Research On Anaerobic Digestion Of Municipal Organic Refuses And Its Nutrient Adjustment And Control

With the increase of the quantity of municipal solid waste (MSW), the treatment of MSW has become an important environmental challenge. Anaerobic digestion treatment is a good approach for resource utilization of municipal organic refuses (MOR). During MOR anaerobic digestion organic fraction of refuses is converted to methane by fermentation. This thesis is based upon microbial nutrient theory and focuses on enhancing conversion efficiency of MOR and methane productivity through adding trace metal ions and adjusting the C/N ratio of MOR by adding sewage biosolids. The influence of coal ash residues to MOR anaerobic digestion is studied sequentially.Considering of economical and safe aspects comprehensively, the optimal addition quantity of trace metal ions-Fe²⁺, Co²⁺ and Ni²⁺ is 0.9-1.2 mg/(L·d), 0.09-0.12 mg/(L·d) and 0.18-0.24 mg/(L·d) correspondingly, according to results of comparative expenriments and single factor experiments of co-digestion for MOR and sewage biosolids. The results show that the biogas productivity, the conversion efficiency of organic fraction, the maximum specific rate of biogas production and methane content in biogas increase by 40%, 15%, 50% and 5% correspondingly, and the stability of digestion system is enhanced, the digestion period is shortened and the problem of the volatile fatty acid accumulation is solved effectively. In addition, Fe²⁺, Co²⁺ and Ni²⁺ can activate bacteria only in methane phase, not in hydrolization-acidification phase. It is an efficient path to enhance anaerobic digestion by adjusting nutritive proportion and adding trace metal ions.The single factor experiments with the refuse containing coal ash residue were carried out. The results show that the biogas productivity, the methane content in biogas, the maximum specific rate of biogas production increase, and digestion period is shortened with the increase of coal ash residue content in raw materials of digestion from 5% to 25%, however, the water consumption increases to reach the certain water content and the volume load rate decreases by 2% to 5%. The trace metal elements in...