【作者】 郭俊元；

【导师】 杨春平；

【作者基本信息】 湖南大学 ， 环境工程， 2013， 博士

【摘要】 我国规模化养殖业的高速发展，带来了巨大的环境压力，其中猪场废水是主要的污染来源，猪场废水含有高浓度有机物和氨氮，是较难处理的一类有机废水。国内外主要采用厌氧—好氧技术方法进行处理，虽然厌氧处理能够很大程度上降解废水中的有机污染物，但是，厌氧出水污染物浓度仍然很高，尤其是氨氮基本没有被去除。对于猪场废水厌氧消化液的处理，应用最多的是生物硝化反硝化，虽然利用硝化菌和反硝化菌可以将废水中的含氮有机物和氨转化为氮气去除，但高浓度的有机物和氨氮通常会加大微生物的处理负荷和冲击负荷，导致废水处理效果不佳。实际工程中，为改善氨氮的去除效果，通常在反硝化脱氮过程中补充碱度或碳源，使得处理成本和运行费用增加。这种情况下，高效去除有机污染物的絮凝技术和以天然沸石为吸附剂的离子交换脱氨氮技术逐渐引起人们的重视。本论文在充分研究微生物絮凝剂去除高浓度有机污染物的作用机制和氧化镁改性沸石吸附回收高浓度氨氮的作用机理的基础上，提出了微生物絮凝与氧化镁改性沸石吸附联合处理猪场废水厌氧消化液的技术，运用中心复合设计建立废水中污染物去除的二次模型，通过絮凝和离子交换技术提高有机污染物的去除效率，实现废水中高浓度氨氮的吸附回收。一方面，从养猪场废水处理厂污泥中分离耐高浓度有机物和氨氮的絮凝微生物，充分研究其利用猪场废水和污泥生产微生物絮凝剂及去除猪场废水厌氧消化液中高浓度有机物的性能和机理。另一方面，采用焙烧的方法将氧化镁分散在天然沸石上，使其获得强碱性活性位并保留微孔结构，充分研究其吸附猪场废水厌氧消化液中高浓度氨氮的性能和动力学过程。以此为基础，运用响应面分析法设计实验，在氧化镁改性沸石处理猪场废水厌氧消化液的混凝过程中加入微生物絮凝剂，对于废水中高浓度有机物和氨氮的去除和吸附回收具有巩固作用，实现氧化镁改性沸石和微生物絮凝剂在处理猪场废水厌氧消化液中的优势互补，最大限度地去除废水中的COD、氨氮和浊度。从湖南省富华养猪场废水处理厂沉淀池污泥中分离出一株高效絮凝微生物菌株R3，通过生理生化实验和16S rDNA鉴定为红球菌属微生物。实验通过优化菌株R3培养基，得出生产絮凝剂的基质组成为（g/L）：蔗糖20、酵母粉4.0、脲1.0、NaCl10、MgSO₄2.0、K₂HPO₄5.0、KH₂PO₄2.0。菌株R3可以有效利用猪场废水和碱热处理的污泥生产微生物絮凝剂，无需添加其他可溶性有机物和氮化合物。实验建立了描述菌株R3生长、絮凝剂MBFR3生产和底物蔗糖消耗的数学模型，三种模型的平均相对误差均小于10%，可以认为建立的菌株发酵动力学模型是可行的。菌株R3生产的微生物絮凝剂MBFR3其有效成分为蛋白质，蛋白质含量达99.7%，平均相对分子量为3.99×10⁵Da。 MBFR3具有良好的絮凝性能，当投加量在10-30mg/L范围内变化时，对4.0g/L高岭土悬液的絮凝率始终保持在90%以上；MBFR3其絮凝性能相对稳定的适用pH值呈弱碱性，当pH=8.0时，絮凝率达到96.8%。MBFR3对猪场废水中的COD、氨氮、浊度有着明显的去除效果，废水pH为7.0-9.0时，随着投加量从5.0mg/L逐渐增加至20mg/L，废水中COD、氨氮、浊度的去除率也随之快速增加至47.2%、41.9%和72.9%。絮凝机理研究表明，胶体颗粒是通过电中和作用和离子架桥作用被MBFR3絮凝沉降的，助凝剂Ca²⁺通过库伦引力将带负电荷的胶体颗粒拉近，并与之形成Ca²⁺—胶体颗粒结合物，MBFR3像一种桥接剂，通过离子键将两个或两个以上的Ca²⁺—胶体颗粒结合物吸附到分子链上，从而完成了胶体颗粒的絮凝。400oC焙烧条件下，将氧化镁按质量比1:4分散负载于浙江缙云天然斜发沸石，制得氧化镁改性沸石。改性沸石对氨氮吸附量可达到24.7mg/g，是天然沸石吸附氨氮量（12.6mg/g）的196.1%。改性沸石投加量在5.0-30g/L范围内变化时，氨氮去除率随着投加量的增加而迅速增加到58.6%。改性沸石吸附氨氮有一个最适pH范围（7.0-9.0），当pH=8.0时，氨氮去除率达到58.9%。改性沸石对氨氮的去除具有快速吸附、缓慢平衡的特点，在反应最初30min内，氨氮去除率迅速增加到49.1%，当反应时间达到80min时，吸附达到平衡。内扩散动力学研究表明NH4+从改性沸石表面扩散到颗粒内部是整个吸附过程的速率控制步骤。吸附等温线研究过程中，随实验温度条件的升高，改性沸石对氨氮的理论吸附量从29.1mg/g下降到27.4mg/g，说明温度对改性沸石的吸附性能有一定影响。相比Freundlich等温线和Tempkin等温线而言，Langmuir等温线能够更好地拟合实验数据。热力学研究过程中发现，氨氮吸附过程是热力学自发过程（ΔG^θ<0），吸附反应是放热反应（ΔHθ<0），改性沸石吸附氨氮的反应增加了固—液界面上物质的无序程度（ΔS^θ<0）。离子交换特征研究表明，Mg²⁺、Ca²⁺是主要的交换阳离子。采用响应面分析法对MBFR3与氧化镁改性沸石联合处理猪场废水厌氧消化液的过程进行了优化，设定的5个影响因子分别为MBFR3投加量（x1），改性沸石投加量（x2）、废水pH值（x₃）、CaCl₂投加量（x4）和反应时间（x5）。响应面实验分别拟合出了关于COD去除率和氨氮去除率的二次模型，确定猪场废水厌氧消化液的最佳絮凝条件为MBFR324mg/L，氧化镁改性沸石12g/L，pH值8.3，CaCl₂0.16g/L，反应时间55min，其中改性沸石可以循环使用6次。最佳絮凝条件下，COD、氨氮、浊度去除率分别为87.9%、86.9%、94.8%。本论文运用响应面法优化了微生物絮凝剂与氧化镁改性沸石联合处理猪场废水厌氧消化液的工艺条件，建立的COD和氨氮去除率的二次模型为实际猪场废水处理工程提供了指导意义和参考价值。针对微生物絮凝剂去除有机物的机理、氧化镁改性沸石吸附去除氨氮的机理、微生物絮凝剂与氧化镁改性沸石联合处理废水的性能和机理等关键问题的研究，有望解决国内外猪场废水厌氧消化液好氧后处理难以取得良好效果的问题。微生物絮凝剂与氧化镁改性沸石联合使用，通过絮凝和离子交换技术提高了有机污染物的去除效率，实现了废水中高浓度氨氮的吸附回收，不仅降低了生化处理成本，而且避免了PAC和PAM在废水处理中的不安全性和二次污染。更多还原

【Abstract】 Over the past decades, with the rapid development of the scale and intensifypoultry farming in our country, the environmental pollution is becoming much moreserious. Nitrogen pollution in livestock wastewater is the most prominent. At homeand abroad, the anaerobic-aerobic method was mainly used in the treatment of swinewastewater, although the most of the organic pollutants in wastewater were degradedin the anaerobic tank, the concentrations of nitrogen were still high in the digestedswine wastewater. Biological systems （biological nitrification–denitrification） haveprovided an effective solution, where ammonium was firstly transformed to nitrite,then to nitrate, and finally to nitrogen gas. However, since biological systems do notrespond well to high shock loads of ammonium, unacceptable peaks over thedischarging levels may frequently appear in the effluent ammonium concentrations.Besides this, the treatment of ammonium nitrogen wastewater of low organic contentby a biological process usually needs to be supplemented with extra carbon source,which may add to the treatment costs. In such solution, the efficient removal oforganic pollutants using bioflocculant has been considered as a potential solution tothe toxicity and the environmental pollution in recent years, and the ammoniumadsorption using zeolites as adsorbent are gaining on interests.Based on the degradation of the high concentration of organic pollutants bybioflocculants and adsorption of high-level of ammonium by MgO-modified zeolite,this paper presents a study of the treatment of digested swine wastewater using thecompound of bioflocculant and MgO-modified zeolite. The response surfacemethodology （RSM） was selected to establish the two quadratic models of COD andammonium removal efficiencies to remove the organic pollutants and recycle the highconcentration of ammonium. On the one hand, the production and performance of thebioflocculant MBFR3from swine wastewater and activated sludge were investigatedin the degradation of the high concentration of organic pollutants. On the other hand,the performance and kinetics characteristics of a zeolite modified by calcined withMgO were examined in the adsorption of high-level of ammonium. On this basis, theremoval of organic pollutants and ammonium was cemented by adding MBFR3in thecoagulation of digested swine wastewater by MgO-modified zeolite, and hence, COD,ammonium and turbidity could be maximized remove from the wastewater. A high flocculant–producing bacteria R3, screened from activated sludge, wasidentified as Rhodococcus Ruder by a series of physiological and biochemicalexperiments and16S rDNA. This paper presents a study of production andperformance of a bioflocculant from bacteria R3, results showed that the optimalcomponent of1.0L fermentation medium for bioflocculant production was distilledwater1.0L,20g sucrose,4.0g urea,1.0g yeast extract,10.0g NaCl,2.0g MgSO₄,5.0g K₂HPO₄, and2.0g KH₂PO₄. The swine wastewater and activated sludgepre–treated by alkaline–thermal （ALT） treatments can be used as substituting mediumfor bioflocculant production, without adding any other organic and nitrogencompounds. The models about the strain growth, bioflocculant production, andconsumption of sucrose were described, through the comparison of experimental dataand the corresponding calculated values from the models, it was found that the datajoint well. Analysis of the purified bioflocculant by chemical methods indicated thatthe main component was a protein （99.7%）, with an approximate molecular weight of3.99×10⁵Da. Flocculating rates of kaolin clay （4.0g/L） was above90%when thebioflocculant （MBFR3） dosage was adjusted in the range of10-30mg/L, andincreased with the increasing dosage, and a maximum flocculating rate of96.8%wasachieved when the pH was adjusted to8.0. This bioflocculant also processed anindustrial potential for treatment of digested swine wastewater, when the pH valuewas adjusted to7.0-9.0and20mg of MBFR3was added into1.0L of the sample, themaximum removal efficiencies of COD, ammonium and turbidity of47.2%,41.9%,and72.9%were achieved. In addition, the flocculation mechanism reflected that theflocculation was completed by charge neutralization and bridging mechanism byaddition Ca²⁺in two steps, coagulation and flocculation. First step was thecoagulation, in which Ca²⁺draw closer to the negatively charged particles throughcolumbic attraction and Ca²⁺–particle complexes were formed. Ca²⁺reduced thethickness of the diffuse double layer of adjacent particles and hence, reducing theinter-particle distance between particles. Second step was the flocculation, in whichbioflocculants act like a bridging agent of two or more Ca²⁺–particle complexes andreduces inter-particle distances through the ionic bond mechanism, and bridgingoccurred after the Ca²⁺–particle complexes adsorbed onto the bioflocculants chains.Restated, particles adsorbed to a bioflocculant molecular chain, and they could adsorbsimultaneously to other chains, leading to the formation of three-dimensional flocs,which were capable of rapid settling.It can be concluded that the zeolite modified by calcined with MgO at400oC has a good performance for ammonium removal with adsorption capacity as high as24.7mg/g, an increase by96.1%compared to the zeolite not calcinated （12.6mg/g）. Arapid increase trend was observed when the zeolite dosage ranging between5and30g/L, and58.6%of ammonium removal efficiency was achieved at zeolite dosage of30g/L. There is an optimum pH range for ammonium adsorption, as solution pH rangingfrom7.0to9.0, the highest ammonium removal efficiency of58.9%was achieved atpH being8.0, and it is likely that ammonium was converted into “free” ammonia（NH3） at pH values above9.0, which can not be exchanged. It is clearly that theammonium removal from digested swine wastewater occurred rapidly within the first30min, and the sorption equilibrium began to establish itself within80min. Theadsorption kinetics indicated that the intraparticle diffusion was the rate-limiting stepfor ammonium adsorption. The adsorption isotherm results indicated that the theoryammonium adsorption capacity of MgO-modified zeolite decreased from29.1mg/g to27.4mg/g with the increasing experimental temperature from25to45oC. Comparedto Freundlich and Tempkin equilibrium, Langmuir model provided the best fit for theequilibrium data. Thermodynamic parameters were also determined in this study, thenegative value of Gibbs free energy change or adsorption energy （ΔG^θ） indicates thespontaneous nature of the adsorption process, the adsorption process was found to beexothermic as confirmed by the negative values of ΔHθ, and the negative value of ΔS^θshowed the decreased randomness at the solid–liquid interface during the adsorptionof ammonium by the modified zeolite. The main mechanisms involved in theadsorption are both ion exchange with mainly Mg²⁺and Ca²⁺and surface orintraparticle sharing between ammonium ions and functional groups, such as alkyl,carboxyl and hydroxyl groups.The central composite design, which is the standard RSM, was selected toinvestigate the interactions of parameters including the dosage of the MBFR3（x1）,modified zeolite （x2）, pH （x₃）,CaCl₂（x4） and contact time （x5）, respectively. The twoquadratic models for the five factors were established with COD and ammoniumremoval rate as the target responses. The optimal flocculent condition obtained fromthe two desirable responses, COD removal rate as100%and ammonium removal rateas100%, which deduced from the frequency of responses, were MBFR3of24mg/L,modified zeolite of12g/L, CaCl₂of0.16g/L, pH of8.3and contact time of55min.Under this optimal condition, COD, ammonium and turbidity removal rates wereappeared as87.9%,86.9%and94.8%, respectively.This dissertation fully focused on the flocculation mechanism of organic matters by bioflocculant MBFR3, the adsorption mechanism of ammonium by MgO-modifiedzeolite, and the performance of the compound of MBFR3and MgO-modified zeolitein the treatment of digested swine wastewater. The research results would provide afeasible way to solve the difficulties to achieve good removal efficiencies ofpollutants in the aerobic post-treatment over the world. The process conditions of thedigested swine wastewater treatment by the compound of MBFR3and MgO-modifiedzeolite were optimized by the RSM, and the two quadratic models of COD andammonium removal efficiencies established provide scientific foundation on theactual projects. The use of the compound was not only improving the pollutantremoval and recycling the ammonium nitrogen, but also avoiding the secondarypollution brought by adding PAC and PAM in wastewater treatment.更多还原