Showing papers by "Fenglin Yang published in 2007"

Characterization of cake layer in submerged membrane bioreactor

Abstract: Cake layer formation on the membrane surface has been a major challenge in the operation of membrane bioreactors (MBRs). In this study, the cake layer formation mechanism in an MBR used for synthetic wastewater treatment was investigated. The major components of cake layer were systematically examined by particle size analyzer (PSA), scanning electron microscopy (SEM), confocal laser scanning microscopy (CLSM), X-ray fluorescence (XRF), energy-diffusive X-ray analyzer (EDX), and Fourier transform infrared (FTIR) spectroscopy. The results indicate that the small particles in sludge suspension had a strong deposit tendency on the membrane surface. The SEM and CLSM analysis exhibited that bacterial clusters and polysaccharides were significant contributors to membrane fouling. The main components of biopolymers were identified as proteins and polysaccharide materials by the FTIR. The examination by EDX and XRF demonstrated that Mg, Al, Ca, Si, and Fe were the major inorganic elements in fouling cake. Furthermore, the results suggest that bridging between deposited biopolymers and inorganic compounds could enhance the compactness of fouling layer. During the operation of MBRs, the biopolymers and inorganic elements in the bioreactor should be controlled to minimize membrane fouling.

Effect of hydraulic retention time on membrane fouling and biomass characteristics in submerged membrane bioreactors

Abstract: In this paper, three identical membrane bioreactors (MBRs) were operated in parallel in order to specify the influence mechanism of hydraulic retention time (HRT) on MBR. The results showed that the removal efficiency of chemical oxygen demand (COD) was stable though it decreased slightly as HRT decreased, but biomass activity and dissolved oxygen (DO) concentration in sludge suspension decreased as HRT decreased. The filamentous bacteria grew easily with decreasing HRT. The extracellular polymeric substances (EPS) concentration and sludge viscosity increased significantly as filamentous bacteria excessively grew. The over growth of filamentous bacteria, the increase of EPS and the decrease of shear stress led to the formation of large and irregular flocs. Furthermore, the mixed liquid suspended solids (MLSS) concentration and sludge viscosity increased significantly as HRT decreased. The results also indicated that sludge viscosity was the predominant factor that affecting hydrodynamic conditions of MBR systems.

Comparison of membrane fouling during short-term filtration of aerobic granular sludge and activated sludge.

Abstract: Aerobic granular sludge was cultivated adopting internal-circulate sequencing batch airlift reactor. The contradistinctive experiment about short-term membrane fouling between aerobic granular sludge system and activated sludge system were investigated. The membrane foulants was also characterized by Fourier transform infrared (FTIR) spectroscopy technique. The results showed that the aerobic granular sludge had excellent denitrification ability; the removal efficiency of TN could reach 90%. The aerobic granular sludge could alleviate membrane fouling effectively. The steady membrane flux of aerobic granular sludge was twice as much as that of activated sludge system. In addition, it was found that the aerobic granular sludge could result in severe membrane pore-blocking, however, the activated sludge could cause severe cake fouling. The major components of the foulants were identified as comprising of proteins and polysaccharide materials.

Generation of hydroxyl radical in aqueous solution by microwave energy using activated carbon as catalyst and its potential in removal of persistent organic substances

Abstract: Salicylic acid (SA, hydroxybenzoic acid) was used as molecular probe to determine hydroxyl radical ( OH) in aqueous solutions, where microwave (MW) radiation was involved and activated carbon (AC) existed. Rapid reaction of OH with SA produced a stable fluorescence product, 2,3-dihydroxybenzoic acid (2,3-DHBA) as well as its homologue, 2,5-DHBA, which were determined by HPLC. Dose of AC, air supply, and MW power proved to be key factors influencing OH generation under MW radiation. The rate of OH generation reached 0.036 μmol s −1 , and the OH yield reached 3.2 μmol in 3 min under a given condition. OH is an active species with high oxidative activity and can initiate free radical reactions. Another experiment was carried out to confirm that organic substance may degrade in aqueous solution by the MW assisted catalytic process. Pentachlorophenol (PCP) was used as target. Results showed that nearly 72–100% degradation (corresponding to 40% and 82% TOC removal) was observed in 60 min for two levels of PCP concentrations (500 and 2000 mg L −1 ), which implies that continuous production of OH during MW radiation supports free radical reactions that benefit PCP degradation.

Carbon membrane-aerated biofilm reactor for synthetic wastewater treatment.

Abstract: A carbon membrane-aerated biofilm reactor (CMABR) was developed to treat synthetic wastewater. Such membrane exhibited a high degree of adhesion and good permeability. Continuous experiments showed that COD and \( {\text{NH}}^{ + }_{4} \)-N removal efficiency were 90 ± 2 and 92 ± 4% at removal rates of 35.6 ± 3.8 g COD/m2 per day and 9.3 ± 0.6 g \( {\text{NH}}^{ + }_{4} \)-N/m2 per day, respectively. After 108 days, effluent total nitrogen (TN) kept at 35 ± 4 mg/L when influent \( {\text{NH}}^{ + }_{4} \)-N increased to 144–164 mg/L and removal efficiency of TN reached 78 ± 3%. Furthermore, Stoichiometric analysis revealed that 70–90% of oxygen supplied was consumed by nitrifier. Scanning electron microscopic (SEM) images and component analysis of penetrating fluid revealed that extracellular polymeric substance (EPS) adhered to pore and that alkaline washing was an effective method to remove them. The study demonstrated that carbon membrane could be used as effective gas-permeable membrane in MABR for wastewater treatment.

Electrochemical Characteristics and Stability of Poly(1,5-diaminoanthraquinone) in Acidic Aqueous Solution

Abstract: The electrochemical characteristics and stability of poly(1,5-diaminoanthraquinone) (P15DAAQ) has been investigated in different acidic aqueous solution by electrochemical methods and Fourier transform infrared spectroscopy (FTIR) Cyclic voltammetry (CV) analysis suggests that electropolymerization consists of two phasesthe deposition of P15DAAQ from the oxidation of 15DAAQ monomers and the polymer growth process The CV and chronoamperometry (CA) data provide the evidence that ion transfers are different between oxidation and reduction processes and are profoundly influenced by the sizes of ion radius during the redox process of P15DAAQ in acid solution The H+ transfer is diffusionless, while the insertion/expulsion of large aqua anions is controlled by diffusion A model is proposed to describe these ion transfer processes In further CA research, the calculated diffusion coefficients of aqua anions in P15DAAQ are in the order of Cl- > S > NO3- > P As a result of stability research, it can be seen t

Electrochemical Characteristics and Stability of Poly(1,5-diaminoanthraquinone) in Acidic

Abstract: The electrochemical characteristics and stability of poly(1,5-diaminoanthraquinone) (P15DAAQ) has been investigated in different acidic aqueous solution by electrochemical methods and Fourier transform infrared spectroscopy (FTIR). Cyclic voltammetry (CV) analysis suggests that electropolymerization consists of two phasesthe deposition of P15DAAQ from the oxidation of 15DAAQ monomers and the polymer growth process. The CV and chronoamperometry (CA) data provide the evidence that ion transfers are different between oxidation and reduction processes and are profoundly influenced by the sizes of ion radius during the redox process of P15DAAQ in acid solution. The H+ transfer is diffusionless, while the insertion/expulsion of large aqua anions is controlled by diffusion. A model is proposed to describe these ion transfer processes. In further CA research, the calculated diffusion coefficients of aqua anions in P15DAAQ are in the order of Cl- > S > NO3- > P . As a result of stability research, it can be seen t...

Intensified anti-nitrated phosphorous-removal sequencing batch membrane bioreactor technique

Abstract: The invention discloses a sequence batch type film bioreactor craft to reinforce denitrifying dephosphorize in sewage disposal and middle water reclaimed technical domain of environmental engineering, which comprises the following steps: cascading anaerobic or anoxybiotic reactor and sequence batch type film bioreactor; using inflow COD to complete the storage of PHB and relive phosphorous; polymerizing phosphoric bacterium under the anaerobic condition of the anaerobic or anoxybiotic reactor; proceeding aerobic nitrated and degraded organic material; yielding water at the same time; mixing the polyphosphoric sludge enriched with PHB and the nitrated liquid enriched with nitrate in the two reactor through sludge diversion and nitrated liquid backflow; removing nitrogen; polymerizing the phosphoric bacterium; choosing nitrate as electron acceptor; excess-absorbing phosphor; realizing synchronous denitrification dephosphorize without adding carbon source and nitrate This invention possesses simple flow process and convenient management, which can be fit for disposing urban sewage with low carbon and high nitrogen phosphor

The effect of polypyrrole-bound anthraquinonedisulphonate dianion on cathodic reduction of oxygen

Abstract: Functionalized polypyrrole (PPy) films were prepared by incorporation of anthraquinonedisulphonate (AQDS) as doping anion during the electropolymerization of pyrrole (Py) monomer at a glassy carbon electrode from aqueous solution. The electrochemical behavior of the PPy-bound AQDS modified electrode and cathodic reduction of oxygen on the resulting polymer film were studied. An obvious surface redox reaction corresponding to AQ/H 2 AQ was observed and the dependence of this reaction on the solution pH was also illustrated. The electrocatalytic ability of the PPy-bound AQDS modified electrode was demonstrated by the electroreduction of oxygen at the optimized pH of 6.3 in a phosphate buffer. The reduced AQDS (H 2 AQ) is responsible for the extraordinary catalytic activity to the oxygen reduction reaction. The PPy layers not only act as an electron mediator, but also facilitate the stability of the modified electrode. It was found that the catalytic reaction occurred in the presence of the bound AQDS and O 2 is in agreement with an electrochemical–chemical (EC) mechanism. The kinetic parameters of oxygen reduction were determined using Koutecky–Levich equation and Tafel polarization technique.

Membrane fouling behavior during filtration of sludge supernatant

Abstract: Colloidal particles and soluble matter in sludge supernatant are major membrane foulants during the operation of membrane bioreactors in wastewater treatment. The article discusses membrane fouling mechanisms during membrane filtration of sludge supernatant liquor. The influence of supernatant turbidity, transmembrane pressure, and crossflow velocity on membrane fouling was systematically investigated. The membrane fouling was characterized by Fourier transform infrared spectroscopy technique. The results showed that the high supernatant turbidity could result in severe membrane fouling because of the accumulation of colloidal particles and soluble matter on the membrane surfaces. High transmembrane pressure could lead to a high flux decline rate because of the formation of a dense cake layer. The crossflow velocity just had a slight influence on membrane fouling, as it was not larger than 0.12 m/s, However the membrane fouling decreased significantly as crossflow velocity increased to 0.24 m/s. The membrane fouling mechanisms of these operational conditions, including supernatant turbidity, transmembrane pressure, and crossflow velocity, were different from each other. Membrane fouling resistance can be predicted using a simple model based on supernatant turbidity, transmembrane pressure, and crossflow velocity. The major components of the foulants were proteins and polysaccharide materials.

[Anti-fouling characteristics of the novel precoating reagent in dynamic membrane bioreactor].

Abstract: Further research was made on precoating reagents in dynamic membrane process, in which novel precoating reagent-polyvinyl alcohol microsphere (PVA-MS) was prepared through emulsive polymerization of PVA and glutaraldehyde (GA). Furthermore, polymerization mechanism and anti-fouling characteristics through adsorption of membrane major fouling substances EPS upon PVA-MS were studied. The results showed that hemiacetals reaction played a major role in emulsive polymerization process, as the quantity of hydroxyl on PVA was decreased a little, PVA-MS surface behaved good hydrophilic, and the adsorption of protein and amylose upon PVA microsphere was stable and low, which was 0.543 mg x g(-1) and 0.694 mg x g(-1) respectively. In addition, PVA-MS surface behaved electronic negativity, which acted electrostatic repulsion to active sludge floc. Upon this characteristics and data, it was concluded that membrane fouling was delayed in microscopy structure. Diameter of PVA-MS in precoating liquid was about 1.14 microm, and Zeta-potential of precoating liquid with different precoating reagent concentration was less than - 39 mV, which made PVA microsphere diffused and stable from each other, then sedimentate rapidly on porous support membrane surface and internal wall of hole path. Besides, the morphology of PVA-MS and dynamic membrane formed from PVA-MS on support membrane were observed through SEM.

Enrichment of denitrifying phosphate accumulating organisms in sequencing batch membrane bioreactors

Abstract: The enrichment and characteristics of denitrifying phosphate accumulating organisms (DPAO), which are capable of utilizing nitrate as electron acceptor, was investigated in a laboratory-scale sequencing batch membrane bioreactors (SBMBR). The results demonstrated that the proportion of DPAO increased from 19.4% to 69.6% of total phosphate accumulating organisms after anaerobic-aerobic and anaerobic-anoxic-aerobic phases. SBMBR system could operate steadily when 120 mg nitrate was added continuously during the anoxic phase every period. Simultaneous phosphate uptake and biological denitrification with good performance could be obtained in SBMBR operated in steady-state. Nitrate and phosphorus removal efficiency were above 100% and 84% respectively during anoxic phase, however, the effluent TP concentration was low than 0.5 mg/L, the total phosphorus removal efficiency was 96.1%. Furthermore, the ammonium nitrogen removal efficiency of SBMBR could be maintained at 92.2%, and the cumulation of nitrite and nitrate was not observed clearly.

[Study on performance characteristics of carbon membrane-aerated biofilm reactor treating municipal wastewater].

Abstract: A carbon membrane-aerated biofilm reactor was developed to treat municipal wastewater. Tests were conducted to investigate oxygen transfer ability of carbon membrane, the bacteria adhesion and reactor's set-up performance. The optimum parameters were determined in terms of intra-membrane pressure, COD and nitrogen ratio and hydraulic retention time (HRT). The results showed that compared with that of other hollow fibres, bacterial suspended exhibited a high degree of adhesion onto carbon membrane and that oxygen transfer coefficient of carbon membrane was 0.36 m/h, so that it was feasible to serve as both biofilm carrier and aerator. NH4(+) -N removal, denitrification and COD removal efficiency could reach 95%, 92% and 88%, respectively, under the conditions of intra-membrane pressure of 0.025 MPa, carbon nitrogen ratio of 5 and HRT of 8 h, and effluent quality could be up to A standard in the national discharge standard of pollutants for municipal wastewater treatment plant (GB 18918-2002) . Furthermore, the system displayed better resistance to shock loads.