Study On Application Of Starch-based Degradable Flocculants In Wastewater Treatment And Sludge Resource Disposal

Starch derivatives with various adsorption and flocculation properties can be obtained when side chains or groups with adsorption and flocculation functions are introduced into the starch framework.Therefore,it has become a research hotspot in sewage treatment and sludge resource disposal.Starch-based degradable flocculant(SDF)was synthesized by using etheriated cationic starch and PAM as the main raw materials and cerium nitrate as the initiator.In this paper,the optimal conditions for SDF synthesis were determined and the SDF was characterized.Secondly,the flocculation effect of SDF in three kinds of sewage was investigated.At the same time,the degradation performance of starch based degradable flocculant was investigated with PAM as comparison.Then SDF and PAM were used to flocculate the aquaculture wastewater,and the flocculation effects of the two were compared.Finally,the composting performance of SDF flocculated sludge was explored through sludge composting experiment,and the compost products were evaluated by planting experiment.The results are as follows:(1)SDF can be successfully grafted by dissolving in water and can be directly used in wastewater treatment.The results showed that amides were introduced into the starch chain,the starch structure was changed,and PAM was successfully grafted onto the starch branched chain.The COD removal rate of SDF in the treatment of printing,dyeing wastewater reached95.56%.The removal rate of COD,SS and light transmittance are 97.6%,99.2% and 98.3%,respectively.The flocculation results of SDF were better than PAM,and the turbidity was reduced by 50% and 43.2%,respectively.(2)SDF can be effectively degraded by microorganisms and can be completely degraded within one year.The experimental results showed that the microorganism proliferation in SDF was faster,the adaptation period of microorganism in PAM medium was 2.5 times that of SDF,and the p H variation in SDF was large,which was caused by microorganism decomposition of SDF.Simulated natural degradation experiments showed that a large number of microbial communities were found in SDF solution after half a year of culture.The p H,relative viscosity and molecular weight changes of SDF decreased by 25.6%,91.4% and 62.98%,respectively,while the corresponding changes of PAM were 23%,58.2% and 18.84%,respectively.The experiments showed that SDF had good degradation performance.(3)SDF can effectively realize the flocculation and dehydration of sludge,and the whole process of composting can be realized after flocculation.The results of sludge flocculation experiment show that the supernatant after SDF flocculation experiment shows good performance in COD removal rate,SS removal rate and turbidity removal rate.Sludge after flocculation has advantages in CST,SRF and vacuum filtration time.SEM scanning micrograph shows that the sludge after SDF flocculation has more voids and uneven surface.The results of compost experiment showed that the temperature in the SDF reactor increased faster.The temperature was higher than 55℃ for 20 days,and the maximum temperature was 68.5℃.The final moisture content decreased by 30.2%,the total weight decreased by about 1/3,and the organic matter content decreased by 15.7%.The temperature of PAM reactor rises slowly,and it does not enter the high temperature period,and the water content only decreases by 10.96%,and the organic matter decreases by 3.5%.The planting experiment showed that SDF compost product was beneficial to the growth of crops.