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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]

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]

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 A2N process with BAF as a nitrification unit was researched aiming at the low carbon and nitrogen ratio domestic wastewater in southern China. According to the problems that effluent ammonia exceeded the standard because of the ammonia carried in surpass sludge and total phosphate couldn't reach the discharge standard when SS of secondary settling tank was high, a secondary BAF was set up, and the total treatment effect of A2N/BAF process was studied. Results showed that the average removal rates of COD, ammonia and TP of A2N stage were 82.0%, 70.9% and 90.0% , respectively. Effluent ammonia concentration of secondary settling tank exceeded 10 mg/L when influent was more than 40 mg/L. Average concentration of COD, TP, ammonia, nitrate and SS in final effluent were 35, 0. 35, 1.06, 8.01 and 7 mg/L, respectively, which had satisfied the A-level of the national standards. [ABSTRACT FROM AUTHOR]

To overcome the shortcoming of biological aerated filter (BAF) on phosphorus removal, poly aluminum chloride (PAC) was dosed into the anoxic tank of anoxic-biological aerated filter (A-BAF). The effects of PAC on the phosphorus, organic matter and nitrogen removal by A-BAF and the head-loss development of BAF were investigated through a lab-scale experiment. The results showed that the addition of PAC had a positive effect on phosphorus removal by A-BAF, but had no effect on the removal of organic matter and nitrogen. With the PAC dosage of 100 mg/L, the TP concentration in effluent was reduced from 2.57 mg/L to 0.34 mg/L, when the influent TP concentration was 3.5 mg/L. The COD, Due to image rights restrictions, multiple line equation(s) cannot be graphically displayed. -N and TN concentration in effluent were 30,1 and 11 mg/L separately, which were similar to those in the effluent without PAC. Meanwhile, the backwashing cycle of BAF was increased from 4 d to 10 d and the specific resistance to filtration of the excess sludge was decreased from 210 x 1012m/kg to 125 x 1012m/kg after PAC dosing. [ABSTRACT FROM AUTHOR]

To improve the treatment efficiency of a gas - water alternate membrane bioreactor (AMBR) and make full use of the membrane module, the efficiency of membrane surface loading on synthetic municipal wastewater treatment by the AMBR was investigated through a lab-scale experiment. The results showed that: the maximum COD, NH4+ - N and TN removal load by AMBR were 84.9, 6.75 and 6.5 g/(m² · d) under the condition of intra-membrane oxygen pressure lower than 200 kPa and the C/N ratio of raw water was 10. The oxygen supply rate and nitrification rate were the main factors for COD and TN removal by AMBR separately, but both of the oxygen supply rate and nitrification rate influenced the NH4+ - N removal. [ABSTRACT FROM AUTHOR]