Study On The Progress Of The Treatment Of Phenol By An Electrochemical Oxidation-biological Technology

Phenol is a kind of toxic and biologically refractory organic pollutants which hadgreat damages in water treatment. Electrochemical oxidation of phenol for completemineralization was so expensive that it could not be widely used. The treatment ofphenol was studied by an electrochemical oxidation-biological technology. First thephenol was degraded by electrochemical oxidation which could interrupt thebenzene ring and improve the biodegradability of the phenol wastewater, and thenthe effluent of electrolysis was transferred into a biological progress for furtherdegradation. The electrochemical oxidation progresses of phenol on Pt electrode andTi/RuO2-TiO2electrode have been studied by cyclic voltammetry. And the effects ofelectrolysis reaction conditions on electrochemical degradation as well asbiodegradation have been investigated. Two kinds of halotolerant bacteria whichwere facultative anaerobes and aerobes were domesticated by wastewater-gradientmethod. Halotolerant aerobes were immobilized with sodium alginate. Thedegradation of electrolysis effluent by halotolerant bacteria had been investigated.The main results were as follows:(1) The nunber of facultative anaerobes was near to1.0×105N/mL, and thenunber of aerobes was near to1.0×106N/mL. The dominant bacteria were formedin the progress of domestication. The COD removal ratio of degradation byimmobilized aerobes was higher than that of free aerobes.(2) The changes of electrochemical oxidation condition of phenol would greatlyimpact on COD removal and biodegradability of the wastewater. The choices of thesupporting electrolyte affected on the electrochemical oxidation of phenol. In thechloride system, chlorophenol was generated and gradually disappeard duringelectrochemical oxidation of phenol. The optimal condition of electrochemicaloxidation of phenol on Pt electrode is as follow: pH=9, i=60mA/cm2, NaCl=20g/L.Under above conditions and electrolysed time of150min，phenol could not bedetected, the COD value reduced to451mg/L, BOD value increased to167mg/L,B/C ratio reached to0.37which was the maximum of the biodegradability inprogress of electrooxidation. After the progress of electrooxidation on Pt anode, phenol wastewater was transferred into a facultative-aerobic progress. The effluentof electrolysis was treated by facultative anaerobes, after two day′s degradation,COD value reduced to317mg/L, B/C reached to0.65. Then, the wastewater wastreated by immobilized anaerobes, after two day′s degradation, COD value reducedto35mg/L, COD removal ratio finally reached to96%.(3) CV analysis showed that oxidation potential on Ti/RuO2-TiO2anode was0.83V which was higher than that on Pt anode. The optimum condition ofelectrochemical oxidation of phenol on Ti/RuO2-TiO2electrode was: pH=10,i=60mA/cm2, NaCl=20g/L. Under above conditions and electrolyzed time of150min，phenol could not be detected, the COD value reduced to519mg/L, BODvalue increased to156mg/L, B/C ratio reached to0.3which was the maximum ofthe biodegradability in the progress of electrochemical oxidation. After theprogress of electrochemical oxidation on Ti/RuO2-TiO2anode, phenol wastewaterwas transferred into a facultative-aerobic progress. The effluent of electrolysis wastreated by facultative anaerobes，after two day′s degradation, COD reduced to384mg/L, B/C reached0.54. Then, the wastewater was treated by immobilizedaerobes, after two day′s degradation, COD value reduced to74mg/L, COD removalratio finally reached to92%.