in the reactor. Thus, theoretical formula together with the actual data provides alternative method for the evaluation of bioenergy potential in AD

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

The effect of mesophilic and thermophilic temperature on the performance of an up-flow anaerobic sludge bed (UASB) reactor

The performance of an anaerobic reactor depends on various factors such as wastewater composition, organic loading rate (OLR), hydraulic retention time (HRT), seed sludge, temperature, and reactor configuration.In the present study, an up-flow anaerobic sludge bed (UASB) reactor was used for the treatment of synthetic wastewater. Specifically, this study was carried out in order to investigate the effect of temperature on the reactor performance when OLR was gradually increased. The reactor was operated at two different temperatures; mesophilic (37°C) and thermophilic (57°C). The maximum COD removal efficiency of the mesophilic operation was low compared tothe thermophilic(75.3and 81.2% respectively). The volatile acid concentration was 80 mg/L throughout the thermophilic and mesophilic experimental study. The MLVSS/MLSS ratio confirms that the utilization of biomass during the thermophilic operation was high. From the study,it was concluded that temperature plays a major role in anaerobic reactor operation,and thermophilic condition provided better reactor performance