ABSTRACT
Objective To screen the flocculatnt-producing strain from activated sludge that can treat azo dyeing wastewater effectively.Methods Screening and rescreening were used to acquire the strain which possesses high efficiency of flocculatant production and the strain was identified.The character of microbial flocculant(MBF) and the ability to treat azo dye wastewater were studied.Results A strain of high-efficiency bioflocculant-producting bacteria(AJ-6),initially identified as Alcaligenes sp,was screened.The bioflocculant produced by the strain was able to flocculate kaolin suspension with 94.4% and fly ash suspension with 98.9% respectively.The flocculation activity distribution tests showed that the active components of the bioflocculant existed in the supernatant fluid after centrifugation.It had good treatment efficiency in treating azo dyes methyl orange wastewater.The maximal efficiencies of removing CODCr and chroma from the wastewater were 81.3% and 94.2%.Compared with the other flocculants,the performance of MBF was better than that of polyacrylamide(PAM),aluminum sulfate,ferrous sulfate.The MBF was more thermostable when treated with 100 ℃ for 30 min,and the animal toxicity test showed that the MBF had no acute toxicity to mice.Conclusion The bioflocculant produced by the strain AJ-6 is applicable to treat azo dyeing wastewater and can be also used for the other wastewater.