【作者】 张翠玲；

【导师】 常青；

【作者基本信息】 兰州交通大学 ， 环境工程， 2019， 博士

【摘要】 近年来,随着我国工业废水排放标准的提高及废水处理技术的不断进步,水体污染物排放的主要来源已逐渐由工业转向农业。农业污染水体因水量大、污染物浓度相对比较低、处理难度大而受到越来越多的关注,其中,农田退水与畜禽养殖废水的污染最为普遍,危害最大,如山东南四湖流域65.06%的总磷来源于畜禽养殖业。论文主要围绕农田退水及畜禽养殖废水这两类农业面源污染中代表性污染物质氨氮、磷和重金属的去除方法及机理展开研究。首先研究了天然及改性沸石对农田退水中氨氮及磷在不同条件下的去除效果,然后利用絮凝沉淀法对畜禽养殖废水中重金属污染物的去除效果进行了研究,并制得了两种对养殖废水中重金属离子具有良好絮凝效果的高分子重金属絮凝剂,探讨了絮凝法除重金属离子的机理及工艺条件。最后,研究了磷酸铵镁沉淀法对养殖废水中的氨氮与磷的最佳处理工艺条件。研究内容和结论有如下三个方面。1.天然及改性沸石脱除农田退水中氮磷的性能。首先利用扫描电镜（SEM）、比表面测定仪（BET）、x射线衍射（XRD）和能谱分析（EDS）等对甘肃白银产沸石的表面形貌、比表面积、孔隙率、物相组成等方面进行表征,采用pH计指示电位滴定法测定了天然及NaCl改性沸石的阳离子交换容量（CEC）。然后分别以改性前后的白银沸石为吸附材料,以模拟农田退水为处理对象,采用静态吸附法对不同条件下沸石的脱氮除磷性能进行研究,并从吸附热力学和吸附动力学的角度探讨了沸石脱氮除磷的机理。相关结论为:（1）电子扫描电镜结果显示天然沸石表面具有发达的孔穴结构;天然沸石的比表面积9.29m²/g;XRD分析得出斜发沸石、伊利石和石英是试验所用矿石的主要矿物成分;EDS测定结果显示,天然沸石铝元素含量为11.36%,硅铝比m_Si/m_Al=4.62,铁含量高达14.55%,使得沸石外观呈砖红色;天然及NaCl改性沸石的阳离子交换容量分别为80mmo1/100g和87.5mmo1/100g。（2）通过正交试验得出用于除氨氮的沸石的最佳改性条件为将4g沸石放入100mL浓度为8%的NaCl溶液中于35℃条件下改性6h;用于除磷的沸石的最佳改性条件为改性剂FeCl₃溶液的浓度是4.5mol/L、焙烧温度为200℃、焙烧时间是4h、沸石粒径为80¹00目,四个因素对改性沸石吸附除磷性能的影响大小次序为焙烧温度>沸石粒径>焙烧时间>氯化铁溶液浓度。（3）沸石粒径、氮磷的初始浓度、接触时间、温度、pH值及沸石投加量等因素都会对改性前后沸石脱氮除磷效果产生影响:沸石改性前后对氮、磷的吸附量均随初始浓度先迅速增加,然后逐渐趋于平缓;都具有“快速吸附、缓慢平衡”的特点,但吸附平衡时间不同;当pH值范围为4⁹时,天然及改性沸石对水中氨氮都有较好的去除效果;pH<8时,沸石吸附磷酸根的量随pH值升高而增大,pH=8时吸附效果最好。（4）共存阳离子对沸石除氨氮影响的大小顺序为:K⁺影响最大,其次为Na⁺,Ca²⁺影响最小;废水中阴离子对沸石除氨氮的影响顺序为:SO₄^2-影响最大,NO₃^-次之,H₂PO₄^-影响最小。（5）沸石对磷的吸附以表面不均匀的多分子层吸附为主,而沸石对氨氮的吸附则以单分子层吸附为主;沸石去除氨氮与磷的过程属于自发进行的过程,此过程中系统的熵值不断增加;准二级动力学模型能很好地描述沸石脱氮除磷的动力学过程。（6）FeCl₃改性沸石对养殖废水中磷的去除率可达75%。2.絮凝沉淀法对养殖废水中重金属的去除性能。文中分别以巯基乙酸（TGA）与左旋半胱氨酸（L-CySH）为材料,通过酰胺化反应将重金属离子的强配位基—巯基引入天然高分子絮凝剂壳聚糖（CTS）,得到了MAC和MCC两种高分子重金属絮凝剂。详尽研究了MAC与MCC两种絮凝剂的制备机理、制备条件及不同环境下絮凝去除养殖废水中重金属离子Cu²⁺、Cd²⁺的性能,同时对改性后絮凝剂的稳定性能及絮体中有价金属的回收性能进行了初步探讨,主要得出了如下结论:（1）通过酰胺化反应可以将重金属离子的强配位基-巯基引入天然高分子絮凝剂CTS的分子链。絮凝剂的最佳制备条件与目标污染物的性质有关,如制备MCC时,选用Cu²⁺、Cd²⁺两种不同目标物的去除率为评价指标时,最佳制备条件并不相同。（2）MAC及MCC与CTS相比,水溶性及絮凝去除养殖废水中重金属离子的能力都显著增强。（3）当用MAC或MCC处理重金属离子及致浊物质共存体系时,重金属离子及致浊物质在絮凝剂的作用下会发生协同作用,使MAC或MCC絮凝除重金属及除浊性能都得到改善。重金属与浊度共存体系中,浊度的最高去除率可达100%。（4）絮体形貌随絮凝剂投加量及预处理水样性质的变化而变化,絮体的分形维数越小,絮体中空隙越多,重金属离子的去除效果越好。（5）共存物质对絮凝剂MAC及MCC絮凝除重金属离子的性能会产生一定程度的影响,影响程度与共存物质的本性、浓度及絮凝剂投加量有关。（6）絮凝剂MAC及MCC与重金属形成的絮体沉降性能较好,残渣稳定,不易产生二次污染,且在一定条件下可实现对有价金属铜等的回收。3.磷酸铵镁沉淀（MAP）法同步去除养殖废水中氨氮与磷的性能。通过单因素试验、正交试验及响应曲面逐步优化了MAP法同步脱养殖废水中氮磷的工艺条件,并探讨了外部条件对磷酸铵镁沉淀纯度的影响,得出的主要结论如下:（1）养殖废水pH值是MAP去除氨氮与磷最重要的影响因素,pH值为10.5时,MAP法去除氨氮与磷效果达到最佳,搅拌速度、搅拌时间、静置时间、废水中氮磷物质的量之比及沉淀剂投加量等因素都会影响脱氮除磷效果,当摩尔比n（Mg）:n（N）:n（P）=1.2:1:1时,氨氮及磷都能取得较好的去除效果。（2）适当浊度的存在有利于氮磷的去除效果,而低浓度的HCO₃^-可以促进应用MAP法对氮磷进行脱除。SO₄^2-的存在不利于氨氮的去除,对磷的去除略有促进作用。（3）pH值对MAP法脱氮除磷的产物磷酸铵镁的纯度影响较大,n（Mg）:n（P）:n（N）、HCO₃^-含量等因素也会影响磷酸铵镁的纯度。（4）采用响应曲面Box-Behnken Design设计,以pH值、n（P）:n（N）、n（Mg）:n（N）为影响因子,分别以氨氮和磷的去除率为响应值,得到氨氮及磷去除率的响应面模型,氨氮的去除率模型极显著,磷的去除率模型显著,两模型均准确可靠。（5）MAP法脱氮的最佳条件为:pH=9.5,n（P）:n（N）=1.08,n（Mg）:n（N）=1.34;除磷的最佳条件为:pH=10.2,n（P）:n（N）=0.99,n（Mg）:n（N）=1.11。在磷酸铵镁沉淀法去除氨氮与磷的过程中,除氨氮与除磷所需的最佳工艺条件并不一致。本研究的成果可为消减农田退水和养殖废水污染、保护农村生态环境提供技术参考。更多还原

【Abstract】 In recent years,with the improvement of China’s industrial wastewater discharge standards and the continuous progress of wastewater treatment technology,the main sources of water pollutant discharge have gradually shifted from industry to agriculture.Due to the large amount of water,relatively low concentration of pollutants and difficulty in treatment,agricultural polluted water has attracted more and more attentions.Among them,the pollution of farmland backwater and livestock and poultry breeding wastewater is the most common and the most harmful.Sixty-five percent of the total phosphorus in the Nansihu river basin in China comes from livestock and poultry breeding industry.In this paper,the removal methods and mechanisms of ammonia nitrogen,phosphorus and heavy metals,which are the representative pollutants in agricultural non-point source pollution,such as farmland backwater and livestock and poultry wastewater,were studied.The removal effects of natural and modified zeolite on ammonia nitrogen and phosphorus in field wastewater were studied under different conditions.The removal effect of heavy metal pollutants in livestock and poultry wastewater was discussed by flocculation sedimentation method,and two kinds of macromolecular heavy metal flocculants with remarkable flocculation effect on heavy metal ions in livestock and poultry wastewater were prepared.The mechanism and process conditions of removing heavy metal ions by flocculation method were investigated.Finally,the optimum conditions for the treatment of ammonia nitrogen and phosphorus in aquaculture wastewater by magnesium ammonium phosphate precipitation were obtained.The contents and main conclusions are as follows.1.Properties of natural and modified zeolite for removal of nitrogen and phosphorus in field effluent.Firstly,the surface morphology,specific surface area,porosity and phase composition of zeolites were characterized by SEM,BET,XRD and EDS respectively.The Cation Exchange Capacity（CEC）of the natural and NaCl modified zeolites are also determined.The artificially simulated nitrogen and phosphorus wastewater were treated with Baiyin zeolite as adsorbent material.The static adsorption method was used to study the nitrogen and phosphorus removal performance of the zeolite under different conditions.The main conclusions of the study are as follows:（1）The results of electron scanning electron microscopy show that the natural zeolite surface has developed pore structure.The specific surface area of natural zeolite is determined by BET method,and the specific surface area of the natural zeolite is 9.29m²/g.XRD analysis shows that the main mineral species of the ore used in the test are clinoptilolite,illite and quartz.EDS determination results show that the content of aluminum is 11.36%,m _Si/m_Al=4.62,and the iron content is as high as 14.55%,so that the appearance of the zeolite is brick red.The CEC of natural and NaCl modified zeolite was determined by pH meter indication potentiometric titration method respectively.The cation exchange capacities of natural and NaCl modified zeolites are 80mmo1/100g and 87.5mmo1/100g,respectively.（2）The optimum conditions for the removal of ammonia nitrogen and phosphorus were obtained by orthogonal experiment.The optimal conditions of NaCl modified zeolites are about NaCl solution at a concentration of 8%,modified time 6h,solid-liquid ratio of4g/100mL,modified temperature 35℃.The optimum conditions of FeCl₃ modified zeolites are about the temperature of 200℃,the particle size of 80¹00 mesh,the roasting time 4h,and the concentration of FeCl₃ is 4.5mol/L.The orthogonal experimental analysis shows that the calcination temperature is the main modified factor,followed by the particle size of zeolite,roasting time,ferric chloride solution concentration.（3）Zeolite particle size,initial concentration of nitrogen and phosphorus,contact time,temperature,pH value and zeolite dosage can influence the removal of nitrogen and phosphorus from the natural and modified zeolite.The adsorption capacity of natural and modified zeolite on nitrogen and phosphorus increases with the initial concentration increases rapidly at first,and then gradually flatten.The adsorption equilibrium time of natural and modified zeolite is slightly different.When the pH value ranges from 4 to 9,natural zeolite and modified zeolite have good removal effect on ammonia nitrogen in water.When the pH value is less than 8,the amount of phosphate adsorption increases with the increases of pH value.The adsorption capacity of zeolite to phosphorus was maximum when the pH value of the solution is 8.（4）The effect of coexist substances with chlorine cation is K⁺>Na⁺>Ca²⁺and the effect coexist substances with sodium anion is SO₄^2->NO₃^->Cl^->H₂PO₄^-.（5）The adsorption of phosphorus by zeolite is dominated by multi-layer adsorption with uneven surface,while the adsorption of ammonia nitrogen by zeolite is dominated by single-layer adsorption.The denitrification and dephosphorization of zeolite are a spontaneous process of entropy increase.Compared with the quasi-first-order kinetic model,the quasi-second-order kinetic model can better describe the kinetic process of nitrogen and phosphorus removal by zeolite adsorption.（6）The removal rate of phosphorus in aquaculture wastewater by modified zeolite can reach 75%.2.Removal of heavy metals from aquaculture wastewater by flocculation and sedimentation.Macromolecular heavy metal flocculants MAC and MCC are prepared by introducing the strong coordination group of heavy metal ions,sulfhydryl group,into the natural macromolecular flocculant chitosan through the amidation reaction between chitosan and thioglycolic acid and l-cysh,respectively.The preparation mechanism,preparation conditions and flocculation performance under different conditions of heavy metal ions of MAC and MCC flocculants are studied in detail.At the same time,the stability of the modified flocculant and the recovery of the valuable metals in the flocculation are also discussed.The main conclusions are as follows:（1）The strong ligand of the heavy metal ions-thiol can be introduced into the molecular chain of natural macromolecular flocculant CTS by the amidation reaction.The optimal preparation conditions of the flocculant are related to the properties of the treatment target,such as the preparation of MCC,and the optimal preparation conditions are very different when the removal rate of Cu²⁺and Cd²⁺different targets are selected as evaluation indexes.（2）Compared with CTS,the water solubility and the ability to remove ions of MAC or MCC are significantly enhanced.（3）The removal efficiencies of heavy mental ions and the turbidity are greatly promoted by the cooperation effects for the water sample containing heavy metal ions and turbidity causing substances.The maximum removal rate of turbidity is up to 100%.（4）The morphology of the aggregates varies with the dosage of flocculant and the changes of the properties of water samples.The smaller the fractal dimension of flocs,the more voids in flocs,the better the removal effect of heavy metal ions.（5）The effect of coexisting substances on the flocculation of removing heavy metal ions can be affected by a certain degree.The influence degree is related to the nature of coexisting substances,concentration and dosage of flocculant.（6）The settling performance of the floc produced by MAC/MCC and heavy metal is good.The residue is stable and it is not easy to produce second pollution.Furthermore,the recovery of valuable metals can be realized under certain conditions.3.Simultaneous removal of ammonia nitrogen and phosphorus from aquaculture wastewater by magnesium ammonium phosphate precipitation（MAP）method.The single factor test,orthogonal test and response surface are used to optimize the process conditions of simultaneous removal of nitrogen and phosphorus from aquaculture wastewater by MAP method.The influence of external conditions on the precipitation purity of magnesium ammonium phosphate is discussed.The main conclusions are as follows.（1）Among the factors affecting the removal of nitrogen and phosphorus by ammonium phosphate precipitation method,the pH value is the most influential factor.When the pH value is 10.5,the MAP method has the best effect on the removal of nitrogen and phosphorus.Stirring speed,stirring time,static time,the ratio of nitrogen and phosphorus content,the amount of magnesium salt and other factors will affect the removal of nitrogen and phosphorus in MAP process.When the molar ratio of magnesium,nitrogen and phosphorus is1.2:1:1,ammonia nitrogen and phosphorus can achieve a better removal effect.（2）When the pH value is 10.5,proper turbidity is beneficial to the removal of nitrogen and phosphorus,while low concentration of HCO₃^-can promote the application of MAP method to remove nitrogen and phosphorus.The presence of SO₄^2-is not conducive to the removal of ammonia nitrogen,but slightly promotes the removal of phosphorus.（3）The pH value has a great influence on the purity of magnesium ammonium phosphate.The purity of magnesium ammonium phosphate can be affected by other factors either.（4）The response surface is designed by Box-behnken Design with pH value,n（P）:n（N）,n（Mg）:n（N）as the influencing factors.Response surface models of nitrogen and phosphorus removal rates are obtained.The removal rate model of ammonia nitrogen is extremely significant,and that of phosphorus is significant.Both models are accurate and reliable（5）The optimum condition of removing ammonia nitrogen and phosphorus by MAP method is pH=9.5,n（P）:n（N）=1.08,n（Mg）:n（N）=1.34;The optimal condition for phosphorus removal is:pH=10.2,n（P）:n（N）=0.99,n（Mg）:n（N）=1.11.In the process of nitrogen and phosphorus removal by magnesium ammonium phosphate precipitation,the optimum conditions for nitrogen removal and phosphorus removal are not consistent.The results of this paper can provide technical reference for reducing the pollution of farmland backwater and aquaculture wastewater and protecting rural ecological environment.更多还原