Study On Residual Sludge Ecological Treatment By Hermetia Illucens

The excess sludge produced in the process of urban sewage treatment has the characteristics of large output,complex composition,containing a variety of harmful substances,etc.If not treated scientifically,it will lead to new ecological environment risks.Because it can survive well in domestic garbage and animal excrement,the saprophytic water flies are mostly used to deal with agricultural organic waste,so as to realize the resource utilization of waste.However,there are few reports on the research on the survival,growth characteristics and ecological treatment of Hermetia illucens in urban residual dehydrated sludge.Therefore,the research on the ecological treatment technology of Hermetia illucens to excess sludge can provide an important theoretical basis for a deeper understanding of the growth characteristics of Hermetia illucens,and provide a scientific basis for the ecological reduction and control of urban excess sludge.In this paper,the dehydrated residual sludge from the Hermetia illucens and the filter press of the first sewage treatment plant of Taian was studied.The effects of different proportion of sludge matrix on the growth characteristics of Hermetia illucens were studied.The migration and transformation of organic matter,nutrient elements and heavy metals in different proportion of sludge matrix were studied.The main research results are as follows:(1)The effect of different sludge substrates on the growth characteristics of the Hermetia illucens showed that the Hermetia illucens could survive and be effectively raised in all sludge substrates,and the body composition showed significant differences due to the different proportion of substrate sludge.The organic carbon content,nitrogen content,phosphorus content and protein content were 15.99~25.85%,30.83~50.15 g/kg,29.27~39.15 g/kg,137.29~178.71 g/kg,respectively.The enrichment effect of heavy metals in the body of Hermetia illucens is different due to the different types and forms of heavy metals.The exchangeable content of heavy metals Cd is high and the bioavailability is high.Hermetia illucens body can enrich 8.54~21.66% of heavy metals Cd in the initial matrix,and only 2.11~4.55% of the initial matrix for heavy metals Cu.(2)Study on the weight reduction effect of sludge substrate showed that the dry weight reduction of the substrate was negatively correlated with the sludge proportion(0~60%)and positively correlated with the organic matter.The addition of wheat bran increased the content of organic matter in the sludge substrate and improved the reduction effect of the substrate.The dry weight reduction of the sludge was positively correlated with the sludge proportion,and the removal rate was the highest(14.72%)when the sludge content was 60%.(3)Study on the ecological treatment of sludge by Hermetia illucens showed that the treatment of sludge substrate by Hermetia illucens can reduce the organic matter content of each group,and the reduction rate is 9.52%-1.13%.In heavy metal experiment,Hermetia illucens larvae could reduce Pb,Cd,Cr and Ni in sludge substrate to different degrees.Among them,Hermetia illucens has better curing effect on Pb and passivation effect on Ni.The proportion of residue Pb in the four forms increased from 4.92~16.31% to 34.38~66.85%,and the proportion of exchangeable Ni decreased by 15.02~33.02%.The heavy metals Pb,Cd,Cr,Ni and Cu in the sludge substrate were accumulated by the Hermetia illucens,and the addition of the Hermetia illucens would have an effect on the formation of the heavy metal form.The passivation effect of Pb was better,and the proportion of residual Pb increased from 4.92~16.31% to 34.38~66.85% before and after treatment by the Hermetia illucens.The treatment of black water fly had certain passivation effect on Cd,Ni and Cr,but it was not obvious.(4)The feasibility study of the resources in the sludge treatment process showed that the protein content of the Hermetia illucens was 13.72~17.71%,and a certain amount of the Hermetia illucens could be harvested as the breeding feed while the sludge was treated,and the metal index of the body weight of the fly met the requirements of GB 13078-2001.And it can be used as compound premixed feed for layers(pigs)and broilers(growing finishing pigs);after treatment,the nutrient elements nitrogen(0.96~2.63%)and phosphorus(2.31~2.96%)in sludge matrix meet the requirements of organic fertilizer,and the heavy metal content meets the requirements of GB 4284-2018,which can be used as farmland fertilizer.