| With the rapid development of urbanism and industry, the categories of pollutants in sewage are increasingly complex.It is difficult to finish the purification tasks of numerous polluted matters, including organic pollutants, nitrogen and heavy metal only making use of a technology of sewage treatment.Therefore, the combination of various technologies have become developmental trend to treating sewage. Nowadays, SBBR (Sequencing Batch Biofilm Reactor) and BER (Biofilm-electrode reactor) are both being explored novel technologies of water treatment.They have respectively advantageous for removal of COD, nitrogen and copper ion.In this study, electrode-biofilm was introduced to the SBBR system of sewage treatment and the study tasks of removing nitrogen, copper ion and simultaneous removal nitrogen and copper ion using electrode-SBBR was brought forward.Based on the theories of biology, electrochemistry and coadjutant effect of each other, the effect on the removal of nitrogen, copper ion and simultaneous nitrogen and copper ion on performance of electrode-SBBR were respectively discussed and the better process conditions of nitrogen and copper ion removal on running of electrode-SBBR system were determined. The capability of nitrogen and copper ion removal were analyzed and appraised on running technique of combined electrode-SBBR.The research could richen the contents of electrics-biology theoretically and could provide scientific foundation for nitrogen and copper ion treatment in sewage practically.According to the components of typical domestic sewage and wastewater contained copper and effluent standard, analytical reagents simulated wastewater. Four sets of reactors in parallel connection were designed and activated sludge from aeration basin of a sewage treatment plant was inoculated to the reactors.According to treating targets, domestication and cultivation of microbes was divided into five phases in sequence, respectively,the sludge domesticated and cultivated, biofilm attached to stuffing, denitrifying microbes cultivated and biofilm attached to the surfaces of electrode, microbes tamed by tiny current and gradient addition of copper ion until the sludge performance was good enough to ensure electrode-SBBR system operating stably.Firstly, the three operating working procedures of electrode-SBBR for three different targets were determined. 8, 6 and 6 operating conditions were respectively designed in accordance with the removal of nitrogen, copper ion and simultaneous nitrogen and copper ion. Considering operating efficiency, the normal operating condition to remove nitrogen was determined as hydraulic retention (HRT) 7.0h, anaerobic 0.5h, aeration 3.5h, settle 3.0h. To remove copper ion, the normal one was determined as HRT 4.5h, anaerobic 4.0h, settle 0.5h. To remove nitrogen and copper ion simultaneously, the normal onewas determined as HRT 7h, anaerobic 0.5h, aeration 4.0h, settle 2.5h.The study on the effects of nitrogen removal on performance of electrode-SBBR in treating sewage: Firstly, the dynamic change of various nitrogens concentration, pH and dissolved oxygen (DO) in whole HRT were investigated. The surprisingly obvious denitrification phenomenon in aerobic phase, namely, simultaneous nitrification and denitrification (SND) was found in this experiment. At the same time, the denitrification in aerobic phase far exceeded what the former and the latter of anaerobic or anoxic phases were achieved in electrode-SBBR system.Furthermore, the causes of come into being these results were respectively analysed from the theories of macroscopical and microcosmic environment Then effects of applied electric current, DO, C/N ratio and nitrate (NO3--N) loading on the removal of nitrogen were respectively examined.The experimental results showed that:①Introduction of electrode in SBBR process contributed to denitrification.The efficiency of denitrification was enhanced as current intensity increased in a certain range.However, higher current intensity resulted in reduction of denitrification efficiency. Meanwhile, it was concluded that the electric field leading to the increase of denitrification rate was largely due to electric current accelerateing denitrification.The maximum total nitrogen (TN) removal rate was 82.86% at an applied current of 80mA.②DO concentration is important parameter in electrod-SBBR system. Concentration of DO must keep a suitable range.The best rate of denitrification was achieved on the DO level of 4mg.L-1, the removal rates of TN, ammoniac nitrogen (NH3-N) and NO3- were achieved respectively of 87.18%, 95.0% and 37.64%.③The increase of C/N ratio contributed to denitrification. However, it had no obvious influence on denitrification as C/N ratio exceeded some numerical value.④As NO3- loading increased from 20mg.L-1 to 40mg.L-1, the removal rates of TN and NO3- respectively heightened 18% and 27%. Whereas, excessive NO3- concentration also decreased the efficiency of denitrification.The experiment results showed the removal rate of chemical oxygen demand (CODCr) remained more than 80% on the condition of electric field when DO concentration exceed 3.0mg.L-1 or C/N ratio exceed 5 in electrode-SBBR system. Experiment indicated current domestication lighten the adverse influence of electric field on activity of heterotrophic bacteria.The study on effects of copper ion removal on performance of electrode-SBBR in treating Sewage: Firstly, the effects of current intensity, accompanying ions, copper ion concentration and pH on the removing copper ion were respectively studied.Then the change of copper ion concentration in total HRT was investigated.The results showed that:①In the same condition,compared with single SBBR technique, the removal rate of copper ion was increased by only about 5% using electrode-SBBR,Experimental results indicated the removal of copper ion was mainly by the biosorption. Meanwhile, the increase of current intensity availed to the removal of copper ion on lower current intensity from 10 to 40mA and a highest copper ion removal efficiency of about 98% was achieved at a current level of 40mA. However, higher current level had bad influence on the efficiency of electro-deposition.②The introduction of certain concentrations of anions (SO42-,NO3-and Cl-) and cations (Zn2+ and Pb2+) to electrode-SBBR system resulted in the increase of effluent copper ion concentration,especially Cl- level of 45mg.L-1 and Pb2+ level of 30mg.L-1 had evident influence on copper ion removal.③The removal efficiency of copper ion overall exceeded 92% as copper ion concentration increased from 10 to 100mg.L-1. The maximum copper ion removal efficiency was 98.48% at an applied copper ion of 30mg.L-1.Effluent copper ion concentrations were above criterion value (1.0mg.L-1) when copper ion loading exceeded 70mg.L-1).④pH had obvious influence on the removing copper ion.The ranges of 4.0 to 4.5 and 9.0 to 10.0 of pH were disadvantageous for the copper ion removal and the latter had more adverse influence on copper ion removal by comparing the former. The highest copper ion removal rate of 97.78% was achieved in the range of 4.5 to 7.5 of pH.⑤The perfect effect of copper ion removal was achieved instantaneously (HRT less than 10min) by biosorption.In aerobic phase. It is adverse to copper ion removal due to COD competing with copper ion for junction of zoogloea. The double actions of biosorption and electro-deposition led to the decrease of copper ion concentration in the beginning phase of sedimentation.Whereas the efficiency of electro-deposition decreased as the settle time prolonged.⑥In process of copper ion removal, the removal rate of COD had not obviously decreased compared with the process of nitrogen removal. It showed copper ion domestication lighten the inhibition of copper ion on activity of bacteria.The study on effects on simultaneous removal of nitrogen and copper ion on performance of electrode-SBBR in treating sewage: the effects of current intensity,DO and C/N ratio on the simultaneous removal of nitrogen and copper ion were studied respectively.The research showed that:①The increase of current intensity in a certain scale availed to removing nitrogen, but not availed to removing copper ion.The impact on copper ion removal was negligible in lower current from 10 to 90mA.Excessive current intensity decreased the removal efficiency of copper ion.The maximum TN removal rate was 67.69% at an applied current of 60mA.②The removal efficiencies of nitrogen, copper ion and COD were enhanced as DO concentration increased in a certain scale.③The increase of C/N ratio contributed to the removal nitrogen and COD, but had no significant influence on copper removal.④In the process of nitrogen removal, above three parameters had little influence on denitri- fication in comparion with the process of copper ion removal.lt indicated that the existence of coppr ion caused inhibitory effect on nitrobacteria and denitrifying bacteria resulting in effect lag.From above results, it was totally concluded that electrode-SBBR was effective upon the removal of nitrogen and copper ion in sewage and synchronously made COD biodegraded highly effectively. The electrode-SBBR technology had greatly wide space of research and application in the future.Finally, the shortages and advice in this paper were put forward and some further researches were suggested on the following directions.
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