| In recent years, demand of people for high quality drinking water is growing continuously with sustained and rapid economic development. Therefor, the pollution of water environment include water resources is increasingly serious which put forward new requirements for drinking water purification process. Especially, the conventional dringking water treatments are powerless to remove ammonia or race synthetic organic matters. In this paper, membranes bioreactors(MBR) are employed as core technology instead of traditional technology to format short-hybrid process to treat water resource loading with ammonia and synthetic organics for improvement of treating efficiencies. Futhermore, MBR is combined with nanofiltration(NF) and powerded activated carbon(PAC), respectively, to form advanced treatment and improve the safety of drinking water.Optimization process is taken in this research to improve the performance of MBR on micro-pollutants removal. Analysis on unit functions of MBR system indicates that aeration process is able to partly remove volatile organic contaminants in raw water, while bio-degradation process is the main way of ammonia and organic matters removal. Enhanced contaminants removal performances are achieved by increasing the stirring intensity of mixed liquor in MBR tank. When HRT is operated at 0.5 hour, satisfactory removal efficiencies on ammonia, total organic matters and trace synthetic organic compounds are obtained. In addition, MBR process could effectively reject microorganisms by filtration and reduce AOC, disinfection by-products and improve the microbial safety of the effluent.On the other hand, nanofiltration is commonly used for drinking water advanced treatment. In this paper, NF is employed as post-processing of MBR to treat micro-polluted water. The results indicate good ammonia removal efficiencies of the hybrid process which is attributed to bio-process of MBR. Moreover, mitigation of membrane fouling caused by MBR process is observed as well as high flux of NF. The hybrid process of MBR and NF also has good removal performance of turbidity, dissolved organics and micro synthetic organic compounds. Concentrated water of NF is back-flowed to MBR for complete treatmemt and cost reduction. The back-flow process causes accumulation of mineral and some orgnic components in MBR, however, which was acceptable and qualified effluent is observed during the whole operation.In order to improve the MBR performance of micro-pllouted water treatment, actived carbon is employed in this study to set up hybrid process with MBR. In the experimental operation, powerded actived carbon(PAC) assisted MBR(PAC/MBR) with PAC adding in PAC bulk showed better performance than a series process of MBR following granular powerded carbon(GAC) filtration. The former has higher removal efficiencies of ammonia, TOC and nitrobenzene as well as much higher nitrobenzene tolerability. In the start-up phase of PAC/MBR process, high density of PAC in the reactor provides high removal efficiency of organic contaminants by adsorption. However the PAC adsorption is useless on shortening the mature process of nitrifying bacteria which costs about 30 days in this study. During the long-term operation, continuous dosing of PAC can increase the removal efficiency of various pollutants stably. In addition, additional PAC can effectively alleviate the membrane fouling process of MBR and extend the cleaning cycle from 5 days to 8 days.Researches about the principle of PAC effects on MBR enhancement showed that in the initial phase of dosing PAC removes trace synthetic organic compounds including nitrobenzene and 2,4,6-trichlorophenol as well as humic acid, fulvic-like and other non biodegradable organic matters by adsorption. PAC becomes microbial carrier which promotes enrichment of microorganisms and improves the biomass and bio-activity of MBR system when the adsorption capacity reduces. Thus, it successfully improves stability of microbial system in MBR. When treating with raw water loading nitrobenzene and other synthetic organic compounds, microorganism acclimation process is observed in MBR system. The maximum degradation rate of activated sludge in MBR and PAC/MBR for nitrobenzene and 2,4,6-trichlorophenol increases from 0.09 and 0.17 μg/(mg MLSS?h) to 1.83 and 2.67 μg/(mg MLSS?h), respectively. Analysis of microbial population shows that the accumulation of Deinococcus is the main reason of microbial degradation capability improvement.Results of pilot scale test show higher removal efficiencies of membrane combination technology on ammonia nitrogen, DOC and UV254 than ozone-activated carbon process. For nitrobenzene remove the performance of hybrid membrane process is slightly lower, however, when treating with raw water containing no more than 100 μg/L nitrobenzene, effluent of hybrid short-cut membrane filtration processes can stably reach the standards. On the other hand, membrane process is able to reduce AOC which can improve the microbial safety of drinking water while AOC concentration increases after ozone process. Moreover, hybrid membrane technology has shorter process and floor space, which is suitable for site improvement of conventional process and improve the safety of drinking water. |
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