Evaluation of on-site biological treatment for landfill leachates and its impact: A size distribution study

A cost effective and widely applied approach for landfill leachate disposal is to discharge it to a municipal wastewater treatment plant (WWTP). The recalcitrant nature of leachate organics and the impact on the downstream WWTPs were comprehensively investigated in this study. Size fractionation by ultrafiltration (UF) and microfiltration (MF) was employed in conjunction with various analyses (TOC, COD, nitrogen species and UV₂₅₄ absorbance) on raw and biologically treated landfill leachates to provide insight into biological treatability. Overall, landfill leachate organics showed bio-refractory properties. Less than half of the organic matter, measured as total organic carbon (TOC), could be removed in the biological processes examined. Size distribution data showed that the <1 thousand Daltons (kDa) fraction is dominant in most untreated and treated landfill leachates, indicating difficulties for membrane treatment. Also, most removal occurred for the <1 kDa fraction in the biological processes, while the intermediate size fractions increased slightly. This may be caused by bio-flocculation and/or partial degradation of larger molecular weight fractions. Organic nitrogen was investigated in this study as one of the first explorations for landfill leachates. Organic nitrogen in landfill leachates was more bio-refractory than other organic matter. UV quenching by landfill leachates was also investigated since it interferes with the UV disinfection at WWTPs. The combination of activated carbon and activated sludge (PACT) showed some effectiveness for reducing UV quenching, indicating that carbon adsorption is a potential method for removal of UV quenching substances. Fourier transform Infrared (FT/IR) data showed that aromatic groups are responsible for the UV quenching phenomenon.     

响应面法优化电解芬顿协同法深度处理老龄垃圾渗滤液

采用电解芬顿法深度处理老龄垃圾渗滤液,选取电量、进水 pH 值、进水氨氮浓度3个因素为变量,CODCr 去除率为响应值进行 Box-Behnken 中心组合设计。利用响应面法对试验结果进行分析,建立了 CODCr 去除率为响应值的二阶多项式模型并进行了方差分析和显著性检验,通过解模型逆矩阵得到最佳条件：单位面积电量为23．26 Ah／dm2、pH 值为3．58、进水氨氮浓度56．78 mg／L。在最佳条件下,CODCr 去除率为96．5％,与模型预测值偏差为4．45％,吻合度较高。对电解芬顿深度处理前后的渗滤液进行 GC-MS 分析,表明电解芬顿协同处理技术能有效降解垃圾渗滤液中难生化降解的有机物,将有机物种类从42种降低至21种,是较有效的深度处理技术。     

投加高效菌处理回灌型垃圾填埋场渗滤液的研究

从垃圾转运站被污染的土壤中筛选出1株高效菌，向垃圾渗滤液中投加该菌株进行厌氧摇瓶试验，结果表明该菌株具有较好的厌氧去除氨氮的性能。将该菌株投加于模拟填埋场生物反应器中，进行了为期282d的试验，结果表明，渗滤液中的氨氮与COD被同时去除，第282天时渗滤液中的COD为770mg／L、NH4^＋ -N为90．1mg／L，大大降低了渗滤液后续处理的难度。     

In situ nitrogen management in controlled bioreactor landfills

The characteristics of leachate from landfills vary according to site-specific conditions. Leachates from “old” landfills are often rich in ammonia nitrogen due to the hydrolysis and fermentation of the nitrogenous fractions of biodegradable substrates, with decreases in concentration mainly attributable to leachate washout. At landfills where leachate containment, collection and recirculation is practiced to accelerate decomposition of readily biodegradable organic constituents, leachate ammonia nitrogen concentrations may accumulate to higher levels than during conventional single pass leaching, thereby creating an ultimate leachate discharge challenge. Landfill leachate treatment options include complex and often costly sequences of external physical–chemical and biological processes for removal of high-strength organics and inorganics, including nitrogen. Therefore, this paper focuses on investigations with bioreactor landfill simulations to demonstrate the potential for in situ nitrogen removal in dedicated nitrification/denitrification zones. Using leachate recirculation, associated system modifications provided separate aerobic and anoxic zones for ammonia nitrogen transformations to nitrate and nitrogen gas, respectively. Results from the three simulated optional stages of methanogenesis, nitrification and denitrification indicated that nitrogen conversion and removal was dependent on the operational stage. Both separate and combined reactor operation with internal leachate recycle provided 95% nitrogen conversion. In contrast, combined reactor operation with single pass leaching provided a conversion efficiency per cycle ranging between 30–52% for nitrification and 16–25% for denitrification, thereby indicating the efficacy of using the landfill itself for attenuation of leachate ammonia nitrogen concentrations to levels acceptable for ultimate discharge.     

Treatment of landfill leachate by the Fenton process

In recent years, studies of leachate treatment by conventional Fenton, photo-Fenton and electro-Fenton processes have indicated that these methods can effectively reduce concentrations of organic contaminants and color. In addition, the process can increase the biodegradable fraction of organic constituents in leachate, particularly in mature or biologically recalcitrant leachate. Oxidation and coagulation both play important roles in the removal of organics. Initial pH, dosages of Fenton reagents, aeration, final pH, reagent addition mode, temperature, and UV irradiation may influence final treatment efficiency. In this paper, current knowledge of performance and economics of Fenton processes for treatment of landfill leachate as reported for laboratory, pilot and full-scale studies is reviewed, with the conclusion that the Fenton process is an important and competitive technology for the treatment or pretreatment of landfill leachate.     

AF-MBBR技术处理高盐垃圾渗滤液的试验研究

采用厌氧生物滤池一好氧移动床工艺（AF—MBBR）处理垃圾卫生填埋场高盐渗滤液。结果表明：好氧移动床生物反应器对渗滤液中的氨氮具有非常高的去除率；但高盐量对AF—MBBR去除COD产生了明显的抑制作用，致使对COD的平均去除率仅为22％。经研究发现从垃圾渗滤液中分离、筛选出的专性耐盐菌，对高盐渗滤液生物处理系统具有显著的强化作用。     

垃圾渗滤液、粪便污水与城市污水合并处理研究

根据广州地区垃圾渗滤液、粪便污水和城市污水水质特点,研究了垃圾渗滤液、粪便污水与城市污水合并处理可行性。结果表明:广州地区垃圾渗滤液、粪便污水与城市污水合并处理重点目标污染物是氨氮和有机物。将垃圾渗滤液、粪便污水与城市污水以适当的比例混合,出水COD、NH3-N和TN可以达到《城镇污水处理厂污染物排放标准》一级B标准或以上。     

生活垃圾渗滤液处理中试研究

开发了一种适于处理高浓度垃圾渗滤液的工艺。试验表明，采用复合厌氧反应器和A／O淹没式生物膜曝气池及碱化吹脱塔技术可以有效地去除渗滤兴中的COD、BOD和氨氮。该成果已用于深圳下垃圾卫生填埋场的设计。     

垃圾填埋场渗滤液处理工程改造升级的设计

介绍了在渗滤液排放标准提高的情况下，北方某城市垃圾填埋场渗滤液处理工程改造升级的设计方案。在分析该渗滤液水质特点和原有简单物化／一级生化工艺缺陷的基础上，提出物化／多级生化／氧化吸附／膜分离组合工艺。该工艺适于高含盐、难降解渗滤液的处理，其出水水质能够达到《生活垃圾填埋污染控制标准》（GB16889-1997）中的一级标准，部分出水经反渗透处理后可达到杂用水水质标准。     

Removal of ammoniacal nitrogen from landfill leachate by irrigation onto vegetated treatment planes.

Leachate is a contaminated liquor resulting from the disposal of solid and liquid wastes at landfill sites that must be treated before discharge. Vegetated leachate treatment planes have been used at landfill sites in the UK but have received little scientific attention. This paper describes studies of model leachate treatment planes with a focus on the removal of ammoniacal nitrogen (NH3-N). Small-scale and field-scale experimental treatment planes were constructed. filled with clay loam soil and vegetated with grass (Agrostis stolonifera). Landfill leachate was applied at hydraulic loading rates ranging from 17-217l/m2/d. An exponential relationship was used to characterise the pattern of NH3-N removal. No relationship was observed between the hydraulic loading rate and the NH3-N removal rate constants (R2 = 0.0039). The daily specific NH3-N mass removal rate was found to be linearly related to the NH3-N concentration at the start of that day of treatment (R2 = 0.35). Possible causes of variation in the rate of NH3-N removal between experiments are discussed. A simple inorganic nitrogen balance indicated that the mass of N-H3-N and NO2-N removed was not accounted for by NO3-N production. Explanations for this apparent nitrogen deficit are discussed.     

垃圾渗滤液为碳源时A~2/O法的脱氮除磷研究

以垃圾渗滤液为碳源,进行了A2/O法的脱氮除磷试验研究.结果表明,在一定范围内,随着垃圾渗滤液投量的增加,A2/O工艺的出水总氮浓度降低,而对总磷的去除率却呈下降趋势.当垃圾渗滤液投量为0.2%时,出水总氮为11.38 mg/L,对总氮的去除率为62.40%,较对照的提高了13.96%;出水总磷为0.21 mg/L,对总磷的去除率为94.35%,较对照的下降了2.61%.当垃圾渗滤液投量为0.4%时,出水总氮为9.16 mg/L,对总氮的去除率为68.59%,较对照的提高了20.15%;出水总磷为0.26 mg/L,对总磷的去除率为92.37%,较对照的下降了4.59%.之后随着垃圾渗滤液投量的进一步提高,出水总氮和总磷浓度均高于对照试验的.可见,适当掺加垃圾渗滤液可提高脱氮效果,解决原水碳源不足的问题.     

Biological nitrogen removal from municipal landfill leachate: low-cost nitrification in biofilters and laboratory scale in-situ denitrification

The slow leaching of nitrogen from solid waste in landfills, resulting in high concentrations of ammonia in the landfill leachate, may last for several decades. The removal of nitrogen from leachate is desirable as nitrogen can trigger eutrophication in lakes and rivers. In the present study, a low-cost nitrification-denitrification process was developed to reduce nitrogen load especially in leachates from small landfills. Nitrification was studied in laboratory and on-site pilot aerobic biofilters with waste materials as filter media (crushed brick in upflow filters and bulking agent of compost in a downflow filter) while denitrification was studied in a laboratory anoxic/anaerobic column filled with landfill waste. In the laboratory nitrification filters, start-up of nitrification took less than 3 weeks and over 90% nitrification of leachate (NH4-N between 60 and 170mg N l(-1), COD between 230 and 1,300 mg l(-1)) was obtained with loading rates between 100 and 130 mgNH4-N l(-1) d at 25 degrees C. In an on-site pilot study a level of nitrification of leachate (NH4-N between 160 and 270 mg N l(-1), COD between 1,300 and 1,600 mg l(-1)) above 90% was achieved in a crushed brick biofilter with a loading rate of 50mg NH4-N l(-1) d even at temperatures as low as 5-10 degrees C. Ammonium concentrations in all biofilter effluents were usually below the detection limit. In the denitrification column. denitrification started within 2 weeks and total oxidised nitrogen in nitrified leachate (TON between 50 and 150mg N l(-1)) usually declined below the detection limit at 25 degrees C, whereas some ammonium, probably originating from the landfill waste used in the column, was detected in the effluent. No adverse effect was observed on the methanation of waste in the denitrification column with a loading rate of 3.8 g TON-N/t-TS(waste) d. In conclusion, nitrification in a low-cost biofilter followed by denitrification in a landfill body appears applicable for the removal of nitrogen in landfill leachate in colder climates.     

PAEs and BPA removal in landfill leachate with Fenton process and its relationship with leachate DOM composition

An increasing attention has been paid to the trace endocrine disrupting compounds (EDCs) in landfill leachate. In this paper, the removal of EDCs including phthalic acid esters (PAEs) and bisphenol A (BPA) from the fresh and mature landfill leachate by Fenton treatment was studied. More than 40% of PAEs and about 62% of BPA were removed from the raw mature leachate while only 20% of PAEs and 37% of BPA in the raw fresh leachate were reduced, respectively. After the fresh and mature leachates were spiked with PAEs to 1.5 mg L^− 1 and BPA to 0.08 mg L^− 1, the removal efficiencies of BPA and PAEs increased to more than 88%. The results indicated that the removing efficiencies of the EDCs in the leachate had a relationship with their concentrations, and that the trace levels of EDCs in leachate challenged the treatment capacity of the Fenton process. Most of the EDCs in the enriched leachate were removed by oxidation, which had no clear correlation with the hydrophobicity of the EDCs. The flocculation played an important role in the removal of di-(2-ethylhexyl) phthalate that could not be completely oxidized in the Fenton process, in that the EDCs with high n-octanol/water partition coefficient inclined to precipitate after the Fenton process. The dissolved organic matter (DOM) in the fresh leachate inhibited the EDCs removal more than the DOM in the mature leachate did. Both the composition of the leachate DOM and the characteristics of the EDCs determined the removing efficiencies of the EDCs in the Fenton process.     

水解/好氧MBR组合工艺处理非稳定期垃圾渗滤液

以非稳定期垃圾填埋场的渗滤液为对象，研究了水解／好氧MBR组合工艺对COD和氮污染物的去除效果和规律。在HRT为1～4．7d、回流比为300％以及进水的COD为400～7600mg／L、氨氮为247．1～1643．8mg／L、TN为258．7～1743mg／L的条件下，对COD、氨氮和TN的去除率分别为80％～88％、〉99％和70％～82．2％，说明该组合工艺对渗滤液中的COD和氮污染物具有较好的去除效果。     

垃圾卫生填埋场渗滤液组合处理工艺设计与调试

针对垃圾渗滤液水质变化较大的特点,采用铁床、铁床沉淀池、超声脱氨氮、UASB反应塔、PSB（光合细菌）反应池、水解酸化池、SBR反应塔、沉淀滤池工艺处理垃圾渗滤液,运行结果表明,该工艺对水质变化具有很强的适应能力,出水水质优于〈生活垃圾填埋污染控制标准〉（GB 16889-1997）的二级排放标准.介绍了该渗滤液处理系统的组成、重要构筑物及其设计参数、工程调试运行和经济分析等情况,总结了该工艺的设计特点.     

渗滤液回灌的氨氮和凯氏氮变化规律

在渗滤液原液回灌和经好氧预处理后回灌两种情况下，考察了垃圾渗滤液中氨氮与凯氏氮浓度的变化规律。结果表明：渗滤液原液回灌会严重抑制垃圾中含氮物质的水解过程，而渗滤液经好氧处理后回灌则可显著加速垃圾中含氮物质的水解过程。     

混凝吸附作用在垃圾渗滤液处理中的应用浅析

垃圾渗滤液具有高COD浓度、高氨氮、高重金属的特点,直接采用常规生物方法难以使处理过程正常运行。物化法作为垃圾渗滤液生物处理的预处理工艺,可降低渗滤液中的生物毒性,为后续生物处理提供良好条件。因此,对垃圾渗滤液预处理方法研究具有重要的理论意义和工程实践意义。     

贵州省垃圾填埋场渗滤液处理技术研究

本文分析了垃圾填埋场渗滤液的来源及水质特征,对国内外垃圾渗滤液的处理方法进行简单综述,针对贵州省垃圾渗滤液水质特征及地形条件,提出相应的渗滤液处理工艺,并分析了各段处理工艺的原理及作用。     

好氧反硝化在短程硝化反硝化工艺中的作用研究

采用SBR反应器处理垃圾渗滤液，研究了短程硝化反硝化过程中好氧反硝化的作用。结果表明，SBR反应器的亚硝化效果良好，氨氮几乎完全被氧化为NO2^- -N；该系统的活性污泥中同时存在能还原NO3^- -N和NO2^- -N的好氧反硝化菌，还原NO3^- -N的好氧反硝化菌和氨氧化菌的数量及其总活性高于NO2^- -N氧化菌，这是SBR反应器能够长期维持亚硝化状态的重要原因；有机物浓度越高则好氧反硝化速率越快，此时氨氮均被氧化为NO2^- -N，当有机物浓度达到某临界值时，好氧反硝化速率几乎保持不变；溶解氧浓度越低则好氧反硝化速率越快，释放出的OH^-会导致pH值升高。好氧反硝化对于维持和促进SBR反应器的短程硝化反硝化具有重要的作用。     

Dissolved organic matter (DOM) in recycled leachate of bioreactor landfill

Landfill leachate needs sufficient treatment before safe disposal. Bioreactor landfill technology could effectively degrade the organic matters in recirculated leachate, hence leaving a leachate stream of low biodegradability. This study characterized the dissolved organic matter (DOM) in the leachate from simulated bioreactor landfill columns with or without presence of trace oxygen. The removal efficiencies of this DOM using coagulation-sedimentation or electrolysis processes were demonstrated. Recirculated leachates were sampled from the simulated landfill columns applying conventional mode, intermittent-aeration mode, and natural aeration mode, whose DOM was fractionated into humic acids (HA), fulvic acids (FA) and hydrophilic fractions (HyI) by the XAD-8 resin combined with the cation exchange resin method. The recirculated leachate had low BOD/COD ratio, high humic substances contents, and high aromatic content. Their HA fraction comprised mainly large molecules (>10 k Da), while the FA and HyI were composed of smaller molecules (<50 k and <4 k Da, respectively). With the presence of oxygen, the TOC contents and the contents of HA, FA and HyI in leachate reduced, with FA and HyI fractions of molecular weight (MW) lower than 4 k Da more readily degraded. The organic matters left in leachates from intermittent-aeration mode and natural aeration mode were of low biodegradability. It was tested in the following sections the effects of coagulation-sedimentation process and of electrolysis process on the removal of residual DOM in recirculated leachate. Coagulation-sedimentation tests revealed that poly ferric sulphate (PFS) could remove more COD (58.1%) from leachate than polyaluminum chloride (PACl) (22.9%), particularly on the HA fraction with MW>10 k Da. Coagulation-sedimentation could not remove most of HyI in leachate. Furthermore, the corresponding BOD/COD ratio was not improved through coagulation. Electrolysis test could also effectively removed HA of MW>10 k Da. However, the biodegradability of treated effluent considerably was improved. The electrolysis could decompose high MW substances and increase biodegradability of recirculated leachate from bioreactor landfill.