Aged Landfill Leachate Research Articles

Electrochemically regulating COD/TN ratio of aged landfill leachate via rapid chlorine-mediated ammonia oxidation with RuO2-IrO2/Ti anode

Electrochemical oxidation process was employed to regulate the ratio of chemical oxygen demand to total nitrogen (COD/TN ratio) of aged landfill leachate, aiming to meet the requirement of biological treatment. The results indicate that the ammonia nitrogen can be rapidly removed through electrogenerated chlorine radicals over a typical chlorine evolution RuO2-IrO2/Ti anode. The increased input current and decreased flow rate are beneficial to COD/TN ratio improvement, and COD/TN ratio can be increased to more than 16 at 1000 mA (input current) and 0.3 L/h (flow rate). According to the obtained experimental data, we present a strategy for COD/TN ratio increase: (i) determining the COD/TN ratio balance coefficient (B) of aged landfill leachate, and selecting the anode with COD/TN ratio adjustment coefficient (TN) >B, where TN represents the ability to regulate COD/TN ratio, and B represents the specific TN to keep the same COD/TN ratio; (ii) performing the wastewater treatment experiments at different control parameters during electrochemical process; (iii) calculating the k of control parameter sensitivity curves to achieve different tolerance abilities, and further preferentially regulating the reaction process to high average current efficiency (ACE) of ammonia nitrogen and low ACE of COD. This work validates that the electrochemical process can increase the COD/TN ratio together with enhancing the biodegradability of such refractory wastewater, and also provides an effective tool for regulation of the COD/TN ratio via complete ammonia oxidation.

Effect of hydrofluoric acid-modified Co3O4/Y-type molecular sieves on MFC performance

Microbial fuel cell (MFC) is a green technology that facilitates resource utilization of wastewater by generating electricity while degrading organic and ammonia nitrogen pollutants. The anode plays a crucial role in the MFC performance, demanding excellent electrochemical performance and high stability. In this paper, a new high-performance anode of Co3O4 composite Y molecular sieve (Co3O4/Y) was prepared, and the effect of the Co3O4 ratio and hydrofluoric acid (HF) modification on the Co3O4/Y performance was also investigated. The results showed that the Co3O4/Y, synthesized through the hydrothermal method with 30 wt% loading of Co3O4 followed by 10 % HF treatment, demonstrated superior electrochemical performance, which had the highest redox peak current density, the largest current response area, and the maximum exchange current density of 0.038 mA/cm2. Four anode catalysts of MFC, namely, blank carbon cloth (CC), Co3O4-CC, Co3O4/Y-CC, and H-Co3O4/Y-CC were prepared, and four groups of MFCs were constructed for the treatment of mixed wastewater consisting of the aged landfill leachate and shale gas fracturing wastewater. Notably, the H-Co3O4/Y-CC group showed the best performance in power generation, achieving a maximum stabilized output voltage (448 mV), a maximum power density (1179 mW/m2), and a minimum apparent internal resistance (466 Ω). Additionally, the removal rate of ammonia nitrogen exceeded 40 % in the mixed wastewater of the 4 groups of MFCs. This study provided a viable strategy for fabricating high-performance MFC anode materials and offered insights into the simultaneous disposal of domestic and industrial wastewater in MFCs.

Development of electrocoagulation-based continuous-flow reactor for leachate treatment: Performance evaluation, energy consumption, modeling, and optimization

This study investigated the performance of continuous-flow electrocoagulation (CFR-EC) reactor for aged landfill leachate treatment with a novel configuration of iron and aluminum electrodes to enhance the applicability of the process. The effects of the applied current density (ACD), initial pH, and hydraulic retention time (HRT) on the percentage removal of COD, TOC, BOD5, color, turbidity, and heavy metals (HMs) were modeled with Box-Behnken design (BBD). The results demonstrated that the models are significant (R2 0.97—p-value < 0.0029 and R2 0.92—p-value < 0.0001 for Fe and Al electrodes). COD, TOC, BOD5, and NH3-N removal were maximized at HRT 50 min (40.0 mL min−1) and pH 11 reaching 59, 64, 55, and 27%, respectively, by applying the ACD of 1.1 mA cm−2 in the CFR-ECFe reactor. The CFR-ECFe reactor presented a higher color (59%) and turbidity reduction (86%) than the CFR-ECAl reactor. At optimum condition, the removal percentages of HMs: Cr6+, Pb2+, As3+, Mg2+, B3+, Mn3+, Ni2+, and Ba2+ were 50, 70, 80, 99, 81, 99, 20, and 65%, respectively. The total process cost for landfill leachate treatment was 0.21 $/m3. The CFR-ECFe was an effective and affordable reactor for pollutant removal from landfill leachate.

Red mud-based polyaluminium ferric chloride flocculant: Preparation, characterisation, and flocculation performance

In this study, red mud was used as a raw material to extract Al and Fe using hydrochloric acid. A highly efficient polyaluminium ferric chloride (PAFC) flocculant was prepared by adjusting the pH of a leaching solution, the molar ratio of Al to Fe, and the polymerisation temperature. The effects of synthesis and flocculation conditions on the flocculation performance of aged landfill leachate were investigated. The results confirmed that PAFC flocculant prepared at a polymerisation pH of 2.5, Al/Fe molar ratio of 8, and polymerisation​ temperature of 70 °C had the optimum effect. The effect of PAFC and commercial polyaluminium ferric chloride flocculants used under different flocculation conditions were compared. The chemical oxygen demand, UV 254 , chroma, total organic carbon, and PAFC settlement height at a flocculant concentration of 1.2 g/L and solution pH of 6 were 72.2%, 79.2%, 82.9%, 82.6%, and 9.5 cm (within 90 min), respectively. The PAFC performed excellently at flocculation and can be used as a simple and potentially low-cost wastewater treatment agent in industrial applications. • Red mud was used to synthesise polyaluminium ferric chloride (PAFC) flocculant. • The COD and TOC of PAFC to landfill leachate were 72.2% and 82.6%, respectively. • PAFC have advantages over commercial PAFC in settlement velocity and TOC removal efficiency.

Efficient treatment of aged landfill leachate containing high ammonia nitrogen concentration using dynamic wave stripping: Insights into influencing factors and kinetic mechanism

Aged landfill leachate is challenging to treat owing to its extremely high ammonia concentration and poor biodegradability. We constructed pilot-scale dynamic wave stripping equipment to separate ammonia from landfill leachate and achieved excellent results. To further expand the usage of pilot-scale equipment in actual water treatment process and implement it in a sewage plant, we established the mass transfer kinetic physics and mathematical model of the dynamic wave stripping process based on the surface renewal theory and the traditional stripping method. The surface renewal theory and the traditional stripping method are employed to analyze the mechanism of various experimental parameters affecting the stripping process, predict the stripping effect of the equipment under different conditions, and verify the calculation results of the model using the kinetic fitting results of the experimental data. These calculation results of the model indicate that the mass transfer kinetic coefficients of ammonia stripping at 20 °C, 25 °C, and 30 °C are 85.62 min, 75.34 min, and 65.88 min, respectively, when the gas–liquid ratio is 129. When the gas–liquid ratios are 62, 129, and 163 at 25 °C, the mass transfer kinetic coefficients of ammonia stripping are 102.61 min, 75.34 min, and 61.43 min, respectively. With increasing temperature and gas–liquid ratio, the particle size and number of bubbles in the wave tube of the stripping equipment gradually decrease and the mass transfer efficiency of free ammonia between the gas and liquid phases improves, enhancing the stripping efficiency of ammonia nitrogen.

Effects of Calcium on the Removal of Ammonium from Aged Landfill Leachate by Struvite Precipitation

Ammonium in landfill leachates is a major contributor to environmental degradation if not effectively treated. However, it could be converted to a valuable fertilizer when it is co-precipitated with phosphate and magnesium as struvite. Low-cost magnesium and phosphate sources are sought to offset the co-precipitation treatment costs, but most of the identified alternative magnesium sources have significant amounts of calcium, which may negatively impact the ammonium removal rates. In this study, the effects of calcium on ammonium removal from high-strength aged field landfill leachate as struvite were investigated. Laboratory-scale batch tests were conducted to assess the effects of the pH, Mg2+:NH4+:PO43−, and Ca2+:Mg2+ molar ratios on ammonium removal. Magnesium chloride salt was used as a model dissolved magnesium source, whereas different compounds derived from dolomite (CaMg(CO3)2) were used as model solid-phase magnesium sources. X-ray powder diffraction and activity ratio diagrams were used to delineate the ammonium removal mechanisms and struvite stability. The ammonium removal rate of the magnesium salt decreased from approximately 97% to 70%, upon increasing the Ca2+:Mg2+ molar ratio from 0 to 1.0, for the Mg2+:NH4+:PO43− molar ratio of 1.25:1:1.25 and pH = 9.5. For similar pH values, as well as the Mg2+:NH4+:PO43− and Ca2+:Mg2+ molar ratios, the ammonium removal rates by the dolomite-derived compounds reached up to 55%, which highlighted the limited availability of magnesium in solid phases, in addition to the negative impacts of calcium. The diffractometric analysis and thermodynamic calculations revealed the stable regions of struvite in the presence of competing solid phases. The new findings in this study could aid in the design of ammonium and phosphate removal and recovery systems by struvite precipitation.

Sonoelectrochemical oxidation of aged landfill leachate with high-efficiency Ti/PANI/PDMS-Ce-PbO2 anode

In this work, a high-performance anode containing polyaniline (PANI) modified intermediate layer and polydimethylsiloxane (PDMS) and Ce co-doped surface layer was prepared. Scanning electron microscope (SEM) and X-ray diffraction (XRD) characterization exhibited that the Ti/PANI-α-PbO2/PDMS-Ce-β-PbO2 electrode (Ti/PANI/PDMS-Ce-PbO2) has denser surface morphology and smaller crystal size compared to the Ti/β-PbO2 electrode (Ti/PbO2). The BET test showed that the specific surface area of the modified PbO2 electrode increased from 0.2591 to 0.2783 m2 g−1, which also means an increase in active sites. The results of linear sweep voltammetry (LSV) indicated that the Ti/PANI/PDMS-Ce-PbO2 electrode has higher oxygen evolution potential of 1.91 V vs.SCE than the Ti/PbO2 electrode (1.74 V vs.SCE), which can effectively reduce the impact of oxygen evolution side reaction on organic pollutants degradation. The fitting results of electrochemical impedance spectroscopy (EIS) exhibited that the impedance of the Ti/PANI/PDMS-Ce-PbO2 electrode was greatly reduced to 39.5 Ω. The modified electrode showed higher current efficiency in the experiment of electrochemical oxidation of gallic acid, proving that the electrocatalytic performance of the modified PbO2 electrode was further improved. Therefore, the Ti/PANI/PDMS-Ce-PbO2 electrode was used for sonoelectrochemical oxidation of aged landfill leachate. The effects of three key parameters on the sonoelectrochemical system were investigated, including current density, initial pH, and ultrasonic power, and the results revealed that the current density played a dominant role. Under the optimal parameters: 42 mA cm−2 current density, initial pH of 6, 50 W ultrasonic power, 61.9% chemical oxygen demand (COD) removal was achieved. Both the ten repeated experiments and the accelerated life tests demonstrate that Ti/PANI/PDMS-Ce-PbO2 electrode has good stability and potential for long-term application. Furthermore, the results of inductively coupled plasma-mass spectrometry (ICP-MS) manifested that the sonoelectrochemical system with Ti/PANI/PDMS-Ce-PbO2 electrode will not cause secondary pollution to the effluent. The analysis results of ultraviolet–visible spectroscopy (UV-Vis) and gas chromatography-mass spectrometry (GC-MS) show that the organic components of the aged landfill leachate changed greatly after the treatment of sonoelectrochemical oxidation, and the refractory substances have been effectively removed.

Effect of hydraulic parameters of leachate treatment process on di(2-ethylhexyl) phthalate removal from aged leachate

ABSTRACT The effect of hydraulic parameters of an anaerobic/anoxic/oxic leachate treatment reactor on the removal of di(2-ethylhexyl) phthalate (DEHP) from aged landfill leachate was studied. The mean DEHP removal efficiencies were 79.5%, 87.1%, 89.7% and 87.8% at hydraulic retention times of 6, 4.5, 3 and 2 d, respectively. The removal efficiency of DEHP was significantly higher when the internal reflux ratio was 200% than others. There was no significant difference among the DEHP removal efficiencies at different external reflux ratios of the reactor. Due to the overall efficiency of the reactor, hydraulic retention time 3 d, internal reflux ratio 200% and external reflux ratio 60%, were considered the optimal hydraulic parameters for DEHP removal from aged leachate. The removal efficiency of DEHP was significantly improved (from 75.7% to 89.1%) after the optimization of hydraulic parameters of the reactor. The removal percentages of DEHP in the anaerobic, anoxic, and oxic units of the reactor were 42.8%, 17.6%, and 15.3%, respectively. The oxic microcosms in the reactor had little effect on DEHP removal. The correlation between DEHP and leachate pollutants indicated that DEHP removal was strongly correlated with leachate COD and NH4 +–N.

Degradation of refractory organic matter in the effluent from a semi-aerobic aged refuse biofilter-treated landfill leachate by a nano-Fe3O4 enhanced ozonation process.

In this study, the transformation and degradation mechanisms of refractory organic matter in biologically treated leachate from a semi-aerobic aged refuse biofilter (SAARB) in a nano-Fe3O4 enhanced ozonation process (nFe3O4-O3) were investigated in batch experiments. A continuous experiment then confirmed the effectiveness of the process for SAARB effluent treatment. In a batch experiment, the effects of influencing factors, including nFe3O4 dosage, O3 dosage and initial pH on the treatment performance of nFe3O4-O3 process, were comprehensively investigated. The results showed that when the nFe3O4 dosage = 6 g L-1, O3 dosage = 0.15 L minute-1 and initial pH = 7, the total organic carbon, absorbance at 254 nm and colour number removal efficiencies were 40.58%, 62.55% and 89.80%, respectively. In addition, most of the humic- and fulvic-like substances in the SAARB effluent were removed, and the condensation degree, aromaticity and humification degree of the organics were substantially reduced. The morphology and elemental valence state analysis showed that the nFe3O4 in the process was relatively stable and could form an nFe3O4-organic complex. Therefore, the probability of organics reacting with hydroxyl radical increased and the oxidation efficiency was enhanced. In the continuous experiment, both the O3 dosage and hydraulic retention time (HRT) were the key influencing factors. The treatment efficiency of the nFe3O4-O3 process was enhanced at a higher O3 dosage and longer HRT. The electrical energy consumption of the continuous nFe3O3-O3 process was calculated to be 17.72 kW h m-3 in SAARB effluent treatment. This study proved the feasibility of biologically treated landfill leachate treatment by the nFe3O3-O3 process.

Sonoelectrochemical activation of peroxymonosulfate: Influencing factors and mechanism of FA degradation, and application on landfill leachate treatment

In this work, sonoelectrochemically activated peroxymonosulfate (US-EC/PMS) was used to degrade fulvic acid (FA) in water. Compared with other technologies, the US-EC/PMS system can achieve higher FA decolorization in a short time. Moreover, the benefits of synergy are more prominent in the US-EC/PMS system. The effects of operating parameters on the sonoelectrochemical degradation of FA were investigated, including initial pH, initial FA concentration, current density, ultrasonic power, PMS dosage. The results showed the initial FA concentration and current density were critical to the degradation of FA. Under optimized parameters: initial pH of 2, 50 mg L−1 initial FA concentration, 30 mA cm−2 current density, 50 W ultrasonic power, 1 mM PMS dosage, the US-EC/PMS system can achieve 93% FA decolorization. The calculation results of current efficiency and energy consumption indicate that the introduction of PMS into the US-EC system has economic applicability. Scavenger experiments and electron paramagnetic resonance suggest that hydroxyl radicals, sulfate radicals, and singlet oxygen were the main ROS produced in the US-EC/PMS system. Accordingly, the possible mechanism of FA degradation by sonoelectrochemical activation PMS was proposed. Finally, the US-EC/PMS system was used to treat the aged landfill leachate. Three-dimensional fluorescence analysis showed that most of the humic substances (Hss) were effectively removed, and the biodegradability of the leachate was considerably improved. In addition, the effective removal of COD, chroma, and ammonia nitrogen were observed, proving that this technology is a powerful means to treat organic wastewater contaminated by Hss.

Heterogeneous activation of peroxymonosulfate by natural chalcopyrite for efficient remediation of groundwater polluted by aged landfill leachate

Natural chalcopyrite (NCP) was used as a low-cost and efficient activator of peroxymonosulfate (PMS) to repair groundwater polluted by aged landfill leachate. The optimal remediation effect of polluted groundwater was achieved at pH 8, PMS concentration 25 mM and NCP dosage 10 g/L via response surface method. The excellent performance of NCP was mainly Fe3+/Fe2+ and Cu2+/Cu+ cycles promoted by sulfur species, which was investigated via XPS analysis. Furthermore, the transformation of SO4•─, •OH and O2•─ were clarified by quenching experiments and ESR. The conversion of organics was revealed by UV–vis spectra and three-dimensional fluorescence spectra. Moreover, the toxicity of polluted groundwater after remediation was significantly reduced through the growth of Chlorella pyrenoidosa. Finally, the flowing experiment using NCP/sand column showed that NCP could effectively activate PMS and thereby restore polluted groundwater.

The Removal of Heavy Metals from the Leachate of Aged Landfill: The Application of the Fenton Process and Nanosilica Absorbent

Since leachate is typically composed of numerous constituents, its management requires special attention. After the raw leachate of Saravan in Rasht (Guilan Province, Iran) was transferred to a laboratory and its specifications were determined, it was subjected to experiments by the bench-scale method. The analyses of pH and heavy metals were performed in the main and control anaerobic reactors at time zero, before precipitation, and two hours after precipitation. After the anaerobic process was over and the optimal retention time was identified in the anaerobic reactor, the removal of heavy metals was analyzed by the Fenton process and nanosilica absorbent in leachate treatment. In the primary anaerobic reactor, the highest and lowest removal rates were 59 and 39% for Ni and Cu, respectively. In the Fenton process with optimal H2O2/Fe+2 ratio, Cu and Hg showed the lowest and highest removal rates of 22.4 and 54.54%, respectively. At the optimal rate of nanosilica absorbent and the retention time of 15 min, As was removed maximally with an efficiency of 38% and Cu was removed minimally. The results revealed that the integration of the anaerobic process with the Fenton process and nanosilica absorbent was very effective in removing heavy metals from the aged landfill leachate.

Removal of Di-n-butyl phthalate from aged leachate under optimal hydraulic condition of leachate treatment process and in the presence of its dominant bacterial strains

The effects of hydraulic condition of reactor and the dominant degrading bacteria on the removal of di-n-butyl phthalate (DBP) from aged landfill leachate by anaerobic/anoxic/oxic (A/A/O) leachate treatment process were investigated. The optimal DBP removal (96.0%) was obtained from aged leachate when the hydraulic retention time (HRT) of the reactor was 3 d, internal reflux ratio of the reactor was 200%, and external reflux ratio of the reactor was 60%, respectively. The removal efficiency of DBP was significantly improved after the inoculation of the dominant DBP-degrading bacteria (Pseudomonas sp. W1) in the reactor. The mean removal efficiencies of DBP before and after inoculation were 94.1% and 97.7%, respectively. Furthermore, the inoculation of dominant DBP-degrading bacteria changed the original sludge structure and characteristics, which was more conducive to the removal of DBP. These results provide theoretical basis for the effective removal of DBP from aged leachate by the biological treatment process.

Aged landfill leachate enhances anaerobic digestion of waste activated sludge

Anaerobic digestion (AD) is considered as a sustainable pathway to recover energy from organic wastes, but the digestive efficiency for waste activated sludge (WAS) is not as expected due to the limitations in WAS hydrolysis. This study proposes an effective strategy to simultaneously treat WAS and landfill leachate, aiming to promote WAS hydrolysis and enhance organics converting to methane. The effects of landfill leachate on the four stages (i.e., solubilization, hydrolysis, acidogenesis, and methanogenesis) of AD of WAS, as well as the effect mechanisms were investigated. Results showed that adding appropriate amounts of landfill leachate could promote the steps of solubilization, hydrolysis and acidogenesis of WAS, but had no-effect on methanogenesis. The hydrolysis and acidogenesis efficiency in the leachate added digesters were 2.0%–8.4% and 35.2%–72.7% higher than the control digester. Mechanism studies indicated that humic acid (HA) contained in the leachate was conducive to the processes of both hydrolysis and acidogenesis, but detrimental to the methanogenesis. Effects of heavy metals (HMs) on AD of WAS was also dose-dependent. Digestive performance was inhibited by excessive HMs but promoted by moderate dosages. Humic acid and metal ions tend to interact to form complexes, and thus relieve their each inhibition effects. It is also found that the stability of sludge flocs was reduced by the leachate through reducing both apparent activation energy (AAE) and median particle size (MPS) of the sludge. Microbial community and diversity results revealed that the relative abundance of microbes responsible for hydrolysis and acidogenesis increased when landfill leachate was present. This research provides a more technically and economically feasible approach to co-treating and co-utilizing WAS and landfill leachate.

From Waste Collection Vehicles to Landfills: Indication of Per- and Polyfluoroalkyl Substance (PFAS) Transformation.

Municipal solid waste contain diverse and significant amounts of per- and polyfluoroalkyl substances (PFAS), and these compounds may transform throughout the "landfilling" process from transport through landfill degradation. Fresh vehicle leachates, from commercial and residential waste collection vehicles at a transfer station, were measured for 51 PFAS. Results were compared to PFAS levels obtained from aged landfill leachate at the disposal facility. The landfill leachate was dominated by perfluoroalkyl acids (PFAAs, including perfluoroalkyl carboxylic acids (PFCAs) and perfluoroalkyl sulfonic acids (PFSAs); 86% of the total PFAS, by median mass concentration), while the majority of PFAS present in commercial and residential waste vehicle leachate were PFAA-precursors (70% and 56% of the total PFAS, by median mass concentration, respectively), suggesting precursor transformation to PFAAs during the course of landfill disposal. In addition, several PFAS, which are not routinely monitored-perfluoropropane sulfonic acid (PFPrS), 8-chloro-perfluoro-1-octane sulfonic acid (8Cl-PFOS), chlorinated polyfluoroether sulfonic acids (6:2, 8:2 Cl-PFESAs), sodium dodecafluoro-3H-4,8-dioxanonanoate (NaDONA), and perfluoro-4-ethylcyclohexanesulfonate (PFECHS)-were detected. Potential degradation pathways were proposed based on published studies: transformation of polyfluoroalkyl phosphate diester (diPAPs) and fluorotelomer sulfonic acids (FTS) to form PFCAs via formation of intermediate products such as fluorotelomer carboxylic acids (FTCAs).

Stability of Nano-ZnO in simulated landfill leachate containing heavy metal ions.

As the presence of nanosized zinc oxide particles (nano-ZnO) in landfill leachate increases, their interaction with coexisting heavy metal ions (HMs) also increases. The interface interaction between nano-ZnO and HMs will influence nano-ZnO stability and therefore affect its bioavailability and environmental impact. In the present study, we investigated the effects of Cu(II), Cr(III), and Cr(VI) ions on the aggregation, sedimentation, and dissolution of nano-ZnO using batch experiments with a view to better understanding their co-effect on the environment. Dynamic light scattering and UV-Vis spectroscopy results show enhanced aggregation of nano-ZnO in the presence of Cr(VI) ions under fresh landfill leachate conditions, in addition to distinct sedimentation of nano-ZnO in the presence of Cr(III) ions in both fresh and aged landfill leachate. In fresh leachate, Cu(II) ions improved the concentration of dissolved Zn from nano-ZnO. However, the effects of Cu(II), Cr(III), and Cr(VI) ions on the aggregation and dissolution of nano-ZnO were markedly reduced in aged landfill leachate. Both acetic and humic acids in landfill leachate significantly affected the stability of nano-ZnO in the presence of HMs. According to the ATR-FTIR results, Cr(III) ions reacted with hydroxyl groups on nano-ZnO to form ZnO-O bonds, which induced chains of nano-ZnO and Cr(III) complexes, and hence the increased of nano-ZnO aggregates. ATR-FTIR shows merely electrostatic adsorption effects between nano-ZnO and Cu(II) or Cr(VI) ions. In brief, the mode of interactions between HMs and nano-ZnO influenced the stability via adsorption and binding effects. The results of the present research provide insight into the potential effects of nano-ZnO on the environment in the presence of HMs in landfill leachate.

Treatment of Aged Landfill Leachate by a Self-Sustained Microbial Fuel Cell-Microbial Electrolysis Cell System

Treatment of Aged Landfill Leachate by a Self-Sustained Microbial Fuel Cell-Microbial Electrolysis Cell System

Advanced treatment of aged landfill leachate through the combination of aged-refuse bioreactor and three-dimensional electrode electro-Fenton process

ABSTRACT A combined process of the aged-refuse bioreactor (ARB)/three-dimensional electrode electro-Fenton (3D-EF) system was developed at lab-scale to treat aged landfill leachate. The optimum operating conditions were found to be 15 L/m3•d hydraulic loading rate for ARB; Fe2+ concentration 1.0 mM, initial pH 3.0, current density 30 mA/cm2 and electrode distance 6 cm for 3D-EF. Under these conditions, the total removal ratios of chemical oxygen demand, NH3–N, total phosphorus and colour were 96.2%, 94.3%, 99.2% and 93.6%, respectively. The microtoxicity of the leachate was substantially reduced after undergoing the hybrid treatment. The ARB process removed a considerable proportion of organic matter, while the 3D-EF system played an important role in removing the residue of recalcitrant substances and post-polish of final effluent. The combined process showed a promising potential for treatment of aged landfill leachate.

In situ mature leachate treatment with hydroxylamine addition in the Aerobic-Anaerobic Recirculation Landfill

In situ aeration combined with leachate recirculation is an effective method of treating carbon and nitrogen pollutants in landfills. In this work, we investigated the effects of in situ treatment of aged landfill leachate in aerobic–anaerobic recirculation-simulated landfill (AARL) and the feasibility of hydroxylamine addition to promote total nitrogen (TN) removal. Results showed that the hydroxylamine-treatment group had high TN removal and simultaneous nitrification and denitrification efficiency. High-throughput sequencing showed that hydroxylamine addition promoted the abundance of Nitrosomonas (ammonia-oxidising bacteria (AOB)) in the aerobic zone. However, nitrite did not accumulate because the nitrite oxidation efficiency of nitrite-oxidising bacteria was higher than the ammonia oxidation efficiency of AOB. Moreover, Methylocaldum was the dominant bacteria in AARL. This study contributed to the development of AARLs for the in situ remediation treatment of mature landfill leachate.

Impacts of different aged landfill leachate on PVC corrosion.

Landfill leachate is generally transferred to in situ facilities for advanced treatmentby using a pipe system. Because of its harmful and complex compounds, leachate may react with pipe materials, leading to corrosion and scaling. This experimental study uses typical PVC pipe material and investigates its anti-corrosion performance by placing the material samples into different aged leachates. By evaluating the changes in different experimental parameters, including calcium, magnesium, and chloride ion concentration, oxidation-reduction potential, dissolved oxygen, and pH, combined with a characterization of the material properties, we infer the main causes of pipe scaling-corrosion. Results show that the scaling is more intense in the younger leachate, and the concentration of calcium ions is the dominant influencing factor. The scaling might be resulted from joint actions of chemical precipitation and microbial metabolic activities. It is expectedthe study to provide useful insights into taking effective actions on anti-clogging, and enhance pipes design by selection of appropriate materials for future modification.