Boron-doped diamond anodic treatment of landfill leachate: evaluation of operating variables and formation of oxidation by-products

Landfill leachate with a low BOD/COD ratio was electrochemically oxidized by means of a boron-doped diamond anode. In addition to organic matter removal, this study addressed the issue of formation of both chlorinated organic compounds and nitrate ions as a result of organic matter and ammonia and/or organic nitrogen electro-oxidation in the presence of chloride ions. A factorial design methodology was implemented to evaluate the statistically important operating variables: treatment time (1-4 h), pH (5-8), current intensity (6.3-8.4 A) and addition of chloride (2500-4500 mg L⁻¹). The process was evaluated on COD, total nitrogen (TN) and colour removal, as well as on the formation of nitrate, nitrite and chlorinated organics. Of the four variables studied, treatment time and pH had a considerable influence on COD and colour removal. On the contrary, none of the variables had a significant effect on the elimination of TN for which an average removal of 61 mg L⁻¹ was obtained. The studied variables exhibited different effects on the four groups of organo-chlorinated compounds considered in this study, namely trihalomethanes (THMs), haloacetonitriles (HANs), haloketons (HKs) and 1,2-dichloroethane (DCA). Further analysis at more intense conditions, i.e. current intensity up to 18 A and reaction time up to 8 h revealed that high levels of decolourization (84%) could be achieved followed by low COD (51%) and ammonia (32%) removals. Apart from DCA, the concentration of chlorinated organics increased continuously with treatment time reaching values as high as 1.9 mg L⁻¹, 753 μg L⁻¹ and 431 μg L⁻¹ of THMs, HANs and HKs, respectively.     

Application of zeolitised coal fly ashes to the depuration of liquid wastes

In this study, the application of some zeolitised fly ashes and synthetic zeolites to the decontamination of the leachate produced in a municipal solid waste (MSW) treatment plant and to the liquid waste from a pig farm was analyzed. Thus, the reduction of organic matter (BOD and COD), ammonium and total nitrogen, phosphorus and metals contents after a zeolite treatment was evaluated. Several synthetic zeolites were tested: some commercial zeolites and other synthetic zeolites and zeolitised ashes obtained after a coal fly ash alkaline hydrothermal process. Two forms of contact between the zeolitic material and the liquid waste were tested: in a stirred tank and in a column. In addition, other variables determined were the amount of zeolite and the residence time. The results showed that zeolites, especially zeolitised fly ash, clearly produced a strong reduction in the leachate nitrogen and phosphorus content.     

A Critical Review of Biological Processes and Technologies for Landfill Leachate Treatment

The most common method to deal with the huge production of municipal wastes is still the disposal in landfills which, however, generates a leachate with high contents of organic and nitrogen pollutants. Requirements must be fixed by law to control leachate release from such landfills, and effective treatment processes and technologies must be applied to reduce its impact on the environment. Biological processes for leachate treatment are discussed in this review, in the former part of which attention is paid to leachate formation and its qualitative and quantitative features, while the latter deals with the state‐of‐the‐art of the most effective biotechnological treatments presently employed. Processes, alternative methods, and technological improvements are compared, with special focus on novel technologies to remove nitrogen pollutants from leachate, highlighting advantages and drawbacks of each treatment.     

Fouling of WO3 nanoparticle-incorporated PSf membranes in ultrafiltration of landfill leachate and dairy a combined wastewaters: An investigation using model

As fouling has always been a major drawback of membrane technology, qualitative and quantitative understanding of membrane fouling mechanisms therefore becomes vital in order to help push membrane separation technologies forward. In this study, firstly, self-cleaning Polysulfone(PSf) membranes were synthesized by incorporation of WO_3nanoparticles(0–2 wt%) and subsequent UV irradiation for efficient ultrafiltration(UF)of landfill leachate and dairy wastewater. The membrane surface properties were characterized by scanning electron microscopy(SEM) and contact angle analysis. It was found that UV-irradiated membranes exhibited higher percent COD removals due to the hydrophilicity and photocatalytic properties of nano-WO_3. Subsequently, in order to analyze the fouling behavior of the membranes, a set of experimental data from cross-flow ultrafiltration of municipal landfill leachate and industrial dairy wastewater at 25 °C was obtained. A new model of membrane fouling was proposed based on a resistance in series concept and was fitted well with all experimental data sets.Almost all relative errors of prediction provided by the proposed model were less than 2.5%. In addition, it was revealed that this newly-developed model exhibited smooth transition between the common successive twostep pore blockage-cake filtration phenomena and thus eliminates the need to use separate equations for different mechanisms.     

Internal leachate quality in a municipal solid waste landfill: vertical, horizontal and temporal variation and impacts of leachate recirculation

The aim of this study was to monitor and characterise internal leachate quality at a Finnish municipal solid waste landfill (Lahti, Kujala, in operation for approximately 50 years) to provide information about its horizontal and vertical variation as well as effects of leachate recirculation on leachate quality. The study area (approximately 4 h) of the landfill had 14 monitoring wells for leachate quality monitoring over a 2-year period. The leachate was monitored for COD, BOD, TKN, NH₄–N, Cl, pH and electric conductivity. The results showed high horizontal and vertical variability in leachate quality between monitoring wells, indicating that age and properties of waste, local conditions (e.g., water table) and degradation and dilution processes have a marked effect on local leachate quality. The mean COD values (642–8037 mg/l) and mean BOD/COD ratios (0.08–0.17) from the different monitoring wells were typical of landfills in the methanogenic phase of degradation. The leachate in the monitoring wells was notably more concentrated than the leachate effluent used for leachate recirculation. In the landfill as a whole the effects of the leachate recirculation on leachate quality, although difficult to distinguish from those caused by other factors, appeared to be minor during the study period.     

DT-RO处理垃圾渗滤液工程介绍

重庆长生桥垃圾卫生填埋渗滤液处理工程,是我国第一座采用碟管式反渗透(DT-RO)技术处理的工程。在半年多的运行中,该系统效能高且稳定。CODCr、TOC和电导率去除率均在99%以上,NH3-N去除率达98%,Ca2+、Ba2+、Mg2+截留率均在99.9%以上,出水中未检出SS。浓缩液回灌于垃圾填埋场,形成回灌型生物反应器。     

“膜生物反应器（MBR）＋反渗透（RO）”工艺处理垃圾渗滤液项目调试运行

通过对广州市兴丰生活垃圾卫生填埋场渗滤液处理厂扩容工程的调试运行,表明采用＂膜生物反应器（MBR）＋反渗透（RO）＂工艺处理垃圾渗滤液存在设备维护简单、处理效果稳定等特点,出水各项指标均优于《生活垃圾填埋场污染控制标准》（GB16889-2008）一般地区一级排放标准要求。     

Comparison of Different Oxidation Methods for Recalcitrance Removal of Landfill Leachate

In this work several oxidation methods, such as conventional ozonation, O₃/UV, O₃/UV/ferrous iron and Fenton oxidation, for the removal of recalcitrant organic matter present in landfill leachates are evaluated. The samples of the leachate are taken after a biological treatment and membrane ultra-filtration (UF). The contribution of the UV radiation and the effect of ferrous iron ions on the ozone process efficiency is discussed. At lower ozone dosages, the partial oxidation efficiency is reduced as compared to conventional ozonation and therefore, a higher degree of mineralization of the organic matter is achieved. Finally, the best results are obtained by the Fenton oxidation, however, based on economic considerations this method is not recommended.     

Combined adsorption and Chemical precipitation process for pretreatment or post-treatment of landfill leachate

Performances of combined adsorption and chemical precipitation were evaluated as one of the options for pretreatment or post-treatment of a municipal solid waste (MSW) landfill leachate and leachate from an industrial solid waste landfill. The COD and color removals of the leachate from a MSW landfill were 35% and 33% at an alum dose of 300 mg/L with preceding PAC (powdered activated carbon) dose of 200 mg/L, respectively. For MSW leachate, the combined adsorption and coagulation process showed 2.3 times higher COD removal at PAC dose of 200 mg/L and alum dose of 500 mg/L than the unit process of adsorption with poor settleability. The COD removal was accomplished mainly by adsorption, while coagulation was a key mechanism of color removal. The COD and color of the biologically treated leachate from an industrial solid waste landfill were removed up to 32% and 68%, respectively, at addition of 490 mgAlum/L and 1,000 mgPAC/L in adsorption-coagulation process with pH control. Combined adsorption and coagulation process with pH control showed better COD and color removal than the process without pH control. The color removal was influenced greatly by pH control, while COD removal was not. No difference in removal efficiency was observed between adsorption-coagulation and coagulation-adsorption. Maximum net increases in the COD and color removals by the adsorption-coagulation process were 40% and 46%, respectively, compared with the removals by sole chemical precipitation. The Freundlich isotherm exclusively described the adsorption of leachate components on the PAC. Thus, a combined adsorption and coagulation process was considered to be effective for pre-treatment or post-treatment of landfill leachate, and has distinct features of simple, flexible, stable and reliable operation against fluctuation of leachate quality and flowrate.     

Leachate production and disposal of kitchen food solid waste by dry fermentation for biogas generation

This laboratory research, which applies anaerobic digestion for a solid phase batch system using kitchen food solid waste (KFSW), is concerned with optimizing leachate production under different conditions. The solid-phase digestion process is expected to be superior to slurry-phase digestion and the so-called “dry fermentation” process. A batch system solid waste reactor was used in the present study. The performance of the reactor was tested under the conditions of constant temperature of 35°C and the reactor active volume was 12 l. On operation day 10, chemical oxygen demand (COD) for leachate extraction parameters such as COD rate, COD loading rate (LR) and COD concentration reached maximum values, and were 135 g COD/d, 11 g COD/1.d, and 214 g/l of COD, respectively. On day 25, accumulative leachate COD reached the top value of 1509.4 g.The pH value of leachate was kept around 4. However, volatile fatty acid (VFA) concentration of leachate fluctuated, especially in the initial period.A high concentration of VFA on day 5 inhibited gas production, but with the decrease of VFA concentration the gas production rate was increased gradually and the sludge acclimated to VFA gradually.The process can be operated at a profit and no unfavorable environmental impact is expected for this type of plant production of biogas using the leachate from dry fermentation. These considerations make it a viable alternative in most countries as a source of energy.