Determination of SCFAs in water using GC-FID. Selection of the separation system

In the present study, an analytical procedure was developed for the determination of short-chain fatty acids (SCFAs) in landfill leachate and municipal wastewater employing injection of aqueous samples to gas chromatograph with flame ionization detector (GC-FID). Chromatographic conditions such as a separation system, injection volume, oven temperature program were investigated and selected. With two columns, one with a polar (polyethylene glycol) and one with a non-polar (dimethylpolisiloxane) stationary phase, good separation of SCFAs, containing from 2 to 8 carbon atoms, was achieved. The sample volume was 2 μL and the temperature program 80 °C (30 s) then 7 °C min⁻¹ to 220 °C (2 min). LOQs values were below 0.25 mg L⁻¹. The concentrations of the acids in the landfill leachate studied ranged from 0.45 ± 0,059 (average ± extended uncertainty) mg L⁻¹ for pentanoic acid to 15.2 ± 0.73 mg L⁻¹ for ethanoic acid. Concentrations of SCFAs in the municipal wastewater were lower than LOQs.     

Determination of Trace Bisphenol A in Leachate by Solid Phase Microextraction Coupled with High Performance Liquid Chromatography

Abstract

A rapid determination method for trace bisphenol A in leachate by solid phase microextraction (SPME) coupled with high performance liquid chromatography (HPLC) was developed. The experimental condition of SPME, such as select operation, solid phase microextraction fibers, pH, extraction time, extraction temperature, desorption time, desorption solution, mode, and the analytical conditions of HPLC were optimized. As compared with the graph that was produced by HPLC alone, the graph by only HPLC couldn't analyze bisphenol A and compared to the results of three solid‐phase microextraction fibers. The linear range was between 0.0128 mg/L and 0.192 mg/L in this method, and the correlative coefficient was 0.9975. Limits of detection, repeatability, and reproducibility were also determined. The limit of detection of this method was 3.25 µg/L (3σ, n=11). The relative standard deviation (RSD, n=3) was 4.4%. The method was used for the determination of trace bisphenol A in leachate of Qingshan landfill and leachate of Liufang landfill. The recoveries were between 94.5% and 103.3%. This method is fast, convenient, sensitive, solvent free, and suitable for the determination of trace bisphenol A in leachate.     

Determination of phenol in landfill leachate by using microchip capillary electrophoresis with end-channel amperometric detection

Phenol, 2,4-dichlorophenol (2,4-DCP), and 2,4,6-trichlorophenol (2,4,6-TCP) were baseline separated by using a homemade microchip CE with an end-channel amperometric detector where a 50 microm Pt microdisk working electrode (WE) and a Pt cathode were integrated onto the microchip itself. Separation parameters such as injection time and voltage, pH of the buffer, online pretreatment condition for WE, reproducibility, and detection potential were investigated. Under the selected separation conditions, the linear ranges for phenol, 2,4-DCP, and 2,4,6-TCP were 2-200, 4-400, and 4-400 microM, respectively. The LODs were 0.4, 0.5, and 0.7 microM for phenol, 2,4-DCP, and 2,4,6-TCP, respectively (S/N = 3). The standard addition method was successfully applied to the analysis of landfill leachate samples and the concentration of phenol in the landfill leachate samples was measured to be 0.32 and 0.21 mM, respectively. The recoveries were in the range of 85-103% and corresponding RSDs were less than 5.5%.     

Development and application of an analytical protocol for evaluation of treatment processes for landfill leachates. I. Development of an analytical protocol for handling organic compounds in complex leachate samples

A strategy is presented for evaluation of treatment procedures for landfill leachate with emphasis on organic pollutants. An analytical scheme, the LAQUA protocol, was developed as a guide for the analytical work. The protocol includes organic as well as metals, inorganic ions, water-quality parameters, and toxicity. The proposed strategy considers the behaviour of both polar and non-polar organic substances at trace levels. For polar substances, phenols were chosen as markers and determined with an automated supported liquid membrane extraction device, coupled on-line to HPLC with a diode-array detector. For non-polar substances, PCBs and 10 unidentified compounds were chosen as markers and analysed by solid-phase extraction combined with supercritical fluid extraction with GC analysis. The chosen measurement strategy, based on the use of marker substances, difference measurements, and versatile data-handling procedures, provided essential information about complex systems at relatively low cost.     

碱法消解—硫氰酸汞吸光光度法测定垃圾渗沥水中氰化物

根据垃圾渗沥水的特性，采用碱法 －过氧化氢氧化消解，消除有机物的干扰，以硫氰酸汞吸光光度法测定氯化物。试验研究提出了的方法简便、准确、可靠。     

再生水灌溉后农田土壤淋溶液DOM光谱学特征

再生水灌溉农业是实现再生水回用的有效途径，其天然优势和操作可行性已得到普遍认可。再生水灌溉农业能够取得良好的生态效益、社会效益和经济效益，但灌溉过程可能导致土壤有机质的性质异化和非定向流失，相关问题尚没有引起足够重视。选取溶解性有机质（DOM）为目标对象，对灌溉过程农业土壤淋溶液DOM谱学信息差异化机制这一科学问题展开研究。以污水源再生水和河水源地表水（参比对照）为灌溉水源，借助一维原状土柱分析灌溉过程对土壤和淋溶液的影响，对土壤表面形貌（SEM）、淋溶液DOM紫外可见光谱（UV-Vis）和三维荧光光谱（3D-EEMs）进行比对，初步掌握灌溉后土壤淋溶液DOM的基础信息。结果表明：灌溉后的土壤团聚体结构松散、表面粗糙，出现细粒组分聚集和粘结的现象。土壤有机质随土壤深度增加逐渐减少，土壤DOM在10～20 cm土层分布最多；灌溉过程能够增加0～30 cm土壤有机质和0～20 cm土壤DOM含量，证明土壤对灌溉水有机物具有截留作用。两种淋溶液DOM的UV-Vis谱图比较相近，均在240～270 nm区间出现吸收平台（源于DOM不饱和双键共轭结构）；相比之下，再生水源土壤淋溶液DOM的芳香化程度更低、结构更简单，两种淋溶液DOM中富里酸含量高于胡敏酸。淋溶液DOM三维荧光光谱仅出现一处荧光峰，位于E_x/E_m=260～270/420～430 nm区域，表明有类腐殖质组分的存在。经与前期研究结果比对，推测氨基酸类物质、类蛋白组分等可能被（灌溉过程）阻滞于土壤体系；自生源（内源）DOM对土壤淋溶液DOM的贡献更大，而外源DOM的影响程度有限。相关结果有助于深度评估再生水灌溉过程农业土壤DOM（或有机质）的流转归趋和生态效应。     

Treatment of landfill leachate by immobilized microorganisms

This paper focuses on the outcome and the main performance of the immobilized microbial that treats landfill leachate. Based on the analysis of COD and ammonia-nitrogen of the influent and effluent, research was done on the high removal efficiency of COD and ammonium nitrogen by immobilized microbial. The leachate composition was analyzed qualitatively using GC-MS before and after being treated. Biological loading of efficient microbial flora on the carrier was measured by Kjeldahl’s method. Finally, the patterns of immobilized microbe were observed through scanning electron microscopy (SEM). The results showed that in immobilized microorganisms system, the efficiencies of COD and nitrogen were 98.3% and 99.9%, respectively. There was a great reduction of organic components in effluent. When the immobilized biomass on the carrier was 38 g·L?1 (H2O), the filamentous microorganism was highly developed. There was no inhibitory effect on the nitrobacteria and nitrococcus, when ammonia was over 200 mg·L?1 and NH3 over 150 mg·L?1. At a high organic loading, it still had good nitrification. This paper also compares the performance of immobilized microbial with free microbial under the same condition. The immobilized microbial technology demonstrated better than the latter in all aspects.     

多孔活性硅胶的制备及吸附性能的研究

以硅酸钠和氯化铵为原料,通过添加表面活性剂制备高吸附活性的多孔硅胶.采用SEM,IR和XRI)等手段对硅胶样品的结构和形貌进行表征,并利用紫外分光光度法研究硅胶样品对垃圾渗滤液中有机污染物的吸附性能.结果表明,合成的硅胶样品是由纳米量级的无定形二氧化硅颗粒组成的多孔性、疏松状物质,对垃圾渗滤液中的有机物分子具有较强的吸...     

阴极催化剂对微生物燃料电池性能的影响

以不同载量的MnO_2/rGO和Pt/C修饰阴极电极构建了生物阴极型双室微生物燃料电池(MFC),考察了不同阴极催化剂修饰MFC对其产电性能以及老龄垃圾渗滤液主要污染物去除效果的影响。结果表明,以MnO_2/rGO修饰MFC阴极电极材料,能显著提高MFC产电性能及对老龄垃圾渗滤液中污染物去除效果;输出电压为372 mV,功率密度为194 mW/m~3(是未经催化剂修饰MFC的两倍),内阻为264Ω,化学需氧量(COD)和氨氮(NH_3-N)去除率分别为58.68%和76.64%。当MnO_2/rGO载量为.0 mg/cm~2时,MFC性能与负载Pt/C的MFC性能接近,但构建成本却明显降低。     

Modeling Biogeochemical Processes in Leachate-Contaminated Soils: A Review

During subsurface transport, reactive solutes are subject to a variety of hydrological, physical and biochemical processes. The major hydrological and physical processes include advection, diffusion and hydrodynamic dispersion, and key biochemical processes are aqueous complexation, precipitation/dissolution, adsorption/desorption, microbial reactions, and redox transformations. The addition of strongly reduced landfill leachate to an aquifer may lead to the development of different redox environments depending on factors such as the redox capacities and reactivities of the reduced and oxidised compounds in the leachate and the aquifer. The prevailing redox environment is key to understanding the fate of pollutants in the aquifer. The local hydrogeologic conditions such as hydraulic conductivity, ion exchange capacity, and buffering capacity of the soil are also important in assessing the potential for groundwater pollution. Attenuating processes such as bacterial growth and metal precipitation, which alter soil characteristics, must be considered to correctly assess environmental impact. A multicomponent reactive solute transport model coupled to kinetic biodegradation and precipitation/dissolution model, and geochemical equilibrium model can be used to assess the impact of contaminants leaking from landfills on groundwater quality. The fluid flow model can also be coupled to the transport model to simulate the clogging of soils using a relationship between permeability and change in soil porosity. This paper discusses the different biogeochemical processes occurring in leachate-contaminated soils and the modeling of the transport and fate of organic and inorganic contaminants under such conditions.