Design And Application Of Technology For Sludge In A Sewage Treatment Plant In A City

Sludge,the residue of sewage treatment,contains a large number of organic and inorganic pollutants,including refractory macromolecules,small molecules,toxic heavy metals,pathogenic bacteria,viruses and so on.A large number of toxic and harmful sludge will be produced in the treatment process of sewage treatment plant.If the sludge is not thoroughly purified and stabilized,or even dumped randomly,groundwater will be seriously polluted and soil ecological environment will be destroyed.How to treat sludge in depth is becoming increasingly prominent.The treatment and disposal of sludge has become the focus of comprehensive environmental management.At the same time,the proper treatment of sludge has become an urgent problem to be solved in the sewage purification and treatment industry.The sludge produced by a large sewage treatment plant in a city is about 80-110 t/d per day.After the planned sewage treatment plant runs,the sludge output of the city reaches about 200 t/d,and the sludge output is huge.The sludge treatment mode of the sewage treatment plant in this city is more complex,the water content of the sludge is higher,the treatment process is not uniform and the management is difficult.At the same time,in the current treatment process,due to the aging of equipment.With the improvement of industry standards,the sludge treatment of the municipal sewage plant has not met the requirements of the government,and it is urgent to improve the sludge disposal methods.Starting from the source and nature of sludge,the study enumerated the pollution caused by the random discharge and landfill of sludge,analysed the present situation and ways of sludge treatment and disposal in a municipal sewage plant.And the study finded the existing problems in sludge disposal in this city,and put forward the construction of a new sludge disposal project according to the present situation of sludge treatment in this city.Based on the prediction of sludge production in this city,the sludge which is 80% water content treatment scale of 200 t/d is determined,and the advantages and disadvantages of sludge landfill,sludge incineration,sludge composting and solar drying were compared.Through comparison,it is determined that sludge deep dewatering technology will reduce sludge water content to about 60%,and then solar drying technology will be used for dewatering.According to the determined process plan,the process and characteristics of sludge deep dewatering and solar drying are analyzed.The selection,process and general layout of the core process units are optimized.The design and research of the sludge pressing system and solar drying system are carried out respectively.After dewatering,the sludge with water content of about 65% entered the solar drying system,and then was treated by solar drying.The water content of sludge is reduced to below 40%.At the same time,the balance relationship between total energy and energy sources was verified.Under unfavorable conditions in winter,besides solar radiation energy,auxiliary energy was needed to provide energy for sludge drying.In other seasons,the energy needed for sludge drying was basically supplied by solar radiation and solar collector.The deodorization and ventilation systems are designed and studied.In the process of project implementation,fresh air supplement system was set up.The air volume is about 35000m3/h and the deodorization air volume is 28000m3/h.The project has been put into operation.The average daily mud intake and water content in and out of the sludge from July 2017 to May 2018 were monitored,and the trend of the data was analyzed.The results showed that the average daily sludge volume of the project had little change,basically stable at 79-82.5 t/d,the water content of sludge entering the system maintained between 80% and 84%,the drying efficiency of the system was better,the water content of sludge discharging was below 40%,which can meet the requirements.When the effect was best,the water content of sludge discharging was as low as 24.3%.While synthetically analyzing the operation effect of process technology and method measures,the economic analysis was carried out for the application of "solar energy drying process" in sludge treatment project of sewage treatment plant in this city.The research showed that the total investment of the project was 69.674 million yuan,and the unit operating cost was 91.56 yuan/t(80% sludge),which had good economic benefits.At the same time,this study puts forward constructive suggestions on environmental management and monitoring in the process of project implementation,which brings certain ecological and social benefits.