Effect Of As(Ⅲ) At Different Concentrations On The Performance Of Activated Sludge In SBR System And The Study Of Arsenite-oxidizing Bacteria

The presence of arsenic in nature has been of great public concern because of its high toxicity. In recent years, a lot of study has been done for arsenic treatment. Activated sludge process is a common method for the treatment of heavy metal, as soon as the arsenic, but there is no report for the affect of the arsenite to the activated sludge system. Firstly, this study researched the affect of the arsenite to the activated sludge system. Two parallel sequencing batch reactors R1and R2were used in this study. Synthetic sewage water was prepared as the feeding for the system, while As(Ⅲ) was only added in the influent of the reactor R1. Furthermore, the concentration of As(Ⅲ) in the influent of R1gradually increased according to the period. The effect of As(Ⅲ) at different concentrations on the activity of activated sludge was studied through testing the effluent quality and evaluating the activated sludge characteristics in these two SBR systems. The main conclusions of this experiment were obtained as follows:(1) during the whole period, the soluble COD in the effluent for the reactor R1is relatively stable at different concentration of As(Ⅲ)(2,10,20mg L-1), while COD removal rate in the rector R1is about5%lower than that in the reactor R2;(2) with stepwise augmentation of As(Ⅲ) concentration in the influent of R1, the characters of activated sludge in R1was influenced:the flocs became disperse and tiny, the settling capacity of activated sludge obviously dropped;(3) based on the periodical microscopic observation of microorganisms in the two reactors during the whole experiment, it is shown that the addition of As(Ⅲ) in R1changed the diversity of microorganisms and the protozoa disappeared in R1.Three strains of microorganisms with high As(Ⅲ)-tolerance were isolated from reactor Rl,which included a strain of yeast and two strains of bacteria. The bacterial strains B1and B2respectively oxidized40%and30%of100mg/L As(Ⅲ) into As(Ⅴ), but the strain of yeast has no As(Ⅲ)-oxidizing activity.