| With the development and improvement of technology, anaerobic biologicalfermentation technology, which has been a significant way in solving environmentalpollution issues and biological energy recovery, is playing a more and more importantrole in environmental area. Anaerobic reactor, as one major part applied for producingmethane in anaerobic biological fermentation technology, have the advantages in highorganic removal efficiency and recovery of energy, good stability and goal achieving indisposal of organic wastewater and energy recovery. The Up-flow Anaerobic SludgeBed (UASB) and the Continuous Stirred Tank Reactor (CSTR) have realizedindustrialization in regular wastewater treatment and energy recycling. In allusion tolow pH of acid waste water, this study discussed about performance characteristics ofUASB and CSTR launched and operated in low pH situations, which was quiteimportant to acid waste water treatment in UASB and CSTR reactors.In the thesis, reactors were firstly run in neutrality conditions, and then in graduallyreduced pH conditions. Transformation laws of COD removal efficiency, biogas yieldand methane content, pH value of inner granule sludge at different height, and biomassand methane producing activity of sludge ate different height were studied in theneutrality launching and pH decreasing processes.Study on the performance of methanogenic fermentation in UASB reactor whichinoculated by granular sludge showed that sludge resistance to acid could be cultivatedin UASB reactor by decreasing pH gradually. In the process of gradually reduced thereactor internals pH, the parameters such as COD removal rate of UASB reactor, thebiogas production and methane content firstly showed a trend of gradually reduce withpH decrease and got the minimum at pH5.5. At pH5.5, the COD removal efficiency wasabout76.8%, the biogas yield was about14L/d and the methane content was about40%.Under acid condition at pH5.5, The biomass respectively decreased to12.07,2.87and0.86gMLVSS/L at the point distance from the bottom of the reactor15cm,30cm and45cm, the maximum specific methane production rate dropped to182.5,215.5and62.4mlCH4/gMlVSS·d, respectively. During the reactor operated at pH5.5, the operatingresults of UASB reactor began gradually improve and tend to be stable. The resultswere80%of COD removal rate,17L/d of biogas production and48%of methanecontent; and the biomass gradually returned to13.25,3.47and1.07gMLVSS/Lrespectively at the point distance from the bottom of the reactor15cm,30cm and45cm,the maximum specific methane production rate respectively returned to224.8,280.5and126.3mlCH4/gMlVSS·d. In the process of gradual declined inside the reactor, thepH value inside the granular sludge also undergone great changes. Experimental resultsshowed that, during the pH inside UASB reactor decreased gradually, the inner pH of the granular sludge which obtained from the point of15cm of the reactor changed a lessextent, because of large particle size; and the inner pH value of the granular sludgewhich at the point at45cm from the bottom of the reactor showed a big margin changevaries with the external environment change of pH due to smaller particle sludgeStudy showed that operating results in CSTR inoculated with flocculent sludgeduring pH’s gradually decreasing were worse than UASB. Moreover, fluctuation rangewas also more obvious than UASB while pH was decreasing. During the reactoroperated at pH5.5, the COD removal efficiency was about67%, the biogas yield wasabout12L/d and the methane content was about35%, the biomass was about6.97gMLVSS/L and the maximum specific methane production rate was about166.46mlCH4/gMlVSS·dOperating characteristics after reactors’ successfully launching in acid conditionsdemonstrated that active sludge, with strong acid resistance, could be domesticated inUASB and CSTR by decreasing pH inside reactors. Active sludge in acid reactors hadmuch better ability in resisting external environment impacts, like COD and pH, than inneutrality conditions. |
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