Determination of Sustainable Critical Flux through a Long-Term Membrane Resistance Model.

A long-term membrane resistance model (LMR) was established to determine the sustainable critical flux, which developed and simulated polymer film fouling successfully in a lab-scale membrane bioreactor (MBR) in this study. The total polymer film fouling resistance in the model was decomposed into the individual components of pore fouling resistance, sludge cake accumulation and cake layer compression resistance. The model effectively simulated the fouling phenomenon in the MBR at different fluxes.

Optimization of MBR hydrodynamics for cake layer fouling control through CFD simulation and RSM design.

Membrane fouling is an important issue for membrane bioreactor (MBR) operation. This paper aims at the investigation and the controlling of reversible membrane fouling due to cake layer formation and foulants deposition by optimizing MBR hydrodynamics through the combination of computational fluid dynamics (CFD) and design of experiment (DOE). The model was validated by comparing simulations with measurements of liquid velocity and dissolved oxygen (DO) concentration in a lab-scale submerged MBR.

Influence of carbon sources on nutrient removal in A/O-MBRs: Availability assessment of internal carbon source.

Both internal carbon source and some external carbon sources were used to improve the nutrient removal in Anaerobic-Anoxic-Oxic-Membrane Bioreactor (A/O-MBRs), and their technical and cost analysis was investigated. The experimental results showed that the nutrient removals were improved by all the carbon source additions. The total nitrogen and phosphorus removal efficiency were higher in the experiments with external carbon source additions than that with internal carbon source addition.

CFD simulation and optimization of membrane scouring and nitrogen removal for an airlift external circulation membrane bioreactor.

Cost-effective membrane fouling control and nitrogen removal performance are of great concern in airlift external circulation membrane bioreactors (AEC-MBRs). Computational fluid dynamics (CFD) model incorporating sub-models of bio-kinetics, oxygen transfer and sludge rheology was developed for the cost-effective optimization of a lab-scale AEC-MBR. The model was calibrated and validated by extensive measurements of water velocities and water quality parameters in the AEC-MBR.

Modifying glass fiber surface with grafting acrylamide by UV-grafting copolymerization for preparation of glass fiber reinforced PVDF composite membrane.

Experimental design and response surface methodology (RSM) were used to optimize the modification of conditions for glass surface grafting with acrylamide (AM) monomer for preparation of a glass fiber reinforced poly(vinylidene fluoride) (PVDF) composite membrane (GFRP-CM). The factors considered for experimental design were the UV (ultraviolet)-irradiation time, the concentrations of the initiator and solvent, and the kinds and concentrations of the silane coupling agent. The optimum operating conditions determined were UV-irradiation time of 25 min, an initiator concentration of 0-0.

Preparation and characterization of PVDF-glass fiber composite membrane reinforced by interfacial UV-grafting copolymerization.

A novel inorganic-organic composite membrane, namely poly(vinylidene fluoride) PVDF-glass fiber (PGF) composite membrane, was prepared and reinforced by interfacial ultraviolet (UV)-grafting copolymerization to improve the interfacial bonding strength between the membrane layer and the glass fiber. The interfacial polymerization between inorganic-organic interfaces is a chemical cross-linking reaction that depends on the functionalized glass fiber with silane coupling (KH570) as the initiator and the polymer solution with acrylamide monomer (AM) as the grafting block. The Fourier transform infrared spectrometer-attenuated total reflectance (FTIR-ATR) spectra and the energy dispersive X-ray (EDX) pictures of the interface between the glass fiber and polymer matrix confirmed that the AM was grafted to the surface of the glass fiber fabric and that the grafting polymer was successfully embedded in the membrane matrix.

[Energy Consumption Comparison and Energy Saving Approaches for Different Wastewater Treatment Processes in a Large-scale Reclaimed Water Plant].

Energy consumption is the main performance indicator of reclaimed water plant (RWP) operation. Methods of specific energy consumption analysis, unit energy consumption analysis and redundancy analysis were applied to investigate the composition and spatio-temporal distribution of energy consumption in Qinghe RWP with inverted A2/O, A2/O and A2/O-MBR processes. And the A2/ O-MBR process was mainly analyzed to identify the main nodes and causes for high energy consumption, approaches for energy saving were explored, and the energy consumption before and after upgrading for energy saving was compared.

Internal carbon source from sludge pretreated by microwave-H2O2 for nutrient removal in A2/O-membrane bioreactors.

To improve the nutrient removal, the feasibility was studied for the organics released from sludge pretreated by microwave-H2O2 process (MHP) to be used as internal carbon source in two A2/O-membrane bioreactors (MBRs). The experiments were conducted for the nutrient removal and the membrane fouling. The results showed that the removal efficiencies of TN and TP were improved by 11% and 28.

Simulation and optimization of airlift external circulation membrane bioreactor using computational fluid dynamics.

The airlift external circulation membrane bioreactor (AEC-MBR) is a new MBR consisting of a separated aeration tank and membrane tank with circulating pipes fixed between the two tanks. The circulating pipe is called a H circulating pipe (HCP) because of its shape. With the complex configuration, it was difficult but necessary to master the AEC-MBR's hydraulic characteristics.

Study of a membrane bioreactor with glass fiber flat grille modules and the modules' optimization based on the local critical flux theory.

A novel flat grille membrane module using inorganic glass fibers as filter media is proposed for use in a membrane bioreactor for wastewater treatment. A model which integrates the concepts of back transport velocity, spatial local critical flux and temporal variation of the local flux has been developed. The membrane module was optimized based on experimental results and calculations using the model.

[Dynamic membrane bioreactor with glass fiber tube covered with organic membrane].

A novel grille form complex membrane module composed of glass fiber covered with organic membrane and the dynamic membrane bioreactor (DMBR) with this complex membrane were studied. The results showed that the flux of the dynamic membrane of glass fiber tube without covering with organic membrane solution was only 4 L/(m2 x h) at a trans-membrane pressure (TMP) of 0.02 MPa.

Performances of biological aerated filter employing hollow fiber membrane segments of surface-improved poly (sulfone) as biofilm carriers.

Using the surface of poly (sulfone) hollow fiber membrane segments as grafted layer, the hydrophilic acrylamide chain was grafted on by UV-photoinduced grafting polymerization. The gained improvement of surface wettability for the modified membrane was tested by measuring the contact-angle as well as FTIR spectra. Then correlation between the hydrophilic ability of support material and the biofilm adherence ability was demonstrated by comparing the pollutant removal rates from urban wastewater via two identical lab-scale up-flow biological aerated filters, one employed the surface wettability modified poly (sulfone) hollow fiber membrane segment as biofilm carrier and the other employed unmodified membrane segment as biofilm carrier.

Inorganic nitrogen removal of toilet wastewater with an airlift external circulation membrane bioreactor.

Removal of inorganic nitrogen (inorganic-N) from toilet wastewater, using a pilot-scale airlift external circulation membrane bioreactor (AEC-MBR) was studied. The results showed that the use of AEC-MBR with limited addition of alkaline reagents and volumetric loading rates of inorganic-N of 0.19-0.

Reuse rate of treated wastewater in water reuse system.

A water quality model for water reuse was made by mathematics induction. The relationship among the reuse rate of treated wastewater (R), pollutant concentration of reused water (Cs), pollutant concentration of influent (C0), removal efficiency of pollutant in wastewater (E), and the standard of reuse water were discussed in this study. According to the experiment result of a toilet wastewater treatment and reuse with membrane bioreactors, R would be set at less than 40%, on which all the concemed parameters could meet with the reuse water standards.

[Reducing sludge production by predation and its factors analysis in conventional activated sludge process].

Reducing excess sludge production induced by Oligochaete is carried out in a pilot scale of conventional activated sludge (CAS) reactor for 345 days. Worms occurred for nearly whole operating period except for the first 20 days, and continuously maintained at high density (over 30 total worms/mgVSS in aeration tank) for 172 days. Three types of worm were found, Aeolosoma hemprichicii and Nais elinguis alternatively dominated, but Pristina aequiseta occasionally presented.

[The influence of mechanical-cleaning membrane module on membrane flux].

An enhanced mechanical-cleaning membrane module M1 and a mechanical-cleaning membrane module M2 were designed in this research. An orthogonal array design was adopted to investigate effects of operational parameters including aeration intensity, membrane flux, MLSS, ratio of suction time and non-suction time on membrane filtration of two membrane module of M1 and M2. The results showed that M1 could weaken the negative influence of disadvantage parameters including high MLSS, high membrane flux, and low aeration intensity on membrane flux.

Minimization of excess sludge production for biological wastewater treatment.

Excess sludge treatment and disposal currently represents a rising challenge for wastewater treatment plants (WWTPs) due to economic, environmental and regulation factors. There is therefore considerable impetus to explore and develop strategies and technologies for reducing excess sludge production in biological wastewater treatment processes. This paper reviews current strategies for reducing sludge production based on these mechanisms: lysis-cryptic growth, uncoupling metabolism, maintenance metabolism, and predation on bacteria.

A pilot scale anoxic/oxic membrane bioreactor (A/O MBR) for woolen mill dyeing wastewater treatment.

A pilot-scale (10 m3/d) anoxic/oxic membrane bioreactor (A/O MBR) was tested for dyeing wastewater treatment of woolen mill without wasting sludge in 125 days operation. Results showed that the effluent quality was excellent, i.e.

Comparison performances of membrane bioreactor and conventional activated sludge prcesses on sludge reduction induced by Oligochaete.

Pilot-scale experiments were carried out to compare sludge reduction induced by Oligochaete in a submerged membrane bioreactor (MBR) and a conventional activated sludge (CAS) reactor for 345 d. Worm growth in the CAS reactor was much better than in the MBR. The average worm density of the aeration tank in the CAS reactor was 71 total worms/mg of volatile suspended solids (VSS), much higher than that in the MBR (10 total worms/mg of VSS).

Sewage treatment by a low energy membrane bioreactor.

A new membrane bioreactor (MBR) was developed for treatment of municipal wastewater. The MBR was mainly made up of an activated sludge reactor and a transverse flow membrane module, with an innovative configuration being in application between them. As a result, the transverse flow membrane module and low recirculation flow rate created advantages, such as lower energy consumption and more resistance to membrane fouling.

[Treatment of wastewater from a toilet for reclamation with a airlift external recirculated membrane bioreactor].

A new type membrane bioreactor(MBR) coupled with a separated immersed membrane unit was studied for treatment of wastewater from a toilet and for reclamation of the treated water. The results showed that the effluent of the MBR was stable with COD < 47 mg/L, BOD5 < 8.5 mg/L, NH3-N < 20 mg/L, when the influent concentration was COD 440-970 mg/L, BOD5 307-612 mg/L, NH3-N 59-111 mg/L.

Determination and discussion hydraulic retention time in membrane bioreactor system.

Based on the microorganism kinetic model, the formula for computing hydraulic retention time in a membrane bioreactor system (MBR) is derived. With considering HRT as an evaluation index a combinational approach was used to discuss factors which have an effect on MBR. As a result, the influencing factors were listed in order from strength to weakness as: maximum specific removal rate K, saturation constant Ks, maintenance coefficient m, maximum specific growth rate mu m and observed yield coefficient Yobs.