Study On Solar Drying And Aerobic Composting Of Municipal Sludge

With the rapid development of China's urban sewage treatment industry,the output of urban sewage sludge increased by about 10% per year.The disposal and utilization of municipal sludge has attracted people's attention.Dehydration sludge moisture content up to 75%~85%,complex composition,perishable,and accompanied by the stench,sludge if not been handled properly,will form the second pollution.The sludge contains large amounts of water,is not easy to pile up,transport and disposal,therefore,must carry out the depth of the sludge dewatering,which is the basis of sludge reduction,harmless and resource treatment,is also a key step.Solar energy is a kind of clean,safe,cheap and renewable green energy,and is inexhaustible.China has abundant solar energy resources,the use of solar energy on the sludge drying process can not only save energy,but also reduce carbon dioxide emissions.In this paper,the dewatering sludge produced in East sewage treatment plant of Handan was studied,and the solar sludge drying and aerobic composting process were carried out,also the compost products with certain fertilizer have been made,which is in order to achieve the target of reduction,harmless and stabilization,and so that the sludge can get resource utilization.First,to test and analyze the influence factors of sun drying of sludge,optimize the sludge drying conditions,then sludge,which water content were 60-70% and 20% respectively after pretreatment by solar drying,and the sludge conditioner were mixed according to the mass ratio of 80:19:1 and 80:18.5:1.5.The mixture was studied on aerobic composting.In this experiment,the changes of parameters in the composting process were studied,the indicators of determining the maturity degree were proposed and the relatively good material ratio was selected,which can be more efficient to carry out the composting and improve the effectiveness of the compost product.In summer,the air temperature in solar greenhouse can rise to around 60 degrees Celsius.after 5 days,the sludge with 20 mm thick,which moisture content is up to83%,can be dried to the moisture content of 30.5%.Air flow rate,temperature,humidity and solar radiation intensity are the main factors affecting the drying rate of sludge.The thickness of sludge have a great influence on drying rate,the thinner thethickness of sludge,the more easily the water was taken away,the drying rate was higher.In a year,the solar energy utilization and the drying rate are low on the month with less irradiation,so the solar energy drying of sludge should be mainly placed in the month of irradiation.Due to the seasonal nature of the solar radiation intensity,the use of more efficient heating equipment is conducive to overcome this problem.In the case of having enough space,it is a good choice for sewage treatment plant in small and medium sized cities,which has rich solar energy,to use solar energy for sludge drying.These piles were mixed according to two ratio above,by analyzing the mixing piles of changes appearance,pile temperature,moisture content,p H,seed germination index,two different ratio of the piles can be completely decomposed after 21 days,products meet the "urban sewage treatment plant sludge disposal of agricultural with mud"(CJ/T 309-2009),and are the qualified products.These indicated that it is feasible to aerobic composting with different water content of sludge and sawdust,straw mixed.