Organic Pollutants In Landfill Leachate Research Articles

Efficiently removing dissolved organic pollutants in landfill leachate concentrate using dual-anode Fe2+/HClO system: The significance of insolubilization based on oxidative coupling of organics

The strategy to mineralize dissolved organics for the decontamination of landfill leachate concentrate (LLC) is expensive. Because mineralization requires high stoichiometric ratio of oxidants (e.g., •OH) or electron transfer (i.e., energy) to the pollutant molecules. Whereas, transferring the dissolved organic pollutants into separable insoluble matters is an energy-saving strategy. Herein, we developed a dual-anode Fe2+/HClO system for removing dissolved organic pollutants in LLC through insolubilization based on oxidative coupling. In this system, the majority of dissolved organic pollutants were transferred into insoluble substances, which could be removed easily. As a result, 89.8 % of the dissolved organic carbon (DOC) in LLC was fast removed in 3 h with a low specific energy consumption (SEC, 4.0 kWh kg−1 COD and 17.6 kWh kg−1 DOC), and the formation of toxic by-products can be well controlled to total organic chlorine (TOCl) < 0.1 mg/L. The formation of insoluble substances was attributed to the oxidative coupling of organic small molecules into the macromolecular ones. This was evidenced by the generation of insoluble compounds with the larger molecular mass, and the formation of coupling or polymerization products of the model pollutant (guaiacol). The predominant mechanism was proposed that Fe(IV) was generated in the dual-anode Fe2+/HClO system, and Fe(IV) oxidized pollutants to produce organic radicals, then the organic radicals coupled and polymerized to form larger molecules and insoluble compounds. This work offers a novel electrochemical method for efficient removal of organic pollutants in LLC with minimal toxic by-products generated, and revealed the significance of oxidative coupling process in the electrochemical Fe2+/HClO system.

Bioremediation of reverse osmosis concentrate generated from the treatment of landfill leachate.

The moisture content of municipal solid waste (MSW) and local precipitation events lead to the leachate generation from MSW landfills. The high concentration of organic pollutants in landfill leachate (LL) makes it hazardous, requiring treatment before disposal into the environment. LL is most commonly treated by reverse osmosis (RO), which generates large volumes of concentrate known as RO concentrate. This investigation aims to stabilize the RO concentrate through an inexpensive and effective bioremediation strategy. A bench-scale aerobic suspended growth reactor study was conducted using three commercial conversion agents, namely EM.1, Bokashi powder, and coir pith powder. Overall bench-scale efficiency of 63% was achieved in this study. The onsite studies were conducted in 7.5-m3 artificial ponds with 46% efficiency amid atmospheric influences and constraints. The overall efficiencies of both bench and field-scale studies were derived by ascertaining the arithmetic mean of the individual efficiency of the following parameters: chemical oxygen demand (COD), biochemical oxygen demand (BOD), and total dissolved solids (TDS). In contrast, the control pond with no conversion agents showed an increase in pollution concentration over the 100 days of retention time. The findings revealed that the investigated technology had a marginally lower evaporation rate and performed relatively well compared to traditional solar evaporation ponds. Moreover, the technology can be easily scaled-up and readily applied for RO concentrate treatment in MSW landfills.

Removal of organic pollutants by effluent recirculation constructed wetlands system treating landfill leachate

The leachate of municipal solid waste landfills contains various types of organic substances, increasing the difficulty of efficient treatment. This study built an effluent recirculation (1:4 ratios) vertical subsurface flow constructed wetlands (CWs) system treating actual landfill leachate (LL). In order to better monitor and evaluate the removal of organic pollutants in LL by CWs, Three-Dimensional Fluorescence (3D-EEM) and Solid Phase Extraction–Gas Chromatography–Mass Spectrometry (SPE–GC–MS) analysis of CWs influent and effluent water was performed to investigate the removal of Dissolved organic matter (DOM), Organochlorine pesticides (OCPs), Organophosphorus pesticide (OPPs), Polycyclic aromatic hydrocarbons (PAHs), and Volatile organic compounds (VOCs). Results showed that during the treatment of LL by CWs, the average removal rate of conventional pollutants (COD, NH4+-N and TP) was over 85%, with a majority of microbial metabolites and humic acids in DOM effectively degraded. The concentrations of OCPs, OPPs, PAHs, and VOCs in the CWs influent LL ranged between 378.6 and 4746.32 ng L−1, accounting for only a small proportion (3.7×10−7–4.6×10−6) of COD. The achieved organic micro-pollutants total removal rates were: OCPs(56.9%), OPPs(41.4%), PAHs(58.3%), and VOCs(78.3%), with relatively higher removal rates observed for DDT (83.6%), dimethoate (89.2%), benzo(a)anthracene (82.0%). Therefore, the effluent recirculation CWs system can effectively remove organic pollutants in LL, indicating that this is a promising technology with good application for the effective treatment of wastewater.

Electrochemical treatment of organic pollutants in landfill leachate using a three-dimensional electrode system

The use of three-dimensional electrode is a new electrochemical oxidation technology for landfill leachate treatment. In this study, a particle electrode was developed using Fe/C granules, which were suspended between the cathode and the anode to create a three-dimensional electrode. The three-dimensional electrode activated sodium persulfate to treat landfill leachate. Fe/C granules were prepared by incorporating iron filings and hydrothermally carbonized biochar into alginate beads. The optimal parameters of the three-dimensional electrode for chemical oxygen demand (COD) removal from landfill leachate were determined based on a series of single factor experiments as an operating voltage of 5V, a sodium persulfate concentration of 28mM, and 1g of Fe/C granules. Treatment with the three-dimensional electrode at optimized conditions achieved 72.9% removal of COD and 99.9% removal of ammonia nitrogen, resulting in landfill leachate being clear and transparent. The changes in total organic carbon, nitrite, and nitrate concentrations indicated that most organic pollution and ammonia nitrogen were converted into CO2 and N2. This study provides an alternative technology for the treatment of refractory organic pollutants.

Experimental Study on Removal of Organics from Landfill Leachate by Stage Aeration AFMBR Process

This paper used a stage aeration anaerobic fluidized bed membrane bioreactor (AFMBR), combined the advantages of membrane bioreactor (MBR) and anaerobic fluidized bed bioreactor (AFBR), put forward to add granular activated carbon (GAC) to make up for the deficiency of AFMBR process, and explored its impact on the process effect. At the same time, it was proposed to utilize the stage aeration to enhance the membrane flux, and to increase the residence time of organic pollutants in the facultative environment through the fluidized bed membrane bioreactor to improve the removal characteristics of organic pollutants in landfill leachate. The influence of aeration rate on the process effect was also investigated. Finally, the relationship between temperature and AFMBR treatment effect was briefly analyzed.

Removal of Refractory Organics from Biologically Treated Landfill Leachate by Microwave Discharge Electrodeless Lamp Assisted Fenton Process

Biologically treated leachate usually contains considerable amount of refractory organics and trace concentrations of xenobiotic pollutants. Removal of refractory organics from biologically treated landfill leachate by a novel microwave discharge electrodeless lamp (MDEL) assisted Fenton process was investigated in the present study in comparison to conventional Fenton and ultraviolet Fenton processes. Conventional Fenton and ultraviolet Fenton processes could substantially remove up to 70% of the refractory organics in a membrane bioreactor treated leachate. MDEL assisted Fenton process achieved excellent removal performance of the refractory components, and the effluent chemical oxygen demand concentration was lower than 100 mg L−1. Most organic matters were transformed into smaller compounds with molecular weights less than 1000 Da. Ten different polycyclic aromatic hydrocarbons were detected in the biologically treated leachate, most of which were effectively removed by MDEL-Fenton treatment. MDEL-Fenton process provides powerful capability in degradation of refractory and xenobiotic organic pollutants in landfill leachate and could be adopted as a single-stage polishing process for biologically treated landfill leachate to meet the stringent discharge limit.

Effective degradation of refractory organic pollutants in landfill leachate by electro-peroxone treatment

A novel electrochemically driven process (E-peroxone) was employed to treat landfill leachate concentrates that were generated from reverse osmosis of biologically pretreated leachate. In the E-peroxone system, O3 was produced from O2 using an ozone generator. The O2 and O3 gas mixture from the ozone generator was then sparged into a reactor that had a carbon–polytetrafluorethylene (carbon–PTFE) cathode, which can convert O2 to H2O2 effectively. The in situ generated H2O2 then reacted with the sparged O3 to produce a very powerful oxidant OH, thus achieving synergy of O3 and H2O2 (i.e., peroxone) on organic pollutant degradation. Up to 87% of the total organic carbon (TOC) was removed from the leachate concentrates after 4h of the E-peroxone process. In comparison, ozonation, conventional peroxone (using externally added H2O2), and electro-Fenton treatment removed only 45%, 65%, and 71% TOC, respectively, under similar reaction conditions in 4h. The results indicate that the E-peroxone process may provide a convenient and effective alternative to conventional advanced oxidation processes for degrading refractory organic pollutants in wastewater.

Advanced Oxidation Processes (AOPs) for reduction of organic pollutants in landfill leachate: a review

Uncontrolled municipal landfill leachate during landfilling can seriously pollute groundwater, surface water and soil. Over the past decades, a variety of Advanced Oxidation Processes (AOPs), primarily utilising hydroxyl radicals to effect water purification, have been frequently investigated for treatment of landfill leachate. This paper first summarises the typical characteristics of organic compounds in leachate, and then reviews the AOPs applied for leachate treatment, including O3-based, UV-based, Fenton-based, and two emerging (ultrasound irradiation and electronic-beam irradiation) AOPs. Finally, some issues in advanced oxidation treatment of landfill leachate are briefly remarked.

Removal of organic pollutants in landfill leachate by biological treatment

Removal of organic pollutants in landfill leachate by biological treatment

Treatment of landfill leachate by combined aged-refuse bioreactor and electro-oxidation

Two-stage aged-refuse bioreactor (ARB) was applied to treat landfill leachate in Shanghai Waste Laogang Disposal Plant. The removal efficiencies of chemical oxygen demand (COD), biological oxygen demand (BOD), total organic carbon (TOC), total nitrogen (TN) and ammonia nitrogen (NH 3–N) of landfill leachate treated by the two-stage bioreactor system were 98.5%, 99.9%, 98.0%, 64.2% and 99.9%, respectively. The COD and BOD in the second stage effluent were 239 and 7 mg l −1, respectively. Thus three types of electrolysis were employed to further treat the second effluent, undivided electrolysis (UDE), divided electrolysis (DE) with Ti/PbO 2 cathode and DE with gas diffusion cathode. All electrolysis processes possessed good color removal effect, while the DE with gas diffusion cathode had the best TOC removal effect. The optimum electrolysis time of leachate was 30 min. The TOC removal efficiencies were 51.4% and 39.7% in anolyte and catholyte, respectively, after 30 min electrolysis at 5 V. In addition, the DE with gas diffusion cathode showed the least energy consumption of 9.8 kWh m −3 at 30 min. The organic pollutants in the leachate were analyzed through a gas chromatography coupled with mass spectrometry (GC–MS) system. Through the two-stage ARB, the species and concentrations of organic pollutants in landfill leachate reduced greatly. Several chlorinated organic compounds were detected in the effluent after the UDE and the anolyte of the DE. In addition, the concentration of absorbable organic halogens (AOX) increased greatly during the electrolysis. Hence, careful consideration should be given in the application of electro-oxidation into the treatment of chloride-containing wastewater.

Attenuation of landfill leachate by UK Triassic sandstone aquifer materials: 2. Sorption and degradation of organic pollutants in laboratory columns

The sorption and degradation of dissolved organic matter (DOM) and 13 organic micropollutants (BTEX, aromatic hydrocarbons, chloro-aromatic and -aliphatic compounds, and pesticides) in acetogenic and methanogenic landfill leachate was studied in laboratory columns containing Triassic sandstone aquifer materials from the English Midlands. Solute sorption and degradation relationships were evaluated using a simple transport model. Relative to predictions, micropollutant sorption was decreased up to eightfold in acetogenic leachate, but increased up to sixfold in methanogenic leachate. This behaviour reflects a combination of interactions between the micropollutants, leachate DOM and aquifer mineral fraction. Sorption of DOM was not significant. Degradation of organic fractions occurred under Mn-reducing and SO 4-reducing conditions. Degradation of some micropollutants occurred exclusively under Mn-reducing conditions. DOM and benzene were not significantly degraded under the conditions and time span (up to 280 days) of the experiments. Most micropollutants were degraded immediately or after a lag phase (32–115 days). Micropollutant degradation rates varied considerably (half-lives of 8 to >2000 days) for the same compounds (e.g., TeCE) in different experiments, and for compounds (e.g., naphthalene, DCB and TeCA) within the same experiment. Degradation of many micropollutants was both simultaneous and sequential, and inhibited by the utilisation of different substrates. This mechanism, in combination with lag phases, controls micropollutant degradation potential in these systems more than the degradation rate. These aquifer materials have a potentially large capacity for in situ bioremediation of organic pollutants in landfill leachate and significant degradation may occur in the Mn-reducing zones of leachate plumes. However, degradation of organic pollutants in acetogenic leachate may be limited in aquifers with low pH buffering capacity and reducible Mn oxides. Contaminants in this leachate present a greater risk to groundwater resources in these aquifers than methanogenic leachate.

Degradation of Organic Pollutants by the Photo-Fenton-Process

The Photo-Fenton-Process utilizing the combinations Fe(II)/H 2 O 2 /UVA and Fe(III) oxalate/H 2 O 2 /UVA was employed with success to degrade biorefractory organic pollutants in landfill leachate. The rate of degradation of the organic pollutants depends on the concentrations of hydrogen peroxide and the iron catalyst, the pH value and the concentration of dissolved oxygen. A comparison of the Photo-Fenton-Process with the H 2 O 2 /Fe(II) process and the H 2 O 2 /UVC process shows that the Photo-Fenton-Process gives a higher COD degradation and a reduced energy consumption of at least 30% compared to the H 2 O 2 /UVC process. By using photogenerated Fe(II) the amount of the iron catalyst required and the volume of sludge produced are strongly reduced.

Degradation of Organic Pollutants by the Photo-Fenton-Process

The Photo-Fenton-Process utilizing the combinations Fe(II)/H2O2/UVA and Fe(III) oxalate/H2O2/UVA was employed with success to degrade biorefractory organic pollutants in landfill leachate. The rate of degradation of the organic pollutants depends on the concentrations of hydrogen peroxide and the iron catalyst, the pH value and the concentration of dissolved oxygen. A comparison of the Photo-Fenton-Process with the H2O2/Fe(II) process and the H2O2/UVC process shows that the Photo-Fenton-Process gives a higher COD degradation and a reduced energy consumption of at least 30% compared to the H2O2/UVC process. By using photogenerated Fe(II) the amount of the iron catalyst required and the volume of sludge produced are strongly reduced.