【作者】 吴莉娜；

【导师】 彭永臻；

【作者基本信息】 北京工业大学 ， 环境工程， 2011， 博士

【摘要】 由于我国的垃圾性质、经济实力和技术水平决定了城市垃圾处理中90%以上是采用卫生填埋法。但垃圾卫生填埋以后,由于垃圾的发酵、雨水的下渗以及地下水位的上升等导致垃圾填埋体内有相当数量的渗滤液。垃圾渗滤液是一种水质水量变化大、微生物营养元素比例失调、氨氮含量高、成分复杂的高浓度有机废水。垃圾渗滤液的特性随环境变化而变化。早期渗滤液有机物和氨氮浓度都很高,但有机物易降解,晚期渗滤液中有机物浓度低且难降解,故高氨氮的有效去除是渗滤液处理的重点和难点。目前对垃圾渗滤液的处理仍以生物法为主,而处理垃圾渗滤液最经济、有效的方法是厌氧-好氧组合工艺。基于以上研究背景,本试验以实际的高氮垃圾渗滤液为研究对象,首先采用“两级UASB–缺氧/好氧（A/O）系统”处理实际城市生活垃圾渗滤液,完全依靠生物处理,通过短程硝化即实现了氨氮的高效去除,降低了处理成本,简化了处理工艺。该工艺运行方式如下:系统进水同一部分A/O工艺出水混合进入到UASB1（一级UASB）,A/O反应器出水中的NOX-‐N（亚硝态氮与硝态氮）作为电子供体,利用原水中丰富的有机碳源在UASB1进行充分的反硝化。在UASB1中,有机物首先作为反硝化碳源被反硝化所利用,同时还通过了厌氧产甲烷去除一部分有机物。剩余有机物在UASB2（二级UASB）中通过产甲烷反应进一步降解。二沉池的污泥回流到A/O工艺缺氧段,回流污泥中的NOX-‐N在此进行反硝化。A/O工艺好氧段主要进行氨氮的硝化。采用“两级UASB–A/O系统”首先对早期渗滤液处理进行了研究。早期渗滤液的C/N很高,易于生物处理,采用两级UASB-A/O系统处理,可取得很好的处理效果。通过在A/O反应器中亚硝态氮累积率为88%的短程硝化,实现了氨氮的几乎完全去除,系统氨氮去除率接近100%。采用“两级UASB–A/O系统”处理晚期渗滤液,在未投外加碳源时,原水中可降解COD几乎全部作为一级UASB的反硝化碳源被利用,A/O池缺氧段反硝化碳源不足。在A/O池的A段投加适当的无水乙酸钠作为碳源后,由于反硝化产生大量的碱度,补充了硝化所消耗的碱度,使pH值维持在一个比较合适的范围,可实现稳定的短程硝化,亚硝累积率由未投加碳源时的20%提高到87%,系统出水氨氮为10 mg/L左右,氨氮的去除率也由未投加碳源时的92%提高到99.6%。只采用两级UASB-A/O工艺处理,其出水总氮浓度不能达到国家最新排放标准（GB16889-2008）中对总氮和氨氮浓度的排放要求。为了进一步降低总氮浓度,A/O反应器出水再进入到SBR中继续处理,即采用两级UASB-A/O-SBR系统深度脱氮。试验结果表明,不论是处理早期还是晚期渗滤液,其最终出水NH₄⁺-N浓度都在15 mg/L以内,NO₂^--N和NO₃^--N浓度也都在4mg/L以内,TN降低到30 mg/L左右,系统TN和NH₄⁺-N去除率都接近100%,故本系统实现了总氮和氨氮的高效和深度去除。对晚期垃圾渗滤液投加碳源方式进行了研究,系统进水采用将原渗滤液与生活污水1:1混合液,且投加外碳源无水乙酸钠,将C/N比由1.7提高到3.0。采用两级UASB-A/O-SBR系统深度脱氮。通过FA与FNA对NOB的联合抑制,在A/O反应器中实现了稳定的短程硝化,其中亚硝态氮积累率大与70%。产生的亚硝态氮和硝态氮在SBR中被彻底去除。最终出水氨氮浓度小于2 mg/L,氨氮的去除率为99%。最终出水总氮浓度为26 mg/L,系统总氮去除率接近98%。为了考察游离氨浓度对城市生活垃圾渗滤液短程硝化的影响,采用“两级UASB- A/O系统”处理城市生活垃圾渗滤液。结果表明,适当的游离氨浓度（大于40 mg/L）可实现稳定的短程硝化,但游离氨浓度很高（大于160 mg/L）会抑制全部的硝化反应,当游离氨浓度降低则会解除这种抑制重新实现稳定的短程硝化。通过对原水进行稀释降低了游离氨浓度,从而得到了稳定的短程硝化,其中氨氮的去除率为98.6%,亚硝态氮积累率为92.17%。可见,游离氨是实现和维持城市生活垃圾渗滤液短程硝化的重要影响因素。为了考察游离氨（free ammonia,FA）、游离亚硝酸（free nitrite acid,FNA）和温度何为垃圾渗滤液短程硝化的主要影响因素,采用“两级UASB - A/O系统”处理实际城市生活垃圾渗滤液。试验共经历3个阶段即高温无短程硝化,高温实现并维持稳定短程硝化、低温实现并维持稳定短程硝化。结果表明,FA是影响短程硝化的决定因素。适当的FA浓度（1 mg/L～30 mg/L）可实现并维持稳定的短程硝化,如在阶段2中亚硝态氮积累率为93%,氨氮的去除率为99%。但FA在250 mg/L会抑制全部的硝化反应。温度并不是影响短程硝化的关键因素,如果FA在合适范围内,即使降低了10℃（如阶段3在16～18℃）,仍然可实现亚硝态氮积累率为88%的短程硝化。当系统内pH值很高（大于8.5）,FNA对短程硝化的影响可忽略不计。可见,FA是实现和维持城市生活垃圾渗滤液短程硝化的主要影响因素。针对C/N比低的晚期垃圾渗滤液,实现短程硝化脱氮和厌氧氨氧化脱氮工艺的结合,达到深度脱氮的目的。采用两级UASB-A/O-SBR系统深度脱氮,在A/O反应器中通过FA对NOB的选择性抑制实现短程硝化脱氮进而产生亚硝态氮,A/O反应器出水回流到UASB1,其中的亚硝态氮与原水中的氨氮在UASB1中发生厌氧氨氧化去除部分氨氮,从而避免了在A/O反应器中高浓度氨氮对硝化反应的抑制。试验结果表明,A/O反应器出水氨氮浓度仅为15 mg/L,亚硝态氮积累率为87.5%。A/O反应器出水进入到SBR中,同时加入8.5 g无水乙酸钠做为碳源进行反硝化,4 h反硝化结束。最终出水总氮仅为29 mg/L,氨氮也只有7 mg/L,亚硝态氮和硝态氮都还剩不到1 mg/L。因此,在整个系统中通过厌氧段的厌氧氨氧化反应和好氧段A/O反应器中的短程硝化以及后续的SBR最终反硝化脱氮,使得整个系统的氨氮和总氮去除率都接近100%,通过多种工艺的组合,在投加碳源最少的情况下实现了垃圾渗滤液氮的高效和深度去除。更多还原

【Abstract】 Sanitary landfill method is commonly used to treat municipal refuse in China. Compared to other means, sanitary landfill is the cheapest. However, landfill leachate, a strongly polluted wastewater, has become the subject of recent interest. Leachate is considered the aqueous effluent generated as a consequence of rainwater percolation through wastes, the inherent water content of wastes themselves and biochemical processes in cells of waste. The pollutant composition of landfill leachate is very complicated, and its characteristics vary a lot depending on the environmental conditions. The concentrations of organic material and ammonia nitrogen are high in fresh leachate, while matured leachate contains relatively lower concentration of organic matter but higher concentration of ammonia nitrogen. High concentration ammonia nitrogen is considered as the main reason for low effciency in biological treatment of landfill leachate. Due to operation costs and other reasons, biological technologies are major methods to treat landfill leachate. The anaerobic-aerobic combined process is considered the most economy and effective method to degrade ammonia for landfill leachate treatment.Based on the above background, first of all, a system of a two-stage UASB and an anoxic/aerobic (A/O) reactor was fully depended on as biological treatment of the municipal landfill leachate without any pre-physicochemical process. Complete ammonium nitrogen removal via nitrite was achieved. The system decreased operational costs and energy consumption, and simplifed the conventional treatment processes as well. The process procedures as follows: Part of the recycled effluent as well as the inffluent of the system was pumped into the first stage UASB (UASB1). The organic compounds of landfill leachate served as the carbon source for denitritation of the recycled effluent in UASB1. Part of the raw organics was firstly depleted as carbon source for denitritation in UASB1, while simultaneous methanogenesis occurred. Most of the organic compounds of the UASB1 effluent were depleted via methanogenesis in UASB2. Recycled sludge from the clarifying tank was pumped into the anoxic zone, the first chamber of the A/O reactor, in which denitrification of NOX--N (nitrite and nitrate nitrogen) of recycled sludge was taken place. Nitrification of ammonia was carried out in the aerobic zone of A/O reactor.The fresh leachate was firstly treated by the system of a two-stage UASB and an anoxic/aerobic (A/O) reactor. The ratio of C/N of fresh leachate is very high. It had a good result of the treatment by using the the system of a two-stage UASB -A/O reactor. Partial nitrification with 88% of nitrite accumulation efficiency took place in the A/O reactor, and the ammonia removal efficiency was nearly 100% in the system.The system of a two-stage UASB -A/O reactor was used to treat mature landfill leachate. First of all, when carbon source did not add up to the system, the COD is used as carbon source of denitrification by the first UASB. It is short of carbon source of denitrification in the A/O reactor. Then, when some carbon source were added up to the first shelve of A/O system to advance the denitrification. Because the denitrification can produce some alkalinity, which it can complement some alkalinity by nitrification consumed, and it maintained pH at a suitable scope. By this way, the stable partial nitrification was successfully achieved. Partial nitrification with 87% of nitrite accumulation efficiency took place in the system. But when some carbon source did not add up to the system, the nitrite accumulation of rate was only 20%. The ammonia concentration of effluent leachate was 10 mg/L. The ammonia removal efficience was 99.6%. But when some carbon source did not add up to the system, the ammonia removal efficience was 92% in the system.But the removal of total nitrogen (TN) could not reach below 40 mg/L which was requested by the release of new national standard for pollution by only using a two-stage UASB -A/O reactor. In order to reduce the TN concentration further, the process was improved. The final effluent of A/O reactor was further treated by SBR. The system of a two-stage UASB-A/O-SBR was utilized to treat both fresh and mature landfill leachate to remove nitrogen thoroughly.The results of the experiment showed as follows: The ammonia nitrogen concentration in the effuent of the system was no more than 15 mg/L. The nitrite nitrogen and nitrate nitrogen concentrations in the effluent were no more than 4 mg/L. The TN concentration was nearly 30 mg/L. The ammonia and TN removal efficiency was nearly 100% in the system Therefore, the two-stage UASB-A/O-SBR system was a highly effcient process to treat both fresh and mature landfill leachate.The experiment investigated the style of carbon source added when mature landfill leachate was treated. The influent leachate is mixed by raw leachate as well as domestic wastewater in a ratio of 1. The external carbon source (sodium acetate anhydrous) is added in order to enhance the C/N ratio from 1.7 to 3.0. The system of a two-stage UASB-A/O-SBR was utilized to treat mature leachate to remove nitrogen thoroughly. Through the cooperative inhibition of the free ammonia (FA) and free nitrite acid (FNA), the particial nitrification is achieved stably in the A/O reactor with more than 70% of the nitrite accumulation ratio. The nitrite and nitrate which are produced by the nitrification could be removed completely in SBR. The ammonia concentration of final effluent is less than 2 mg/L, and its removal efficiency is 99%. The total nitrogen mass concentration of final effluent is about 26 mg/L, and its removal efficiency is about 98%.A system consisted of two - stage UASB- A/O reactor was used to study the partial nitrification of the municipal landfill leachate with high ammonia concentration. The study which used real landfill leachate showed that if the concentration of FA was more than 40 mg/L, a stable partical nitrification could be successfully achieved. But if the FA concentration was more than 160 mg/L, the nitrification could be inhibited. And raw leachate was diluted in order to degrade the concentration of FA. Then the partical nitrification was restored. Partical nitrification with 92.17% of nitrite accumulation efficiency took place in the system, and the ammonia removal efficiency was 98.6% in the system. In a word, the concentration of FA was an important factor to achieve a short-cut nitrification of the municipal landfill leachate.In order to investigate the effects of free ammonia (FA), temperature and free nitrite acid (FNA) on partial nitrification, a system consisting of a two - stage UASB and an A/O reactor was used to treat leachate from municipal landfill. The results for three phases showed that a suitable FA concentration range exhibited negligible effect on partial nitrification. In this experiment when FA concentration was between 1 mg/L and 30 mg/L , stable partial nitrification could be achieved and maintained successfully. However, when FA concentration was over 250 mg/L, the entire nitrification process could be inhibited. Temperature was not the key factor to partial nitrification. In the third phase, although the temperature was very low (16℃～18℃), partial nitrification occurred and was successfully maintained with a nitrite accumulation rate of 88% in the A/O reactor. When pH was more than 8.5, the influence of FNA on partial nitrification was minimal. In conclusion, FA concentration was a major factor to achieve a partial nitrification of municipal landfill leachate.Particial nitrification - anaerobic ammonium oxidation process were used to treat mature leachate in order to remove nitrogen thoroughly. The system of a two-stage UASB-A/O-SBR was utilized to treat mature landfill leachate this stage. In the A/O reactor, FA concentration inhibited only NOB but not AOB. Thus, stable partial nitrification was obtained. Part of the recycled effluent of A/O reactor as well as the inffluent of the system was pumped into UASB1. The nitrite of the recycled effluent and part of the inffluent ammonia nitrogen were removed by Anammox. Because part of the ammonia nitrogen was removed, the inhibition of the high concentration of ammonia nitrogen was avoided. The results of the experiment showed as follows: The ammonia nitrogen concentration in the effuent of the system was only 15 mg/L. Nitrite accumulation efficiency was 87.5%.The effluent of A/O reactor was further treated by SBR. The external carbon source was added into SBR. Denitrification was ceased after the 4th hour. After denitrification, the nitrite nitrogen and nitrate nitrogen concentrations of final effluent were less than 1 mg/L. The TN concentration of final effluent was only 29 mg/L and the ammonia nitrogen concentration of final effluent was 7 mg/L.Therefore, the ammonia nitrogen and TN removal efficiency could reach nearly about 100% by the Anammox of anaerobic, the particial nitrification of A/O reactor and the denitrification of SBR. This combined process is the most economy and high effciency method in biological treatment of landfill leachate.更多还原