Baoan Li

Mixed pharmaceutical wastewater treatment by integrated membrane-aerated biofilm reactor (MABR) system--a pilot-scale study.

A pilot-scale integrated membrane-aerated biofilm reactor (MABR) system, consisted of hydrolysis/acidification pretreatment, MABR process and activated carbon adsorption post-processing, was designed to treat the high-loading mixed pharmaceutical wastewater. A study of MABR process was conducted to investigate the effect of aeration condition, circulation flow rate and water quality on performance over 260 days. The performances of these processes were evaluated by the removal efficiency of COD, BOD(5), turbidity, NH(4)(+)-N and TN. MABR process could effectively remove above 90% of COD and 98% of ammonia. The capacities per unit volume of MABR could reach up to 1311 gCOD/m(3)d and 48.2 gNH(4)(+)-N/m(3)d with single membrane aeration, and the oxygen utilization rate could be as high as 45%. After post-processing, the effluent of integrated treatment MABR system kept stable with COD below 200 mg/L and NH(4)(+)-N below 3 mg/L.

Bacterial community shift along with the changes in operational conditions in a membrane-aerated biofilm reactor

Membrane-aerated biofilm reactor (MABR) is a promising wastewater treatment process. Although bacteria inhabiting the MABR biofilm are important in wastewater treatment, the community composition and its correlation with operating conditions were less clear. A laboratory-scale MABR was designed to investigate the shift of bacterial community through a complete operational process by pyrosequencing the bacterial 16S rRNA genes. From around 19,000 sequences, 175 bacterial genera were retrieved, mainly belonging to Betaproteobacteria, Gammaproteobacteria, Alphaproteobacteria, Bacteroidetes, and Actinobacteria. A large number of unclassified bacterial sequences were also detected in the biofilm, suggesting a wide variety of uncharacterized species in MABR. Redundancy analysis (RDA) revealed that influent chemical oxygen demand (COD), NH4-N, and NaHCO3 concentrations could exert distinct influences on the composition of the bacterial community. The influent COD and NaHCO3 concentrations stimulated proliferation of denitrification-related species such as Dokdonella, Azospira, Hydrogenophaga, Rhodocyclaceae, and Thauera, while inhibiting the growth of Acidovorax and Sinobacteraceae. Some denitrifying Thermomonas spp. tended to survive in NH4-N-rich environments, while Flavobacterium preferred to inhabit NH4-N-poor or COD-rich environments. Conversely, the influent NH4-N and NaHCO3, to some extent, appeared to be the growth-promoting factors for nitrifying bacteria. Furthermore, the presence of potential aerobic denitrifiers such as Comamonas, Enterobacter, and Aeromonas indicated that MABR could have the capability of simultaneous aerobic and anoxic denitrification particularly during treatment of low-ammonia nitrogen sewage.

Surface modification of PVDF hollow fiber membrane and its application in membrane aerated biofilm reactor (MABR).

A novel composite hollow fiber membrane for membrane aerated biofilm rector (MABR) was prepared by coating L-3,4-dihydroxyphenylalanine (DOPA) on the surface of PVDF membrane. MABR process study was conducted to test the performances of the original and modified membranes for 166 days. The results indicate that coated membrane showed 2 times higher gas flux, lower water contact angle (declined from 86.5° to 52°), and significantly improved surface roughness. The modified membrane displayed an excellent MABR performance. Its COD, NH4(+)-N and TN removal efficiencies were kept above 90%, 98.8% and 84.2% during the first 4-month experiment. By tracking experiment at 0.01 MPa, to achieve COD removal efficiency of 85.9%, half an hour is required with the modified membrane, instead of 6h using the original one. Besides, faster NH4(+)-N and TN removal at 0.01 MPa were also achieved with DOPA composite membrane.

Treatment of pharmaceutical wastewater for reuse by coupled membrane-aerated biofilm reactor (MABR) system

The high-concentration pharmaceutical intermediate wastewater treatment was studied experimentally by using a coupled membrane-aerated biofilm reactor (MABR) system, which included ozone oxidation as pre-treatment, MABR biochemical method, and improved coagulation–flocculation technology as post-treatment. First, the influence of ozone production rate and reaction time on chemical oxygen demand (COD) reduction and biochemical oxygen demand (BOD5)/COD (B/C) ratio was explored. 53% COD reduction and an increase of B/C ratio from 0.22 to 0.46 were achieved under the conditions of 6 g h−1 of dose and 30 min of reaction time. Subsequently, multi-group continuous experiments were conducted to investigate the effect of hydraulic retention time (HRT), aeration pressure, and flow velocity on C and N removals in MABR system. With 24 h HRT, aeration pressure of 0.15 MPa, and flow velocity of 0.08 m s−1, 95% COD removal and 92% total nitrogen (TN) reduction were obtained simultaneously in the MABR process. Finally, the improved coagulation–flocculation was applied using polyaluminium chloride (PAC, 1.2 g L−1) combined with polyacrylamide (PAM, 2 mg L−1) and magnetic powder (8–10 g L−1) to generate excellent effluent quality for industrial reuse in China (GB/T 19923-2005). In conclusion, O3-MABR-improved coagulation/flocculation technology was feasible for treating pharmaceutical intermediate wastewater for reuse.

Preparation and Characterization of Thermal Conductive Composite Membranes of Aligned Esterified Carbon Nanotubes/Poly(vinylidene fluoride)

Esterified carbon nanotubes (MWCNT-COOC16H33) were prepared. Composite membranes were fabricated. An alternating current (AC) electric field was applied to the membrane structure orientation. The structures and properties of composite membranes were investigated. The fillers induced the β phase of PVDF; the electric field further enhanced the β phase and made more orderly structures. The fillers arranged along with the electric field and formed a thermal channel. The thermal conductivities of composite membranes were improved by MWCNT-COOC16H33. When the MWCNT-COOC16H33 content reached 5%, the thermal conductivity of composite membrane was 56.05% higher than pure PVDF and even 57.18% higher after alignment. GRAPHICAL ABSTRACT

Assessing the performance and microbial structure of biofilms adhering on aerated membranes for domestic saline sewage treatment

The presence of high salt concentration has always been considered as a common inhibitor that hampers effective municipal wastewater treatment. In this study, a bench-scale membrane-aerated biofilm reactor (MABR) was first introduced to degrade and remove the carbon and nitrogen pollutants under saline conditions. At influent concentrations of 220 mg CODCr per L and 32 mg NH4–N per L with an HRT of 24 h and salinity level of 3%, the reactor demonstrated excellent CODCr, NH4–N and TN removal efficiencies of 92.8%, 98.5% and 70.6%, respectively. Alphaproteobacteria, Anaerolineae, Gammaproteobacteria, Betaproteobacteria and Flavobacteria were the major functional classes in bacterial community. Candidatus Nitrososphaera exhibited stronger salt resistance compared with Nitrosomonas, and was probably the dominant nitrifier. Although the microbial diversity (Shannon–Wiener index) changed slightly along with the increasing salinity from 0.4% to 3%, the community composition substantially altered mainly through a fluctuant process via the growth of halophilic bacteria and the reduction of halotolerant bacteria. The halotolerant bacteria was mainly affiliated with Anaerolineae and Ignavibacteria while the halophilic bacteria mainly belonged to Alphaproteobacteria and Anaerolineae. The succession ensured a stable performance of the system under salty environments. This research suggests that MABR has the potential to effectively treat domestic saline sewage.

Nitrogen removal performance of municipal reverse osmosis concentrate with low C/N ratio by membrane-aerated biofilm reactor

A membrane-aerated biofilm reactor was employed to investigate the nitrogen removal of one typical municipal reverse osmosis(RO) concentrate with a high total nitrogen (TN) concentration and a low C/ N ratio. The effects of operational conditions, including the aeration pressure, the hydraulic retention time and the C/N ratio, on the systematic performance were evaluated. The nitrogen removal mechanism was evaluated by monitoring the effluent concentrations of nitrogen contents. Furthermore, the microbial tolerance with elevated salinity was identified. The results indicated that the optimal TN removal efficiency of 79.2% was achieved of the aeration pressure of 0.02 MPa, hydraulic retention time of 24 h, and the C/N ratio of 5.8, respectively. It is essential to supplement the carbon source for the targeted RO concentrate to promote the denitrification process. The inhibitory effect of salinity on denitrifying bacteria and nitrite oxidizing bacteria was significant, revealing the limited TN removal capacity of the conditions in this work. The TN removal efficiency remained more than 70% with the addition of salt (NaCl) amount below 20 g/L. This work preliminarily demonstrated the MABR feasibility for the nitrogen removal of municipal RO concentrate with low C/N ratio and provided technical guidance for further scale-up application.

Investigation of membrane-aerated biofilm reactor (MABR) for the treatment of crude oil wastewater from offshore oil platforms

AbstractMembrane-aerated biofilm reactor (MABR) was designed to treat oilfield produced wastewater from offshore oil platform. The effects of suspended solids (SS) of influent, intra-membrane air pressure, and feed flow velocity on chemical oxygen demand (COD), oil, and ammonia nitrogen (-N) removals were investigated through a 160-d process study. The results indicate: (a) high influent SS resulted in the formation of a barrier layer containing insoluble SS on the outside surface of biofilm which significantly reduced the mass transfer of -N and organic substrates from wastewater to the biofilm; (b) under the condition of feed flow velocity of 0.01u2009m/s, with the increase in intra-membrane air pressure, the oxygen permeate flux of hollow fiber membrane was enhanced and -N removal efficiency at 0.12u2009MPa was up to 95%; (c) under the condition of intra-membrane air pressure of 0.08u2009MPa, with the increase in flow velocity, the performance of MABR was significantly enhanced, the best removal efficiencies of CO...

A High-Performance Heat Exchanger Using Modified Polyvinylidene Fluoride-Based Hollow Fibers

Plastic heat exchangers has the shortcomings of bulky, thick pipe wall with large thermal resistance, poor heat transfer, aging of plastic and a narrow temperature range. The key to increase the heat transfer performance of heat exchanger is improving thermal performance of heat conduction.To enhance heat transfer effects and expand the temperature range of using plastic heat exchanger, PVDF with good temperature resistance is used as matrix and modification with graphite fillers to prepare composite hollow fiber which has the advantage of small diameter, thin wall and good thermal conductivity. Also, composite materials hollow fibers are used to prepare shell and tube hollow fiber heat exchanger.The testing of water - water system for our heat exchanger module has been done, and the results indicate that adding graphite is helpful to improve thermal conductivity of PVDF-based heat conductive hollow fiber heat exchanger to a certain extent.hen the content of graphite is 3%, the heat transfer effect is the best.

Study on Calcium and Magnesium Fouling of Vacuum Membrane Distillation

In this paper, calcium and magnesium fouling on membrane distillation process was investigated. The effect of less soluble salts with single component or multi component on flux and membrane fouling was examined, by means of synthesizing seawater. The results showed that the fouling caused by calcium carbonate and calcium sulfate was mainly formed by the attachment of the insoluble substance on the fibers. The calcium sulfate caused the blocking at inlet hole of the module. If there were less soluble salts with multi components in the feed, calcium carbonate was the main form of the fouling.