Antibiotics in the environment: mini review

Knowledge of pharmaceuticals in the environment is merely minute. Pharmaceuticals can enter the aquatic environment through the sewage treatment systems when they are excreted by people, or if they are disposed in the home. They can also enter sewage treatment works or waterways as a result of discharges from pharmaceutical manufacturing plants or medical establishments. The emission routes of veterinary drugs and feed additives to surface water are more complex than those of human pharmaceuticals. Emission to the surface water can take place either directly, when the animals are kept on pasture or indirectly by run-off and leaching through the soil. From an environmental side, the major effect of antibiotics is the toxic effect that may be exerted on aquatic organisms and disruption of the ecological balance. In addition, the presence of antibiotics in natural systems leads to the development of multi-resistant strains of bacteria. This paper outlines the different anticipated exposure routes to the environment, present knowledge of occurrence, fate and effect of pharmaceuticals

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

Effect of effluent circulation and hydraulic retention time (HRT) on the performance of a modified anaerobic baffled reactor (MABR) during start-up period

Effluent 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 2d and an OLR of 0.75kgCODm(-3)d(-1)). The pH profiles, volatile acids (HOAc) occurrence and biogas production during the start-up period showed favourable conditions in the reactor. In addition, the effect of HRT variations (4, 3, 2 and 1d) 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