Decolorization Of Dyeing Wastewater By Aspergillus Flavus A5p1 Immobilized With Polyurethane Foam

China is a large textile industry country,and a large number of related enterprises discharge wastewater every year.Most dyes are refractory substances that are discharged directly into the environment without treatment,which will lead to degradation of the quality of receiving water and destruction of the overall ecological balance.Biological method is favored as an environmentally friendly treatment method,but the traditional biological method has some problems such as poor stability.Biological immobilization technology is one of the strategies to solve such problems.In this paper,the practical wastewater is taken as the research object,and the research work is carried out from the following three aspects:（1）using immobilization technology to shorten the decolorization cycle of practical dyeing wastewater;（2）using cheap and easily available materials as culture medium to reduce the cost of treatment;（3）constructing a reactor so as to be continuous wastewater treatment.The decolorization rate curve of Aspergillus flavus A5P1 to practical dyeing wastewater was almost the same as that of cell growth.The decolorization rate increased continuously and reached the highest decolorization rate of 61%on the fifth day,and the biomass also reached the maximum of 2.8 g·L^-1on the fifth day.When polyurethane foam D-0 was used to immobilize A5P1 to decolorize dyeing wastewater,the decolorization rate on the first day was 1.7 times that of the unimmobilized A5P1,and the decolorization rate reached 66%on the second day.while the maximum decolorization rate of free cells was 61%on the fifth day.It can be seen that the immobilization shortened the treatment cycle of dyeing wastewater.Soybean powder,corn powder,bran powder and ammonium sulfate were selected as nitrogen sources and sucrose as carbon source to optimize the composition and dosage of the culture medium.The final optimized culture medium was determined as follows:0.4%sucrose,0.3%bran powder,pH=5.0,dyeing wastewater as the substrate.Compared with the original culture medium,the total cost decreased by 95%.When the optimized medium was applied to immobilized cells,the change trend of pH was similar to the decolorization rate,both of which increased first and then flattened.The decolorization rate increased rapidly in the initial stage and reached the highest decolorization rate of 71%on the second day.The factors affecting decolorization of dyeing wastewater from immobilized Aspergillus flavus A5P1 were investigated by shaking flask culture.It was found that the effect of temperature was not significant in the range of25℃⁴0℃,the optimum initial pH value was 5.0,the decolorization process of different concentration wastewater was similar,and the maximum decolorization rate of raw wastewater is higher than that of diluted wastewater.The reuse of immobilized cells was investigated in shaking flask,the decolorization rate gradually decreased from 63%to 55%after four reuses.After that,an aerated reactor was built and operated to observe the decolorization of the practical dyeing wastewater.It was found that during the 25 days of reactor operation,the decolorization rate maintained at about 67%in the first 22 days and the highest decolorization rate was 70%.It can be seen that the stability of the system is good.