Advanced Treatment Of Landfill Leachate Research Articles

Single-atom cobalt enables efficient catalytic ozonation for advanced wastewater treatment: Mechanisms and application

Heterogeneous catalytic ozonation (HCO) triggered by single-atom catalysts (SACs) is an emerging and promising advanced wastewater treatment technology. The catalytic ozonation mechanisms involving single-atom sites and the application of SACs-based HCO require further exploration. Herein, a single-atom Co catalyst with Co-N4 active sites was synthesized for HCO. Oxalic acid (OA) and p-hydroxybenzoic acid (pHBA) with different structural and chemical properties were utilized as the model contaminants. Compared with ozonation and Co nanoparticle-based HCO, single-atom Co-based HCO exhibited superior removal for the two model pollutants, with the removal rate constants of 0.098 and 0.076 min−1 for OA and pHBA, respectively. In the single-atom Co-based HCO, ozone was decomposed and converted to nonradical ROS of surface-adsorbed atomic oxygen (*Oad) and singlet oxygen (1O2). OA was mainly removed on the catalyst surface, relying on the adsorption by the catalyst and the oxidation of *Oad, while electron-rich pHBA was oxidized by O3 and 1O2 in solution. Furthermore, using 3-5 mm Al2O3 pellets as the carrier, single-atom Co doped carbon-Al2O3 pellets were fabricated and applied for the advanced treatment of landfill leachate, and the COD decreased from 110 mg/L to 38 mg/L after treatment. This work provided new insights into the oxidation mechanisms and applications of SACs-based HCO.

In-situ generation of bifunctional reagents via Al/C microelectrolysis for efficient coagulation–Fenton oxidation treatment of leachate MBR effluent

Coagulation–Fenton oxidation stands as a prevalent method for organic pollutant removal from MBR effluent in landfill leachate. However, its dependence on intricate coagulant preparation and hazardous H2O2 handling presents challenges in logistics. Herein, a novel Al0/C–N, Cl composite was developed via high-energy ball milling and high-temperature sintering, which facilitates in situ generation of H2O2 and aluminum salt coagulant upon stirring in oxygen-containing aqueous solutions. Under conditions of 2 g/L Al0/C–N, Cl and initial pH 9, H2O2 production achieved 459 mg/L within 1 h, yielding an Al3+/H2O2 bifunctional reagent. Subsequent coagulation in MBR effluent and Fenton oxidation achieved removal efficiencies of 85.5 %, 76.4 %, and 99.3 % for UV254, total organic carbon, and chromaticity, respectively. The efficient degradation of refractory fulvic-like substances was obtained from this novel “coagulation–Fenton” hybrid process without additional coagulants and H2O2. These results illustrated that the hybrid process is a promising and efficient technology for the advanced treatment of landfill leachate.

Methanogenesis kinetics of organic matter of the leachate in an up-flow anaerobic sludge blanket reactor

Understanding the treatment of leachate mediated by the development of anaerobic sludge makes it possible to create an effective design process of biodegradation technology. This study used an up-flow anaerobic sludge blanket (UASB) reactor equipped with a gas–liquid-solid separator to capture CH4 for treating landfill leachate to improve understanding of methanogenesis kinetics of organic matter. The performance of UASB was able to remove 154.75 g/L of chemical oxygen demand (COD) content of the leachate originally anticipated to emit 2.99 L of CH4 production into the atmosphere. The trend in the variation of internal mass transfer (IMT) factor was close to the global mass transfer factor; however, it was far higher than that of external mass transfer (EMT) factor. After 30 days of the experiment, methanogenesis kinetics of organic matter of the leachate were supported mainly by the breakdown of complex molecules. The rate-limiting step of CH4 desorption was controlled by IMT at the beginning and then by EMT after 30 days of the experiment. The strongly decreased EMT factor was counterbalanced by an increased value of the IMT factor at before 5 days of the experiment. It would be of interest to predict the methanogenesis kinetics of CH4 desorption using the Generalized Fulazzaky equations, which cannot be evaluated using other models. Analysis of the methanogenesis kinetics of organic matter of the leachate provides a new insight into the performance of UASB reactor, which may contribute to advanced treatment of landfill leachate in the future.

Advanced treatment of landfill leachate by catalytic ozonation with MnCeOx/γ-Al2O3 catalyst

Ozonation combined with an efficient and stable catalyst has been demonstrated to be a feasible solution in for removing refractory contaminants from landfill leachate. In this study, MnCeOx/γ-Al2O3 catalyst fabricated with impregnation method was adopted as ozone catalyst for advanced treatment of landfill leachate biochemical effluent (LLBE). The optimized Mn80Ce20Ox/γ-Al2O3 catalyst was fabricated with Mn/Ce molar ratio of 4:1, a metal oxide loading amount of 3.1 wt%, and calcination temperature of 500 °C. By treating LLBE, the removal of chemical oxygen demand (COD) and UV254 in 120 min reached 82.4 % and 96.3 %, respectively, with ozone dose of 15.3 mg L−1, catalyst dosage of 250 g L−1, and the initial pH of 5. The Mn80Ce20Ox/γ-Al2O3 catalyzed ozonation process conformed to pseudo-first-order kinetics with degradation rate constants of 0.0171 min−1 and 0.0313 min−1 for COD and UV254, respectively, which were 3.4 and 2.8 times higher than those of ozonation alone. The MnCeOx/γ-Al2O3 also showed satisfactory catalytic activity and stability based on eight times catalytic ozonation treatments on LLBE.

Electrochemical Oxidation of Landfill Leachate after Biological Treatment by Electro-Fenton System with Corroding Electrode of Iron.

Electrochemical oxidation of landfill leachate after biological treatment by a novel electrochemical system, which was constructed by introducing a corroding electrode of iron (Fec) between a boron-doped diamond (BDD) anode and carbon felt (CF) cathode (named as BDD–Fec–CF), was investigated in the present study. Response surface methodology (RSM) with Box–Behnken (BBD) statistical experiment design was applied to optimize the experimental conditions. Effects of variables including current density, electrolytic time and pH on chemical oxygen demand (COD) and ammonia nitrogen (NH3-N) removal efficiency were analyzed. Results showed that electrolytic time was more important than current density and pH for both COD and NH3-N degradation. Based on analysis of variance (ANOVA) under the optimum conditions (current density of 25 mA·cm−2, electrolytic time of 9 h and pH of 11), the removal efficiencies for COD and NH3-N were 81.3% and 99.8%, respectively. In the BDD–Fec–CF system, organic pollutants were oxidized by electrochemical and Fenton oxidation under acidic conditions. Under alkaline conditions, coagulation by Fe(OH)3 and oxidation by Fe(VI) have great contribution on organic compounds degradation. What is more, species of organic compounds before and after electrochemical treatment were analyzed by GC–MS, with 56 kinds components detected before treatment and only 16 kinds left after treatment. These results demonstrated that electrochemical oxidation by the BDD–Fec–CF system has great potential for the advanced treatment of landfill leachate.

Hydrogen peroxide and peroxymonosulfate intensifying Fe−doped NiC−Al2O3−framework−based catalytic ozonation for advanced treatment of landfill leachate: Performance and mechanisms

The biotreated effluent of landfill leachate still contains numerous refractory organic contaminants, which poses potential threats to human health and ecosystems. Influenced by landfill ages and other factors, the concentration of organic matter varies. Heterogeneous catalytic ozonation (HCO) is a promising technology for advanced wastewater treatment. Aiming to achieve the up−to−standard discharge of low−concentration landfill leachate (COD ≈ 108 mg·L−1) and improve the biodegradability of high−concentration landfill leachate (COD ≈ 1720 mg·L−1), the active component Fe was incorporated into a firm Ni−induced C−Al2O3−framework (NiCAF) composite support to synthesize a Fe−NiCAF catalyst for efficient catalytic ozonation. When the Fe−NiCAF dosage was 4 g·L−1, the gas flow rate was 0.5 L·min−1, and the ozone concentration was 20.0 mg·L−1, the COD of low−concentration landfill leachate effluent decreased to 43 mg·L−1, and the COD removal rate constant of low−concentration landfill leachate was 154% higher than that of pure ozone. For high−concentration landfill leachate with the BOD5/COD of 0.058, the COD removal efficiency in Fe−NiCAF/O3 increased from 39% to 57% compared with ozonation, and the effluent BOD5/COD increased to 0.282. Furthermore, the addition of hydrogen peroxide (H2O2) and peroxymonosulfate (PMS) can further enhance the treatment performance of Fe−NiCAF/O3 process and different strengthening mechanisms were revealed. The results indicated that surface hydroxyls on the Fe−NiCAF catalyst surface were the main catalytic sites for ozone, and hydroxyl radical (•OH) and singlet oxygen (1O2) were identified as the main reactive oxygen species for the removal of organics in landfill leachate. Adding H2O2 can promote the generation of •OH for nonselective degradation of various organics, while PMS mainly enhanced the production of 1O2 to decompose macromolecular humus. This work highlighted an efficient Fe−NiCAF ozone catalyst and an innovative peroxide intensified HCO strategy for the advanced treatment of landfill leachate.

Advanced treatment of landfill leachate through combined Anammox-based biotreatment, O3/H2O2 oxidation, and activated carbon adsorption: technical performance, surrogate-based control strategy, and operational cost analysis

The complexity of landfill leachate makes it difficult to treat it with a single biological/ physical/chemical process. Moreover, the dynamic leachate characteristics pose a challenge for effective process control. Therefore, a combined treatment, consisting of a one-stage partial nitrification-Anammox process, an O3/H2O2 process, and a granular activated carbon filtration (GAC) process, was investigated. Meanwhile, a novel surrogate-based ozone dose control strategy for O3/H2O2 process was evaluated. Results show that this three-stage process offers high removal of total nitrogen (> 90%), COD (chemical oxygen demand, 60–82%), and micropollutants (atrazine, alachlor, carbamazepine, and bisphenol A, > 96%), satisfying discharge requirements. In the combined post-treatment, ozone dosing for COD removal can be real-time controlled by UVA254 reduction monitoring, based on a specific correlation between COD and UVA254 changes. On the other hand, O3/H2O2 pre-treatment controlled at a 50% UVA254 reduction shows to be the optimal point, when adsorption is designed as the main step for COD removal. Cost analysis shows that post-treatment with low (high) organic load i.e., COD ≤ (≥)540 mg/L, a combination with O3/H2O2 (GAC) as the main step appears to be more cost-effective. Therefore, a dynamic operation strategy in response to the leachate change is recommended.

Advanced treatment of landfill leachate using integrated coagulation/ photo-Fenton process through in-situ generated nascent Al3+ and H2O2 by Cl, N co-doped aluminum-graphite composite

Herein, we report an integrated coagulation/ photo-Fenton (CPF) process for advanced treatment of mature landfill leachate using nascent aluminum ions as coagulant and hydrogen peroxide (H2O2) as oxidant for Fenton reaction, which were in-situ produced by a novel chlorine and nitrogen co-doped aluminum-graphite (Cl, N-Al-Gr) composite. The coagulation of the MBR-treated landfill leachate was performed by nascent aluminum ions generated in Cl, N-Al-Gr/O2 system; and the resulting coagulation effluent was treated by photo-Fenton oxidation in the presence of ultraviolet (UVA). The Cl, N-Al-Gr composite exhibited excellent performance for in-situ H2O2 production (813.9 mg/L). The humic substances in landfill leachate could promote the cycle of Fe3+/Fe2+, and the removal efficiency of total organic carbon (TOC) and color was 88.1% and 97.6%, respectively under the optimized condition. The current study suggested that “coagulation + Fenton” process using nascent Al3+ as coagulant and in-situ generated H2O2 for Fenton oxidation could be a new way for wastewater treatment.

Experimental study on advanced treatment of landfill leachate by ultraviolet catalytic persulfate

Landfill leachate is characterized by complex composition and difficult degradation. In this paper, we compared the effects of advanced treatment of ultraviolet (UV) system, persulfate (PS) system and ultraviolet/persulfate (UV/PS) system on landfill leachate. The results showed that the UV/PS system had the best removal efficiency. When the initial concentration of humic acid was 200 mg/L, the dosing of PS was 25 mmol/L, and the initial pH was 4, the maximum removal rates of UV 254 and TOC were 89.62% and 76.17%. Namely, the value of SUVA 254 decreased to 7.6603 L/(m ⋅ mg). It follows that the UV/PS system is effective in the removal of humic acid in the landfill leachate. In addition, this paper investigated the effects of temperature, initial pH and dosing ratio of chemicals on the treatment of leachate by UV/PS system. It was found that the optimal process conditions were 35 °C, pH = 4, dosing ratio = 2, and 24 h of operation. Under these conditions, the maximum removal rates of COD and TOC were 82.64% and 66.69%. The removal capacity of the system was in accordance with the pseudo-second-order kinetic equation. Therefore, this paper can provide a reference for the advanced treatment of landfill leachate. • An advanced oxidation technology for the removal of landfill leachate after biochemical treatment was presented. • Humic acid was used as a model for organic matter. The value of SUVA 254 decreased to 7.660315 L/ (m ⋅ mg) under the optimum conditions. • Under the optimal conditions, the removal rates of COD and TOC of landfill leachate after biochemical treatment reached 82.64% and 66.69%. • SR-AOPs are more efficient, economical and widely applicable compared to other technologies for deep treatment of landfill leachate.

Energy-efficient for advanced oxidation of bio-treated landfill leachate effluent by reactive electrochemical membranes (REMs): Laboratory and pilot scale studies

This study for the first time investigated the advanced treatment of bio-treated landfill leachate effluent using a novel reactive electrochemical membrane (REM) technology at the laboratory and pilot scales. At the laboratory scale, RuO2-Ir-REM, Ti4O7-REM, and β-PbO2-REM featured similar properties in pore size and water flux. Although RuO2-Ir-REM holds more reactive sites than the other two REMs, β-PbO2-REM and Ti4O7-REM featured higher oxidation ability than RuO2-Ir-REM, causing their high yield of hydroxyl radical. Consequently, β-PbO2-REM and Ti4O7-REM performed better than RuO2-Ir-REM, which removed total organic carbon and ammonia nitrogen by 70%–76% and 100%, respectively, after 45 minutes of treatment. Fluorescence spectroscopy analysis showed that humic acid-like substances were oxidized by the REM treatment. Using the β-PbO2-REM in the lab-scale setup with the solutions circulated, we observed a greater removal of chemical oxygen demand (COD) at a higher applied current or a faster water flux. The pilot system with four large size of β-PbO2-REMs modules in series was developed based on the lab-scale setup, which steadily treated landfill leachate in compliance with the disposal regulations of China, at an energy consumption of 3.6 kWh/m3. Also, a single-pass REM can effectively prevent the transformation of chloride to chlorate and perchlorate. Our study showed REM technology is a powerful and promising process for the advanced treatment of landfill leachate.

Long-term removals of organic micro-pollutants in reactive media of horizontal subsurface flow constructed wetland treating landfill leachate

In this work, the removals of organic micro-pollutants (OMPs), i.e. DEP, DBP, 2,6-DTBP, BHT, and DEHP in sand, clay and iron powder mixed media of horizontal subsurface flow constructed wetland (HSSF) from landfill leachate were investigated over 3 years period. The biodegradation was mainly responsible for the removals of DEP, DBP, 2,6-DTBP and BHT whereas DEHP was initially removed through adsorption and formation of iron-organic complex and then subsequently biodegraded during long-term operation as OMP degrading microbial consortium attached to the reactive media was enriched. This study demonstrates that an application of reactive HSSF system can be a viable option for advanced landfill leachate treatment to meet ecological safety level.

Landfill leachate treatment through the combination of genetically engineered bacteria Rhodococcus erythropolis expressing Nirs and AMO and membrane filtration processes

This study developed a process of genetically engineered bacteria Rhodococcus erythropolis expressing Nirs and AMO combined with membrane bioreactor (MBR), nanofiltration (NF) and reverse osmosis (RO) membrane (pRho-NA-MNR) for advanced treatment of landfill leachate. Results demonstrated that pRho-NA-MNR presented higher removal rate of chemical oxygen demand (COD), biological oxygen demand (BOD), ammonia nitrogen (N–NH4), total nitrogen (TN) and total organic carbon (TOC) than activated sludge (AS-MNR) system. Administration of pRho-NA increased nitrification by converting N–NH4 to nitrite (N–NO2) and Nitrate (N–NO3), and promoting denitrification by converting N–NO2 to nitrogen (N2) in the landfill leachate treatment, promoted the pH control, increased sludge activity and effluent yield, shortened phase length adaptation under alternating aerobic-anoxic conditions. pRho-NA increased the nitration and denitrifying rate in the aerobic and anaerobic stage in the system by increasing Cyt cd1 and Cyt c expression in the activated sludge. Nitrogen removal by nitrification and denitrification was positively correlated to the concentration of Nirs and AMO expression. Treatment with pRho-NA promoted pollutant removal efficiency of membrane bioreactor, nanofiltration and reverse osmosis membrane processes in landfill leachate. In conclusion, data suggest that pRho-NA-MNR facilitates the formation of granular sludge and enhances comparable removal of nitrogen and organic compounds, indicating the practice of this process should be considered in landfill leachate treatment system.

阴离子交换纤维对垃圾渗滤液深度处理效果的研究

阴离子交换纤维对垃圾渗滤液深度处理效果的研究

高级氧化技术用于垃圾渗滤液的预处理及末端处理

高级氧化技术用于垃圾渗滤液的预处理及末端处理

Advanced landfill leachate treatment using iron-carbon microelectrolysis- Fenton process: Process optimization and column experiments

A novel hydrogen peroxide-enhanced iron-carbon (Fe-C) microelectrolysis reactor was proposed for the pretreatment of mature landfill leachate. This reactor, combining microelectrolysis with Fenton process, revealed high treatment efficiency. The operating variables, including Fe-C dosage, H2O2 concentration and initial pH, were optimized by the response surface methodology (RSM), regarding the chemical oxygen demand (COD) removal efficiency and biochemical oxygen demand: chemical oxygen demand (BOD5/COD) as the responses. The highest COD removal (74.59%) and BOD5/COD (0.50) was obtained at optimal conditions of Fe-C dosage 55.72g/L, H2O2 concentration 12.32mL/L and initial pH 3.12. Three-dimensional excitation and emission matrix (3D-EEM) fluorescence spectroscopy and molecular weight (MW) distribution demonstrated that high molecular weight fractions such as refractory fulvic-like substances in leachate were effectively destroyed during the combined processes, which should be attributed to the combination oxidative effect of microelectrolysis and Fenton. The fixed-bed column experiments were performed and the breakthrough curves at different flow rates were evaluated to determine the practical applicability of the combined process. All these results show that the hydrogen peroxide-enhanced iron-carbon (Fe-C) microelectrolysis reactor is a promising and efficient technology for the treatment of mature landfill leachate.

Advanced treatment of landfill leachate using anaerobic–aerobic process: Organic removal by simultaneous denitritation and methanogenesis and nitrogen removal via nitrite

A novel biological system coupling an UASB and a SBR was established to treat landfill leachate. In order to enhance organics and nitrogen removal, simultaneous denitritation and methanogenesis (SDM) was performed in the UASB. Free ammonia (FA) inhibition on nitrite-oxidizing bacteria (NOB) and process control was used to achieve nitrite pathway in the SBR. Results over 623days showed that the maximum organic removal rate in the UASB and the maximum ammonium oxidization rate in the SBR was 12.7kgCOD/m3d and 0.96kgN/m3d, respectively. The system achieved COD, TN, and NH4+−N removal efficiencies of 93.5%, 99.5%, and 99.1%, respectively. By using FA inhibition coupled with process control, the nitrite pathway was started-up in the SBR at low temperatures (14.0–18.2°C) and was maintained for 142days at temperatures below 15°C (the lowest level was 9.0°C). The predominant ammonia-oxidizing bacteria (AOB) explains essentially stable nitritation obtained.

Study on Advanced Treatment of Landfill Leachate by Sludge-Based Activated Carbon

Sludge-based Activated Carbon(SAC) was carried out on the method of chemical activation and high temperature pyrolysis, using municipal sludge as the main raw materials, mixed with a small amount of corn straw. Through the analysis of characterization of activated carbon, the best quality blending ratio of straw is 10% ; the dynamic adsorption results of tail liquid of landfill leachate show that SAC can effectively remove most of harmful substances in the tail liquid of landfill leachate and the effluent reached the vertical ground surface standard of the standard for pollution control on the landfill site for domestic waste .

Combined processes of two-stage Fenton-biological anaerobic filter–biological aerated filter for advanced treatment of landfill leachate

There are numerous non-biodegradable organic materials in the mature landfill leachate. To meet the new discharge standard of China, additional advanced treatment is needed for the effluent from the biological treatment processes of leachate. In this study, a combined process including two stages of “Fenton-biological anaerobic filter (BANF)–biological aerated filter (BAF)” was evaluated to address the advanced treatment need. The Fenton oxidation was applied to reduce chemical oxygen demand (COD) and enhance biodegradability of refractory organics, and the BANF–BAF process was then applied to remove the total nitrogen (TN). The treatment achieved effluent concentrations of COD<70mg/L, TN<40mg/L and NH3–N<10mg/L. The removal efficiency of COD and TN were 96.1% and 95.9%, respectively. The effluent quality met the new discharge standard for Pollution Control on the Landfill Site of Municipal Solid of PR China (GB16889-2008). The operation cost of these processes was about 36.1CHY/t (5.70USD/t).

Advanced Landfill Leachate Treatment Using the Tubular Membrane Bio-Electro Reactor

The paper studied advanced landfill leachate treatment with tubular membrane bio-electro reactor. The results showed that the tubular membrane flux be stability, COD of effluent be 350～650 mg L-1, while COD of feed water is 500～800 mgL-1, and the removal of COD reached 25%～45%.

Advanced landfill leachate treatment with least sludge production using modified Fenton process

This research was undertaken to investigate various operating conditions of Fenton treatment process for minimizing the sludge production and maximizing COD as well as colour removal from landfill leachate. Sample was collected from Matuaill and fill site, one of the major landfill sites of Dhaka City Corporation. For optimum pH value of 5 and optimum dosages of Fenton reagents having H2O2/Fe2+ molar ratio of 1.3 the highest removal of COD and colour were found 68% and 87% respectively with massive sludge production of 75%. The COD and colour removal efficiencies with a three-step dosing of reagents were 11% and 7% higher respectively with 17% less sludge production than those with single dosing of individual Fenton treatment process. Also recycling of Fenton sludge enhanced COD removal efficiency by 6% having similar colour removal efficiency and reduced sludge production significantly by 38%. With all optimum parameters, the highest removal of COD and colour were found 84% and 93% respectively with sludge production of 30% through multiple dosing of Fenton reagents with sludge recirculation. Conversely, pretreatment with extended aeration before Fenton process provided the achievement of 89% COD and 97% colour removals having less sludge volume reduction.