【作者】 杨雪；

【导师】 杜茂安；

【作者基本信息】 哈尔滨工业大学 ， 市政工程， 2012， 博士

【摘要】 城市污水厂的剩余污泥已经成为主要的环境污染问题之一，由于剩余污泥中蕴藏大量的有机物资源，可以进行资源化处理，同时剩余污泥发酵产酸是进行污泥资源化处理的热点研究方向之一。产生的挥发酸(VFAs)因为可以作为补充碳源解决污水厂运行过程中出现的碳源不足问题，所以具有重要的实际应用意义。基于此，本文在已有研究的基础上，结合污泥厌氧发酵理论的代谢过程及机制，比较研究了强化污泥发酵产酸的处理技术，并对各发酵过程的动力学及机理进行了阐述，同时以强碱性处理后的发酵液为进水进一步实现了连续流工艺产酸，最后对发酵液碳源的应用途径进行了探索研究。首先以序批实验的方式探索了强化污泥厌氧发酵的几种技术，以污水厂剩余污泥为研究对象，采用自主设计的发酵装置比较研究了碱处理、投加β-环糊精(β-CD)、投加蒽醌-2,6-二磺酸钠(AQDS)强化污泥发酵产酸的效能。结果表明，碱性条件下（pH=8.0-10.0），VFAs积累量随着pH的升高而增加，当pH升高至12.0时，由于极端条件严重抑制了微生物的代谢过程，导致VFAs积累量大幅降低。投加β-CD也可以促进污泥的厌氧发酵产酸过程，在低投加量条件下(0.05g/gTSS和0.1g/gTSS)，VFAs的增加趋势不明显，当投加量高于0.15g/gTSS时，VFAs的积累量开始明显增加。其中，β-CD投加量(x)与VFAs积累量(y)之间呈较好的正相关性，拟合方程为y=2319.43x+134.74，R2=0.981。投加AQDS后的产酸过程与投加β-CD实验组类似，在AQDS投加量较低时促进效果不明显，而当投加量增加到3mM和5mM时，VFAs积累量可以达到511.6mg/L和562.8mg/L，是同期空白对照组的2.5倍和2.7倍左右。进一步的机理分析结果表明，三种强化发酵产酸方式下的VFAs组分均是以乙酸和丙酸为主，二者之和占总VFAs的比例最大可以分别达到76.2%(pH=10.0)、88.2%(β-CD)、100%(AQDS)，表现为乙酸-丙酸的发酵特征。大分子有机底物（蛋白质和总糖）的水解过程符合一级动力学模型，碱性条件下的水解速率高于其他条件，而β-CD和AQDS在促进水解过程时均存在一个投加阈值，即二者在低投加量条件下对水解速率的影响较小，但在高投加量时水解速率常数则显著提高，投加量的阈值分别为0.15g/gTSS和3mM。对产酸过程的微生物种群组成及动态变化过程通过聚合酶链式反应技术及变性梯度凝胶电泳技术（PCR-DGGE）进行分析，结果显示不同强化技术对种群组成具有明显的选择性，在最佳的产酸条件下的微生物种群表现为：pH=10.0时，Acinetobacter sp.和Acidovorax sp.是发酵体系中的产酸优势种群；β-CD投加量为0.2g/gTSS时， Dethiosulfatibacter aminovorans strain、 Clostridiaceaebacterium、Enterobacter sp.和Parabacteroides sp.为产酸优势种群；AQDS投加量为3mM时，Clostridiaceae bacterium、Clostridium symbiosum strain、Acidovorax sp.为产酸优势种群。鉴于强碱性(pH=12.0)处理技术在促进大分子有机物溶解方面的独特优势，试验中以强碱性处理后的发酵液为进水，采用连续搅拌反应器(CSTR)为发酵产酸的主体装置，考察了连续流产酸效果及工艺过程的微生物学机理。结果表明，高负荷（蛋白质浓度为2000mg/L）条件下，工艺在6.5d时即可进入产酸稳定期，平均的产酸效率为210.6mg VFAs/g VSS，蛋白质的平均去除率为62.5%。低负荷运行的结果表明，低负荷启动时的适应期明显增长，需要15d才能达到稳定，平均产酸效率为84.7mgVFAs/gVSS，蛋白质的平均去除率约为64.6%。进水负荷对于工艺中的微生物功能菌群具有一定选择性，但是Bacteroides sp.是稳定存在于两种进水工艺中的优势产酸种群，为今后产酸菌的筛选提供了非常有利的信息。最后探索研究了厌氧产酸发酵液碳源的应用，结果表明：(1)碱处理发酵液可以成功用来进行聚羟基脂肪酸酯(polyhydroxyalkanoates,PHA)合成，试验中采用SBR反应器，工艺运行了50d，最高的PHA合成量为420.5mg/gMLSS，高于同期对照试验以乙酸钠为单一碳源时的最大PHA合成量，但是由于底物成分的复杂性，PHA的产生和有机质的降解较对照试验均有所滞后。PHA的主要组分是聚-β-羟丁酸(poly-β-hydroxybutyrate, PHB)，微生物种群特征的PCR-DGGE分析结果显示，Alcaligenes sp.、Pseudomonas sp.是工艺中合成PHA的主要功能种群；(2)污泥酸性厌氧发酵液可以作为反硝化除磷过程的碳源，但投加初期的除磷效果会略受冲击，逐渐可以恢复反硝化除磷特性，长期的运行证实了以发酵液为碳源的反硝化除磷工艺稳定性要优于同期对照工艺，吸磷速率可达到4.23mg PO43--P/g MLSS·h。更多还原

【Abstract】 The wasted activated sludge (WAS) cause a serious environmental pollutedproblem. However, plenty of organic sources are stored in sluldge folcs, and therecovery of these organics is very important and meaningful, especially theaccumulation of volatile fatty acids (VFAs). The fermentative VFAs can be used ascomplementary carbon sources to enhance the removal of nitrogen and phosphorus.Thus, based on the existed studies and mechanisms of anaerobic digestion, thisstudy compared three different methods to enhance the fermentation of WAS, andinvestigated the dymatic formula and mechanism pathway of VFAs producing, andthen investigated the continuous VFAs producing process and the applications ofVFAs as external carbon sources.Firstly, three different enhanced methods were adopted in VFAs procution,such as alkaline pretreatment, addition of β-CD, and the addition of AQDS. Theresults revealed that VFAs increased from pH8.0to10.0but decreased when pHwas12.0. The addition of β-CD enhanced the VFAs producing. The VFAs slightlyincreased with lower β-CD dosage, but obvious increase was observed when β-CDdosage was higher than0.15g/gTSS. The simulated formula between β-CD additionand VFAs production was y=2319.43x+134.74and the corresponding R2was0.981.The AQDS addition showed the similar influences by β-CD. When the AQDSdosage was higher than3mM, VFAs production reached511.6mg/L and562.8mg/Lwhich was2.5and2.7fold than control test.In these three different fermentation processes, the main VFAs were acetic andpropionic acid, which accounted for76.2%at pH=10.0,88.2%with,100%withAQDS. The degradation of complex organics (including protein and carbohydrate)were accorded with first-order model, and the hydrolysis rate under alkalinecondition was higher than other conditions. With addition of β-CD and AQDS, therewas a threshold value of0.15g/gTSS and3mM, respectively. When the β-CD andAQDS dosages were higher than the threshold values, the hydrolysis rates weremuch higher than the relative lower dosages. The polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE) was adopted to studymicroorganism communities. The results showed that obvious changes were happened with different enhancements. At pH=10.0, Acinetobacter sp. andAcidovorax sp. were the dominant acid producing bateria. With β-CD addition of0.2g/gTSS, Dethiosulfatibacter aminovorans strain, Clostridiaceae bacterium,Enterobacter sp., and Parabacteroides sp. were the dominant acid producing bateria.With β-CD addition of3mM, Clostridiaceae bacterium, Clostridium symbiosumstrain, Acidovorax sp. were the dominant acid producing bateria.Due to the obvious predominance of alkalic enhancement, taking alkalic pre-fermentation liquid as influent and CSTR as main fermentation reactor, thecontinuous VFAs producing performance and relative microorganism communitieswere studied. The results revealed that average VFAs-producing efficiency was210.6mgVFAs/gVSS and the protein removal efficiency was62.5%after6.5d. Thelower loading influent was then introduced, and the results indicated that the meanVFAs-producing efficiency was84.7mgVFAs/gVSS and the mean protein removalefficiency was64.6%after15d. However, about30%protein was still remained ineffluent because the protein was sort of complex and refractory organics. Thedifferent loading rate influenced the functional microorganism communities, theBacteroides sp. was always the predominant VFAs-producing bacteria in these twoprocesses, which was promosing bacteria for screening of VFAs-producing bacteria.The application of carbon sources in fermentation liquid was investigated, andthe results revealed that:(1) The polyhydroxyalkanoates (PHA) can be synthesizedby carbon sources in alkaline fermentation liquid taking SBR as reactor, during theprocess of50days. The maximum PHA content reached420.5mg/g MLSS whichwas higher than PHA content synthesized by acetic acid as the carbon source. And,due to the complexity of fermentation liquid, the PHA producing and organicsremoval were both delayed. The main component of PHA was poly-β-hydroxybutyrate (PHB). The PCR-DGGE results revealed that Alcaligenes sp. andPseudomonas sp. were both the predominant microorganism communities;(2) Thefermentation liquid also can be used as influent for denitrifying phosphorus removal.At initial phase, the phosphorus removal was influenced, but for longer applicationthe denitrifying phosphorus removal was more stable than control test by traditionalcarbon source.The phosphorus uptake rate reached4.23mg PO43--P/g MLSS·husing fermentation liquid as influent.更多还原