Use of Fenton reaction for the treatment of leachate from composting of different wastes

The oxidation of leachate coming from the composting of two organic wastes (wastewater sludge and organic fraction of municipal solid wastes) using the Fenton's reagent was studied using different ratios [Fe(2+)]/[COD](0) and maintaining a ratio [H(2)O(2)]/[COD](0) equal to 1. The optimal conditions for Fenton reaction were found at a ratio [Fe(2+)]/[COD](0) equal to 0.1. Both leachates were significantly oxidized under these conditions in terms of COD removal (77 and 75% for leachate from wastewater sludge composting and leachate from organic fraction of municipal solid wastes, respectively) and BOD(5) removal (90 and 98% for leachate from wastewater sludge composting and leachate from organic fraction of municipal solid wastes, respectively). Fenton's reagent was found to oxidize preferably biodegradable organic matter of leachate. In consequence, a decrease in the biodegradability of leachates was observed after Fenton treatment for both leachates. Nevertheless, Fenton reaction proved to be a feasible technique for the oxidation of the leachate under study, and it can be considered a suitable treatment for this type of wastewaters.     

Cross-flow leaching of alkali and alkaline-earth metals from sawdust and wheat straw – Modelling of the process

Cross-flow washing of wheat straw and beech sawdust with water was carried out in order to leach the alkali and alkaline earth metals from them. Incremental concentration change (C = Δm/ΔV) of alkali and alkaline-earth metals in the leachate was plotted against the wash water volume. Maximum increase in Δm/ΔV was achieved after passing 0.04 to 0.06 dm³ of water through the washed biomass. After passing 0.2 dm³ of water through the biomass, leaching of alkali metals was practically completed. Concentration of potassium ion was predominant in the leachate. From the whole amount of alkali and alkaline-earth metal ions, found in the aqueous phase after washing, K⁺ ions make about 80% in case of wheat straw and 64% in case of beech sawdust. Concentration of other considered metal ions was much less comparing to the potassium ones.Change in the pH and electrical conductivity (EC) were measured after passing of each portion of wash water through the biomass. Change of the EC against the wash water volume follows fairly the change of leachate composition. Based on the experimental results, the process of alkali and alkaline-earth metals leaching was modelled assuming the cross-flow scheme of leaching process. Proposed model follows fairly the experimental data. Discrepancy between the experimental and calculated values for alkaline-earth metals in case of beech sawdust is attributed to a different leaching mechanism.     

Modelling migration of contaminants from waste disposal facility

Waste disposal facility design must involve some form of barrier that separates the waste from the groundwater system located below it. This barrier is intended to minimize the migration of contaminants from the waste facility. Natural clay deposits and compacted clay liners of a certain minimum thickness are often used to prevent leachate from flowing down towards groundwater. The finite difference numerical model developed in this study is validated for two case studies. Subsequently, a study was conducted by taking the finite mass of a leachate at the top of the liner; the variation of the maximum concentration of the pollutant in the liner is then determined. From the concentration profiles generated, the optimum clay barrier thickness required to prevent migration of contaminants to the aquifer located below can also be determined.     

垃圾填埋场渗透滤液对地下水环境的影响与控制

分析了太原市垃圾卫生填埋场渗滤液的来源、组成及对环境的影响 ,提出几点控制措施 ,减少填埋处置对环境的污染     

城市垃圾填埋场渗滤液处理工艺及其研究进展

垃圾渗滤液污染物浓度高 ,水质水量变化大 ,是国内外污水处理的难题。综述了垃圾渗滤液的生物、物理化学、土地和循环回灌处理法 ,分析了各种处理方法的特点 ,讨论了国内外渗滤液处理研究的进展 ,列举了我国几大垃圾填埋场渗滤液处理工艺。认为生物法与物理化学法结合将是未来渗滤液处理研究的主要方向。经济高效的脱氨氮方法能大大提高后续生物处理效率     

COD fractions of leachate from aerobic and anaerobic pilot scale landfill reactors

One of the most important problems with designing and maintaining a landfill is managing leachate that generated when water passes through the waste. In this study, leachate samples taken from aerobic and anaerobic landfill reactors operated with and without leachate recirculation are investigated in terms of biodegradable and non-biodegradable fractions of COD. The operation time is 600 days for anaerobic reactors and 250 days for aerobic reactors. Results of this study show that while the values of soluble inert COD to total COD in the leachate of aerobic landfill with leachate recirculation and aerobic dry reactors are determined around 40%, this rate was found around 30% in the leachate of anaerobic landfill with leachate recirculation and traditional landfill reactors. The reason for this difference is that the aerobic reactors generated much more microbial products. Because of this condition, it can be concluded that total inert COD/total COD ratios of the aerobic reactors were 60%, whereas those of anaerobic reactors were 50%. This study is important for modeling, design, and operation of landfill leachate treatment systems and determination of discharge limits.     

Decomposition of toxic pollutants in landfill leachate by ozone after coagulation treatment

This study deals with evaluation of organic matter from Mexico City waste sanitary landfill leachate of Bordo Poniente (including domestic and industrial) by ozonation after a coagulation treatment with Fe2(SO4)(3) (2.5 g/L at pH 4-5). The content of humic substances after the coagulation treatment decreases up to 70%. Then leachate obtained from a solid with initial COD=1511 mg/L and the pH 8.5 was treated by ozone. The aqueous samples by a UV-vis and HPLC technique were analyzed. The partial identification of the initial composition of the organic matter as well as of intermediates and final products was carried out after the extraction of the initial and ozonated leachate with benzene, chloroform:methanol (2:1) and hexane. Then the extracts with a gas chromatograph with mass detector and FID were analyzed. In the HPLC results we identify malonic and oxalic acids. The initial concentrations of these acids were 19 mg/L and 214 mg/L, respectively. The oxalic acid is formatted and accumulated in ozonation. The obtained results show that the color disappears (visually) at 100% during 5 min of ozonation. The organic substances, extracted with chloroform-methanol, may be destructed during 15 min of ozonation; the organic matter, extracted with benzene, destructs completely by ozone during 5 min, and the organic compounds extracted with hexane have a low ozonation rate. The toxic compounds presented in leachate decompose completely during 15 min of ozonation. The ozonation rate constants for each group of organics (as observed constants) were calculated applying simplified mathematical model and the recurrent least square method using the program MATLAB 6.5.     

垃圾渗滤液中污染组分动态变化规律的模拟研究

通过室内垃圾柱淋滤装置对锦州市南山垃圾填埋场渗滤液水质变化规律进行了模拟研究,并利用实验数据绘制出了渗滤液中污染组分的浓度变化曲线,分析了垃圾场中渗滤液污染物组分的变化特征以及造成这种变化的相关原因。从而为今后垃圾渗滤液污染地下水的防治提供理论上的依据。     

ADVANCED LEACHATE TREATMENT AT THE STEWARTBY LANDFILL SITE

Landfill liquor (leachate) is produced by complex microbial processes within a landfill site. The long retention period, typically in excess of many years, ensures that easily-biodegradable materials disappear rapidly, whereas intractable (hard) Chemical Oxygen Demand (COD) substances decay slowly. The resultant liquor is often difficult to treat biologically due to high concentrations of Ammoniacal N (amm.N) and low concentrations of nutrient Phosphorus (P) and Biochemical Oxygen Demand (BOD).
The advanced treatment process adopted at the Stewartby landfill site has been based on extensive laboratory trials by WRG Ltd (formerly Shanks Ltd), with technical input from Birse Process Engineering Ltd. This has significantly reduced the risks involved in plant scale-up.
The particular choice of treatment process reflects the stringent discharge consent and the wide variety of waste received at the site, in particular, the presence of hazardous waste producing a leachate which is especially difficult to treat.
Treatment is based on the activated sludge process, assisted by Powdered Activated Carbon (PAC) dosing. The leachate is heated to improve oxidation of amm.N and the process stream also includes Dissolved Air Flotation (DAF) and Sand Filtration to remove suspended solids (SS) and P. Odour control is provided by a two-stage activated carbon unit.
Results from the full-scale treatment plant have been excellent, averaging 70% COD removal and almost 100% amm.N removal and fully satisfying the sewer discharge consents imposed by Anglian Water and the Environment Agency.
This paper describes the laboratory trials, process design and commissioning of the leachate treatment plant at the Stewartby landfill site.     

Xenobiotic organic compounds in leachates from ten Danish MSW landfills--chemical analysis and toxicity tests

A monitoring program comprising chemical analysis and biological toxicity testing of leachate samples from 10 Danish landfills (six engineered and four uncontrolled) revealed the presence of 55 different xenobiotic organic compounds (XOCs) and 10 degradation products of XOCs. The compounds belong to the following groups: BTEX, C3-benzenes, bicyclo compounds, napthalenes, chlorinated aliphatics, phenols (chloro-, methyl-, dimethyl, nonyl-), pesticides, and phthalates. Concentrations of single XOCs ranged from <0.1 to 2220 microg/L. A pesticide screening including 101 different compounds resulted in detection of 18 pesticides and three degradation products. The findings of degradation products of toluene, phenols, phthalates, pesticides, and nonylphenol ethoxylates show that degradation occurred inside the landfills. In biotests with bacteria and algae it was found that the non-volatile organic compounds were toxic as the samples only needed to be pre-concentrated from 1.3 to 9.4 times to give 50% inhibition of the test organisms. One of the ten samples proved to be genotoxic in the umuC test after 141 times pre-concentration. A major part of the organic chemicals causing toxicity remains unknown and it is recommended to combine chemical analyses and biotests in future monitoring programs.