Experimental Study On The Combined Treatment Of Kitchen Wastes And Residual Sludge In UASB Reactors

In recent years, energy shortages and environmental pollution problems havebecome the bottleneck of sustainable development in China. It’s urgent to improveenergy efficiency and to control environmental pollution, at the same time, it is alsoneed to speed up the development and utilization of renewable energy. Kitchenwastes and residual sludge are important raw material of biomass energy. Theirnature makes it diffculty to treat, therefore, the treatment now lacks of utilization.Because of the large amounts of organic matter and nutrient elements in kitchenwastes and residual sludge, it is an inevitable development trend in the21st century,to make the processing of them harmless, decrement, recycling.Using the anaerobic digestion of kitchen wastes and residual sludge mixture byUASB reactor, we can not only solve the disposal problems, but also get clean energymethane gas. In this experiment the kitchen wastes and residual sludge were used asraw material, and collected from a hall in Hunan university and a sewage plant inChangsha. Under the condition of the medium temperature, continuous anaerobicdigestion was conducted by the use of UASB reactor, and the important influencefactors in the process of anaerobic digestion was studied and analyzed.This experiment mainly includes five phases: rejuvenation stage, domesticationstage, digestive process phase, recovery phase after acidification and acid recoveryphase after digestion process.In the rejuvenation stage, the right amount of NaHCO3buffer solution and traceelements should be put into, which is conducive for microbial to recover theiractivity timely; In acclimatization stage, and the proportion of mixing liquid ofkitchen wastes and residual sludge was improved gradually in the inflow, then themicrobe will gradually adapt it and have the ability to manage mixing liquid ofkitchen wastes and residual sludge will be improved; In the recovery phase afteracidification, some measures, such as, the use of right amount of NaHCO3buffersolution, the reduce of the water concentration and the decrease of hydraulicretention time, and so on, can be taken to promote recovery in a timely manner.In the digestive process phase, for the good growth and metabolism ofmicrobial,it is important to maintain good pH and VFA steady-state equilibrium ofthe UASB reactor. After the domestication stage, when the volume load increasedfrom the4.0gCOD/(L·d) gradually to18.0gCOD/(L·d), two reactors operatednormally in less than16.0gCOD/(L·d) volume load, gas production reached the maximum in the16.0gCOD/(L·d), that is21.19L/d and19.05L/d, and the produceof methane from is respectively11.65L/d and10.29L/d, and methane productionrate is0.23L/gCOD and0.20L/gCOD; In the Acidizing recovery phase afterdigestion process, in which the volume load was more than20gCOD/(L·d), thereactor began to become unstable. Experimental results showed that und er thecondition of medium temperature, it is feasible to use the UASB reactor to makeanaerobic digestion process of mixing waste liquid of kitchen wastes and residualsludge. The establishment of gas dynamics model for anaerobic process is full of highcredibility and can provide experiment basis for engineering application.