Urban Landfill Leachate Research Articles

Antibiotic Indexing and Heavy Metal Reduction Potential of Four Multi-metal Tolerant Bacterial Strains in Real-Time Sanitary Landfill Leachate Matrix.

Sanitary leachate from urban landfills is known to be contaminated with multi-metals and residual antibiotics. Current research edges on exploring the multi-metal and antibiotic sensitivity profile of four indigenous strains, "Brevibacillus spp. Leclercia spp. Pseudescherichia spp., and Brucella spp." isolated from the leachate of a sanitary landfill in a tropical region. Indigenous isolates were observed to be antibiotic-resistant and have high tolerance against eight of the ten tested metals except Cu & Co. It was observed that interaction with multi-metals in laboratory conditions significantly altered the cell morphology of bacterial strains, as depicted by Scanning Electron Microscope. Metal adsorption onto the microbial surface was deciphered through Electron Dispersive Spectrometer analysis and elemental mapping. Application of isolated strains into real-time leachate matrix exhibits a complete reduction of Ag and Zn and for other tested metals. Their response to these toxicants may facilitate their application in bioremediation-based treatment technologies for urban landfill leachate.

Study on Resistivity Imaging of Urban Landfill Leachate Channel Using 3D Electrical Resistivity Tomography with Annular Electrode Configuration

Urban garbage landfills are distributed mostly in a nearly circular shape with complex internal and external environments. The conditions on the top of the landfills are not conducive to the layout of electrical measuring lines and electrodes, resulting in difficulties in using the conventional linear or rectangular mesh high density electrical surveying system to achieve good results for the detection of leachate channel under the garbage body. This paper proposed 3D electrical resistivity tomography (ERT) method by annular electrode configuration with electrodes placed around the landfill. Through numerical simulation and indoor physical simulation experiments, we have discussed the feasibility and effectiveness of this method for circling the pollution range and channel location of landfill leachate. The study shows that the 3D ERT method with annular electrode configuration can effectively detect the spatial location and extension of garbage leachate channel, reflect the leakage of garbage leachate in landfills, and thus provide technical support for the fine detection of garbage leachate channel.

Anammox-Based Processes for Mature Leachate Treatment in SBR: A Modelling Study

Mature landfill leachates are characterized by high levels of ammoniacal nitrogen which must be reduced for discharge in the sewer system and further treatment in municipal wastewater treatment plants. The use of anammox-based processes can allow for an efficient treatment of ammonium-rich leachates. In this work, two real scale sequencing batch reactors (SBRs), designed to initially perform partial nitritation/anammox (PN/A) and simultaneous partial nitrification and denitrification (SPND) for the treatment of ammonium-rich urban landfill leachate, were modelled using BioWin 6.0 in order to enable plant-wide modelling and optimizing. The constructed models were calibrated and validated using data from long- and short-term (one cycle) SBR operation and fit well to the main physical-chemical parameters (i.e., ammonium, nitrite and nitrate concentrations) measured during short-term (one cycle) operations. Despite the different strategies in terms of dissolved oxygen (DO) concentrations and aeration and mixing patterns applied for SBR operation, the models allowed for understanding that in both reactors the PN/A process was shown as the main contributor to nitrogen removal when the availability of organic carbon was low. Indeed, in both SBRs, the activity of nitrite oxidizing bacteria was inhibited due to high levels of free ammonia, whereas anammox bacteria were active due to the simultaneous presence of ammonium and nitrite and their ability to recover from DO inhibition. Increasing the external carbon addition, a prompt decrease of the anammox biomass was observed, with SPND becoming the main nitrogen removal mechanism. Models were also applied to estimate the production rates of nitrous oxide by aerobic ammonia oxidizing bacteria and heterotrophic denitrifiers. The models were found to be a robust tool for understanding the effects of different operating conditions (i.e, temperature, cycle phases, DO concentration, external carbon addition) on the nitrogen removal performances of the two reactors, assessing the contribution of the different bacterial groups involved.

Ozone-driven processes for mature urban landfill leachate treatment: Organic matter degradation, biodegradability enhancement and treatment costs for different reactors configuration

In this work, the application of ozone-driven processes for the treatment of mature landfill leachate was investigated by testing different system setups. As a first approach, ozonation (O3-only) was tested, using a porous ceramic diffuser combined with a bubble column (BC), and the best operational conditions were established for leachate treatment (initial pH = 9.0; inlet ozone dose = 18 mg O3/min). Then, a novel photoreactor (FluHelik) was coupled in series with the bubble column, using a diffuser or a Venturi to inject ozone into the fluid stream. The FluHelik/BC-Venturi setup led to the highest efficiency, treating 50% more leachate than BC-alone using the same ozone dose and reaction time (3 h). Following, the oxidation ability of ozone combined with H2O2 and/or UVC for leachate treatment was assessed. The highest synergistic effect was obtained for the O3/UVC process, with pseudo-first-order rate constant for DOC and COD removal, 2.0 and 1.4 times higher than for the O3-only, respectively. Ozone-driven processes considerably enhanced the leachate biodegradability from 17% to 79% (O3/H2O2), 81% (O3-only), 85% (O3/H2O2/UVC) and 91% (O3/UVC), after a 3 h reaction period. With FluHelik/BC-Venturi system, the O3/UVC process stands out as the most efficient and cost-effective (6.0 €/m3), ensuring an effluent that meets discharge legal limit for COD (150 mg/L) after further biological oxidation.

Removal of ammoniacal nitrogen from municipal landfill leachate with floating <i>Typha domingensis</i> (Typhaceae)

A promising method for the treatment of effluents is the use of floating macrophytes. Ammoniacal nitrogen is a typical compound present in urban landfill leachates and its removal is important due its toxicity to several organisms. Therefore, the study evaluated Typha domingensis survival and nitrification potential artificially floating in domestic solid waste leachate. Plants were exposed for 35 days to leachate (100, 75 and 50 %) and to rainwater with N:P:K (control). Dissolved oxygen (DO) of the treatments was periodically measured, and ammoniacal nitrogen, nitrite and nitrate were analyzed before and after exposure. At the end of the experiment, plant survival rate was calculated. After two weeks, DO increased twice in the control, three times in 50 % leachate, four times in 75 % leachate, and eight times in 100 % leachate. At the end of the experiment, ammoniacal nitrogen was no longer detected, there was a significant reduction of nitrite, and a significant increase of nitrate in the treatments containing leachate. Plant survival was higher in those individuals exposed to 100 % leachate and decreased at lower leachate concentrations: 98 %, 94 %, 92 %, and 86 %. The study demonstrated that the ammoniacal nitrogen concentration of the leachate was not toxic to T. domingensis, and that it was efficient in the removal of this compound from the effluent, indicating that the species may be used artificially floating for the removal of this contaminant from domestic solid waste landfill leachate when in low concentrations.

Advanced evaluation of landfill leachate treatments by low and high-resolution mass spectrometry focusing on microcontaminant removal

Conventional wastewater treatments are not usually effective in the remediation of specific landfill leachates due to their high content in toxic and recalcitrant compounds. Advanced and intensive treatments are needed for the decontamination and possible recycling of these effluents. Here, the combination of advanced oxidation processes (solar photo-Fenton) and an aerobic biological reactor have been applied to treat urban landfill leachates. The effectiveness of the proposed treatment line was also evaluated considering the removal of organic microcontaminants (OMCs) identified in the different phases, which is an innovative practice. The analytical strategy included: (i) a target approach (115 analytes) by liquid chromatography-mass spectrometry (LC–MS/MS); and two suspect approaches using (ii) LC-high-resolution MS (database with >1300 compounds) and (iii) gas-chromatography-MS (database with >900 compounds). OMCs on the treated landfill leachate was reduced up to 94% of the initial concentration. 8 target compounds (mainly pharmaceuticals) out of 115 target analytes represented 85% of the OMC concentration in the raw leachate: cotinine, diclofenac, gabapentin, ketoprofen, lidocaine, mecoprop, nicotine and trigonelline. 3 non-previously reported OMCs were confirmed: di-n-nonyl phthalate, o-phenylphenol and tonalide. Leachate partially oxidized by solar photo-Fenton process can be successfully incorporated to biological systems to complete the treatment by means of specifically adapted biomass.

Stability of partial nitritation in a sequencing batch reactor fed with high ammonium strength old urban landfill leachate

The aim of this study is to investigate the stability of partial nitritation in a lab-scale sequencing batch reactor (PN-SBR) fed with high ammonium strength old municipal landfill leachate without pH adjustment, bicarbonate addition and low dissolved oxygen control. Long sludge retention of over 120 days was applied for the PN-SBR. The PN-SBR, which run over 250 days used the old urban landfill leachate containing 3096 mg NH₄⁺-N l⁻1, 12960 mg HCO₃ l⁻1, and influent HCO₃⁻:NH₄⁺ molar ratio of 1.06. After 75 days of operation, the partial nitritation achieved stability when the effluent nitrite to ammonium molar ratio obtained in the range of 1.0–1.32, which were suitable for feeding to an anammox reactor. The effluent NO₃⁻-N concentration was always below 20 mg N l⁻1. The maximum FA concentration reached 506 mg NH3-N l−1 at hour 26th during the cycle of 73 h. Even though old land fill leachate mainly contained refractory COD, COD removal efficiency achieved about 11%. The OUR tests show that the maximum growth rate μmax, Ko, Ks and yield coefficient YX/N of AOB were 0.12 day−1, 1.35 mg O2 l−1, 53 mg NH4+-N l−1 and 0.26 mgVSS mg−1 NH4+-N, respectively.

Geochemical processes in compacted clay in contact with an acid landfill leachate: laboratory experiments and modelling results

AbstractClays are commonly used as liners in urban landfills. However, the reactive processes with landfill leachates, and in particular the role of accessory minerals is poorly known. The aim of this work is to evaluate the diffusion of a synthetic urban landfill leachate through compacted natural smectite-illitic clays containing carbonates and sulfates and to predict the functioning of the clay liner for different minor mineral proportions. The leachate, characterized by acidic pH conditions and high organic matter content, is a typical aqueous solution formed in the acetogenic phase of organic matter degradation in urban landfill areas. Medium-scale (11 cm) laboratory diffusion tests were performed over 77 days. Chloride diffusion coefficients, porosity changes, cation exchange constants and the sulfate reduction rate were quantitatively assessed by means of reactive transport modelling. The exchange capacity of the clays is responsible for NH4+retention. However, the presence or absence of gypsum in the initial clay rock controls the functioning of the liner. Gypsum dissolution ensures a high sulfate concentration in the porewater and enhances the acetate consumption via sulfate reduction. Gypsum dissolution and the concomitant calcite precipitation do not significantly alter the porosity of the clay rock.

Achieving nitrogen removal via nitrite pathway from urban landfill leachate using the synergetic inhibition of free ammonia and free nitrous acid on nitrifying bacteria activity

In this study, a biological system consisting of an up-flow anaerobic sludge blanket (UASB) and anoxic-oxic (A/O) reactor was established for the advanced treatment of high ammonium urban landfill leachate. The inhibitory effect of free ammonia (FA) and free nitrous acid (FNA) on the nitrifying bacterial activity was used to achieve stable nitritation in the A/O reactor. The results demonstrated that the biological system achieved chemical oxygen demand (COD), total nitrogen (TN) and NH(4)(+)-N removal efficiencies of 95.3, 84.6 and 99.2%, respectively at a low carbon-to-nitrogen ratio of 3:1. Simultaneous denitritation and methanogenesis in the UASB could improve the removal of COD and TN. Nitritation with above 90% nitrite accumulation was successfully achieved in the A/O reactor by synergetic inhibition of FA and FNA on the activity of nitrite oxidizing bacteria (NOB). Fluorescence in situ hybridization (FISH) analysis showed that ammonia oxidizing bacteria (AOB) was dominant and was considered to be responsible for the satisfactory nitritation performance.

Biological Treatment of High Ammonium Content Urban Landfill Leachate Using an Anaerobic-Aerobic Process

Biological system consisting of an up-flow anaerobic sludge blanket (UASB) and anoxic-oxic (A/O) reactor was applied to treat high ammonium content urban landfill leachate. Inhibitory effect of free ammonia (FA) and free nitrous acid (FNA) on nitrifying bacteria activity was used to achieve nitrogen removal via nitrite pathway in the A/O. Results demonstrated that removed efficiencies of COD, total nitrogen (TN) and NH4+-N were 95.3%, 84.6 %and 99.2%, respectively. Stable nitrite pathway with above 90% nitrite accumulation was successfully achieved in the A/O reactor by synergetic inhibition of FA and FNA on the activity of nitrite oxidizing bacteria (NOB). Moreover, Fluorescence in situ hybridization (FISH) analysis showed that AOB was dominant microorganism.

Co-digestion of used oils and urban landfill leachates with sewage sludge and the effect on the biogas production

This paper evaluates the potential of mesophilic anaerobic digestion (AD) in the treatment of used oils and landfill leachates through co-digestion of the sludge produced in a wastewater treatment plant (WWTP). Biomethane potential (BMP) tests were performed on two different co-substrates and on WWTP sludge. The biogas production per kg of fresh matter of the sludge generated in a WWTP was only 6.1Nl/kg due to its low volatile solids concentration. Biogas production of landfill leachates per kg of fresh matter was found to be low (12.4Nl/kg). The biogas production per kg of fresh matter for the used oil over a period of 47days (not completely degraded) was 970.6Nl/kg. Used oil was selected as co-substrate according to these results. Anaerobic co-digestion of sludge and used oil was conducted in a pilot plant fed in semi-continuous regime in the mesophilic range (38°C) to obtain their adequate mixture in order to ensure the correct function of the process. The optimum oil percentage in the mixture was 19% (volatile solids basis). Once the appropriate mixture was obtained the co-digestion process was carried out in the digester of the Pobla de Farnals WWTP. The co-digestion process improved the performance of volatile matter removal (showing an 11% increase over the period without co-digestion) as well as the biogas production (a 23.5% increase over the period without co-digestion) without disturbing the anaerobic digestion process. The total production of biogas per day in the WWTP increased over the period without co-digestion.

Processes comparison for nickel and chrome removal from urban landfill leachate

This study aims to examine the feasibility of chemical, physical and biological processes on municipal landfills leachates, to mainly evaluate Nickel (Ni) and Chrome (Cr) removal. Flocculation/coagulation methods were investigated on laboratory scale, by dosing ferric chloride (FeCl3) and aluminium polychloride to three leachates, at a natural pH of 8. The oxidation treatment with sodium permanganate (NaMnO4), applied on the leachate with higher metals content, defined an increment of Ni (from 9 to 50%) and Cr (from 31 to 80%) removals, compared with the previous chemical treatments. Further, the metals biosorption capacity on the biomass flocs was investigated in a pilot scale membrane bioreactor, previously tested on laboratory scale. The different percentages of added leachate showed efficiencies up to 93% for Cr and 58% for Ni, defining the different removal roles of the adsorption and of the membrane layer effect.

Treatment improvement of urban landfill leachates by Fenton-like process using ZVI

The aim of the present study addresses the applicability of the Fenton-like zero valent iron (ZVI) process on the remediation of several landfill leachate samples coming from different points of an existing treatment plant: initial effluent (ERaw), after biological treatment (EPost-Bio) and depurated effluent (ETreat). The effects of pH and Fe0 concentration were determined for ERaw and ETreat. It was observed that the use of low pH values enhances the treatment efficiency. Moreover, the increase on iron load leads to higher COD removals until a certain point after which the catalyst starts to show radical scavenger effect. The low efficiency attained for ERaw (COD removal always below 8%) indicates that this methodology is not suitable for this effluent. However, final ETreat within the legal limits for discharge were attained when pH=2 was used with 38% of COD removal. The utilization of iron shavings as catalyst in the Fenton-like process showed to be a suitable and economical solution on the remediation of ETreat and EPost-Bio with high COD abatements (up to 60%) leading to streams able to be released to the municipal sewage. Since the real plant often does not comply with regulatory thresholds and according to our results, it seems advisable to implement this technology after the bio-reactor for substituting the already existing physico-chemical treatment.

Diffusion of landfill leachate through compacted natural clays containing small amounts of carbonates and sulfates

Abstract Diffusion of a synthetic urban landfill leachate through compacted natural illitic clays and the role of reactive accessory minerals (carbonates and gypsum) in the geochemical behavior of major soluble ions are evaluated. The leachate is composed of NH 4 + and Na+ (0.25 M) balanced by Cl− (0.25 M), acetate (0.1 M) and HCO 3 - (0.15 M). The pH is 7.8 and it is typical of the mature stage of organic matter degradation within an urban landfill. Laboratory scale diffusion tests were performed over 4 months (long term experiment, LT) and 2 weeks (short term experiment, ST). The ST experiments were designed to allow the measurement of the Cl− gradient as a diffusion tracer in the compacted clay. In the LT experiments the chemical gradients were already at steady state, but geochemical reactions involving dissolution of gypsum and precipitation of calcite were observed. Evolution of pore-water chemistry, mineralogy, cation exchange properties, and the specific surface of clays were determined. Numerical simulations were carried out using the geochemical code RETRASO. Chloride transport, precipitation of carbonates, pH buffering, and Ca2+/ NH 4 + cation exchange reactions took place in the laboratory tests. Apparent Cl− diffusion coefficients were determined by direct modeling of the ST tests and validated with the LT experiments. These coefficients were considered in the simulation of transport coupled with experimentally calculated exchange constants and dissolution/precipitation reactions of gypsum and carbonates. Sulfate reduction coupled with acetate oxidation has been proven to be relevant in the sample with significant concentration of SO 4 2 - (Bailen). This process also includes significant precipitation of carbonates (mainly calcite) and causes a decrease of SO 4 2 - in the porewater.

Study on Coupled Oxidation and Microwave Process in Treating Urban Landfill Leachate by Fenton and Fenton-Like Reaction

In study, Microwave Irradiation enhanced Fenton-Like Process was introduced as a novel technology in the treatment of Landfill Leachate containing refractory organic matters. The sample leachate with initial COD loading of 11434 ~12067 mg•L−1 was collected from the Laohuchong (Shenyang, China) City Landfill. Fenton (FeSO4/H2O2) and Fenton-like (iron tailings/H2O2) reagents coupling with Microwave Irradiation were both studied. The Microwave Irradiation enhanced Fenton-Like Process was conducted under the optimal conditions as follows: 480W of microwave power, 3 min of radiation time, 3.0 of initial pH, 100mL•L−1 of H2O2 and 2g•L−1 of iron tailings. The removal rates of leachate samples with initial COD =11928 mg•L−1 using 1.5g.L-1 FeSO4 and 2.0g.L-1 iron tailings are 45.1% and 42.3% respectively on the condition of 320W MW radiated for 3 min at room temperature. The highest removal rate of the MW Fenton-Like Process is about 46% under the optimum conditions. It demonstrates the Fenton-Like reagent can be used as a substitution of Fenton reagent in Landfill Leachate applications which has extensive application prospect and extraordinary significance in aspects of resource utilization of waste materials and cost saving.

Microbial fuel cell application in landfill leachate treatment

The feasibility of using microbial fuel cells (MFCs) in landfill leachate treatment and electricity production was assessed under high levels of nitrogen concentration (6033 mg N L −1) and conductivity (73,588 μS cm −1). An air-cathode MFC was used over a period of 155 days to treat urban landfill leachate. Up to 8.5 kg COD m −3 d −1 of biodegradable organic matter was removed at the same time as electricity (344 mW m −3) was produced. Nitrogen compounds suffered transformations in the MFC. Ammonium was oxidized to nitrite using oxygen diffused from the membrane. However, at high free ammonia concentrations (around 900 mg N-NH 3 L −1), the activity of nitrifier microorganisms was inhibited. Ammonium reduction was also resulted from ammonium transfer through the membrane or from ammonia loss. High salinity content benefited the MFC performance increasing power production and decreasing the internal resistance.

Systematic model development for partial nitrification of landfill leachate in a SBR

This study deals with partial nitrification in a sequencing batch reactor (PN-SBR) treating raw urban landfill leachate. In order to enhance process insight (e.g. quantify interactions between aeration, CO(2) stripping, alkalinity, pH, nitrification kinetics), a mathematical model has been set up. Following a systematic procedure, the model was successfully constructed, calibrated and validated using data from short-term (one cycle) operation of the PN-SBR. The evaluation of the model revealed a good fit to the main physical-chemical measurements (ammonium, nitrite, nitrate and inorganic carbon), confirmed by statistical tests. Good model fits were also obtained for pH, despite a slight bias in pH prediction, probably caused by the high salinity of the leachate. Future work will be addressed to the model-based evaluation of the interaction of different factors (aeration, stripping, pH, inhibitions, among others) and their impact on the process performance.

The effect of urban landfill leachate characteristics on the coexistence of anammox bacteria and heterotrophic denitrifiers

Heterotrophic denitrification coexists with the anammox process contributing to N removal owing to the biodegradable organic matter supply from urban landfill leachate and the decay of microorganisms. Both biomasses consumed nitrite increasing the nitrite requirements of the system. The aim of this paper is the study of the causes which induce the system to decrease nitrogen removal efficiency. In this study, urban landfill leachate has been treated in an anammox Sequencing Batch Reactor (SBR) for 360 days. The anammox reactor treated on average 0.24 kgN m(-3) d(-1) obtaining nitrogen removal efficiencies up to 89%. The results demonstrated that i) a suitable influent nitrite to ammonium molar ratio is a crucial factor to avoid troubles in the anammox reactor performance; ii) an excess of nitrite implied nitrite accumulation in the reactor; iii) a lower nitrite supply than the necessary for the system could force a loss of specific anammox activity due to nitrite competition with denitrifiers. These results pointed out the importance of the previous partial-nitritation process control in order to obtain a correct influent nitrite to ammonium molar ratio for the anammox reactor. In addition, sudden variation of the leachate characteristics must be avoided.

Nitrogen removal from landfill leachate using the SBR technology

Landfill leachate is a concern in the wastewater field due to its toxicity, high ammonium and low biodegradable organic matter concentrations. The aim of this paper is to study the reliability of landfill leachate treatment using Sequencing Batch Reactor (SBR) technology for biological nitrogen removal. During the study the SBR pilot plant treated successfully 0.48 kg N·m−3 d−1 of urban landfill leachate. Furthermore, high nitrogen removal efficiencies (80%, on average) have been achieved by the operational conditions applied (step‐feed strategy and alternating anoxic‐aerobic conditions).

Mercury speciation in urban landfill leachate by cold vapor generation atomic absorption spectrometry using ion exchange and amalgamation

0 is produced and then measured by cold vapor atomic absorption spectrometry (CV AAS). Hg org does not interact with the resin and is mixed with NaBH 4 at the exit of the column producing volatile species of Hg that are then amalgamated by a gauze of Au/Pt. Mercury is removed from the gauze by heating to 600 °C and subsequently measured by CV AAS. For Hg inorg and Hg org speciation in urban landfill leachate, the samples are centrifuged, filtered and treated with HCl. The detection limits (3 s) of Hg inorg and Hg org are 9 and 12 ng L -1 of Hg, respectively. The analysis frequency is 22 h -1 .