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PubMed2001

[Landfill leachate treatment by anaerobic process and electrochemical oxidation].

This study was conducted to develop a two-stage process of UASB and electrochemical oxidation for the treatment of Hong Kong leachate. The leachate, containing 4750 mg/L of chemical oxygen demand (COD) and 1310 mg/L of ammoniacal nitrogen (NH3-N), was first treated in a UASB (upflow anaerobic sludge blanket) reactor at 37 degrees C. The process removed on average 66% of COD with 6.1 days of hydraulic retention time (HRT), corresponding to an organic loading rate COD of 0.78 g/(L.d). The UASB effluent, which had an average pH of 8.9, COD of 1610 mg/L and NH3-N of 1480 mg/L, was then further treated by electrochemical oxidation in a batch reactor with recirculation. With the addition of 2000 mg/L of chloride (in the form of sodium chloride) and at a current density of 32.3 mA/cm2, 87% of COD and 100% of NH3-N were removed from the UASB effluent in six hours. The energy consumption was < 55 kW.h/kg COD. The final effluent contained no residual NH3-N and only 209 mg/L of COD. In this paper, some basic problems in electrochemical oxidation, such as the effects of the operation parameters, the mechanism of the process, and assessment of the energy requirements were discussed in detail.

Anaerobiosis↗
PubMed2002

Photo-assisted fenton oxidation of refractory organics in UASB-pretreated leachate.

Nearly 91% of organic pollutants in Hong Kong leachate could be effectively removed by the UASB (upflow anaerobic sludge blanket) process followed by the fenton coagulation. The COD (chemical oxygen demand) of leachate was lowered from an average of 5620 mg/L to 1910 mg/L after the UASB treatment at 37 degrees C, and was further lowered to 513 mg/L after fenton coagulation. The remaining refractory residues could be further removed by photochemical oxidation with the addition of H2O2. The BOD/COD ratio was greatly increased from 0.062 to 0.142, indicating the biodegradability of organic residues was improved. The photochemical oxidation for the fenton-coagulation supernatant was most effective at pH 3-4, with the addition of 800 mg/L of H2O2, and UV radiation time of 30 minutes. The final effluent contained only 148 mg/L of COD, 21 mg/L of BOD (biochemical oxygen demand) and 56 mg/L of TOC (total organic carbon).

Bacteria, Anaerobic↗
PubMed2003

Combined anaerobic-aerobic treatment of landfill leachates under mesophilic, submesophilic and psychrophilic conditions.

As a first step of treatment of landfill leachates (total COD--1,430-3,810 mg/l, total nitrogen 90-162 mg/l), a performance of laboratory UASB reactors has been investigated under mesophilic (30 degrees C), sub-mesophilic (20 degrees C) and psychrophilic (10 degrees C) conditions. Under hydraulic retention times (HRT) of around 7 h, when the average organic loading rates (OLR) were around 5 g COD/l/day, the total COD removal accounted for 81% (on the average) with the effluent concentrations close to anaerobic biodegradability limit (0.25 g COD/l) for mesophilic and sub-mesophilic regimes. The psychrophilic treatment conducted under the average HRT of 8 h and the average OLR of 4.22 g COD/l/day showed a total COD removal of 47% producing the effluents (0.75 g COD/l) more suitable for subsequent biological nitrogen removal. All three anaerobic regimes used for leachate treatment were quite efficient for elimination of heavy metals (Fe, Zn, Cu, Pb, Cd) by concomitant precipitation in the form of insoluble sulphides inside the sludge bed. The application of aerobic/anoxic biofilter as a sole polishing step for psychrophilic anaerobic effluents was acceptable for elimination of biodegradable COD and nitrogen approaching the current standards for direct discharge of treated wastewater.

Bacteria, Aerobic↗
PubMed2003

Hazardous waste landfill leachate treatment using an activated sludge-membrane system.

This research was aimed to investigate the capability of a combined system of activated sludge and microfiltration processes with backflushing technique to reduce organic carbon and nitrogen compounds in hazardous landfill leachates. The experiments included acclimation, batch and continuous processes. The continuous process was conducted with a 24 hour HRT (Hydraulic Retention Time), and the SRT (Solid Retention Time) ranged from 16 to 36 days. The aeration basin volume was 5 L and the membrane filter used was a hollow fiber module made from polypropylene with pore size of 0.2 microm. The batch process (without membrane separation) achieved its steady state condition over a period of 33 days. The removal of COD, BOD5 and ammonia-N were 52.5%, 94.3% and 75.5%, respectively. The kinetic parameters obtained are as followed: the maximum specific growth rate constant (microm): 0.96/day and the saturation substrate constant (Ks): 16,445.32 mg/L. The high value of Ks indicated that the leachate was not easily biodegraded. The continuous process revealed that the system with SRT of 32 days was more stable than that of 16 and 24 days. The reduction of COD, BOD5 and ammonia-N were 31.3%; 66% and 98%, respectively. The stable flux was achieved around 5 L/m2 x hour.

Bioreactors↗
PubMed2003

[PRB technology in situ remediation of groundwater polluted by landfill leachate].

In this paper three reaction media zero valent iron (ZVI), a mixture of ZVI and activated carbon, a mixture of the ZVI and zeolites were used to design three kinds of permeable reactive barrier (PRB), viz. reactors A, B and C and to study the feasibility and the efficiency of the PRB technology in the remediation of leachate-polluted groundwater. The designs of the reactors took into account the relation of the permeability of the reactor with the permeability of the aquifer. The results indicated that the COD removal ratios of the reactor A, B and C were more than 80%, 90% and 70% respectively and the value of the BOD5/COD increased from 0.32 up to 0.781, 0.728, 0.716 respectively. Total nitrogen decreased from 50 mg/L to less than 10 mg/L and the removal ratio of the ammonium ranged from 78%-91%. Zeolites of the reactor C manifested effectiveness in the removal of heavy metals and hardness. The removal ratios of Mn ion, Zn ion and hardness were up to 90%, 80%, 81% respectively. These results indicate that PRB technology is an efficient method for the treatment of leachate-contaminated groundwater.

Bioreactors↗
PubMed2004

Heavy metal pollution from Russian landfill leachates and its elimination together with other contaminants.

Systematic monitoring of raw leachates (RL) from the operating landfill "Khmet'yevo" during December, 2001--June, 2002 with regard to heavy metals (HM) revealed that these RL were moderately contaminated with Fe, Zn, Pb and Cd (Cu is present in non-dangerous concentrations). This contamination depends on season--the winter leachates are less polluted compared to the summer ones. For removal of HM together with removal of bulk COD, the UASB reactors were applied where, besides elimination of the major part of organic matter, concomitant precipitation of HM in the form of insoluble sulphides inside the sludge bed occurred due to development of the process of biological sulphate reduction. Both removal processes were quite efficient even during operation under submesophilic and psychrophilic conditions (20-10 degrees C). The subsequent submesophilic aerobic-anoxic treatment of submesophilic anaerobic effluents led to only 75% of total inorganic N removal due to COD deficiency for denitrification created by a too efficient anaerobic step. On the contrary, psychrophilic anaerobic effluents (richer in COD compared to the submesophilic ones) were more suitable for subsequent aerobic-anoxic treatment giving the total N removal of 95 and 92% at 20 and 10 degrees C, respectively. The final effluent is approaching the current national standards for direct discharge of treated wastewater.

Bacteria, Aerobic↗
PubMed2004

Assessment of androgenicity in leachates from Swedish landfills and treatments for its elimination.

An in vitro recombinant yeast strain, transfected with the human androgen receptor was used to assess androgenic hormone disrupting potencies in leachates from Swedish landfills. It was shown that components in extracts of these affected the androgenic receptor and promoted a response in the beta-galactosidase marker system. Levels were within the range of those determined for domestic sewage effluents but lower than the highest levels found in an industrial effluent. These leachates finally enter receiving waters with or without wastewater treatment. Evidence was found for transformation during some of the wastewater treatments.

Humans↗
PubMed2004

Removal of high concentrated ammonia nitrogen from landfill leachate by landfilled waste layer.

The landfill of municipal solid waste (MSW) could be regarded as denitrification reactor and involved in ammonia nitrogen biological removal process. In this research, the process was applied to municipal solid waste collected in Shanghai, China, which was characterized by high food waste content. The NH4(+) removal efficiency in the system of SBR nitrifying reactor followed by fresh and matured landfilled waste layer in series was studied. In the nitrifying reactor, above 90% of NH4(+) in leachate was oxidized to NO2(-) and NO3(-). Then high concentrated NO2 and N3(-) were removed in the way of denitrification process in fresh landfilled waste layer. At the same time, degradation of fresh landfilled waste was accelerated. Up to the day 120, 136.5 gC/(kg dry waste) and 17.9 gN/(kg dry waste) were converted from waste layer. It accounted for 50.15% and 86.89% of the total carbon and nitrogen content of preliminary fresh waste, which was 4.42 times and 5.17 times higher than that of reference column respectively. After filtering through matured landfilled waste, BOD5 concentration in leachate dropped to below 100 mg/L, which would not affect following nitrification adversely. Because the matured landfilled waste acted as a well methanogenic reactor, 23% of carbon produced accumulatively from fresh landfilled waste degradation was converted into CH4.

Ammonia↗
PubMed2005

Variations of dominant microbial populations in groundwater in response to the leachate from Laogang Landfill.

Temporal changes of dominant microbial populations in groundwater in response to the leachate from Shanghai Laogang Landfill were investigated. Concentrations of dissolved redox-relevant species in groundwater suggested that the dominating redox process had changed from denitrification to methane-production/sulfate-reduction due to landfilling. Dominant microbial populations were determined using restriction fragment length polymorphism( RFLP) analyses of 16S rRNA gene libraries, which were further studied by sequencing and phylogenetic analyses. The results indicated that obvious shifts of dominant microbial populations had occurred in groundwater in response to the pollution of leachate. The closest relatives of some dominant clones are accordant with the dominating redox processes determined by hydrochemical analyses, based on the GenBank's indications on the ability to perform redox reactions.

Bacteria↗
PubMed2005

Leachate pre-treatment strategies before recirculation in landfill bioreactors.

Nitrified leachate recirculation represents a promising strategy for a more sustainable landfill management. Our objective was to determine the reactions involved in nitrate reduction in municipal solid waste batch biodegradation tests. Anaerobic digestion of waste in the three control reactors showed a good reproducibility. In two test reactors, nitrate was added at various moments of the waste degradation process. We observed that: (1) H2S concentration controlled the nitrate reduction pathway: above a certain threshold of H2S, dissimilatory nitrate reduction to ammonium (DNRA) replaced denitrification. (2) N2O/N2 ratio varied with the organic carbon concentration: the lower the easily biodegradable carbon concentration, the higher the N2O/N2 ratio. (3) N2 was consumed after denitrification. The possibility of a nitrogen fixation reaction in the presence of NH4 is discussed. Nitrified leachate recirculation during acidogenesis should be avoided because of higher H2S production which could induce DNRA.

Bacteria, Anaerobic↗
PubMed2006

[Kinetics of Electro-Fenton treatment of leachate from municipal solid waste incinerator].

SPR electrode was used in Electrio-Fenton treatment on the effluent from biological and coagulative treatments of solid waste incinerator leachate, at the same time, the kinetics model for the COD effluent concentration were set up. The result indicated that the disposal curve of COD confirm to the pseudo third order kinetics, and the formula is c(t) = (2kt + c(0)(-2))(-0.5), in which the c(t) is the COD concentration of treatment effluent. With the statistical analysis to the disposal curve of COD from Electro-Fenton treatment in different conditions, the experience mathematics model of k value was set up, in which the current density, pH value and COD concentration of influent are effective factors. Moreover, with the comparison between the simulative COD of effluent and the experimental results, it was showed that this kinetic model could be used to investigate the COD disposal efficiency of Electro-Fenton treatment on the effluent from biological and coagulative treatments of solid waste incinerator leachate preferably.

Catalysis↗
PubMed2007

A new approach for the recovery of precious metals from solution and from leachates derived from electronic scrap.

A new approach is described for the recovery of precious metals (PMs: Au, Pd and Ag) with >99% efficiency from aqueous solution utilising biogas produced during the aerobic growth of Klebsiella pneumoniae. Gold was recovered from electronic scrap leachate ( approximately 95%) by this method, with some selectivity against Cu. The recovered PM solids all contained metal and sulphur as determined by energy dispersive X-ray microanalysis (EDX). X-ray powder diffraction analysis (XRD) showed no crystalline metal sulphur compounds but a crystalline palladium amine was recorded. Silver was recovered as a sulphide (found by EDX), carbonate and oxide (found by XRD). EDX analysis of the Au-precipitate showed mainly gold and sulphur, with some metallic Au(0) detected by XRD. The gold compound was shock-sensitive; upon grinding it detonated to leave a sooty black deposit.

Aerobiosis↗
PubMed2002

Characterisation of sequential leachate discharges of mining waste rock dumps in the Tinto and Odiel rivers.

Mining waste rock dumps (WRDs) are potential sources of pollution, which after rainfall produce leachate discharges, loaded with acid mining drainage (AMD). The discharges generally occur in two phases: initial rapid leaching over a period of 1-7 days, followed by a period of variable duration during which leaching decelerates. The relative preponderance of each phase depends on the characteristics of the WRD, including its antecedent hydrological condition, and the temporal pattern and amount of rainfall.

Environmental Monitoring↗
PubMed1999

Speciation of inorganic arsenic and selenium in leachates from landfills in relation to water quality assessment.

Speciation of arsenic and selenium was carried out on water samples taken from rivers used as water intake points in the vicinity of landfill areas used for land-based waste disposal system. Leachates from these landfill areas may contaminate the river water through underground seepage or overflowing, especially after a heavy downpour. Preconcentration of the chemical species was done using a mixture of ammonium pyrrolidinethiocarbamate-chloroform (APDTC-CHCl3). Because only the reduced forms of both arsenic and selenium species could be extracted by the preconcentrating mixture, suitable reducing agents such as 25% sodium thiosulfate for As(III) and 6M HCl for Se(IV) were used throughout the studies. Care was taken to exclude the interfering elements such as the alkali and alkali earth metals from the inorganic arsenic and selenium species by introducing 12% EDTA solution as the masking agent. The extracted mixture was irradiated in a thermal neutron flux of 4 x 10(12)/cm/s from a TRIGA Mk.II reactor at the Malaysia Institute of Nuclear Technology Research (MINT). Gamma rays of 559 keV and 297 keV from 76As and 75Se, respectively, were used in the quantitative determination of the inorganic species. Mixed standards of As(III) and Se(IV) used in the percentage efficiency procedure were prepared from salts of Analar grade. The water quality evaluation was viewed from the ratio of the inorganic species present.

Arsenic↗
PubMed2002

Remediation of an old landsfill site: soil analysis, leachate quality and gas production.

The Baltic Sea Region has a large number of landfills that need remediation after care routines and control, in order to avoid future emissions to the environment and to fulfil the demands in the EU Waste Council Directive on the landfill of waste. Based on the Måsalycke test screening, an excavation of whole or of parts of the landfill can be seen as a potential measure for some of the old landfills. The material excavated in the test was screened into the fractions: < 18 mm, 18-50 mm and > 50 mm. The coarsest fraction (> 50 mm) contained 50% wood and paper. The medium-sized fraction (18-50 mm) contained stones and indefinable soil-like material, while the fine fraction contained peat-like material with some other small waste components. The spectral analysis of heavy metals indicated only high concentrations of zinc and there was no significant difference between the fine and the medium-sized fractions. The medium sized and the unsorted fraction was moisturized and refilled into the pit. The methane content in the landfill gas from the pit was 50-57% in the sorted material with a flow of 8-17 l/min and 38-57% in the unsorted fraction with a flow of 2-13 l/min during the first 1.5 year. The Måsalycke landfill is in the methanogenic phase and leachate concentrations are normal. Landfill mining can be used to prolong the landfill lifetime and/or used as a tool for remedial actions in contaminated sites.

Conservation of Natural Resources↗
PubMed2001

Enrichment and characterization of an anammox bacterium from a rotating biological contactor treating ammonium-rich leachate.

Anaerobic ammonium oxidation with nitrite to N2 (anammox) is a recently discovered microbial reaction with interesting potential for nitrogen removal from wastewater. We enriched an anammox culture from a rotating disk contactor (near Kölliken, Switzerland) that was used to treat ammonium-rich leachate with low organic carbon content. This enrichment led to a relative population size of 88% anammox bacteria. The microorganism carrying out the anammox reaction was identified by analysis of the 16S rDNA sequence and by fluorescence in situ hybridization (FISH) with 16S-rRNA-targeting probes. The percentage sequence identity between the 16S rDNA sequences of the Kölliken anammox organism and the archetype anammox strain Candidatus Brocadia anammoxidans was 90.9%, but between 98.5 and 98.9% with Candidatus Kuenenia stuttgartiensis, an organism identified in biofilms by molecular methods. The Kölliken culture catalyzed the anaerobic oxidation of ammonium with nitrite in a manner seemingly identical to that of Candidatus B. anammoxidans, but exhibited higher tolerance to phosphate (up to 20 mM) and to nitrite (up to 13 mM) and was active at lower cell densities. Anammox activity was observed only between pH 6.5 and 9, with an optimum at pH 8 and a temperature optimum at 37 degrees C. Hydroxylamine and hydrazine, which are intermediates of the anammox reaction of Candidatus B. anammoxidans, were utilized by the Kölliken organisms, and approximately 15% of the nitrite utilized during autotrophic growth was converted to nitrate. Electron microscopy showed a protein-rich region in the center of the cells surrounded by a doughnut-shaped region containing ribosomes and DNA. This doughnut-shape region was observed with FISH as having a higher fluorescence intensity. Similar to Candidatus B. anammoxidans, the Kölliken anammox organism typically formed homogenous clusters containing up to several hundred cells within an extracellular matrix.

Bacteria↗
PubMed2006

Short-term bioassay responses to sludge products and leachate.

Recycling of sewage sludge is needed in a sustainable society. Quality aspects of sludge include hygiene (pathogens), nutrients (N and P), and toxicants (metals and organics). Metals are of particular concern because they are not degradable, but their hazards are related to their bioavailability and chemical speciation. In this article, the effect on sludge quality of two treatment methods, incineration and pelletization, has been determined for digested sludge from two treatment plants. The combined effect of nutrients and toxicants in sludge and sludge product was determined for spring wheat, Triticum aestivum, and the toxicity of the leachate water was determined for water fleas, Daphnia magna, and seeds of lettuce, Lactuca sativa. Toxicity Identification Evaluation was used to determine whether metals were possible toxicants. The results indicated that incineration decreased toxicity, whereas leachability of metals and the fertilizing effect was unaffected. Pelletization seemed to increase toxicity and leachability of metals and also decreased the fertilizing effect of the sludge. Thus, the results suggest that pelletization of digested sewage sludge increased the toxicity of the sludge and thus decreased the quality of the sludge, whereas incineration apparently reduced toxicity for the two sludges tested.

Animals↗
PubMed2006

Changes in organic matter biodegradability influencing sulfate reduction in an aquifer contaminated by landfill leachate.

In situ experiments were conducted to measure sulfate reduction rates and identify rate-limiting factors in a shallow, alluvial aquifer contaminated with municipal landfill leachate. Single-well, push-pull tests conducted in a well adjacent to the landfill with > 8 mM dissolved organic carbon (DOC) exhibited a sulfate reduction rate of 3.2 mumol SO4(-2) (L sediment)(-1) day(-1), a value in close agreement with laboratory-derived estimates. Identical tests conducted in wells located 90 m downgradient where DOC levels remained high (> 3 mM) showed no detectable sulfate consumption, and laboratory assays confirmed this observation. However, the rates of sulfate reduction in sediment samples obtained from this site were three times larger when they were amended with filter-sterilized groundwater from the upgradient location. The effect of various amendments on sulfate reduction rates was further examined in laboratory incubations using sediment collected from the downgradient site amended with 35S sulfate. Unamended sediments showed only weak conversion of the tracer to 35S sulfide (5 to 7 cpm/cm2), whereas the addition of Desulfovibrio cells increased 35S sulfide production to 44 cpm/cm2. However, the application of heat-killed Desulfovibrio had a similar stimulatory effect, as did a lactate amendment. Collectively, these findings indicate that the lack of measurable sulfate reduction at the downgradient site was not due to the absence of the necessary metabolic potential, the presence of lower sulfate concentration, or the quantity of electron donor, but by its biodegradability. The findings also indicate that field bioaugmentation attempts should be interpreted with caution.

Biodegradation, Environmental↗