Experimental Study On The Combined Anaerobic Digestion Of Kitchen Wastes And Residual Sludge

As the production is increasing, the damage of kitchen wastes to the environment is becoming more and more serious, leading to a big problem in the municipal soild waste treatment. With rich nutrients, kitchen wastes have high biodegradability, but the hydrolysis rate in the process of anaerobic digestion is so fast that the organic acid can be easily accumulated. Meanwhile, kitchen wastes contain rich salt and oil, which makes the microbial activity in the reactor susceptible to be restrained. On the other hand, as a big problem of wastewater treatment in our country,the slow hydrolysis process of residual sludge leads to lack of microbial nutrition supply, due to the low biological availability, limiting the reaction rate of anaerobic digestion and affecting biogas production, so common methods such as landfill are used, which occupies land, and can easily cause secondary pollution. The research aims to solve kitchen wastes and residual sludge treatment problems synchronously, and the biological energy can be obtained,which has great research significance.Experimental study on anaerobic digestion of kitchen wastes and residual sludge was conducted in UASB reactors at room temperature and high temperature conditions, respectively. Changes of the indicators such as effluent COD concentration, COD removal rate, p H value, content of VFA, the biogas production are explored in the whole continuous flow anaerobic digestion experiment from the rejuvenation of microbes in granular sludge cultivation, domestication to the last stage of digestion treatment, and the temperature influence on the working state of each stage are examined. What's more, the advantages and disadvantages of different temperature coordination treatment are analyzed in order to provide reference basis for the practical engineering application.The results show as follows:(1) Kitchen wastes and residual sludge coordination treatment under room temperature is feasible. After a long time domestication with daily fluctuations in temperature and temperature difference between day and night,microbes can form good adaptability to temperature changes. The best volume load of digestion under room temperature is 13 g COD/(L·d), with the COD removal rate basically over 80%. The biogas production rate changes with temperature fluctuation,the average gas rate is 0.23L/g COD in the processing phase, and methane content is between 58% ~ 85.1%.( 2) The kitchen wastes and residual sludge coordination treatment under the condition of high temperature can greatly improve the volumeload and the rate of producing gas. The gas production reaches the maximum of 50.3L/d when the volume load is 29gCOD/(L·d), with the COD removal rate over 85%,the average gas rate is 0.43L/g COD in the processing phase, and methane content is between 56%~80.4%.( 3) The net output energy in different temperatures is associated with the energy conversion efficiency of methane recovery unit, different cities and regions can choose digestion in different temperature conditions according to their own conditions and requirements.