| China has faced the shortage of water and energy resource, with the rapid development of gradual increasing of urban population. Sewage recycling could effectively address the increasingly serious issues, and thus has become one of hottest research points for environmental experts and scholars. Membrane biotechnology emerges as a promising method for sewage recycling due to its high efficiency and low cost. Compared with the aerobic biological treatment, anaerobic process features an important advantage that the organic matters in the waste water can be transformed into recycling energy sources (CH4). However, traditional membranes in anaerobic membrane biological treatment not only suffer from the trade-off relationship between selectivity and permeability, but also are limited by fouling. To address these problems, carbon-nanotube-based hollow fiber membranes (CNT-HFM) are prepared in this study. The coupling of the membrane separation technology and electrochemical technology can be realized by applying electrical bias on the membrane, and can be further applied to a new anaerobic membrane bioreactor designed independently to deal with the low-concentration domestic sewage for the purpose of improving the effluent quality of wastewater, production of the biogas and anti-fouling properties of the membrane modules. The main contents and results are shown as follows:CNT-HFMs were prepared with an acidification-spinning-calcination method. The membrane surfaces featured a randomly pore channel structure formed by the staggered nanotubes. This membrane structure was stable with a high porosity. As a result, their pure water flux was twice that of commercial organic hollow fiber membranes (PVDF-HFM). Moreover, the CNT-HFMs possessed a good electrical conductivity, separation performance and anti-pollution capacity. After applying an electrical bias on the membranes, a better anti-pollution capacity, membrane separation performance and membrane reproduction capacity could be achieved compared with the organic membranes. The electrical repulsive interaction between the membrane and pollutant would be enhanced due to the electrical bias on the membranes, bringing about a thinner fouling layer. After the secondary cleanliness, their water recovery rate of the permeate flux could reach 88.27%, which was 1.5 times more than that of organic membranes.It is discovered that temperatures could affect the processing effectiveness of the anaerobic MBR. With the decrease of temperatures from 40 ? to 30? to 20?, the COD removal efficiencies of the biological removal fell from 88.4% to 78.5%, and then to 38.1%. But the total removal rate was 95.7%,92.7% and 81.7%, respectively, indicating that there was little influence on the COD removal efficiency at the membrane separation stage and the COD concentration of effluent after the membrane separation was always below 70 mg/L. It suggested that the anaerobic MBR process was advantageous than traditional anaerobic activated sludge process in COD removal efficiency.Comparison of the general anaerobic MBR using the organic membrane and the new anaerobic MBR showed that the three-phase separator in the common UASB could be replaced by an inner cylinder with a cone shape added in the inside of reactor, which could improve the efficiency of collecting biogas. The production of the biogas increases from 281.95 mL/d to 396.12 mL/d. The setting of a circle of round distributive holes could hinder the sludge particulates from depositing on the membrane surface and retard the membrane fouling. In the comparison experiments of PVDF-HFM, CNT-HFM and CNT-HFM (-1.0 V), the membrane separation on the COD removal contribution value is the highest by applying a negative bias on the membrane, namely,14.9%. In the course of the CNT-HFM (-1.0 V) operation, the increment and the growth of the trans-membrane pressure was the lowest, only half of the PVDF-HFM. All these results showed a more excellent performance of CNT-HFM on the separation performance and the ability to retard fouling. |
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