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A submerged membrane bioreactor (MBR) employed for nitrobenzene-contain water resource treatment was operated for investigation of system effectiveness and for specification of nitrobenzene (NB) removal pathway. Two sludge retention times (2 and 25 d) that regulated biomass content in MBR were adopted to evaluate the importance of activated sludge for NB removal through biodegradation way. From a long-term examination, both of organic biodegradation by activated sludge and rejection by fresh and/or fouled membrane were the major ways to remove organic matters including NB. However, activated sludge played a rather significant role in NB removal. A lengthening solid retention time form 2 to 25 d in MBR resulted in a significantly improvement of removal efficiency in dissolved organic matters, ammonia-N and NB, due mainly to the continuous accumulation of biomass within bulk. Especially, the NB removal efficiency displayed an apparently positive correlation with the biomass content. After sludge acclimation process, the MBR was able to remove NB by a removal rate at 1.266 mg/(gMLSS h), equivalent to the NB removal efficiency up to 80%. In addition, by Fluorescence excitation-emission matrix observation, it was found that biomass growth and accumulation could also impact the effective removal of organic fractions, as that there were obvious selectivity of organic removal by biodegradation of activated sludge. The experimental results obtained herein are very useful to recognize the refractory organics removal pathway in MBR, and to understand the importance of activated sludge. [ABSTRACT FROM PUBLISHER]

A laboratory-scale flat-sheet membrane bioreactor (MBR) was employed to treat real micro-polluted surface water loaded with 2,4,6-trichlorophenol (2,4,6-TCP). MBR treatment performances were evaluated in terms of dissolved organic matters (DOM) degradation, target trace organic (2,4,6-TCP) removal, and effluent bio-stability improvement. The experimental results showed that the removal efficiency of DOM related closely with the biomass content in MBR. With continuous growth and accumulation of biomass under a long sludge retention time (SRT), stable DOM removal efficiency above 50% could be obtained, resulted in an effluent DOM kept below 2.0 mg TOC/L. Upon the steady state of MBR, more than 90% 2,4,6-TCP was removed by synergistic function of aeration volatilization, biological degradation, and activated sludge adsorption. The removal pathways of 2,4,6-TCP were specified by series of batch-scale trials, and corresponding contributions were estimated. It was revealed that fresh ultrafiltration rejection took a major responsible for 2,4,6-TCP removal in the start-up phase, which rejected about 15% 2,4,6-TCP. In comparison, for a steady state where had a high biomass content around 450 mg/L, biodegradation was the main pathway for 2,4,6-TCP removal, reflected by that above 300 μg/L 2,4,6-TCP was eliminated by microorganism degradation within no more than 1.2 h. The results herein claimed that MBR is a feasible way to treat micro-polluted water resource, and its removal pathway specification gave reliable guidance for MBR application. [ABSTRACT FROM PUBLISHER]

Simultaneous nitrogen and phosphorus removal by denitrifying phosphorus accumulating organisms (DPAO) from domestic wastewater with a low C/N was studied in a pilot-scale A2N/BAF process. Through long-term investigation for more than 820 d, it was evidenced that the A2N/BAF performed well on COD,-N and TP removals with efficiencies averaged at 84, 97 and 90%, respectively. Phosphorus removal in the system was mainly attributed to the function of DPAO through the analysis of phosphorus uptake and nitrate consumption, and the relative phosphorus uptake activity of DPAO/PAO was approximately 70.3%. Moreover, the microbial diversity and dominant bacterial community in the A2N/BAF was investigated with high-throughput sequencing. It was revealed that the A2N/BAF sludge had comparatively less diversity than seed sludge and shared several common dominant taxonomic bacteria with seed sludge, while long-term operation also shifted the microbial community. The A2N/BAF system was feasible for the treatment of low C/N wastewaters without any additional carbon source, which gave a new insight for efficient removal of organic and nutrients simultaneously. [ABSTRACT FROM AUTHOR]

The objective of this experiment was to investigate the influence of SO 3 2- dosage, pH value, initial perfluorooctane sulfonate(PFOS)concentration as well as coexisting substances on the degradation and defluorination of PFOS by VUV-SO 3 2- process. The results indicated that the increase of SO 3 2- dosage could lead to rise in the concentration of active species hydrated electron(e aq - ) and thus enhance the degradation and defluorination of PFOS. As the concentration of SO 3 2- increased from 1 mmol·L -1 to 20 mmol·L -1 , the degradation and defluorination rates of PFOS increased from 45% and 40% to 97% and 63%, respectively. The degradation and defluorination of PFOS were also enhanced with the increment of the solution pH values, and the defluorination was more sensitive to the pH values. In addition, more PFOS was degraded with the increase of initial PFOS mass concentration, although the degradation and defluorination rates of PFOS were reduced. When the initial PFOS mass concentration changed from 1 mg·L -1 to 50 mg·L -1 , the degradation amount of PFOS after four hrs increased by about 50 times, probably due to the higher utilization proportion of e aq - at high pollutants concentration. Last but not least, the influence of co-existing substances, Cl - and HCO 3 - , on PFOS degradation could be neglected, whereas their effects on defluorination were observed. Defluorination of PFOS was enhanced with the increased Cl - concentration, however, increased first and then decreased with the increment of HCO 3 - concentration. It was also found that the presence of humic acid(HA) lowered degradation as well as defluorination of PFOS owing to the blockage of effective UV light and trapping of active species for photochemical reaction.