Pathogenic Bacteria and Antibiotic Resistance Gene Removal Using Up-flow Anaerobic Sludge Blanket (UASB)
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The search for effective wastewater management strategies continues and never stops due to the importance of ensuring a safe environment for all organisms. The Upflow Anaerobic Sludge Blanket (UASB) reactor is cost-effective, produces less quantity of sludge and also has a smaller size. Such importance makes it an ideal treatment technology which requires a lot of study to know its capabilities and how they can be improved. The main aim of this study was to assess the effectiveness of the UASB reactor in bacterial pathogen and antibiotic resistance genes removal. The pathogens that were considered were total coliforms with focus on Escherichia coli and Enterococcus. Effects of organic loading rates (OLR) and hydraulic retention time (HRT) were also considered. Qualitative antibiotic resistance genes for sulfamethoxazole sul (I, II, III), tetracycline tet (A, B, C, D, G, K, L, M, O, otr B) and erythromycin erm (A, B, C and msr A) were studied. There were four sampling periods which were used with no specific intervals between, but the first sample was taking when the reactor was 75 days old. Inlet and outlet samples were analysed. The results showed a high percentage removal of pathogenic microorganisms during period 2 with 100% removal of E. coli, 78.5% of other coliforms, 82.5% of Enterococcus and 99.2% of total bacteria on plate count. Pathogen removal of period 1 was not effective may be due to microbial communities not stabilized enough though the HRT was one of the longest. The antibiotic resistance gene test also recorded period 2 having the ability to remove tetracycline resistance genes (tet E, L, O and otr B). PCR was used which was not quantitative and the number of antibiotic resistance genes may have decreased significantly. However, this is impossible to evaluate because theoretically even if there was one gene, it could cause a positive PCR reaction. Furthermore, tet D was removed in period 1 and period 3 samples while sulfamethoxazole and erythromycin were not removed in any period. It was found that tet A and M were in all periods except period 4 but the UASB reactor was not able to remove them while tet B, tet K, sul II and erm A and B were absent in all the samples that were analysed.
Master's thesis in Environmental engineering