Abstract:Municipal sewage treatment plants yield lots of sewage sludge and the sludge has complex composition. Improper disposal will cause environmental pollution problem. Proper sludge treatment is important to solve this problem. Traditional sludge disposal methods such as incineration and landfill have the drawbacks of high energy consumption and soil pollution problem. Anaerobic carbon fixation is a new sludge disposal method, which has good application prospect. This study adopted anaerobic carbon fixation to treat dried sludge. The thermogravimetric analysis was carried out to assess the effect of process parameters (carbonization temperature and time) on the degree of anaerobic carbon fixation of dried sludge. The influence of process parameters on the physicochemical properties, nutrient indicators, heavy metal content and seed germination index of sludge were investigated and the optimum process conditions were determined by extreme difference analysis of orthogonal tests, taking seed germination index as evaluation indicator. The results indicated that high carbonization temperature and long carbonization time were crucial to ensure that anaerobic carbon fixation of sludge fully completed. Process parameters had significant effects on the properties of sludge. Various performance indicators of sludge treated by anaerobic carbon fixation could meet the standard of municipal sewage treatment plant sludge disposal for landscaping purpose (GBT23486-2009), so the treated sludge could be used as landscaping substrate. The optimum carbonization temperature and time were determined as 600℃ and 1.5h, respectively. In this condition, sludge anaerobic carbon fixation fully completed and the content of toxic and harmful substances such as soluble salts and water-soluble heavy metals in treated sludge were low, which was conductive to seed germination. Seed germination index reached 138.79%, far higher than national production quality standard (70%). Anaerobic carbon fixation treatment and effective process parameters adjustment open up new possibility for sludge resource utilization.