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PubMed2006

Acute toxicity of leachates of tire wear material to Daphnia magna--variability and toxic components.

Large amounts of tire rubber are deposited along the roads due to tread wear. Several compounds may leach from the rubber and cause toxicity to aquatic organisms. To investigate the toxic effects of tire wear material from different tires, rubber was abraded from the treads of twenty-five tires. Leachates were prepared by allowing the rubber to equilibrate with dilution water at 44 degrees C for 72 h. Then the rubber was filtered from the leachates, and test organisms (Daphnia magna) were added. Forty-eight hour EC50s ranged from 0.5 to >10.0 g l(-1). The toxicity identification evaluation (TIE) indicated that non-polar organic compounds caused most of the toxicity. UV exposure of the filtered tire leachates caused no significant increase in toxicity. However, when tested as unfiltered leachates (the rubber was not filtered from the leachates before addition of D. magna) photo-enhanced toxicity was considerable for some tires, which means that test procedures are important when testing tire leachates for aquatic (photo) toxicity. The acute toxicity of tire wear for Daphnia magna was found to be <40 times a predicted environmental concentration based on reports on the concentration of a tire component found in environmental samples, which emphasizes the need for a more extensive risk assessment of tire wear for the environment.

Animals↗
PubMed2006

Fractionation of dissolved organic matter in mature landfill leachate and its recycling by ultrafiltration and evaporation combined processes.

XAD resin procedure was used to isolate dissolved organic matter (DOM) of a mature leachate collected from a municipal solid waste landfill in Beijing, China. The fulvic acids fraction dominated in collected leachate, accounting for 64% of DOM as dissolved organic carbon (DOC), and a high concentration of humic substances (HS) with a value of 441 mg l(-1) was found in the leachate. Molecular size distribution of DOM was also done by using batch ultrafiltration (UF) technique. Two major parts of the molecules of DOM were distributed in the regions of smaller than 1 kDa and 1-3.5 kDa, containing 45% and 43% of DOM as DOC, respectively. The laboratory-scale experiments were conducted to investigate and to develop an overall concept for mature leachate recycling based on UF and evaporation combined processes. Separation factor (SF) was applied to evaluate separation efficiency of UF. The data indicate that SF is strongly correlated with concentration factor. Second retentate from two-stage UF contained relatively high amount of DOM comprising 91% of HS and an insignificant concentration of heavy metals. The SF value for two-stage UF was more than 10. These results demonstrate that two-stage UF could effectively separate and refine HS in mature leachate from inorganic components. For achieving the main requirements as a fertilizer product, second retentate was further concentrated by evaporation, and contents of organic matter and dry-solids were obtained 13 wt.% and 25 wt.%, respectively. This study confirmed the feasibility of recycling HS from mature leachate.

Membranes, Artificial↗
PubMed2005

Oxidative damage induced in brains and livers of mice by landfill leachate.

The effects of the Xingou municipal landfill leachate on levels of thiobarbituric acid reactive substances (TBARS) and the activities of Cu,Zn-superoxide dismutase (Cu,Zn-SOD), Se-dependent glutathione peroxidase (Se-dependent GPx), and catalase (CAT) were investigated in brains and livers of Kunming albino mice of both sexes, using chemical oxygen demand (COD(Cr)) as a measure of leachate concentration. The results show that leachate caused lipid peroxidation and change of antioxidative status in brains and livers of mice. There was a sex difference in the response of antioxidative status, and female mice were more sensitive than male mice. Exposure to leachate at all concentrations tested caused significant increases of TBARS levels in brains and livers from mice of both sexes. For brains, Cu,Zn-SOD and Se-dependent GPx activities were significantly increased at high concentration (COD(Cr) 240 mg/L) for male mice, but the activities of both antioxidative enzymes were significantly increased at low concentration (COD(Cr) 60 mg/L) and decreased at high concentration (COD(Cr) 240 mg/L) for female mice; CAT activities remained unchanged for male mice and were significantly decreased for female mice at high concentration (COD(Cr) 240 mg/L). For livers, Cu,Zn-SOD and Se-dependent GPx activities were significantly increased at high concentrations (COD(Cr) 120 and 240 mg/L) for male mice, but the activities of both antioxidative enzymes were significantly increased at low concentration (COD(Cr) 30 or 60 mg/L) and decreased at high concentration (COD(Cr) 240 mg/L) for female mice; CAT activities were significantly increased for male mice at all concentrations tested and decreased for female mice at high concentrations (COD(Cr) 120 and 240 mg/L). These results suggest that leachate exposure can cause oxidative damage on brains and livers of mice. The results also suggest that leachate might induce toxicity in mammals by the free-radical-damage mechanism.

Animals↗
PubMed2005

Identification of metal toxicity in sewage sludge leachate.

Sewage sludge is a source of organic matter and nutrients with the potential for being used as a fertilizer. However, metals in sewage sludge might accumulate in soil after repeated sludge applications, and metal concentrations might reach concentrations that are toxic to microorganisms, soil organisms and/or plants. This toxicity might change with time due to kinetic factors or abiotic factors such as freezing, drying or rainfall. The objective of this study was to determine toxicity of sewage sludge leachate from a lysimeter with 50 cm of sludge applied. Attempts were also made to identify the cause of toxicity of the sludge leachate by toxicity identification and evaluation (TIE) techniques. Sludge leachate was collected monthly during 1 experimental year (August 2001 to August 2002). Metal concentrations were analysed, and the toxicity was determined with Daphnia magna (48-h immobility). The effect of EDTA or sodium thiosulphate addition, filtration through a CM-resin or a Millex-resin on toxicity was also tested. The results showed that toxicity of the sludge leachate apparently varied during the year, and that filtration through the CM-resin reduced most of the toxicity followed by the addition of EDTA. None of the other treatments reduced the toxicity of the sludge leachate. This indicated that one or more metals were responsible for the observed toxicity. Further calculations of toxic units (TU) suggested that Zn contributed most to the toxicity. Results also indicated that Ca concentrations in the sludge leachate reduced the toxicity of Zn.

Animals↗
PubMed2004

Evolution of clog formation with time in columns permeated with synthetic landfill leachate.

Laboratory column tests conducted to gain insight regarding the biological and chemical clogging mechanisms in a porous medium are presented. To seed the porous medium with landfill bacteria, a mixture of Keele Valley Landfill and synthetic leachate permeated through the column under anaerobic conditions for the first 9 days of operation. After this, 100% synthetic leachate was used. The synthetic leachate approximated Keele Valley Landfill leachate in chemical composition but contained negligible suspended solids and bacteria compared with real leachate. The removal of volatile fatty acids (VFAs), primarily acetate, in leachate as it passed through the medium was highly correlated with the precipitation of calcium carbonate (CaCO(3(s))) from solution. The columns experienced a decrease in drainable porosity from an initial value of about 0.38 to less than 0.1 after steady state chemical oxygen demand (COD) removal, resulting in a five-order magnitude decrease in hydraulic conductivity. The decrease in drainable porosity prior to steady state COD removal was primarily due to the growth of a biofilm on the medium surface. After steady state COD removal, calcium precipitation was at least equally responsible for the decrease in drainable porosity as biofilm growth. Clog composition analyses showed that CaCO(3(s)) was the dominant clog constituent and that 99% of the carbonate in the clog material was bound to calcium.

Acetates↗
PubMed2005

Ozonation of a landfill leachate: evaluation of toxicity removal and biodegradability improvement.

This work shows an evaluation of treatments for the leachate produced at the Gramacho Municipal Landfill in Rio de Janeiro state, Brazil. This leachate has very peculiar characteristics, with a high salinity level and very low biodegradability (BOD(5)/COD of 0.05). A sequence of processes was employed in the treatment of this leachate. Initially, a physicochemical treatment was used, while the second stage consisted of application of ozone to improve the biodegradability of the leachate. The final stage comprised a biological treatment. The physical-chemical treatment led to COD and DOC removal levels of 40 and 25%, respectively, with the use of Al(2)(SO(4))(3). The sequence of treatments proposed brought good results, with an increase in the BOD(5)/COD ratio from 0.05 to 0.3 after ozonation. The toxicity tests performed using Brachydanio rerio and Poecilia vivipara showed that the toxicity of the leachate had hardly been reduced by ozonation. These results are in agreement with the fact that, despite the higher BOD(5)/COD ratio, the biological process did not present a good performance. The total average removal levels of COD and DOC achieved using the combined treatment were 73 and 63%, respectively, for an ozone dose of 3.0 gL(-1) by the leachate.

Animals↗
PubMed2005

Physico-chemical treatments for removal of recalcitrant contaminants from landfill leachate.

In this paper, the technical applicability and treatment performance of physico-chemical techniques (individual and/or combined) for landfill leachate are reviewed. A particular focus is given to coagulation-flocculation, chemical precipitation, ammonium stripping, membrane filtration and adsorption. The advantages and limitations of various techniques are evaluated. Their operating conditions such as pH, dose required, characteristics of leachate in terms of chemical oxygen demand (COD) and NH3-N concentration and treatment efficiency are compared. It is evident from the survey of 118 papers (1983-2005) that none of the individual physico-chemical techniques is universally applicable or highly effective for the removal of recalcitrant compounds from stabilized leachate. Among the treatments reviewed in this article, adsorption, membrane filtration and chemical precipitation are the most frequently applied and studied worldwide. Both activated carbon adsorption and nanofiltration are effective for over 95% COD removal with COD concentrations ranging from 5690 to 17,000 mg/L. About 98% removal of NH3-N with an initial concentration ranging from 3260 to 5618 mg/L has been achieved using struvite precipitation. A combination of physico-chemical and biological treatments has demonstrated its effectiveness for the treatment of stabilized leachate. Almost complete removal of COD and NH3-N has been accomplished by a combination of reverse osmosis (RO) and an upflow anaerobic sludge blanket (UASB) with an initial COD concentration of 35,000 mg/L and NH3-N concentration of 1600 mg/L and/or RO and activated sludge with an initial COD concentration of 6440 mg/L and NH3-N concentration of 1153 mg/L. It is important to note that the selection of the most suitable treatment method for landfill leachate depends on the characteristics of landfill leachate, technical applicability and constraints, effluent discharge alternatives, cost-effectiveness, regulatory requirements and environmental impact.

Chemistry, Physical↗
PubMed2006

Soluble substrate concentrations in leachate from field scale MSW test cells.

We have monitored non-biodegradable soluble COD of leachates derived from two different landfill test cells, which were constructed at Odayeri Sanitary Landfill and operated with (C2) and without (C1) leachate recirculation for 1080 days. Refuse height and the placement area of test cells were 5m and 1250m(2) (25mx50m), respectively. For leachates of both cells, initial inert soluble COD fraction (f(non)) increased from it is initial value of 0.01 to around 0.1 after 300 days of operation. Due to the development of anaerobic conditions, the value showed an increasing trend and the maximum value of 0.4 was reached on day 600. Several suitable models were also fitted to the experimental data on the basis of statistical reasoning. So as to evaluate the goodness of obtained fits, the calculated values of the sum of squares due to error (SSE), R-square, the residual degrees of freedom (DFE), adjusted R-square, and root mean square errors (RMSE) associated with the model results were compared. Logistic model for C1 test cell and Gompertz model for C2 test cell gave the best fits to the experimental data. Moreover, using the fitted model parameters, pollution loads, and BOD/COD ratios in leachates from C1 (control) and C2 (recirculation) cells were estimated and deeply discussed. The results of the study can be satisfactorily used to predict change in the composition of leachate over time, which may help to obtain better effluent quality in biological treatment of leachate.

Anaerobiosis↗
PubMed2006

Mathematical simulation and long-term monitoring of leachate components from two different landfill cells.

In this study we monitored for 920 days the sulfate (SO(4)(2-)), chloride (Cl(-)), chemical oxygen demand (COD) and biological oxygen demand (BOD) parameters in leachate produced in two large-scale test cells at the Odayeri Sanitary Landfill, Istanbul, Turkey. We present a mathematical model of these parameter concentrations in leachates of two test cells with one being the control (C1) and the other (C2) leachate recirculation. The relationship between these parameters and refuse age is simulated by a mathematical formula. The unknown constants of the simulation formula are solved by the least squares method, which minimizes the squared total of deviation from the model of the actual data using a MATLAB computer program. A good fit was obtained between the measured data and model simulations. COD concentrations in leachate from C1 and C2 rapidly attained their maximum values of 75 and 70 g/l, respectively, after 1 month of landfilling. BOD to COD ratios are around 0.8 for both test cells during the acidogenic phase; this ratio then decreased to 0.06. A sharp decrease in the concentration of Cl(-) from 14 to 15 g/l was observed after approximately 2 months of operation, followed by a slow decrease. SO(4)(2-) concentrations rapidly reached a maximum value of 2000 mg/l within 45 days; development of anaerobic conditions caused a sharp decrease to around 75 mg/l for C2 and 450 mg/l for C1 after 5 months of operation. The results showed that there appeared to be little improvement in leachate quality by leachate recirculation in terms of COD and BOD values, however, it is determined that the pollution loads more rapidly reached minimum values within the C2 test cell.

Chlorides↗
PubMed2006

Leachate pretreatment for enhancing organic matter conversion in landfill bioreactor.

Direct recycling of leachate from refuse of high food waste content was shown to ineffectively stabilize the refuse. This work aims at evaluating the effects of three pretreatments of leachate on the refuse stabilization efficiency were investigated. Pretreatment of leachate using an anaerobic upflow filtration bioreactor (UFB) or a well-decomposed waste layer could reduce the COD and provide methanogens, both were beneficial to establish early methanogenesis status. Using an aerobic sequential batch reactor (SBR) to pretreat the leachate could reduce its COD to 1000 mg l(-1), but the fully developed methanogenesis phase would be built up in a later stage. The organic matters in the effluent leachate inhibited both the hydrolysis/acidogenesis and the methanogenesis steps in the refuse. With the dilution and acid neutralization effects by the recycled leachate, a favorable methanogenetic environment could be produced from the column's top, which moved downward along, and finally made the breakthrough of the column.

Anaerobiosis↗
PubMed2005

Municipal sludge leachate-induced genotoxicity in mice--a subacute study.

Inappropriate disposal of municipal sludge (MS) results in the leaching of toxic metals and organic chemicals, which can contaminate the surface and ground water leading to the serious health hazards. In this study, the genotoxic potential of the leachate prepared from MS sample was examined in mouse bone marrow cells through chromosomal aberrations (CA), micronucleus test (MT) and comet assay. Analysis of metals and physicochemical parameters of the leachate was also carried out to correlate the genotoxic results. The dried sludge showed high concentrations of heavy metals, viz. Cr, Cu, Pb and Ni. However, in 10% leachate, concentrations of these metals were manifold lower than that of obtained in dried sludge. Male mice orally gavaged to leachates (0.1-0.4 ml/mouse/day) for 15 days revealed significant (P<0.01, P<0.001) inhibition of mitotic index (MI) and induction of chromatid/chromosome fragments and breaks in all the treatment groups. The effect was observed to be dose-dependent. Treatment of mice with leachates also induced significant (P<0.001) frequencies of micronucleated polychromatic erythrocytes (MNPCE). The results of comet assay revealed a statistically significant (P<0.05 and <0.01) DNA damage in bone marrow cells exposed to 0.2-0.4 ml/mouse/day. Findings of the present study indicate that the constant exposure of MS leachate can cause genotoxic effects in mammals and suggest risks in human population.

Animals↗
PubMed2005

Comparative biomonitoring of leachates from hazardous solid waste of two industries using Allium test.

Hazardous industrial wastes are inevitable source of environmental pollution. Leachates from these wastes might contaminate the origins of potable water and affect human health. The study was carried out to determine the possible genotoxic effects of leachates from solid waste of a metal and dye industry using the Allium cepa chromosome aberrations assay. The 10% leachates were prepared from solid wastes obtained from both the industries and examined for the presence of heavy metal content and genotoxicity. To simulate the field and laboratory conditions, A. cepa bulbs were exposed through soil and aqueous medium for 48 h to 2.5-10% leachates. The results revealed that both metal waste leachate (MWL) and dye waste leachate (DWL) contained high concentrations of chromium, nickel and iron that significantly induced cytogenetic alterations. Significant inhibition of mitotic index (MI), inductions of chromosomal/mitotic aberrations (CA/MA) and micronuclei (MN) formation were found in all experimental groups exposed to MWL and DWL. The effects observed were concentration dependent and the frequency of aberrations was higher with treatment of MWL than DWL. The MI was severely inhibited at 10% aqueous exposure it was 4.59+/-0.69 (P<0.001) in MWL and almost half to that induced by DWL that was 8.62+/-0.69 (P<0.05). Significant frequency of CA/MA and MN induced by MWL was 14.21 (P<0.001) and 0.33 (P<0.001) whereas CA/MA and MN induced by DWL was 7.81 (P<0.001) and 0.13 (P<0.05) in the aqueous medium. The investigations inferred that abnormalities caused by MWL were higher than DWL both in soil and aqueous media. These toxic responses may have relied on raised heavy metal concentrations of metal-based than dye industrial wastes.

Chromosome Aberrations↗
PubMed2006

Research on leachate recirculation from different types of landfills.

Landfills can produce a great amount of leachate containing highly concentrated organic matter. This is especially true for the initial leachate from landfilled municipal solid wastes (MSW) that generally has concentrations of COD(Cr) and BOD(5) up to 80,000 and 50,000mg/L, respectively. The leachate could be disposed by means of recirculating technique, which decomposes the organics through the action of proliferating microorganisms and thereby purifies the leachate, and simultaneously accelerates organic decomposition through water saturation control. Data from experimental results indicated that leachate recirculating could reduce the organic concentration considerably, with a maximum reduction rate of COD(Cr) over 95%; and, using a semi-aerobic process, NH(3)-N concentration of treated leachate could be under 10mg/L. In addition, the organic concentration in MSW decreased greatly.

Aerobiosis↗
PubMed2005

Acute toxicity test of leachates from traditional and sustainable landfills using luminescent bacteria.

Landfilling is a fundamental step in any waste management strategy, but it can constitute a hazard for the environment for a long time. The need to protect the environment from potential landfill emissions makes risk assessment a decision tool of extreme necessity. The heterogeneity of wastes and the complexity of physical, chemical and biological processes that occur in the body of a landfill need specific procedures in order to evaluate the groundwater risk for the environment. Given the complexity of the composition of landfill leachates, the exact contribution of each potential toxic substance cannot be known precisely. Some reference contaminants that constitute the hazard (toxicity) of leachate have to be found to perform the risk assessment. A preliminary ecotoxicological investigation with luminescent bacteria has been carried out on different leachates from traditional and sustainable landfills in order to rank the chemicals that better characterize the leachate (heavy metals, ammonia and dissolved organic content). The attention has been focused on ammonia because it is present in high concentration and can last for centuries and can seriously contaminate the groundwater. The results showed that the toxicity of the leachate might reliably depend on the ammonia concentration and that the leachate toxicity is considerably lower in sustainable landfills where the ammonia had been degraded. This has an important consequence because if the containment system fails (as usually occur within 30-50yr), the risk of groundwater contamination will be calculated easier only in terms of the probability that the ammonia concentration is higher than a reference concentration.

Aliivibrio fischeri↗
PubMed2006

Use of zeolitised coal fly ash for landfill leachate treatment: a pilot plant study.

Treatment of municipal solid waste (MSW) landfill leachate generally results in low percentages of nutrient removal due to the high concentration and accumulation of refractory compounds. For this reason, individual physical, chemical and biological processes have been used for the treatment of raw landfill leachate and sometimes for the mixture of domestic wastewater and landfill leachate. In this work, the possibility of treating landfill leachate was tested in a bench-scale pilot plant by a two-step method combining adsorption and coagulation-flocculation. Zeolite synthesized from coal fly ash, a by-product of coal-fired power stations, was used in this study both as a decantation aid reagent and as an adsorbent of COD and NH4-N. The coagulation-flocculation step was performed by the use of aluminium sulphate and a polyelectrolyte (ACTIPOL A-401). The leachate was collected directly from a storage unit of the organic fraction of MSW, before it was composted. For this reason the raw leachate was diluted before treatment. The sludge was recirculated to enhance the removal efficiency of nutrients as well as to optimize flocculant saving and to decrease sludge production. The results showed that it is possible to remove 43%, 53% and 82% of COD, NH4-N, and suspended solids, respectively. Therefore, this method may be an alternative for ammonium removal, as well as a suitable pre- or post-treatment step, in combination with other processes in order to meet regulatory limits.

Alum Compounds↗
PubMed2004

Removal and transformation of recalcitrant organic matter from stabilized saline landfill leachates by coagulation-ozonation coupling processes.

The Bordo Poniente sanitary landfill in Mexico City currently receives 11,500 ton/day of solid wastes. The landfill has been in operation since 1985, in what was formerly Texcoco Lake, now a dried-up lakebed. The physico-chemical characteristics of the leachate generated by this particular landfill are altered by the incorporation of freatic saline water present in the area. This paper reports the results from a study evaluating coagulation and ozonation as alternative processes for removing and transforming recalcitrant organic matter from stabilized saline landfill leachate. Coagulation with ferric sulfate was found to remove up to 67% of COD and 96% of leachate color. The remaining 33% COD was removed with ozone. Recalcitrant organic matter removal by ozonation is limited by the reaction kinetic due mainly to ozone's low reactivity with the organic compounds present in the leachates (amines, amides, alcohols, aliphatic compounds, and carboxylic acids). However, ozone contributes greatly to changing the recalcitrant characteristics of organic matter. Leachate biodegradability was found to be significantly enhanced through ozonation: BOD(5) values reach 265%, and the BOD(5)/COD ratio increases from 0.003 to 0.015. Infrared analysis of ozonated leachates shows that the main by-products of recalcitrant organic matter ozonation are an increase in the hydroxyl and carboxylic groups, and the presence of aldehydes groups.

Hydrogen-Ion Concentration↗
PubMed1999

Genotoxicity of leachates from a landfill using three bioassays.

In the city of Queretaro, around 500 tons of solid wastes are produced everyday and are deposited in a landfill. This is the result of social and economic activities of human beings or from their normal physiological functions. As a result of rain, leachates are produced, which, if not handled and treated correctly, may pollute the underground water. Among the bioassays developed for the detection of mutagenicity in environmental pollutants, plant systems have been proven to be sensitive, cheap, and effective. The purpose of this study was to determine the presence of genotoxic agents in the leachates of the landfill of the city using three bioassays: Tradescantia-micronucleus (Trad-MCN), Tradescantia stamen hair mutations (Trad-SHM) and Allium root anaphase aberrations (AL-RAA) and make a comparison of the results in the three assays. Leachates were sampled during both the dry and rainy seasons. Plant cuttings of Tradescantia or the roots of Allium were treated by submerging them in the leachates. Three replicates of each sample were analyzed in each of the three bioassays. As expected the samples of leachates collected during the dry season showed a higher genotoxicity than those collected during the rainy season. In conclusion, there are substances present in the leachates capable of inducing genotoxicity in the plant assays. On the other hand, the plant assays showed different degrees of sensitivity: the more sensitive was the Trad-MCN bioassay and the less sensitive the Trad-SHM assay. Therefore, when analyzing environmental pollutants it is recommended to use a battery of bioassays.

Allium↗
PubMed2001

Biological control of leachate from municipal landfills.

Landfilling is still a popular way for municipal solid waste (MSW) treatment. Leachate generated from landfills is becoming a great threat to the surroundings as it contains high concentrations of toxic substances. How to control leachate migration and to protect environmental pollution is now a concern for many environmentalists. In this work, eight effective microorganisms (EMs) were isolated from wastewater, sludge and soil samples by enrichment culturing techniques and used for leachate migration control in columns and pilot experiments. The preliminary experiments reveal that the EMs could remove 25% and 40% of chemical oxygen demand (COD) from leachate in fine sand and sabulous clay columns, respectively. An aquifer system was designed to simulate in-situ control for leachate migration with EMs. The EMs were injected into the simulated aquifer and formed a permeable biological barrier. The experimental results show that the barrier removed 95% of COD and approximately 100% inorganic nitrogen, that is, nitrate-N plus nitrite-N plus ammonia-N, from the migrating leachate. CO2 production, redox potential and microbial number were monitored simultaneously in the aquifer during the experiment to assess the EMs' activities and the effect of the bio-barrier. The data indicate that the EMs isolated in this work had high activities and were effective for organic and nitrogenous contaminant removal throughout the experiment.

Biodegradation, Environmental↗