Jinling Wu

Indigenous somatic coliphage removal from a real municipal wastewater by a submerged membrane bioreactor

The membrane bioreactor (MBR) features many advantages, such as its excellent effluent quality and compactness. Moreover, the MBR is well known for its disinfectant capacity. This paper investigates virus removal performance for municipal wastewater using a submerged MBR and the operational conditions affecting the virus removal using indigenous somatic coliphages (SC) as an indicator for viruses. The results revealed that the municipal wastewater acquired by the Qinghe Municipal Wastewater Treatment Plant, Beijing, contained an SC concentration of (2.81+/-1.51)x10(4)PFU ml(-1), which varies seasonally due to spontaneous decay. In the MBR system, the biomass process dominates SC removal. Membrane rejection is an essential supplement of biomass process for SC removal. In this paper, the relative contributions of biomass process and membrane rejection during the start-up and steady operational periods are discussed in detail. The major factors affecting SC removal are biodegradation, membrane pore size, and gel layer formation on the membrane. During long-term experiments, it was demonstrated that high inoculated sludge concentration, long hydraulic retention time, moderate fouling layer, and non-frequent chemical cleaning are favorable for high SC removal in MBR systems.

Use of ozonation to mitigate fouling in a long-term membrane bioreactor.

In order to confirm the effect of ozonation on fouling mitigation in long-term membrane bioreactors (MBRs), parallel operation of two MBRs with and without ozonation was repeated in triplicate with different dosing modes. A number of mixed liquor properties and removal of pollutants in both MBRs were investigated. Membrane fouling was effectively retarded by ozonation in long-term MBRs. The best dosage was 0.25 mg g(-1)-SS at 1 day intervals. A slow formation of a gel layer on membrane surface was the result of the low organics in the supernatant and the low extractable extra-cellular polymeric substances in the MBR-ozone system. Ozonation also enlarged suspended flocs by reducing zeta-potential and increasing hydrophobicity, thus enhancing flocculability of the particles in the mixed liquor. The microbial activity was somewhat inhibited, however, the effluent quality of the system was not affected. These findings indicate the feasibility of using ozone to improve MBR efficiency.

Structural mechanism of DNA recognition by the p202 HINa domain: insights into the inhibition of Aim2-mediated inflammatory signalling

The HIN-200 family of proteins play significant roles in inflammation-related processes. Among them, AIM2 (absent in melanoma 2) and IFI16 (γ-interferon-inducible protein 16) recognize double-stranded DNA to initiate inflammatory responses. In contrast, p202, a mouse interferon-inducible protein containing two HIN domains (HINa and HINb), has been reported to inhibit Aim2-mediated inflammatory signalling in mouse. To understand the inhibitory mechanism, the crystal structure of the p202 HINa domain in complex with a 20 bp DNA was determined, in which p202 HINa nonspecifically recognizes both strands of DNA through electrostatic attraction. The p202 HINa domain binds DNA more tightly than does AIM2 HIN, and the DNA-binding mode of p202 HINa is different from that of the AIM2 HIN and IFI16 HINb domains. These results, together with the reported data on p202 HINb, lead to an interaction model for full-length p202 and dsDNA which provides a conceivable mechanism for the negative regulation of Aim2 inflammasome activation by p202.

pH Adjusting to Reduce Fouling Propensity of Activated Sludge Mixed Liquor in Membrane Bioreactors

The effect of adjusting pH on membrane filterability of activated sludge mixed liquor in membrane bioreactors (MBRs) was studied. The properties of the mixed liquor were analyzed to investigate the mechanisms. The results indicated that moderately adjusting pH was effective to improve the membrane filterability of the mixed liquor. HCl addition provided H+, which reduced the zeta-potential of the colloidal particles. NaOH addition at pH of 8.0–9.0 released some extractable extra-cellular polymeric substances (eEPS) to the supernatant. Re-flocculation occurred. The fouling propensity of the mixed liquor was therefore reduced. Microbial activity was not significantly affected within the pH of 6.0–9.0.

EFFECT OF OPERATIONAL CONDITIONS ON MEMBRANE PERMEABILITY IN A COAGULATION–MICROFILTRATION PROCESS FOR WATER PURIFICATION

ABSTRACT A coagulation–microfiltration combination process was used in treatment of simulative surface water. The effects of operational conditions such as filtration time, ceasing time and aeration intensity on the membrane permeability and organic removals were investigated. Experiment results showed that the membrane permeability could be improved through changing the operational conditions. Decreasing the filtration time or increasing the ratio of filtration time/ceasing time was favorable to enhance the membrane permeability. As the aeration intensity increased, the membrane permeability was also enlarged to some extent, but was not improved obviously anymore when the aeration intensity was over the critical value of around 4 m3 h−1. Different wash methods to remove membrane fouling were attempted. The results suggested that coagulation in the process mainly led to change of the deposit cake-caused membrane fouling, which could be physically removed by surface wash. Organic removals, in terms of OC and UV254, apparently varied with the operational conditions. An inverse relationship between organic removals and membrane permeability was found. Lower membrane permeability led to higher OC and UV254 removals.