Thermal Hydrolysis Pre-treatment Of Sludge Combing High Temperature Anaerobic Digestion Technology Pilot Test And The Research Of Methanogens Community Structure Diversity

With the increasing emphasis on the environmental pollution control, the quantity and scale of urban sewage treatment plants are increasing, and the amount of sludge generated is also increasing. The sludge is rich in organic matter, nitrogen, phosphorus and other plant nutrient elements, but also contains heavy metals, pathogenic bacteria and other toxic and harmful substances, so reasonable disposal of sludge has become an important issue. Anaerobic digestion is the most widely used methods of sludge stabilization and recycling. With the national sustainable development and environmental regulations introduced, the technology will have a more broad prospects for development. In this paper, taking the primary sludge and excess sludge of waste water treatment plant in Qingdao city as the research object, the CambiTM Thermal Hydrolysis Pre-Treatment(THP) technology was studied to investigate the effect of THP on the high temperature anaerobic digestion of sludge, at the same time, the community structure diversity of methanogens in anaerobic digestion sludge was studied with the combination of molecular microbiology technology from the microscopic point of view. The main conclusions of this paper are as follows:(1) After THP, the average particle size of sludge was smaller, and the organic matter was released, which was favorable for the improvement of the efficiency of the subsequent anaerobic digestion treatment. Primary sludge after THP, large organic matter particles were hydrolyzed into small particles or small molecular matters that easy to be degraded. The average particle size of sludge reduced from 233.37μm to 129.17μm; Excess sludge after THP, the organic matter was effectively dissolved, the average particle size of excess sludge reduced from 44.66μm to 9.07μm. After THP, the SCOD, soluble carbohydrate and soluble protein of the primary sludge and excess sludge were 13, 95, 19 times and 45, 19, 29 times, respectively, and the content of dissolved organic matter in the sludge was improved.(2) THP treatment can effectively improve the gas production performance of the sludge anaerobic digestion, and also improve the gas content of the sludge anaerobic digestion. After THP, the effects of different temperatures on the performance of sludge high temperature anaerobic digestion show: under the condition of 53℃, the gas production rate of Pt(primary sludge after THP), Wt(excess sludge after THP) were increased by 21.93% and 33.12% respectively compared to P(primary sludge) and W(excess sludge), P:Wt(1:3) and Pt:Wt(1:3) were increased by 12.36% and 16.28% compared with P:W(1:3). Under the condition of 55℃, the gas production rate of Pt, Wt were increased by 19.96% and 39.14% respectively compared to P and W, P:Wt(1:3) and Pt:Wt(1:3) were increased by 26.44% and 31.13% compared with P:W(1:3). Compared with 53℃, the high temperature anaerobic digestion of sludge at 55℃ made higher gas production, the rate of anaerobic digestion gas production of P, Pt, W, Wt, P:W(1:3), P:Wt(1:3) and Pt:Wt(1:3) at 55℃ were increased by 3.69%, 2.00%, 6.70%, 11.52%, 4.56%, 17.66% and 17.91% compared with 53℃, and the conversion efficiency of VSR, SCOD, soluble carbohydrate and soluble protein were also better than that of 53℃.(3) Improvement of gas production performance of sludge after THP on high temperature anaerobic digestion was related to the species, contents and the community structure of the dominant methanogens. Taking 53℃ and 55℃ for example, the species richness index of excess sludge before and after THP is 2.07, 1.81 and 2.32, 1.81; after THP, the proportion of the dominant methanogens in anaerobic digestion system become higher, the dominant methanogens at 53℃ anaerobic digestion system increased from 72.92% to 81.25%, the dominant methanogens at 55℃ anaerobic digestion system increased from 12.50% to 22.92%, compared to sludge before THP. the gas production performance of sludge become higher as long as the dominant methanogens become more; Under the condition of 53℃and 55℃, the species and community structure of the dominant methanogens in the anaerobic digestion system of the sludge were changed, which resulted in the change of the gas production performance in different temperatures.