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PubMed2003

Serial water balance method for predicting leachate generation in landfills.

This paper presents the "Serial Water Balance" method for predicting leachate generation in landfills. This procedure makes it possible to calculate the total leachate likely to be generated, by estimating an individual cell by cell water balance. This new development considers the interaction effects between cells, through the execution of simple field capacity tests on solid waste samples under different loading conditions. The procedure described in this paper simulates the effect induced by fluid percolating from a cell at an upper layer to cells in the immediately subjacent layer. The method described here was applied to the landfill in Nuevo Laredo, Tamaulipas (Mexico), after first ascertaining information regarding: duration of construction time, exposure time, surface area, the quantity of waste, number of confining cells, and local weather conditions. In a full-scale test case the suggested method has predicted 67% of the leachate produced in a period of 4 years. Further testing and more detailed analysis of the composition of the waste used in the calculations, may improve the accuracy in predicting leachate production. Even though this SWB methodology was applied to a landfill subject to extreme climatological conditions (high daytime temperatures), it is possible to adapt the methodology to solid waste disposal sites in regions with more humid or moderate climates.

Climate↗
PubMed2005

Physico-chemical treatment of Merida landfill leachate for chemical oxygen demand reduction by coagulation.

In order to determine the optimal dosage and type of coagulant for the physico-chemical treatment of leachate from the sanitary landfill of Merida, Mexico, a total of 864 jar tests were performed. Four metallic coagulants (ferric chloride, ferric sulphate, aluminium polychloride and aluminium sulphate) with doses ranging between 50 and 300 mg L(-1) and two polyelectrolytes (high-density anionic and cationic reagents) with doses from 2 to 12 mg L(-1) were tested. Neither an adequate type of coagulant nor an optimal dose could be found. The removal of contaminants was measured as total and dissolved chemical oxygen demand (COD). Soluble COD removal efficiencies were low, from 0 to 47%, with a 4% average value only. These low values of organic material removal were attributed to the particular characteristics of the Merida landfill leachate (low suspended solids concentration), so even with sweep-floc coagulation (300 mg L(-1) dose) only low COD removal efficiencies were obtained. A study of the suspended particle size distribution of the leachate was conducted in order to explain the poor performance. The particle size distribution ranged from 0.375 to 948.2 microm, with an average value of 22.97 microm. In a second step the optimal pH for physico-chemical treatment of these leachates was determined. Finally a greater than 90% removal of organic material, measured as suspended COD, was obtained at pH 2, which was considered as the optimal value.

Alum Compounds↗
PubMed2002

Changes in the quality of landfill leachates from recent and aged municipal solid waste.

A leachate study was conducted at the Etueffont landfill (Belfort, France), to examine differences in leachate composition between old and new areas of the fill and their seasonal evolution. It was based on hourly (1999), monthly (1998-1999) and annual (1993 to 1998) samplings of domestic landfill leachate. Variations in flow rate, rainfall, temperature, electrical conductivity, O2, pH, Cl, SO4, Zn, Cu, Fe, Ni, HCO3, NO3, NH4, BOD and COD were monitored. The results from monthly samplings showed close coupling between flow and concentrations of all parameters measured in the leachate. Indeed, these latter parameters decreased with increasing flow rates. Also, mass emissions per unit waste mass decreased with increasing waste age. The hourly monitoring pointed out an increase in electrical conductivity, chloride and COD concentrations in the middle of the day. This was most likely attributable to temperature fluctuations.

Environmental Monitoring↗
PubMed2002

Solubility and adsorption characteristics of Pb in leachate from MSW incinerator bottom ash.

The solubility and adsorption characteristics of Pb in leachate from municipal solid waste incineration (MSWI) bottom ash was studied by batch experiments. The solubility of Pb in leachate was 1-2 orders of magnitude lower than that of Pb in carbonate solutions. Adsorption experiments showed bottom ash have high adsorption capacity for Pb. To evaluate a controlling component in bottom ash, quartz, Al and Fe powder as well as their ions were examined over wide ranges of pH at 25 degrees C. The results showed that only Fe powder had high adsorption capacities for Pb, indicating that iron oxides in bottom ash would be one major adsorbent for Pb. Adsorption diagram, constructed by using the data of adsorption experiments, fitted the experimental data of Pb in leachate very well. It suggests that the decrease of Pb solubility in leachate is mainly due to adsorption reaction.

Adsorption↗
PubMedDate not supplied

Effect of flue gas desulfurization residue on plant establishment and soil and leachate quality.

Effects on soil quality and crop establishment after incorporation of flue gas desulfurization by-product (FGD) into soil as an amendment was assessed in a mesocosm study. Mesocosm units received applications equivalent to 0, 2.5, 5.0, 7.5, and 10% FGD residue [0, 25, 50, 75, and 100 tons acre(-1)]. Germination, biomass production, and elemental composition of corn (Zea mays L. var. Dekalb DK-683), soybean [Glycine max (L.) Merr. var. Haskell Pupa 94], radish (Raphanus sativus L. var. Sparkler), and cotton (Gossypius hirsutus L. var. Deltapine 51) were determined. The quality of leachates and soil were also determined periodically. Flue gas desulfurization residue did not affect germination and all application rates stimulated aboveground biomass. Plants grown in FGD-amended soil contained significantly elevated tissue concentrations of As, B, Se, and Mo. The FGD residue elevated surface soil pH from 5.5 (Control) to 8.1 (at 10% FGD). Leachate pH was unaffected by FGD, but salinity rose sharply with increasing application rates of FGD. Leachates contained higher concentrations of B, with small increases in Se and As. Flue gas desulfurization residue application caused an increase in total B, As, Mo, Se, and extractable Ca in the soil, but decreased Mn and Zn. Using FGD residues could have beneficial effects on crop establishment without detrimental effects on soil or leachate quality, at an optimum rate of approximately 2.5%. This material could alleviate surface acidity, and B and Mo deficiencies in plants.

Agriculture↗
PubMedDate not supplied

Sorption of arsenic from soil-washing leachate by surfactant-modified zeolite.

Post-treatment of leachate from soil-washing remedial actions may be necessary depending on the amounts of dissolved contaminants present. Uptake of arsenic species by surfactant-modified zeolite (SMZ) from a synthetic soil leachate (pH of approximately 12 [NaOH]) was measured as a test of SMZ as a post-treatment sorbent. Batch sorption isotherms were prepared using leachate to SMZ ratios from 40:1 to 4:1, and temperatures of 25 and 15 degrees C. Equilibrium levels of dissolved and total solution arsenic were similar. At each temperature, sorption appeared to reach a plateau or maximum, then decreased at the highest solution concentration, corresponding to the lowest amount of zeolite added (2.5 g). A maximum sorption value of 72.0 mmol of arsenic per kg of SMZ (5400 mg/kg) was observed at 25 degrees C, and 42.1 mmol/kg (3150 mg/kg) at 15 degrees C. Total arsenic recoveries varied from 74 to 125%. Surfactant-modified zeolite removed up to 97% of dissolved organic carbon and decolorized the leachate solutions. Excluding the points for the highest arsenic to SMZ ratio, the sorption isotherms were well described by the linearized form of the Langmuir equation, with coefficients of determination greater than 0.90 at both temperatures. Sorption of arsenic by SMZ is attributed to anion exchange with counterions on the surfactant head groups, and/or partitioning of organic carbon-complexed arsenic into the surfactant bilayer.

Adsorption↗
PubMed2006

Leachate detoxification by combination of biological and TiO2-photocatalytic processes.

Landfill leachates are a problematic wastewater due to their variable concentration, volume changing in time and presence of refractory and hazardous components. In this paper, the results of a new approach to photocatalysis assisted by biological process for the detoxification of stabilised landfill leachate are presented. The biologically pre-treated leachate still contained a significant amount of non-biodegradable COD and TOC amounting to 500 and 200 mg/L, respectively. The 300 min of photocatalytic treatment (UVC/TiO2) brought about a significant decrease in more than 80% refractory organics remaining in leachate. The effect of pH and catalyst loading on mineralisation, colour removal rate and biodegradability (BOD/COD) improvement in the photoreactor were discussed. The bio-accessibility of formed photocatalytic oxidation intermediates was confirmed by oxygen uptake rate (OUR) measurements. Consequently, a part of COD was successfully removed in post-biological treatment.

Biodegradation, Environmental↗
PubMed2001

Biological ammonia removal from anaerobically pre-treated landfill leachate in sequencing batch reactors (SBR).

The aim of the study was to investigate both the use of the SBR technology in biological ammonia removal from landfill leachate, and the suitability of raw landfill leachate as external carbon source in denitrification step. The SBR was fed with diluted leachate for the first 42 days and then the effluent of UASBR was used as the feed. The SBR was operated intermittently with a cycle time of 24 hours. The effluent NH4(+)-N values of less than 5 mg NH4(+)-N L-1 was consistently observed for the initial NH4(+)-N levels of as high as 1000 mg NH4(+)-N L-1. The nitrification rates for the first, second and third stages were found as 5.7, 46.8 and 102.8 mg NH4(+)-N L-1 h-1, respectively. The difference of the nitrification rates in the 2nd and 3rd stages originated from increasing adaption of the sludge as well as increasing biomass concentration (10.5 mg NH4(+)-N g-1 VSS h-1). No significant accumulation of NO2(-)-N has been observed during the study and NO2(-)-N/NOx(-)-N ratios measured in the 1st aerobic phase and the SBR effluent were less than 7%. The denitrification rates for the second (raw leachate as carbon source) and the third (Ca(CH3COO)2 as carbon source) stages were determined as 45.7 mg NOx(-)-N L-1 h-1 (or 9.85 mg NOx(-)-N g-1 VSS h-1) and 125.7 mg NOx(-)-N L-1 h-1 (or 12.88 mg NOx(-)-N g-1 VSS h-1), respectively.

Ammonia↗
PubMed2001

Exceptionally high-rate nitrification in sequencing batch reactors treating high ammonia landfill leachate.

The nitrogen removal capacity of a suspended culture system treating mature landfill leachate was investigated. Leachate containing high ammonium levels of 300-900 mg N/L was nitrified in a bench scale sequencing batch reactor. Leachate from four different landfills was treated over a two year period for the removal of nitrogen. In this time, a highly specific nitrifying culture was attained that delivered exceptionally high rates of ammonia removal. No sludge was wasted from the system to increase the throughput and up to 13 g/L of MLSS was obtained. Settleability of the purely nitrifying biomass was excellent with SVI less than 40 mL/g, even at the high sludge concentrations. Nitrification rates up to 246 mg N/(L h) (5.91 g N/(L d)) and specific nitrification rates of 36 mg N/(gVSS h) (880 mg N/(gVSS d)) were obtained. The loading to the system at this time allowed complete nitrification of the leachate with a hydraulic retention time of only 5 hours. Following these successful treatability studies, a full-scale plant was designed and built at one of the landfills investigated.

Ammonia↗
PubMed2003

Occurrence and removal of endocrine disrupters in landfill leachate treatment plants.

Endocrine disrupting compounds can affect the hormone system in organisms. Industrial chemicals with estrogenic effects were detected in large quantities in landfill leachates. Membrane technology has proven to be an effective barrier to these substances and thus widely applied in the treatment of landfill leachate. The removal techniques under investigation are membrane bioreactors, nanofiltration, activated carbon adsorption, ozonation as well as reverse osmosis. Investigations were conducted at two different landfill leachate treatment plants with a variety of process configurations. The xenoestrogenic substances nonylphenol and bisphenol A were detected in high microg/L-ranges in raw landfill leachate. Membrane bioreactors (MBRs) were capable of removing more than 80% of the nonylphenol load. Final effluent concentrations range between 1-12 microg/L nonylphenol and 3-30 microg/L bisphenol A respectively. Reverse osmosis treatment proved to be less effective in nonylphenol and bisphenol A removal than MBR with further polishing stages like nanofiltration and activated carbon adsorption.

Bioreactors↗
PubMed2003

Sequential anaerobic/aerobic biotreatment of bark leachate.

Bark leachate is generated from sawmill operations such as log storage sites and contains polymeric tannins, carbohydrates, organic acids, phenolic and resin compounds. The present study was aimed at assessing the performance of a sequential anaerobic and aerobic treatment, for both chemical oxygen demand (COD) and phenol removal, under various combinations of operational conditions, in the continuous mode. After anaerobic treatment in a five litres upflow anaerobic sludge bed (UASB) reactor, the leachate was directed into two parallel aerobic reactors, either an activated sludge unit or a fixed film submerged filter (packed with polyethylene Flexirings), both of a volume of one litre and oxygenated by air diffusion. For a leachate of 22 gCOD/l, an overall COD removal of 96-98% was achieved at an hydraulic residence time (HRT) of 4 days for the anaerobic reactor and one day for either aerobic systems. The phenol concentration generally increased after anaerobic treatment but was below the detection limit (50 ppb) after aerobic polishing. Radiorespirometric microcosms with 14C-labelled phenol confirmed that phenol was mineralized in the aerobic reactors. The performances of both aerobic systems were similar for COD and phenol removal. Thus, a sequential anaerobic/aerobic treatment was able to effectively address the contamination of a bark leachate discharge, including phenols.

Bacteria, Aerobic↗
PubMed2003

Evaluation of the start-up of an integrated municipal solid waste and leachate treatment system.

A pilot-scale experiment was set up in the laboratory with the purpose of investigating the most relevant aspects of the anaerobic digestion of municipal solid wastes (MSW), which are necessary for the preparation of future feasibility studies and cost-benefit analyses. The experiment consisted of a comparative analysis among three different lines of operation, each one consisting of three anaerobic MSW reactors (with unit volume of 700 L): conventional landfill (line 1), raw leachate recycling (line 2), and integrated treatment, with seeded leachate recycling (line 3). So, a UASB reactor was installed in the integrated treatment line with the purpose of removing the organic load of the leachate of the MSW reactors and utilising the biological sludge produced for inoculation of the waste digestion. The endogenous inoculation promoted in line 3, by means of recirculation of the leachate and return of the exceeding biological sludge produced in the UASB reactor, has favoured the initial fermentation stage and also the acceleration of the methanogenic phase.

Bacteria, Anaerobic↗
PubMed2005

Anaerobic treatment of Hong Kong leachate followed by chemical oxidation.

Landfill leachate of Hong Kong was first treated by the upflow anaerobic sludge blanket (UASB) process. At 37 degrees C, pH 7.1-8.5 and a HRT of 5.1-6.6 days, the process removed 66-90% of COD in the leachate for loading rates of 1-2.4 g-COD/l day depending on the strength of landfill leachate. The final effluent contained 1440-1910 mg-COD/l and 70-91 mg-BOD/l. About 92.5% of the total COD removed was converted to methane and the rest was converted to biomass with an average net growth yield of 0.053 g-VSS/g-COD-removed. The granules developed in the UASB reactor were 0.5-1.5 mm in size and exhibited good settleability. The UASB effluent was then further polished by two oxidation processes. The UASB-ozonation process removed 93.0% of the 12900 mg/l of COD from the raw leachate. The UASB-Fenton-ozonation process improved the COD removal efficiency to 99.3%. The final effluent had only 85 mg/l of COD and 10 mg/l of BOD5. Ozonation was most effectively conducted at pH 7-8 with the addition of 300 mg/l of H2O2 and for the duration of 30 min. Ozonation also significantly improved the biodegradability of the organic residues. Nearly 50% of these residues could be used as carbon source in denitrification.

Anaerobiosis↗
PubMed2006

[Effects of leachate recirculation volume on its characteristic and landfill stabilization rate].

Impacts of recirculation volume on leachate characteristic and landfill stabilization rate were studied. Four simulated bioreactor landfill columns were operated weekly with different recirculation ratios, respectively 5.3%, 2.7%, 0.67% leachate and 0.33% water, in this comparative research. The results indicate that simulated reactor with 5.3% recirculation ratio has the most rapidly stabilization rate and release the most organic pollutant. The shortest methane generation delay was also observed in this column. While simulated reactor with 2.7% recirculation ratio formed the best microbe environment and kept the highest reactor temperature 35 degrees C. It also had the best impactive load capacity and treating efficiency to leachate, and removal of COD was 77% and BOD5 was 88% respectively. In actual projects, appropriate leachate recirculation volume should be chosen according to design purpose of landfill sites.

Bioreactors↗
PubMed2006

[Study on the application of absorption spectrum to the treatment of landfill leachate by membrane technology].

Molecular weight (MW) distributions of organics in the Bei Shenshu landfill leachate and their permeation from membranes were determined and studied by absorption spectrum, and the removal rates of organics with various molecular weight were measured. A new FTIR preparation method of wastewater sample used in the determination of landfill leachate was proposed in the present paper. The results showed that the aromatics in landfill leachate were mainly related to the organics with MW < 2 500, whereas the distribution of total organics was dispersal comparatively. The removal rates of various humic compounds and oils in landfill leachate were estimated in accordance with the change in FTIR absorbance of permeation from membranes at three characteristic wave numbers 2 930, 2 960 and 3 030 cm(-1), indicating that the defined membrane treatment process can removed organics with relevant MW fractions effectively.

English Abstract↗
PubMed2026

Potential survival strategies of novel comammox and nitrite-oxidizing Nitrospira synthesizing osmoprotectants in a wastewater microbiome treating high-ammonia brackish landfill leachate.

BACKGROUND: In the late stages of landfill operation, leachate becomes brackish and contains high concentrations of ammonia with limited organic carbon. At leachate treatment facilities, it is typically subjected to nitrification followed by denitrification, with methanol supplied as an external electron donor. This unique environment may harbor novel microorganisms, including nitrifiers. Although a variety of microorganisms are involved in nitrification, their substrate specificity and salinity tolerance remain insufficiently understood. In this study, a genome-centric metagenome analysis was conducted on the microbiome from a leachate treatment facility at a closed landfill. RESULTS: A total of 68 metagenome-assembled genomes (MAGs) were reconstructed, including 64 putative novel species. Among these, two Nitrospira MAGs were recovered: a novel complete ammonia-oxidizing bacterium (comammox), Nitrospira LAS72 (88.72% completeness, 2.10% contamination), and canonical nitrite-oxidizing Nitrospira LAS18 (99.98% completeness, 2.29% contamination). Comparative genomic analysis with 260 publicly available Nitrospira genomes revealed that LAS18 represents a new sub-lineage within lineage VII of the Nitrospira genus. Two ammonia-oxidizing archaea (AOA), Candidatus Nitrosocosmicus LAS21 and Nitrosarchaeum LAS73, were also identified, while canonical ammonia-oxidizing bacteria were not detected. Given the brackish conditions (1.23% salinity) and the methanol-fed operation of the treatment facility, the genomic potential for osmotic stress adaptation and methanol metabolism was investigated. Comammox Nitrospira LAS72 harbors biosynthetic pathways for several compatible solutes (osmoprotectants), including glycine betaine, proline, trehalose, and L-glutamate. Moreover, comammox Nitrospira LAS72 possesses genetic potential for oxidizing formaldehyde, suggesting that it may exploit these methanol-derived intermediates as energy sources. These features indicate that LAS72 may withstand osmotic fluctuations through the production of various osmoprotectants and thrive under the unique conditions of a methanol-fed environment. CONCLUSIONS: The discovery of novel comammox Nitrospira and canonical Nitrospira forming a new sub-lineage within lineage VII of the Nitrospira genus in an ammonia-rich brackish environment provides the first genomic evidence for evolutionary adaptation among nitrifiers to saline, methanol-fed environments. These findings enhance our understanding of the ecological and evolutionary dynamics shaping nitrifier communities in complex treatment ecosystems. Video Abstract.

Ammonia↗
PubMed2003

Distributed model of solid waste anaerobic digestion: effects of leachate recirculation and pH adjustment.

A distributed model of solid waste digestion in a 1-D bioreactor with leachate recirculation and pH adjustment was developed to analyze the balance between the rates of polymer hydrolysis/acidogenesis and methanogenesis during the anaerobic digestion of municipal solid waste (MSW). The model was calibrated on previously published experimental data generated in 2-L reactors filled with shredded refuse and operated with leachate recirculation and neutralization. Based on model simulations, both waste degradation and methane production were stimulated when inhibition was prevented rapidly from the start, throughout the reactor volume, by leachate recirculation and neutralization. An optimal strategy to reduce the time needed for solid waste digestion is discussed.

Anaerobiosis↗
PubMed2001

Chlorothalonil and chlorpyrifos degradation products in golf course leachate.

Chlorothalonil and chlorpyrifos are commonly used to control disease and insect pests on golf course greens. While they are relatively immobile in the soil profile, their respective soil degradation products, 4-hydroxy-2,5,6-trichloroisophthalonitrile and 3,5,6-trichloropyridin-2-ol are more polar and may be present in golf course green leachate. To investigate this possibility, six stainless steel lysimeters were constructed into two practice greens at a country club in a northern Atlanta, Georgia suburb. Over a period of 1 year after rainfall events, lysimeter leachate samples were collected into glass bottles, filtered and directly analyzed by HPLC with UV detection. Chlorpyrifos was not detected in any sample and chlorothalonil was detected only in one sample, at a concentration of 0.12 mg liter-1. With a limit of quantitation of 0.05 mg liter-1, hydroxychlorothalonil and trichloropyridinol were detected in 87% and 63% of the samples at maximum and median concentrations of 2.21 and 0.55 mg liter-1 for hydroxychlorothalonil and 1.77 and 0.15 mg liter-1 for trichloropyridinol. Golf course green leachate often mixes with surface water, thus more data may be warranted to determine the persistence and ecological significance of chronic exposure to these compounds of organisms in the aquatic environment.

Biodegradation, Environmental↗