Treatment of industrial landfill leachate by means of evaporation and reverse osmosis

Investigating the partitioning behavior of per- and polyfluoroalkyl substances (PFAS) during thermal landfill leachate evaporation

Thermal landfill leachate evaporator systems can reduce the volume of leachate by up to 97%, while releasing water vapor and producing residuals (volume-reduced leachate and sludge) that are managed on-site. On-site thermal evaporators offer landfill operators leachate management autonomy without being subject to increasingly stringent wastewater treatment plant requirements. However, little is known about the partitioning of PFAS within these systems, nor the extent to which PFAS may be emitted into the environment via vapor. In this study, feed leachate, residual evaporated leachate, sludge, and condensed vapor were sampled at two active full-scale thermal landfill leachate evaporators and from a laboratory-scale leachate evaporation experiment. Samples were analyzed for 91 PFAS via ultra-high pressure liquid chromatography - tandem mass spectrometry (UHPLC-MS/MS). Similar trends were observed from Evaporator 1, Evaporator 2, and the laboratory-scale evaporator; ∑PFAS were concentrated in the residual evaporated leachate during evaporation by a factor of 5.3 to 20. All condensed vapors sampled (n = 5) contained PFAS, predominantly 5:3 fluorotelomer carboxylic acid (5:3FTCA), (full-scale vapors 729 - 4087 ng/L PFAS; lab-scale vapor 61.0 ng/L PFAS). For Evaporators 1 and 2, an estimated 9 - 24% and 10%, respectively, of the PFAS mass entering the evaporators in leachate was released with vapor during the days of sample collection. '.

A combined treatment system of O3/UV oxidation and activated carbon adsorption: emerging contaminants in hospital wastewater

Researchers have recently focused their attention on emerging contaminants (ECs) in wastewater because they pose serious health and environmental risks. Because ECs are persistent in the environment and have the ability to disrupt the physiology of target receptors, they have been labeled as contaminants of recent environmental concern. For removing various ECs, a variety of treatment technologies have been developed, including biological, chemical, and physical methods. However, no single technology can currently effectively remove ECs, whereas hybrid systems have consistently proven to be more effective. Furthermore, the majority of existing technologies are energy and resource intensive, as well as expensive to maintain and operate. Furthermore, the majority of advanced treatment technologies that have been proposed have yet to be evaluated for large-scale feasibility. Some ECs, particularly pharmaceuticals and pesticides, were found to be significantly removed using a hybrid technique that included ozone/UV and granular activated carbon (GAC). Besides, the removal of effluent parameters (TDS, COD, TOC) was enhanced through the GAC surface oxidization as a catalyst with NaOH before the process and by ozone within the procedure as well.

Chitosan grafted tetracarboxylic functionalized magnetic nanoparticles for removal of Pb(II) from an aqueous environment

In this study, the chitosan-grafted tetracarboxylic functionalized magnetic nanoparticle (Fe₃O₄@TCA@CS) was synthesized via in situ co-precipitation process and amidation reaction to improve efficiency of adsorption process and obtain cost-effective adsorbents for removal of toxic Pb(II) metal from aqueous environment. The Fe₃O₄@TCA@CS nanocomposite was analyzed by FTIR, TEM-EDX, TGA, XRD, BET, and Zeta potential. The performance of Fe₃O₄@TCA@CS for Pb(II) ions adsorption was achieved as a function of pH, dose, contact time, initial Pb(II) concentration, and temperature. The influence of coexisting ions such as Na⁺, Ca²⁺, Mg²⁺, and Cd²⁺on removal efficiency of Pb(II) was also investigated. The results revealed that the coexisting ions had little influence on Pb(II) removal efficiency. The pseudo-first-order and Freundlich models were better to describe the adsorption of Pb(II) onto Fe₃O₄@TCA@CS and the maximum adsorption capacity of Pb(II) was 204.92 mg/g at pH:5.5; adsorbent dose: 0.015 g; and temperature: 298 K. Thermodynamic studies revealed that the Pb(II) adsorption onto Fe₃O₄@TCA@CS was an exothermic process. In conclusion, the study provides a new, simple, low-cost, and effective chitosan-based magnetic nanocomposite as a promising adsorbent with excellent adsorption capacity, magnetic separation, and reusability for Pb(II) removal from an aqueous environment.

Performance of integrated sequencing batch reactor (SBR) and reverse osmosis (RO) process for leachate treatment: effect of pH

PURPOSE

In this paper the performance and effectiveness of the reverse osmosis (RO) process for the biologically pretreated leachate was investigated. The RO process was carried out separately for two different pH: 8.0 and 9.3.

METHODS

A general pollution parameters as well as organic and inorganic indicators were determined in raw, biologically pretreated and RO treated leachate. The performance characteristics of the reverse osmosis system were made on the basis of permeate flux, electroconductivity removal rate, concentration factor and efficiency in removal of analyzed parameters.

RESULTS

The use of SBR pretreatment had very good efficiency in BOD (97.3%) and ammonia nitrogen (95.4%) removal. The lowest effectivity was observed for chloride (11.6%), boron (3.9%) and TDS (1.2%). Pretreated leachate was subjected to RO system. The normalized average flux was 0.53 (42.3 L/m²·h) for pH = 8.0 and 0.68 (33.5 L/m²·h) for pH = 9.3. The lower membrane fouling at higher pH can be explained by electrostatic repulsion between the negatively charged membrane surface and organic substances. Independently of the process pH, a two-step membrane fouling was observed. The greatest differences in removal rates were observed for boron, which had a higher retention rate at higher pH, and ammonia nitrogen, whose removal rate decreased at higher pH. The obtained permeate pH after RO process was lower than the feed pH in two analyzed value of pH.

CONCLUSIONS

The higher flux value at pH = 9.3 is result of high content of organic matter in leachate, which is better rejected at higher pH because of higher electrostatic repulsion between organic matter and membrane surface. This indicates that the organic matter content should be taken into account when determining the operating parameters (pH values) of the RO system.

Solidification/stabilization of landfill leachate concentrate contaminants using solid alkali-activated geopolymers with a high liquid solid ratio and fixing rate

Landfill leachate concentrate (LLC) is a highly toxic wastewater that contains many refractory contaminants. One of the technical and economic treatment methods is solidification/stabilization (S/S), where the contaminants of LLC can be sealed in one step to achieve zero wastewater discharge. This study presents the S/S of LLC contaminants using solid alkali-activated geopolymers prepared from blast furnace slag (BFS) and powdery sodium silicate. The stability of the formed geopolymer was studied through unconfined compressive strength (UCS) and leaching tests. The strongest UCS was obtained when the modulus of the activator was 1.16 with a high liquid/solid ratio of 0.64. BFS-based geopolymers presented excellent LLC S/S efficiency. The S/S rates of TOC, COD_Cr, NH₃-N, Cl^-, and SO₄^2- were 81%, 89%, 97%, 97%, and 78%, respectively. The S/S rates of heavy metals, i.e., Cd and Pb, were all more than 99%. The results of microstructure characterization showed that the S/S mechanism of LLC pollutants was the dual effect of physical closure and chemical stability. Cl^- and SO₄^2- were respectively stabilized in the crystal lattice by Friedel's salt and calcium sulfate, respectively, while organic matter and NH₃-N were physically encapsulated in the dense structure of the geopolymer. Overall, BFS based geopolymers demonstrated high treatment capacity and excellent S/S efficiency, and have a potential application prospects in LLC treatment.

Progress and prospects in mitigation of landfill leachate pollution: Risk, pollution potential, treatment and challenges

The escalating loads of municipal solid waste (MSW) end up in open dumps and landfills, producing continuous flows of landfill leachate. The risk of incorporating highly toxic landfill leachate into environment is important to be evaluated and measured in order to facilitate decision making for landfill leachate management and treatment. Leachate pollution index (LPI) provides quantitative measures of the potential environmental pollution by landfill leachate and information about the environmental quality adjacent to a particular landfill. According to LPI values, most developing countries show high pollution potentials from leachate, mainly due to high organic waste composition and low level of waste management techniques. A special focus on leachate characterization studies with LPI and its integration to treatment, which has not been focused in previous reviews on landfill leachate, is given here. Further, the current review provides a summary related to leachate generation, composition, characterization, risk assessment and treatment together with challenges and perspectives in the sector with its focus to developing nations. Potential commercial and industrial applications of landfill leachate is discussed in the study to provide insights into its sustainable management which is original for the study.

Resource recovery toward sustainability through nutrient removal from landfill leachate

This study investigated the feasibility of integrated ammonium stripping and/or coconut shell waste-based activated carbon (CSWAC) adsorption in treating leachate samples. To valorize unused biomass for water treatment application, the adsorbent originated from coconut shell waste. To enhance its performance for target pollutants, the adsorbent was pretreated with ozone and NaOH. The effects of pH, temperature, and airflow rate on the removal of ammoniacal nitrogen (NH₃-N) and refractory pollutants were studied during stripping alone. The removal performances of refractory compounds in this study were compared to those of other treatments previously reported. To contribute new knowledge to the field of study, perspectives on nutrients removal and recovery like phosphorus and nitrogen are presented. It was found that the ammonium stripping and adsorption treatment using the ozonated CSWAC attained an almost complete removal (99%) of NH₃-N and 90% of COD with initial NH₃-N and COD concentrations of 2500 mg/L and 20,000 mg/L, respectively, at optimized conditions. With the COD of treated effluents higher than 200 mg/L, the combined treatments were not satisfactory enough to remove target refractory compounds. Therefore, further biological processes are required to complete their biodegradation to meet the effluent limit set by environmental legislation. As this work has contributed to resource recovery as the driving force of landfill management, it is important to note the investment and operational expenses, engineering applicability of the technologies, and their environmental concerns and benefits. If properly managed, nutrient recovery from waste streams offers environmental and socio-economic benefits that would improve public health and create jobs for the local community.

Bioelectrochemical treatment of municipal solid waste landfill mature leachate and dairy wastewater as co-substrates

Despite solid wastes' landfill disposal limitation due to recent European legislation, landfill leachate disposal remains a significant problem and will be for many years in the future, since its production may persist for years after a site's closure. Among process technologies proposed for its treatment, microbial fuel cells (MFCs) can be effective, achieving both contaminant removal and simultaneous energy recovery. Start-up and operation of two dual-chamber MFCs with different electrodes' structure, fed with mature municipal solid waste landfill leachate, are reported in this study. Influent (a mix of dairy wastewater and mature landfill leachate at varying proportions) was fed to the anodic chambers of the units, under different conditions. The maximum COD removal efficiency achieved was 84.9% at low leachate/dairy mix, and 66.3% with 7.6% coulombic efficiency (CE) at a leachate/dairy ratio of 20%. Operational issues and effects of cells' architecture and electrode materials on systems' performance are analyzed and discussed.

State-of-the-Art and Opportunities for Forward Osmosis in Sewage Concentration and Wastewater Treatment

The application of membrane technologies for wastewater treatment to recover water and nutrients from different types of wastewater can be an effective strategy to mitigate the water shortage and provide resource recovery for sustainable development of industrialisation and urbanisation. Forward osmosis (FO), driven by the osmotic pressure difference between solutions divided by a semi-permeable membrane, has been recognised as a potential energy-efficient filtration process with a low tendency for fouling and a strong ability to filtrate highly polluted wastewater. The application of FO for wastewater treatment has received significant attention in research and attracted technological effort in recent years. In this review, we review the state-of-the-art application of FO technology for sewage concentration and wastewater treatment both as an independent treatment process and in combination with other treatment processes. We also provide an outlook of the future prospects and recommendations for the improvement of membrane performance, fouling control and system optimisation from the perspectives of membrane materials, operating condition optimisation, draw solution selection, and multiple technologies combination.

Development of a treatment train for the remediation of a hazardous industrial waste landfill leachate: A big challenge

This study focuses on the development of a treatment train for a leachate from a hazardous industrial waste landfill (HIWL) previously treated by: (i) catalytic oxidation with hydrogen peroxide (H₂O₂) for sulphide and sulphite conversion into oxidized sulphur species, including sulphate, and (ii) chemical precipitation of sulphate as barite. The complete treatment line counted on four more stages: (iii) 1^st biological oxidation for removal of biodegradable organic compounds and nitrogen species, (iv) coagulation with ferric chloride (coagulant dose of 100 mg Fe L^-1, pH 2.8) for removal of a fraction of recalcitrant organics and suspended solids, (v) photo-Fenton oxidation using ultraviolet A (UVA) radiation (PF-UVA) (pH 2.8, initial total dissolved iron content of 140 mg L^-1, treatment time of ~4 h) for recalcitrant organics degradation and biodegradability improvement, and (vi) 2^nd biological oxidation for removal of the biodegradable organic matter resulting from the PF-UVA process. The use of anodic oxidation or photoelectro-Fenton processes in stage (v) demonstrated to be unfeasible. A chemical oxygen demand (COD) below 1000 mg O₂ L^-1, a common limit imposed by municipal wastewater treatment plants (MWWTPs) to effluents discharged into the municipal sewer, was achieved after a feasible treatment time (~4 h) using the multistep approach. The remediation of the HIWL leachate proved to be a big challenge.

Excellent adsorptive performance of a new nanocomposite for removal of toxic Pb(II) from aqueous environment: Adsorption mechanism and modeling analysis

Herein, a novel nanocomposite (Fe₃O₄@TATS@ATA) was prepared and used for adsorptive removal of Pb(II) ions from aqueous environment. The magnetic nanocomposite (Fe₃O₄@TATS@ATA) was characterized using FTIR, TEM, SEM, EDX, element mapping analysis (EMA), TGA analysis, XRD patterns, VSM, BET analysis, XPS spectrum, and zeta potential. The FTIR study confirmed the modification of Fe₃O₄ nanoparticles with triaminetriethoxysilane and 2-aminoterephthalic acid while XPS analysis (with peaks at 283.6, 285.1, 286.3, 284.5.0, 288.4 eV) displayed the presence of CSi, CN, OCNH, CC/CC and OCO functional groups, respectively on Fe₃O₄@TATS@ATA. The BET surface area, average pore size, pore volume and magnetization saturation for Fe₃O₄@TATS@ATA were found to be 114 m²/g, 6.4 nm, 0.054 cm^-3/g, and 22 emu/g, respectively. The adsorption isotherm data showed that Pb(II) adsorption onto Fe₃O₄@TATS@ATA fitted to Langmuir and Dubinin-Raduskevich isotherm model due to better R² value which was greater than 0.9 and q_m of Pb(II) was 205.2 mg/g at pH 5.7 in 150 min. Adsorption kinetics data displayed that Pb(II) adsorption onto Fe₃O₄@TATS@ATA was fitted to the pseudo-second-order and Elovich kinetic models. Thermodynamic outcomes exhibited the exothermic and spontaneous nature of adsorption. Results showed that Fe₃O₄@TATS@ATA nanocomposite was promising material for efficient removal of toxic Pb(II) from aqueous environment.

Ammonia removal and recovery from municipal landfill leachates by heating

In this research, ammonia evaporation capacity under atmospheric and vacuum pressure conditions, as well as distillation capacity of different concentrations of landfill leachates, were evaluated. Simple evaporation and vacuum pressure evaporation tests showed high NH₃-N removal efficiencies, ranging from 95% to 98% for raw landfill leachates, indicating that vacuum pressure would not be necessary during ammonia removal and recovery processes when applying temperature of 300 °C. Distillations tests also showed the promising NH₃-N recovery potential in ultra-concentrated leachates (over 100 gNH₃-N/L) in the order of 91%-94% in few minutes, evaporating a small portion of landfill leachate. The results presented encourages the recovery of ammonia from landfill leachate and its industrial and agricultural, highlighting its feasibility as well as simultaneously preventing the ammonia release to water bodies or the atmosphere.

Improved oxidation of refractory organics in concentrated leachate by a Fe2+-enhanced O3/H2O2 process

Concentrated leachate from membrane processes, which contains a mass of refractory organics and salt, has become a new problem for wastewater engineers. In this study, removal of organic contaminants in concentrated landfill leachate was investigated by applying the ferrous ion (Fe²⁺) catalyzed O₃/H₂O₂ process. The maximum chemical oxygen demand (COD) and absorbance at 254 nm (UV₂₅₄) removal efficiencies under the optimal conditions (initial pH = 3.0, Fe²⁺ dosage = 6.500 mM, H₂O₂ dosage = 18.8 mM and O₃ dosage = 52.65 mg min^-1) were 48.82% and 63.59%, respectively. These were higher than those achieved using the Fe²⁺/O₃, O₃/H₂O₂, and O₃ processes, and biodegradability of the leachate was improved significantly. Moreover, compared with other processes, the Fe²⁺ had a stronger catalytic effect. Molecular distribution analysis and three-dimensional excitation and emission matrix analysis both indicated that the fulvic acid and humic acid in the concentrated leachate were greatly degraded. Ultraviolet-visible spectra showed that the Fe²⁺/O₃/H₂O₂ process mainly destroyed unsaturated bonds and decreased the aromatic degree of the leachate. The reaction mechanism of the Fe²⁺/O₃/H₂O₂ process mainly was attributed to three factors: (1) O₃ and H₂O₂ reacting to produce ^•OH; (2) H₂O₂ and O₃ decomposing into ^•OH through the oxidation of Fe²⁺ to Fe³⁺; and (3) coagulation by Fe (OH)₃. The ^•OH can rapidly degrade recalcitrant organics, and coagulation also increases the removal of organic matter. Therefore, the Fe²⁺/O₃/H₂O₂ process was an effective method for treating concentrated landfill leachate.

Hooped Amino-Group Chains in Porous Organic Polymers for Enhancing Heavy Metal Ion Removal

By adjusting the stretch state of a triethylenetetramine (TETA) chain in an amine-functionalized porous organic polymer (POP), two adsorbents were designed to study the rational microenvironment for heavy metal ion removal. The quantum calculation elucidated that the hooped amino chains in FC-POP-CH₂TETA-H exhibited stronger interactions with Pb(II) than the extended one in FC-POP-CH₂TETA-E, not only through metal-ligand chelation but also metal coordination. The high binding energy of -2624 kJ mol^-1 as well as the constructed microenvironment by the hooped amino chains ensured an extremely high Pb(II) capacity of 1134 mg g^-1 on FC-POP-CH₂TETA-H. Meanwhile, no more than 5 min to approach adsorption equilibrium revealed its ultrafast adsorption rate. It also showed excellent broad removal capability for multiple metal ions and nonsensitivity to pH. Therefore, by controlling the microenvironmental structures with suitable porosity, functional group stretching states, and coordination modes, the removal efficiency of heavy metal ions would be significantly enhanced, which further provided a promising strategy for designing a rational microenvironment to improve the task-specific separation properties.

Constituent transformation mechanism of concentrated leachate after incineration at different temperatures

Spraying concentrated leachate into an incineration furnace and burning is encouraged by the Chinese government as a harmless method for leachate treatment. In this research, the constituent transformation mechanism was studied, by X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy-dispersive spectrometry (EDS), of residues after burning the concentrated leachate in a muffle furnace at different temperatures (750 °C, 850 °C, 900 °C, 1000 °C, and 1100 °C). XRD results showed that the main components of the residues were metal chlorides and calcium salt crystals and that the peak position of most of these crystals changed little because their crystal structure was stable at high temperatures. SEM results illustrated that the higher the burning temperature, the smaller the solid particles, and the looser the structures of the residues. EDS analysis showed that S atoms in the concentrated leachate were usually transformed into gaseous compounds during incineration, whereas most of the Cl atoms could be fastened onto solid residues if an appropriate temperature was maintained. This study concluded that 900 °C was the best burning temperature for spraying concentrated leachate into the furnace. In addition, this study suggested that material selection for the nozzle and flue gas pipelines must pay more attention to corrosion caused by gaseous sulfur compounds. Similarly, material selection for the inner wall of the incinerator furnace should pay more attention to corrosion caused by Cl atoms. This means that the municipal solid waste (MSW) incineration power plants should incorporate various and appropriate corrosion-resistant materials according to the different regions of the incinerator.

Targeted removal of organic foulants in landfill leachate in forward osmosis system integrated with biochar/activated carbon treatment

Forward osmosis (FO) has been adopted to treat complex wastewater such as landfill leachate due to its high rejection of organics. In this study, the in-line adsorptive process using biochar (BC) or powdered activated carbon (PAC) was applied to a cross flow FO system to enhance the mitigation of the FO membrane fouling from landfill leachate. The changes in the leachate composition along the treatments were tracked by excitation emission matrix-parallel factor analysis (EEM-PARAFAC) to identify tryptophan-like (C1), fulvic-like (C2), and humic-like (C3) components. After a single operation of FO, the C1 was found to be the main constituent responsible for membrane fouling irrespective of varying operation conditions regarding draw solute concentrations and flow rates. Both sorbents (i.e., BC and PAC) exhibited the preferential removal behavior towards C1 > C2 > C3, which was well supported by their individual adsorption isotherm model parameters. The addition of in-line adsorption treatment to FO resulted in substantial improvements in the filtered volume (>57%) and the flux recovery (>80%) compared to the single FO operation. Without chemical cleaning of membrane, the flux was fully recovered at a dose of 10 g/L BC or 0.3 g/L of PAC. A significant and negative correlation was found between the flux recovery and the C1 of the feed leachate or the corresponding spectral peak intensity (p < 0.05) for the integrated FO system, suggesting the potential of using on-line fluorescence monitoring for the performance of the integrated system in terms of fouling mitigation. This study provided a new insight into the effectiveness of BC or PAC adsorption as the in-line integration with an FO system for the targeted removal of FO membrane foulants in landfill leachate.

Development of an integrated treatment strategy for a leather tannery landfill leachate

This study aimed at developing an efficient multistage treatment strategy for a complex industrial landfill leachate: a leather tannery landfill leachate. Based on the leachate physicochemical characteristics, the following treatment train was delineated and tested: (i) initial biological process for removal of biodegradable organics, ammonium and alkalinity, (ii) coagulation/flocculation process for total removal of chromium and partial removal of recalcitrant organics and suspended solids, (iii) advanced oxidation process (AOP) or electrochemical AOP (EAOP) for degradation of recalcitrant organics and biodegradability enhancement, and (iv) final biological polishing step. Two initial biological treatment configurations were applied: one comprising nitrification and the other nitrification-denitrification. Coagulation/flocculation was optimized in terms of pH, coagulant dosage (iron(III) chloride) and flocculant nature and dosage. The following AOPs/EAOPs were tested: Fenton, photo-Fenton with UVA or UVC radiation (PF-UVA or PF-UVC), anodic oxidation (AO), electro-Fenton (EF) and photoelectro-Fenton with UVA radiation (PEF-UVA). The biological nitrification-denitrification was beneficial not only because it avoided the need for alkalinity addition during nitrification and decreased the amount of substrate added during denitrification, as expected. Over and above that, it reduced the acid consumption in the coagulation/flocculation, avoided the application of an additional stage comprising nitrites oxidation to nitrates prior to the AOP/EAOP, and improved the efficiency of Fenton's reaction based processes. Following nitrification-denitrification, the coagulation/flocculation was maximized at pH 3.0 and 400 mg Fe L^-1 with no flocculant addition. The PEF-UVA process was the best AOP/EAOP. The final leachate fulfilled the discharge limits into waterbodies.

A sustainability assessment for use on land or wastewater treatment of the digestate from bio-waste

The sustainability of use on land or by processing in a wastewater treatment plant of the digestate from bio-waste was investigated. Sustainability was assessed following a triple bottom line approach entailing environmental, social and economic consequences. A methodology for developing an integrated sustainability indicator was also defined. Global warming and acidification were about 40 kgCO_2eq/m³ and 0.7 molcH⁺_eq/m³ and 90 kgCO_2eq/m³ and 1.1 molcH⁺_eq/m³ for wastewater treatment and use on land, respectively. The impact on human health for use on land was about 3.5 × 10^-4 (DALY), six times higher than wastewater treatment but quite negligible when compared to the DALY associated with other diseases in the same area. Costs calculated for wastewater treatment ranged from about 18 €/m³ up to 35 €/m³, about ten times higher than those related to use on land. The integrated sustainability indicator that was developed indicated higher sustainability for use on land and the relevant influence of such finding with respect to the environmental consequences.

Sulphur compounds removal from an industrial landfill leachate by catalytic oxidation and chemical precipitation: From a hazardous effluent to a value-added product

This study focused on the removal of sulphur compounds from a high-strength leachate of a hazardous industrial waste landfill. Firstly, sulphides (0.5 g L^-1) and sulphites (2.5 g L^-1) were catalytic oxidised at natural pH (8.7). Air or H₂O₂ were applied as oxidants and metals present in the leachate were used as catalysts. Distinct air flow rates and H₂O₂:sulphur molar ratios were tested. Concentrations of sulphide and sulphite lower than 1.0 mg L^-1 (emission limit value - ELV) were obtained after 5-h oxygenation or 1-min peroxidation under the best conditions, i.e. air flow rate of 1 L_air L_leachate^-1 min^-1 and H₂O₂:sulphur stoichiometric ratio. Aeration was considered unsafe since >33 volatile organic compounds (VOCs) and hydrogen sulphide (H₂S) were released to the atmosphere. Thus, only the H₂O₂-oxidised leachate pursued treatment. Sulphates (13 g L^-1) were removed by chemical precipitation as ettringite or barite applying different reactants contents and pH values. Without pH correction, sulphate contents below 2.0 g L^-1 (ELV) were achieved using a [Ca²⁺]:[Al³⁺]:[SO₄^2-] molar ratio of 12:4:3 (2-fold stoichiometry) and a [Ba²⁺]:[SO₄^2-] molar ratio of 1.0:1.0 (1-fold stoichiometry). The analysis of precipitates by X-ray diffraction (XRD) showed a three-phase ettringite (only 67% corresponding to ettringite itself) and single-phase barite. Barite precipitation proved to be more appealing since a value-added product was obtained and, furthermore, less reactants were required. After sulphur compounds removal using H₂O₂-driven catalytic oxidation and chemical precipitation through barite, the leachate was suitable for biological treatment, despite the high salinity, and a high fraction of the organic load (46%) could be biologically oxidised.

Mathematical simulation to improve municipal solid waste leachate management: a closed landfill case

This article presents an example of the application of simulation tools to estimate the post-closure evolution of leachate in a non-hazardous waste landfill. The objective of this work is to predict the behavior of leachate after the closure of the landfill for use as basic information with which to design the leachate management strategy in the following years. The MODUELO 4.0 mathematical landfill simulation software package was used for this purpose. The results of the simulation show that the concentrations in the leachate increase during the post-closure period, from values close to 2200 mg/L of COD and 1500 mg/L of NH₄⁺ at the time of landfill closure to 3200 mg/L of COD and 5300 mg/L of NH₄⁺ 20 years later. This increase is mainly due to the reduction in the flows, from 105 to 17 m³/day on average, since the surface lining was installed. Consequently, pollutant fluxes decrease to values below 100 kg/day in both COD and NH₄⁺ 3 months after closure. This evolution indicates that the management of this leachate will be simpler in the future, especially if it is co-treated with urban wastewater, as its contribution decreases. On the other hand, external water connections to the leachate collectors may cause a relevant increase in the volume of the global landfill effluent. Controlling runoff management and underground infiltrations could lead to important savings in leachate treatment during the aftercare phase.

Enhancing forward osmosis water recovery from landfill leachate by desalinating brine and recovering ammonia in a microbial desalination cell

In this work, a microbial desalination cell (MDC) was employed to desalinate the FO treated leachate for reduction of both salinity and chemical oxygen demand (COD). The FO recovered 51.5% water from a raw leachate and the recovery increased to 83.5% from the concentrated leachate after desalination in the MDC fed with either acetate or another leachate as an electron source and at a different hydraulic retention time (HRT). Easily-degraded substrate like acetate and a long HRT resulted in a low conductivity desalinated effluent. Ammonia was also recovered in the MDC cathode with a recovery efficiency varying from 11 to 64%, affected by current generation and HRT. Significant COD reduction, as high as 65.4%, was observed in the desalination chamber and attributed to the decrease of both organic and inorganic compounds via diffusion and electricity-driven movement.

Comparison of NF-RO and RO-NF for the Treatment of Mature Landfill Leachates: A Guide for Landfill Operators

Reverse osmosis (RO) and nanofiltration (NF) are among the state-of-the-art technologies for treating landfill leachates. Due to the complexity and variance in the composition of leachates, numerous combinations of multiple technologies are used for their treatment. One process chain for the treatment of raw leachate is RO followed by further concentration of RO-retentate using NF (RO-NF scheme). The aptness of this process train used by some landfill sites around the world (usually with the aim of volume reduction so as to re-inject the concentrate into the landfill) is questionable. This study investigated two schemes RO-NF and NF-RO (nanofiltration of raw leachate followed by reverse osmosis of NF permeate) to identify their merits/demerits. Experiments were conducted in bench scale using commercial membranes: DOW Filmtec NF270 and SW30HR. Filtration trials were performed at different pressures to compare the water and solute transports in the individual stages of the two schemes. Based on the water fluxes and compositions of retentates and permeates; osmotic pressures, energy demands, and other possible operational advantages were discussed. NF-RO offers some advantages and flexibility for leachate treatment besides being energy efficient compared to RO-NF, wherein osmotic pressure steadily increases during operation in turn increasing operation and maintenance costs.

Impact of different schemes for treating landfill leachate

Different technological schemes for treating the leachate generated by an existing landfill were compared in a life cycle perspective. On-site advanced processes based on reverse osmosis and evaporation were compared to conventional off-site co-treatment with civil sewage in wastewater treatment plant (WWTP). The inventories of the different scenarios were built by both direct observation of existing facilities and by retrieving data from the literature and similar equipment. Particular care was given for evaluating the energetic and chemical needs for operating the on-site advanced treatments. The evaporation system required 40 kW h/m³ of electricity and 18.5 kW h/m³ of heat, whereas reverse osmosis needed only 8.5 kW h/m³ of electricity. On the other hand the amount of liquid concentrate returned by the evaporation system was only about 0.03 m³/m³ instead of about 0.30 m³/m³ returned by reverse osmosis. The evaporation system also consumed the highest amount of chemicals. Life cycle analysis showed that the impact categories most affected by the different options were human toxicity, both non-cancer and cancer, together with freshwater ecotoxicity. The uncertainty analysis highlighted the major contribution associated with direct emissions from the processes. On the basis of mean values, the qualitative trends were substantially confirmed.

Quantitative dynamics of ammonia-oxidizers during biological stabilization of municipal landfill leachate pretreated by Fenton's reagent at neutral pH

The application of multi-stage systems including biological step, for the treatment of leachate from municipal landfills, is economically and technologically justified. When microbial activity is utilized as 2nd stage of treatment, the task of 1st stage is to increase the bioavailability of organic matter. In this work, the effect of advanced oxidation process by Fenton's reagent for treatment efficiency of landfill leachate in the sequencing batch reactor was assessed. The quantitative dynamics of bacteria taking a part in ammonia removal process was evaluated by determination of number of DNA copies of 16S rRNA and amoA. Products of neutral pH chemical oxidation, had a definite positive impact on the quantity of β-proteobacteria 16S rRNA, whereas the same gene specified for Nitrospira sp. as well as amoA did not show a significant increase during the process of biological treatment, regardless of whether the reactor was fed with raw leachate or chemically pre-treated.

Energy consumption by forward osmosis treatment of landfill leachate for water recovery

Forward osmosis (FO) is an alternative approach for treating landfill leachate with potential advantages of reducing leachate volume and recovering high quality water for direct discharge or reuse. However, energy consumption by FO treatment of leachate has not been examined before. Herein, the operational factors such as recirculation rates and draw concentrations were studied for their effects on the quantified energy consumption by an FO system treating actual leachate collected from two different landfills. It was found that the energy consumption increased with a higher recirculation rate and decreased with a higher draw concentration, and higher water recovery tended to reduce energy consumption. The highest energy consumption was 0.276±0.033kWhm^-3 with the recirculation rate of 110mLmin^-1 and 1-M draw concentration, while the lowest of 0.005±0.000kWhm^-3 was obtained with 30mLmin^-1 recirculation and 3-M draw concentration. The leachate with lower concentrations of the contaminants had a much lower requirement for energy, benefited from its higher water recovery. Osmotic backwashing appeared to be more effective for removing foulants, but precise understanding of membrane fouling and its controlling methods will need a long-term study. The results of this work have implied that FO treatment of leachate could be energy efficient, especially with the use of a suitable draw solute that can be regenerated in an energy efficient way and/or through combination with other treatment technologies that can reduce contaminant concentrations before FO treatment, which warrants further investigation.

Heterogeneous adsorption behavior of landfill leachate on granular activated carbon revealed by fluorescence excitation emission matrix (EEM)-parallel factor analysis (PARAFAC)

Heterogeneous adsorption behavior of landfill leachate on granular activated carbon (GAC) was investigated by fluorescence excitation-emission matrix (EEM) combined with parallel factor analysis (PARAFAC). The equilibrium adsorption of two leachates on GAC was well described by simple Langmuir and Freundlich isotherm models. More nonlinear isotherm and a slower adsorption rate were found for the leachate with the higher values of specific UV absorbance and humification index, suggesting that the leachate containing more aromatic content and condensed structures might have less accessible sites of GAC surface and a lower degree of diffusive adsorption. Such differences in the adsorption behavior were found even within the bulk leachate as revealed by the dissimilarity in the isotherm and kinetic model parameters between two identified PARAFAC components. For both leachates, terrestrial humic-like fluorescence (C1) component, which is likely associated with relatively large sized and condensed aromatic structures, exhibited a higher isotherm nonlinearity and a slower kinetic rate for GAC adsorption than microbial humic-like (C2) component. Our results were consistent with size exclusion effects, a well-known GAC adsorption mechanism. This study demonstrated the promising benefit of using EEM-PARAFAC for GAC adsorption processes of landfill leachate through fast monitoring of the influent and treated leachate, which can provide valuable information on optimizing treatment processes and predicting further environmental impacts of the treated effluent.

Immobilized materials for removal of toxic metal ions from surface/groundwaters and aqueous waste streams

Heavy metals from industrial processes are of special concern because they produce chronic poisoning in the aquatic environment. More strict environmental regulations on the discharge of toxic metals require the development of various technologies for their removal from polluted streams (i.e. industrial wastewater, mine waters, landfill leachate, and groundwater). The separation of toxic metal ions using immobilized materials (novel sorbents and membranes with doped ligands), due to their high selectivity and removal efficiency, increased stability, and low energy requirements, is promising for improving the environmental quality. This critical review is aimed at studying immobilized materials as potential remediation agents for the elimination of numerous toxic metal (e.g. Pb, Cd, Hg, and As) ions from polluted streams. This study covers the general characteristics of immobilized materials and separation processes, understanding of the metal ion removal mechanisms, a review of the application of immobilized materials for the removal of toxic metal ions, as well as the impacts of various parameters on the removal efficiency. In addition, emerging trends and opportunities in the field of remediation technologies using these materials are addressed.

Optimized evaporation technique for leachate treatment: Small scale implementation

This paper introduces an optimized evaporation technique for leachate treatment. For this purpose and in order to study the feasibility and measure the effectiveness of the forced evaporation, three cuboidal steel tubs were designed and implemented. The first control-tub was installed at the ground level to monitor natural evaporation. Similarly, the second and the third tub, models under investigation, were installed respectively at the ground level (equipped-tub 1) and out of the ground level (equipped-tub 2), and provided with special equipment to accelerate the evaporation process. The obtained results showed that the evaporation rate at the equipped-tubs was much accelerated with respect to the control-tub. It was accelerated five times in the winter period, where the evaporation rate was increased from a value of 0.37 mm/day to reach a value of 1.50 mm/day. In the summer period, the evaporation rate was accelerated more than three times and it increased from a value of 3.06 mm/day to reach a value of 10.25 mm/day. Overall, the optimized evaporation technique can be applied effectively either under electric or solar energy supply, and will accelerate the evaporation rate from three to five times whatever the season temperature.

The effect of temperature on the biodegradation properties of municipal solid waste

The aim of this study is to analyse the effect of temperature on the biodegradation and settlement properties of municipal solid waste by using bioreactors. Three kinds of controlled temperature were performed during the biodegradation test; the variation of weight, leachate and biogas production were carefully monitored. The degradation test indicated that more leachate leaked out owing to the external compression and polymer hydrolysis reaction in the aerobic phase, which could lead to the decrease of biodegradation rate in the anaerobic phase. A proper temperature range in favour of enhancing biodegradation of refuse was obtained, which ranged from 22 °C to 45 °C. Finally, an empirical equation of biodegradation ratio was proposed, which incorporated the temperature effect. In the end, the validation of this proposed model is verified, and is proved to be reasonable for predicting degradation velocity in landfills.

A study of shear strength properties of municipal solid waste in Chongqing landfill, China

The aim of this study is to analyze the effect of biodegradation on the shear strength of municipal solid waste (MSW), leachate, and biogas production. The direct shear (DS) test shows that the shear strength of waste in the initial stages is mainly depended on its composition and inter-structure. After the waste has been in a landfill for 30 days, the waste's increased biodegradation exhibited a great influence on the waste's shear strength. The increase of moisture content in the waste mass might cause a decrease of its shear strength. Tri-axial tests under consolidation-drained (CD) condition show that the shear strength of the cohesion and friction angle for degraded samples increased when the defined axial strain increased from 5 to 20 %. The cohesion varied from 35.90 to 66.42 kPa and the drained friction angle ranged between 29° and 38°. The measurements of shear strength properties are utilized to assess the slope stability of landfills.

Escherichia coli growth and transport in the presence of nanosilver under variable growth conditions

Nanosilver (silver nanoparticles) has the ability to anchor to the bacterial cell membrane and subsequently penetrate it, thereby causing structural changes (i.e., permeability) in the cell membrane and death of the cell. The bacterial responses to the presence of nanosilver usually vary depending on the concentration of nanosilver particles, exposure time and the bacterial physiological stage. Since bacterial anabolism dependents upon a stoichiometric ratio of carbon and inorganic elements (nutrients), the macronutrient ratio, i.e. carbon to nitrogen ratio (C/N) thus plays an important role of bacterial responses to the exposure of nanosilver. This study investigated the responses of Escherichia coli to the exposure of nanosilver under variable growth conditions. It was discovered that E. coli grown under different growth conditions had different responses to the presence of nanosilver. E. coli had least resistance to the toxicity of nanosilver when cultured under carbon-limited conditions. However, the presence of rhamnolipid, a commonly utilized biosurfactant for soil remediation increased the resistance of E. coli to nanosilver. The transport of E. coli cultured under carbon-limited conditions was further studied in silica sand columns. E. coli adsorption in silica sand increased when cultured in the presence of nanosilver. On the contrary, E. coli adsorption in silica sand was significantly reduced when cultured in the presence of rhamnolipid.

Application of cetyltrimethylammonium bromide bentonite-titanium dioxide photocatalysis technology for pretreatment of aging leachate

Organobentonite-photocatalysis technology was applied to pretreat aging leachate containing refractory pollutants. The organobentonite was synthesized by organic modifier cetyltrimethylammonium bromide (CTMAB) and natural bentonite. In characterization experiments, we could confirm that organic functional groups of cetyltrimethylammonium (CTMA(+)) cations were successfully loaded on the surface of bentonite. The combination of CTMAB2.5 adsorption and TiO2 photocatalysis was superior to either running separately. Furthermore, removal efficiency of simultaneously utilizing CTMAB2.5 and TiO2 was better than them in succession. The combination technology was feasible and was optimized by response surface methodology (RSM) with COD and NH3-N removal rate as the target responses. The optimal operation conditions calculated from the regression equations were CTMAB2.5 dosage of 7.5 g/L, pH at 3.5, TiO2 dosage of 1.63 g/L, and reaction time for 60.02 min, which maintained the removal of COD and NH3-N at 82% and 37%, respectively.

Wool graft polyacrylamidoxime as the adsorbent for both cationic and anionic toxic ions from aqueous solutions

Wool graft polyacrylamidoxime (W-g-PAO) was synthesized using coarse wool as the raw keratin material. The W-g-PAO can be used as the cheap and excellent adsorbent for the removal of both cationic and anionic toxic ions from waste water. The approach can be extended to the modification of other waste raw keratin materials and used them as the blocks for the fabrication of functional materials.

Removal of toxic metal ions from landfill leachate by complementary sorption and transport across polymer inclusion membranes

In this study, performance of a lab-scale two-step treatment system was evaluated for removal of toxic metal ions from landfill leachate. The technology of polymer inclusion membranes (PIMs) was the first step, while the second step of the treatment system was based on sorption on impregnated resin. The PIMs were synthesized from cellulose triacetate as a support, macrocyclic compound i.e. alkyl derivative of resorcinarene as a ionic carrier and o-nitrophenyl pentyl ether as a plasticizer. The transport experiments through PIM were carried out in a permeation cell, in which the membrane film was tightly clamped between two cell compartments. The sorption tests were carried out using a column filled with a resin impregnated with resorcinarene derivative. The obtained results show the good performance with respect to the removal of heavy metals from landfill leachate with the overall removal efficiency of 99%, 88% and 55% for Pb(II), Cd(II) and Zn(II) ions, respectively. Moreover the contents of metal ions in the leachate sample after treatment system were below permissible limit for wastewater according to the Polish Standards.

Role of electrode materials for the anodic oxidation of a real landfill leachate--comparison between Ti-Ru-Sn ternary oxide, PbO(2) and boron-doped diamond anode

In this paper the electrocatalytic properties of Ti-Ru-Sn ternary oxide (TiRuSnO(2)), PbO(2) and boron-doped diamond (BDD) anodes have been compared for the electrochemical oxidation of a real landfill leachate from an old municipal solid waste landfill (average values of COD 780 mg dm(-3) and NH(4)(+)-N266 mg dm(-3)). The experiments have been performed using an undivided flow cell equipped with a stainless steel cathode, under constant current of 2 A and flow-rate of 420 dm(3) h(-1). The performance of the electrodes has been compared measuring the time evolution of aromatic compounds, COD, ammonium, colour removal, current efficiency and energy consumption. The experimental results indicated that after 8 h of electrolyses TiRuSnO(2) anode yields only 35% COD, 52% colour and 65% ammonium removal. Using PbO(2) ammonium and colour were completely removed but a residual COD (i.e. 115 mg dm(-3)) was present. On the contrary BDD enables complete COD, colour and ammonium removal due to the electrogeneration of hydroxyl radicals from water discharge and active chlorine from chloride ions oxidation. BDD also exhibits greater current efficiency along with a significantly lower energy cost than other electrodes. These results indicated that the electrochemical oxidation with BDD anode is an effective process for the treatment of landfill leachate.

Evaluation of on-site biological treatment for landfill leachates and its impact: A size distribution study

A cost effective and widely applied approach for landfill leachate disposal is to discharge it to a municipal wastewater treatment plant (WWTP). The recalcitrant nature of leachate organics and the impact on the downstream WWTPs were comprehensively investigated in this study. Size fractionation by ultrafiltration (UF) and microfiltration (MF) was employed in conjunction with various analyses (TOC, COD, nitrogen species and UV(254) absorbance) on raw and biologically treated landfill leachates to provide insight into biological treatability. Overall, landfill leachate organics showed bio-refractory properties. Less than half of the organic matter, measured as total organic carbon (TOC), could be removed in the biological processes examined. Size distribution data showed that the <1 thousand Daltons (kDa) fraction is dominant in most untreated and treated landfill leachates, indicating difficulties for membrane treatment. Also, most removal occurred for the <1 kDa fraction in the biological processes, while the intermediate size fractions increased slightly. This may be caused by bio-flocculation and/or partial degradation of larger molecular weight fractions. Organic nitrogen was investigated in this study as one of the first explorations for landfill leachates. Organic nitrogen in landfill leachates was more bio-refractory than other organic matter. UV quenching by landfill leachates was also investigated since it interferes with the UV disinfection at WWTPs. The combination of activated carbon and activated sludge (PACT) showed some effectiveness for reducing UV quenching, indicating that carbon adsorption is a potential method for removal of UV quenching substances. Fourier transform Infrared (FT/IR) data showed that aromatic groups are responsible for the UV quenching phenomenon.

Cascade bioreactor with submerged biofilm for aerobic treatment of Tunisian landfill leachate

A bioreactor cascade with a submerged biofilm is proposed to treat young landfill leachate of jbel chakir landfill site south west from capital Tunis, Tunisia. The prototype was run under different organic loading charges varying from 0.6 to 16.3 kg TOC m(-3)day(-1). Without initial pH adjustment total organic carbon (TOC) removal rate varied between 65% and 97%. The total reduction of COD reached 92% at a hydraulic retention time of 36 h. However, the removal of total kjeldahl nitrogen for loading charges of 0.5 kg Nm(-3)day(-1) reached 75%. The adjustment of pH to 7.5 improved nitrogen removal to a rate of 85% for loading charge of 1 kg Nm(-3)day(-1). The main bacterial groups responsible for a simultaneous removal of organic carbon and nitrogen belonged to Bacillus, Actinomyces, Pseudomonas and Burkholderia genera. These selected isolates showed a great capacity of degradation at different leachate concentrations of total organic carbon.

Mathematical model analysis of Fenton oxidation of landfill leachate

The treatment of concentrated landfill leachate rejected from reverse osmosis (RO) with Fenton process was studied, and the system model was developed through the examination of reaction kinetics. The leachate is typically non-biodegradable with low BOD(5)/COD ratio 0.01. The oxidation reactions of Fenton process was found to be a two-stage process, where a fast initial reaction (H(2)O(2)/Fe(2+)) was followed by a much slower one (H(2)O(2)/Fe(3+)). A simple and more accurate mathematics model based on COD and TOC removals has been derived successfully to describe the two-stage reaction kinetics. The two corresponding parameters involved in this model have been identified as the initial reaction rate and the maximum oxidation removal efficiency, respectively. It was found to be very useful for evaluating the performance of Fenton system and/or for process design using the two parameters under different experimental conditions.

Ammonium nitrogen removal from coking wastewater by chemical precipitation recycle technology

Ammonium nitrogen removal from wastewater has been of considerable concern for several decades. In the present research, we examined chemical precipitation recycle technology (CPRT) for ammonium nitrogen removal from coking wastewater. The pyrolysate resulting from magnesium ammonium phosphate (MAP) pyrogenation in sodium hydroxide (NaOH) solution was recycled for ammonium nitrogen removal from coking wastewater. The objective of this study was to investigate the conditions for MAP pyrogenation and to characterize of MAP pyrolysate for its feasibility in recycling. Furthermore, MAP pyrolysate was characterized by scanning electron microscope (FESEM), transmission electron microscope (TEM), Fourier transform infrared spectroscopy (FTIR) as well as X-ray diffraction (XRD). The MAP pyrolysate could be produced at the optimal condition of a hydroxyl (OH(-)) to ammonium molar ratio of 2:1, a heating temperature of 110 degrees C, and a heating time of 3h. Surface characterization analysis indicated that the main component of the pyrolysate was amorphous magnesium sodium phosphate (MgNaPO(4)). The pyrolysate could be recycled as a magnesium and phosphate source at an optimum pH of 9.5. When the recycle times were increased, the ammonium nitrogen removal ratio gradually decreased if the pyrolysate was used without supplementation. When the recycle times were increased, the ammonium nitrogen removal efficiency was not decreased if the added pyrolysate was supplemented with MgCl(2).6H(2)O plus Na(2)HPO(4).12H(2)O during treatment. A high ammonium nitrogen removal ratio was obtained by using pre-formed MAP as seeding material.

Treatment of the methanogenic landfill leachate with thin open channel reverse osmosis membrane modules

A leachate purification system, equipped with the thin open channel spiral wound modules, is studied in this paper. In Phase I, effluent from an activated sludge process followed by the flocculation/sedimentation process was fed into the landfill leachate treatment unit. After 2 wk of operation, the permeate flux dropped dramatically, from an average value of 6.5l/m(2)/h to 4.23 l/m(2)/h. The significant decline of membrane flux was likely caused by membrane fouling. In Phase II, raw leachate was fed directly into the reverse osmosis leachate treatment system. An average flux of 7.8l/m(2)/h was maintained at an initial trans-membrane pressure difference of 20 bar, which increased to 40 bar before membrane chemical cleaning. An average recovery rate of 70% was achieved. Throughout the observation in Phase II, an average reduction rate of 98.2% for the dissolved solids was obtained. The reduction rate of COD was greater than 99.5% with a constant level of the permeate COD. Chloride was eliminated by more than 99%, while over 98% of NH(4)-N was reduced. A negligible permeate flux drop was observed after cleaning the membrane effectively. The study shows that direct reverse osmosis membrane filtration with thin open channel spiral wound modules is able to achieve satisfactory results in terms of water quality, process stability and membrane flux. The obtained quality of the permeate quality in this study met the German standards for leachate discharge. At the end of each filtration cycle, the membrane was maintained through alkaline chemical cleaning in order to remove any irreversible membrane fouling. After the maintenance procedure, the membrane flux was found to recover to the initial value.

Nitrogen removal via nitrite from municipal landfill leachate

A system consisting of a two-stage up-flow anaerobic sludge blanket (UASB), an anoxic/aerobic (A/O) reactor and a sequencing batch reactor (SBR), was used to treat landfill leachate. During operation, denitrification and methanogenesis took place simultaneously in the first stage UASB, and the effluent chemical oxygen demand (COD) was further removed in the second stage UASB. Then the denitrification of nitrite and nitrate in the returned sludge by using the residual COD was accomplished in the A/O reactor, and ammonia was removed via nitrite in it. Last but not least, the residual ammonia was removed in SBR as well as nitrite and nitrate which were produced by nitrification. The results over 120 d (60 d for phase I and 60 d for phase II) were as follows: when the total nitrogen (TN) concentration of influent leachate was about 2500 mg/L and the ammonia nitrogen concentration was about 2000 mg/L, the short-cut nitrification with 85%-90% nitrite accumulation was achieved stably in the A/O reactor. The TN and ammonia nitrogen removal efficiencies of the system were 98% and 97%, respectively. The residual ammonia, nitrite and nitrate produced during nitrification in the A/O reactor could be washed out almost completely in SBR. The TN and ammonia nitrogen concentrations of final effluent were about 39 mg/L and 12 mg/L, respectively.