Biodegradation of tetracycline antibiotics in A/O moving-bed biofilm reactor systems.

An anaerobic/aerobic moving-bed biofilm (A/O-MBBR) reactor system was constructed, and the treatment efficiency of aqueous antibiotics in wastewater was investigated. The effects of antibiotics on the microbial communities in the A/O-MBBR were also investigated. Under the optimized reaction conditions, removal of tetracycline antibiotics (TCs) was studied in a series of experiments. When a low concentration of tetracycline (TC) was added to the reactor system, high removal efficiency of conventional pollutants (TC concentration decreased from 10 turn to 2.8 µg L-1) was achieved. When mixed TCs (50 µg L-1) were added to the system, the removal efficiencies of chlortetracycline (CTC), TC and oxytetracycline (OTC) reached 52.03, 41.79, and 38.42%, respectively. TC degradation was decreased to 21.16% when the antibiotic concentration was 500 µg L-1; exposure to this TC concentration destroyed the community structure of the activated sludge bacteria in the reactor. The products of the biodegradation analysis revealed the possible degradation pathways functioning in the experimental A/O-MBBRs.

Evaluation of biological removal efficiency in a UCT process treating municipal wastewater during start-up stage.

This study reports the performance of University of Cape Town (UCT) municipal wastewater treatment plant, during the startup stage with the focus on the relationship between hydraulic retention time (HRT) and biological nutrient removal (BNR) efficiency. The entire experimental period was 144 days, divided into four periods. Results showed that the removal efficiency of TN, NH4+-N, and Kjeldahl nitrogen (KN) was closely related to the HRT. Furthermore, the biodegradation kinetics analysis was used to calculate the specific degradation rates of pollutants. The GPS-X modeling was also used to examine the effect of the UCT pilot plant on BNR. The UCT pilot plant used in this study achieved high BNR efficiency even during the startup stage. With HRT of 24 hr (Period 1, day 1-40, data set 1-10), the highest levels of TN, NH(4+)-N and KN removal efficiency were approximately 72, 76 and 78%, respectively. The COD showed consistent high removal efficiency, with the highest level of approximately 96% at HRT of 15 hr (Period 3, day 81-120, data set 21-30). The TP removal efficiency rose at first and subsequently decreased abruptly. The maximum removal efficiency was 85% with HRT of 19 hr (Period 2, day 41-80, data set 11-20). With the optimal HRT 19 hr, the average removal efficiency values of COD, TP, TN, NH(4+)-N and KN were 89, 80, 65, 67 and 68%, respectively. The GPS-X modeling results indicated that the UCT process was effective in COD, TP and TN removal.

[Microbial community structure of beer wastewater treatment plants analyzed by PCR-DGGE technique].

The microbial community structure of beer wastewater treatment plants with hydrolyze-acidification and SBR process was studied by PCR amplification and denaturing gradient gel electrophoresis (DGGE) based 16S rDNA. Activated sludge samples were collected from both hydrolyze-acidification tank and SBR tank at different depth and disposal period. The total DNA was extracted and the 16S rDNA was amplified by universal primer. The microbial community structure was analyzed by denaturing gradient gel electrophoresis, compared with the DGGE band pattern of the screened high efficient bacteria. The PCR products were cloned and sequenced to analyze the microbial community in phylogenic evolution. The DGGE pattern showed that the microbial community in hydrolyze-acidification tank changed with the variation of depth both in microbial structure and population, and at the depth of two-meter the microbial community was relatively rich, the dominant bands were notable. The microbial community in SBR tank at different depths and different disposal periods (precipitation period, inflow period, aeration period) were consistent respectively, but the dominant bands were different. Sequences of y2, 23, 25, 31, h5, 15 yielded high homogeneity with the strains uncultured Thermotogales sp., Comamonas sp. WT OTU1, Agrobacterium tumefaciens, Bacillus subtilis, Bdellovibrio bacteriovorus, Comamonas testosteroni from GenBank. The 16S rDNA sequences of the dominant bands were not completely same with that of the high efficient bacteria, which indicated that the strains screened were not the dominant strains in actual process.