Study On Aerobic Composting And Anaerobic Digestion Of Sewage Sludge And Garden Waste For Producing Biological Carbon Soil

At present,the process of urbanization in China is accelerating,which leads to the huge production of municipal sludge.Effective treatment of transforming sewage sludge into biological carbon soil for land use is considered as a way to realize sewage sludge recycling.However,whether toxic and harmful substances in sludge will enter the soil and affect the environment and human body is a problem that needs to be solved at this stage.In this paper,aerobic composting and anaerobic digestion of sewage sludge and garde waste to produce biological carbon soil were studied experimentally,and the changes of key influencing parameters and toxic and harmful substances in the two processes were monitored.In this paper,the variation law of temperature,pH,EC value and the properties of composting products during the process of aerobic composting with mixed sewage sludge and garden waste were studied.Aerobic composting experiments of dewatered sewage sludge(DS):garden waste(GW)=1:0,1:1 and 1:2 ratios were carried out respectively.The results showed that DS:GW=1:2 was conducive to faster reaching and maintaining high temperature period and make for nitrogen conservation,with the lowest EC value.Water content,pH,organic matter,fecal coliform bacteria,total bacteria and total nutrients(TN+TP+TK)of compost products were all up to the standards.Total nutrient content was the highest,and seed germination index was the highest,reaching 76.2%,which was conducive to the improvement of soil nutrients and biological growtho of plant.The content of Hg in compost products exceeded the standard limit of acidic soil for land improvement and garden or park standards,but it met the requirements of forestland soil,neutral and alkaline soil of garden or park,neutral and alkaline soil of land improvement.Single sludge compost products could be applied to forestland soil,neutral and alkaline soil of land improvement,but did not meet the requirements of standard for seed germination index of garden or park.In this paper,methane production performance,the change rule of NH4+-N,pH and the properties of digested products during the process of anaerobic digestion of mixed sewage sludge and garden wastes were studied.The anaerobic digestion experiments of excess sludge(ES):garden wastes(GW)=1:0,1:2,1:1 and 2:1,and thermal hydrolysis sludge(THS):garden wastes(GW)=1:0,1:2,1:1 and 2:1 were carried out respectively.The results showed that the anaerobic digestion mixed of ES and GW significantly improved the methane production perfonnance,and when the mixed ratio of ES and GW was 1:2,the methane content remained stable at more than 80%;the anaerobic digestion mixed of THS and GW did not significantly improve the methane production performance,but because of the high temperature pretreatment of THS,its seed germination index was higher than that of ES,and when THS:GW was 1:1,the seed germination index reached 88.5%;the pH,organic matter,fecal coliform bacteria,total bacterial count,total nutrients of the anaerobic digestion products of mixed sewage sludge and garden wastes were all up to the standard,but the seed germination index of digestion products of ES:GW=1:0 and THS:GW=l:2 digestion products did not reach the standard limit of garden or park mud;the Hg content of digestion products exceeded the standard limit of acid soil of land improvement and garden or park,and the EC value of products exceeded the standard limit of acid soil of garden or park.Through the standard limit of argillaceous soil for garden or park,digestion products meet the requirements of applying to forestland soil,neutral and alkaline soil of land improving.