Removal Of Mtbe By Adsorption Cooperated With Biodegradation

Biodegradation of MTBE by Methylibium petroleiphilum PM1 was investigated in this paper.The results showed that the optimum pH was 7.0 for PM1 and oxygen was essential to the degradation.In the reaction system with cells of 0.92g/L,47mg/LMTBE could be degraded completely in three hours which reflected the high metabolic capability of PM1.The intermediates such as ter/-butyl alcohol(TBA),2-hydroxy isobutyrate (HIBA) and formic acid were detected during MTBE degradation.It was presumed that isopropanol was not the intermediate of MTBE degradation. Furthermore,the degradation of MTBE could be enhanced by the addition of readily metabolizable organic substrates such as yeast extract,beef extract and tryptone.The adsorption equilibrium and kinetics of MTBE onto granular activated carbon(GAC) have been studied in the present work.The equilibrium data could be fitted by both the Langmuir isotherm model and the Freundlich isotherm model which reflected that GAC had good capacity adsorbing MTBE.The maximum sorption capacity of GAC for MTBE was 204.1mg/g.Analysis of mechanism revealed that at the initial stage of adsorption,external mass transfer was the main rate controlling step.When the amounts of organic molecule which have reached external activated carbon increased to a certain degree,the sorption process became intraparticle-diffusion-controlled.In the solution with cells of 0.12g/L,the regeneration rate of activated carbon was 52.9%.The biodegration by PM1 made MTBE desorb from GAC,so the adsorption sites opened again forming the function of adsorption cooperated with biodegration.The packed-bed reactor with GAC to degrade MTBE continuously was developed.Compared with the two bio-membrance treatments respectively using activated sludge and pure strain of PM1,it was found the reactor with pure strain of PM1 could remove MTBE more efficiently. Though this treatment required more time before the membrane started up successfully,the removal rate was still high,because the GAC could adsorb MTBE efficiently when the cells concentration was low.The removal rate kept above 90%since the biomembrane hung up successfully and TBA was deteceted in the effluent water.The result of microbial community DNA profiling determined by denaturing gradient gel electrophoresis(DGGE) indicated that PM1 was the predominant bacterium during the whole stable operation.Moreover,the removal rate of the reactor could be advanced by the addition of yeast extract.