| Along with a large number of urban sludge generated in our country, it has causedserious impact on the environment. As one of the important sludge treatmenttechnologies, anaerobic digestion is widely used in European and American countries,and the development of it has also been vigorously encouraged in our country. Highsolid content of sludge anaerobic digestion has many advantages; it can create necessaryconditions for the ultimate disposal of dewatered sludge. Pilot study of the "thermalhydrolysis-thermophilic single stage anaerobic digestion" and "thermal hydrolysis-thermophilic&mesophilic two-stage anaerobic digestion" process were conducted forthe treatment of sludge of8%9%solid content, which aimed at the feasibility of highsolid content of sludge anaerobic digestion applying to engineering practice.The research results show that, for the "thermal hydrolysis–thermophilic singlestage anaerobic digestion" process, when thermal hydrolysis’s HRT was3days, theremoval rate of organic matter increased along with the HRT of single stage anaerobicdigestion extended. The shortest HRT to meet the requirements of national standards forremoval rate of organic matter was20days. Therefore, overall consideration of theremoval rate of organic matter and methane production rate,25days was the best HRTof "thermal hydrolysis–thermophilic single stage anaerobic digestion" technology, andthe removal rate of organic matter was42.69%, the methane production rate was0.212m3CH4/kgVSSadd,0.496m3CH4/kgVSSremand0.449m3CH4/（m3·d）. Compared with thetraditional sludge anaerobic digestion, under the same HRT, high solid content ofsludge anaerobic digestion can achieve the same removal rate of organic matter andmethane production rate.For the "thermal hydrolysis-thermophilic&mesophilic two-stage anaerobicdigestion" process, when the HRT of thermal hydrolysis was3days and the total HRTof two-stage anaerobic digestion was25days, the removal rate of organic matter was44.01%, the methane production rate was0.231m3CH4/kgVSSadd,0.525m3CH4/kgVSSremand0.523m3CH4/（m3·d）, which performed better than the single stageanaerobic digestion.As an example, if processing500ton dewatered sludge （moisture content80%） perday in Guangzhou city. When compared "thermal hydrolysis-thermophilic& mesophilic two-stage anaerobic digestion-drying" with direct drying process, thedifference of investment costs is not big, both for260000yuan per ton sludge or so（moisture content80%）, but the operating costs of the former is only124.91yuan perton sludge per day （moisture content80%）,45yuan per ton sludge per day （moisturecontent80%） lower than the latter.The optimal technical parameters of high solid content of sludge anaerobicdigestion process are: thermal hydrolysis70℃,3days; Thermophilic anaerobicdigestion55℃,12.5days; Mesophilic anaerobic digestion35℃,12.5days. Anaerobicdigestion can be used as a necessary process for sludge treatment and disposal. When noheavy metals contained, sludge could be disposalled for land use after anaerobicdigestion-deep dewatering; when some heavy metals contained, sludge could bedisposalled ultimately after anaerobic digestion-deep dewatering and drying. |
