Study On The Effect Of Ultrasonic Pretreatment Within Medium-low Intensity On The Peromance Of Anaerobic Digestion Treating Sludge Along With Its Dewatering Ability

Anaerobic digestion process is considered as an important means to realize sludge stabilization,harmlessness,reduction and resource utilization.However,sludge anaerobic digestion still has the problem of low conversion efficiency.The reason is that the microbial transformation rate of sludge anaerobic digestion is low.Therefore,in order to improve the reaction rate and conversion rate of anaerobic digestion,it is necessary to propose solutions to its constraints.In this paper,the effects of ultrasonic pretreatment on anaerobic digestion and dewatering performance of sludge were studied at laboratory level and pilot-scale engineering level.Based on the results of pilot-scale experiments,the feasibility of ultrasound-enhanced anaerobic digestion of sludge was explored from three aspects: social benefits,economic benefits and environmental benefits.During the experiment,the following phenomena were observed: 1)The most beneficial conditions for improving sludge dewatering performance are sound energy density of 0.170W/mL,treatment time of 23 S and treatment temperature of 22 C.Under these conditions,the moisture content of sludge cake decreases from 84% to 73.4%.2)The results of batch anaerobic reactions of sludge under four mixing ratios showed that the digestibility of sludge treated with 50% ultrasound was the highest(71.63%);The digestibility and stagnation of sludge were improved with the increase of sludge ratio.3)The results of pilot-scale experiments on semi-continuous anaerobic fermentation of sludge show that the more ultrasonic pretreatment is added,the better the cumulative gas production and gas quality of anaerobic fermentation of sludge are.However,considering the gas production situation,total gas production,stability of the reaction and treatment cost,the optimal engineering conditions are determined to be 40% ultrasonic pretreatment of sludge.4)Under the condition of 40% ultrasound treatment of sludge,it was found that adding 40% ultrasound pretreatment of sludge could increase the degradation efficiency of organic matter by 5.67%,shorten the anaerobic digestion period by 7-10 days,and improve the dewatering performance by 1.40% on average.Finally,based on the experimental results of the pilot project,the economic analysis of the anaerobic digestion of sludge pretreated by ultrasound shows that the ultrasonic pretreatment equipment can bring four main benefits to the anaerobic digestion of sludge: 1)Upgrading anaerobic digestion of sludge to produce biogas(338,000 yuan);2)Shorten sludge digestion cycle(258,000 yuan);3)Improve sludge dewatering performance(33,000 yuan);4)Save the amount of sludge dewatering agent(156,000 yuan).The cumulative annual income exceeds 780,000 yuan,and the return period of investment is less than 8 years.