【作者】 赵全保；

【导师】 俞汉青；

【作者基本信息】 中国科学技术大学 ， 分析化学， 2008， 博士

【摘要】 厌氧生物处理技术在去除污染物的同时生成氢气或者甲烷,具有广阔的应用前景。但厌氧反应器的运行容易出现不稳定的问题,限制了它的推广应用。因此,很有必要实现对厌氧反应器的在线监测。但目前尚缺少针对厌氧反应器的实用检测方法和技术。本论文以上流式厌氧污泥床（UASB）反应器为对象,研究了有机废水连续厌氧发酵产氢工艺特性,优化了系统的主要工艺参数;以监测和优化厌氧产甲烷反应器的运行为目的,分别研发出了液相产物的监测系统和气相产物的监测系统,并对厌氧反应器的预警因子及其机制进行了系统的探索。主要研究内容和结果如下:1、研究了pH和水力停留时间（HRT）对连续流产氢UASB反应器的液相产物和氢气产生的影响。研究表明:液相产物中以丁酸和乙酸为主,己酸和戊酸在某些pH值下含量较高;在pH=7.0和9.0时氢气产率较高,说明反应器中存在对碱性环境较为适应的产氢微生物;通过热力学分析解析了戊酸和己酸的生成途径,发现在戊酸和已酸的生成过程中,氢气作为反应物而被消耗,以致H₂产率的降低,因此应改变反应器的运行条件以减少戊酸和己酸的生成;在HRT从30h逐渐降到3h的过程中,氢气的分压和产率变化不明显,液相产物以丁酸为主,底物降解效率保持在92%以上,说明HRT对产氢反应器的影响并不明显。2、将产氢UASB反应器的底物由蔗糖改变为乳糖后,氢气的分压和氢气产率出现明显的下降,同时己酸浓度迅速降低,乙酸和丙酸含量显著升高,高的乙酸产率对氢气的生成并没有做出贡献,证明反应器中同型产乙酸反应的存在。3、以UASB反应器的液相产物为监测对象,设计并研制了基于单片机、放大器、数据采集芯片的pH电极信号的数据采集和控制电路,研发了基于步进电机、精密滴定管和精密平移台的精密滴定装置,编写了基于Visual Basic语言的用于自动滴定的用户界面程序;将三者有机接合在一起,构建了用于测定厌氧反应器挥发性有机酸VFA浓度和碱度的自动滴定系统;将该系统应用于两步滴定法和五点滴定法的验证,发现滴定结果与气相色谱测定结果具有较好的相关性,测试结果证明该系统的具有良好的精密度和重现性;根据酸碱平衡理论,推导出用于VFA、碳酸盐和磷酸盐滴定的六点滴定模型,并通过滴定实验证明该模型对VFA和碳酸盐的测定结果优于两步法和五点法;该系统也能够用于对磷酸盐的测定。4、以UASB反应器的气相产物为监测对象,基于红外气体传感器和数据采集器,并通过Visual Basic编程,构建了反应器主要气相产物CH₄和CO₂的在线监测系统;利用该系统对UASB产甲烷反应器进行了监测和分析,结果表明该系统可以连续精准、稳定地测定反应器中CO₂和CH₄的实时浓度,能够连续准确地反映厌氧反应器的产气状态。5、集成本研究研发的液相VFA滴定系统和气相CH₄和CO₂监测系统,分析了底物浓度负荷和水力负荷对产甲烷UASB反应器的影响。当进水浓度负荷达到25g/L COD后,UASB反应器开始出现“酸败”现象:VFA滴定系统监测到了VFA的积累过程,但此时CH₄/CO₂分压和pH无明显变化;发现了辅酶F₄₂₀荧光峰对浓度负荷的敏感性,说明它可以用于预测酸败现象的发生;UASB反应器对水力负荷的承受能力要高于浓度负荷,反应器在5g/LCOD和8h的HRT条件下仍能保持较稳定的出水质量和较高的产甲烷菌活性,同时也证明所研制厌氧反应器在线监测系统的稳定性和有效性。更多还原

【Abstract】 Anaerobic process could be used to degrade pollutants and generate energy （hydrogen or methane）simultaneously.It is cost-effective and environmentally friendly,and therefore becomes a favorable technique in the fields of both environmental and energy engineering.However,anaerobic reactors sometimes become unstable after the changes of environmental conditions or operating factors, which limits its application.Therefore,it is important to find out appropriate ways to monitor anaerobic reactors.In the present study,the technical aspects of fermentative biohydrogen production were investigated with an upflow anaerobic sludge blanket（UASB） reactor.The main operating parameters were optimized,and the thermodynamic analysis of biohydrogen production process was also performed.To monitor methanogenic reactors,a system for determining the liquor products and another for gas products were developed.The factors to cause the running errors of the monitoring system were investigated systematically and in depth.Main contents and results of the present work are as follows:1.The influences of pH,one of the main operating parameters,on biohydrogen production in a UASB reactor were studied.As the pH was increased from 6.1 to 9.5, the main aqueous products were butyrate and acetate,while the concentrations of caproate and valerate were significant at several pH levels.The maximum H₂ partial pressure was observed at pH 7.5,while both maximum H₂ production rate and H₂ yield were found at pH 7.0 and 9.0.This indicates that some microbes in the reactor preferred basic culture conditions.With a thermodynamic analysis,possible metabolic pathways for the formation of caproate and valerate were proposed.Results indicate that H₂ might be a reactant and could be consumed in the formation of valerate and caproate.2.In a similar way,the influences of hydraulic retention time（HRT）,another important operating parameter,on biohydrogen production were also evaluated.After the HRT was decreased from 30h to 3h,the H₂ pressure changed slightly,while the max H₂ yield was found at an HRT 30h.The main aqueous product was butyrate,and the substrate degradation efficiency kept above 97%.The experimental results demonstrated that the influence of HRT on biohydrogen production was not significant.3.After the substrate was shifted from 10g/L sucrose to 10g COD/L lactose, both H₂ partial pressure and H₂ yield dropped.The caproate concentration decreased, while the acetate and propionate concentrations increased.Acetate became the main aqueous product,but the H₂ partial pressure and H₂ yield dropped to 0.07 atm and 0.008 mol-H₂/mol-sugar,respectively,which indicates that the homoacetogenic bacteria might exist in the reactor.4.Based on single chip microcomputer,amplifier and data acquisition chip,a circuit board was designed and printed to acquisition pH signals and control titration actions.With a stepping motor,burette and precision linear stage,a titration apparatus was fabricated to dose titrating solution quantitatively.A user interface program was compiled for controlling the titration process,and an online titration system to measure VFA and carbonate was assembled with the three parts above.This system had a good precision and repeatability,and was used to verify the 2-step and 5-point titration methods.The VFA titration results had a close correlation with those from the GC method.A 6-point titration model was developed according to the acid and alkali equilibrium theory.This model was used to measure VFA,bicarbonate and phosphate.The 6-point titration model was verified by the titration system,and had achieved satisfying results with the measurement of VFA and bicarbonate.5、With Infrared methane/carbon dioxide sensors,data acquisition unit and programming with Visual Basic language,an online CH₄/CO₂ monitoring system for anaerobic reactors was developed.This system was applied to a methanogenic UASB reactor.The monitoring data show that this monitoring system could record and display the gas partial pressure in situ.It was appropriate for biogas monitoring with a good precision. 6.The VFA titration system and CO₂/CH₄ online monitoring system were integrated to monitor a lab-scale UASB methanogenic reactor.The COD concentration of the influent and the hydraulic retention time（HRT）were changed respectively and the reactor responses were monitored.After the influent COD reached 25g/L,the VFA concentration increased gradually and finally the reactor failed.The increase in VFA concentration from 96 mg/L to 1505 mg/L was recorded by the titration system before the effluent pH and the CH₄ partial pressure decreased suddenly,which demonstrates that the VFA titration system worked well and could give an earlier warning of the VFA-increasing risk.Fluorescence of coenzyme F₄₂₀ could also be used for predicting acidification of the reactor.The UASB reactor had a low VFA concentration and stable CH₄/CO₂ partial pressure when the HRT was changed from 41h to 8h,indicating that the reactor had a better adaptability to an HRT shock than to a COD concentration shock.更多还原