Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Leachate”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 199 records · Page 11Linked to original sources
PubMed2004

The application of bioflocculant for the removal of humic acids from stabilized landfill leachates.

The evaluation of bioflocculant, in comparison with traditional inorganic coagulants, for the removal of humic acids from landfill leachates stabilized by biological treatment, was performed using conventional jar-test coagulation experiments. The optimized conditions (pH and coagulant dosage) were identified for the treatment of synthetic solutions as well as for biologically pre-treated landfill leachates. It was found that the application of bioflocculant was quite efficient in the removal of humic acids from synthetic solutions as well as in the reduction of COD content from real landfill leachates. The optimal pH value was found to be between 7 and 7.5, while a 20 mg/l bioflocculant dosage was sufficient in providing more than 85% humic acid removal. The results were comparable with those obtained by the application of conventional coagulants such as alum or polyaluminum chloride; therefore, bioflocculant can be considered as a viable alternative in the treatment of landfill leachates applying coagulation.

Biodegradation, Environmental↗
PubMed2004

Biological nutrient removal from pre-treated landfill leachate in a sequencing batch reactor.

Biological treatment of landfill leachate usually results in low nutrient removals because of high chemical oxygen demand (COD), high ammonium-N content and the presence of toxic compounds such as heavy metals. Landfill leachate with high COD content was pre-treated by coagulation-flocculation with lime followed by air stripping of ammonia at pH=12. Nutrient removal from pre-treated leachate was carried out using a lab-scale sequencing batch reactor (SBR). Three different operations consisting of different numbers of steps were tested and their performances were compared. These operations were the three-step anaerobic (An)/anoxic (Ax)/oxic (Ox); the four-step (An/Ox/Ax/Ox), and the five-step (An/Ax/Ox/Ax/Ox) operations with total residence time of seven hours each. Experiments were carried out using three consecutive operations with a total cycle time of 21 h at a constant sludge age of 10 days. The lowest effluent nutrient levels were realized by using the five-step operation which resulted in effluent COD, NH4-N and PO4-P contents of 1,400, 107 and 65 mg l(-1), respectively, at the end of 21 h. Addition of domestic wastewater (1/1, v/v) and powdered activated carbon (PAC, 1 g l(-1)) to the pre-treated leachate improved nutrient removals in the five-step SBR operation, resulting in 75% COD, 44% NH4-N and 44% PO4-P removals after 21 hours of operation.

Bacteria, Anaerobic↗
PubMed2006

Ammonia removal from leachate solution using natural Chinese clinoptilolite.

This paper assesses the potential of natural Chinese clinoptilolite for ammonia removal from the leachate solution of sewage sludge. In batch study the effects of relevant parameters, such as contact time, initial ammonia concentration and particle size of clinoptilolite, were examined respectively. The results show that the data obtained from batch studies were fit to Langmuir and Freundlich isotherms and the Langmuir isotherms reflect more reasonable for ammonium ion uptake onto clinoptilolite; the clinoptilolite adsorption process has been proved effective, at laboratory scale, the maximum adsorption capacity of the clinoptilolite, for ammonium concentration ranging from 11.12 to 115.16 mg NH(4)-N L(-1) in leachate solution, was about 1.74 mg NH(4)-Ng(-1); the time to adsorption equilibrium was 2.5 h in leachate solution and 1.5 h more than for in NH(4)Cl synthetic solution; ammonium adsorption increased with decreasing clinoptilolite particle size; the ammonia removal capacity of clinoptilolite increased with increasing initial ammonia concentration. It is believed that as adsorption agent for NH(4)-N removal from sludge leachate, natural Chinese clinoptilolite can be feasible.

Adsorption↗
PubMed2006

Degradation of recalcitrant compounds from stabilized landfill leachate using a combination of ozone-GAC adsorption treatment.

Laboratory experiments were undertaken to investigate the treatment performances of ozonation alone and/or its combination with granular activated carbon (GAC) adsorption for raw leachate from the NENT landfill (in Hong Kong). To improve its removal of recalcitrant contaminants from the leachate, the surface of GAC was oxidized with ozone prior to treatment. With respect to ozone dose and pH, the removal of COD and/or NH(3)-N from ozonation alone and combined ozone-GAC adsorption were evaluated and compared to those of other physico-chemical treatments in some reported studies. The removal mechanism of recalcitrant compounds by ozone-GAC adsorption treatment was presented. Among the various treatments studied, the combination of ozone-GAC adsorption using ozone-modified GAC had the highest removal for COD (86%) and/or NH(3)-N (92%) compared to ozonation alone (COD: 35%; NH(3)-N: 50%) at the same initial COD and/or NH(3)-N concentrations of 8000 and 2620 mg/L, respectively. Although the integrated treatment was more effective than ozonation alone for treating stabilized leachate, the results suggested that it could not generate treated effluent that complied with the COD limit of lower than 200 mg/L and the NH(3)-N discharge standard of less than 5 mg/L. Therefore, further biological treatments to complement the degradation of the leachate are still required to meet the environmental legislation.

Adsorption↗
PubMed2006

Influence of temperature on the electrical conductivity of leachate from municipal solid waste.

A bioreactor landfill is designed to manage municipal solid waste, through accelerated waste biodegradation, and stabilisation of the process by means of the controlled addition of liquid, i.e. leachate recirculation. The measurement of electrical resistivity by Electrical Resistivity Tomography (ERT) allows to monitor water content present in the bioreactors. Variations in electrical resistivity are linked to variations in moisture content and temperature. In order to overcome this ambiguity, two laboratory experiments were carried out to establish a relationship between temperature and electrical conductivity: the first set of measurements was made for leachate alone, whereas the second set was made with two different granular media saturated with leachate. Both experiments confirm a well known increase in conductivity of about 2% degrees C(-1). However, higher suspended matter concentrations lead to a lower dependence of electrical conductivity on temperature. Furthermore, for various porous media saturated with an identical leachate, the higher the specific surface of the granular matrix, the lower the effective bulk electrical conductivity. These observations show that a correct understanding of the electrical properties of liquids requires the nature and (in particular) the size of the electrical charge carriers to be taken into account.

Bioreactors↗
PubMed2005

Characteristics of landfill leachates in central Taiwan.

Due to the complex nature of landfill leachates, the leachate treatment plants have difficulty to meet the current Taiwan EPA's effluent standards. Three typical types of landfills, closed landfill A, mixed landfill B (disposal of MSW with bottom ashes from MSW incinerators) and direct MSW landfill C, (disposal of MSW only), are investigated in this research in order to have a better understanding of characteristics of leachates. Factors investigated in this research include landfill age, pH, BOD, COD, TS, DS, VS, seasons, metals (Pb, Ca, Cd, Hg, Cr, Cu, Fe, K, Mg, Mn, Na, Ni, and Zn), humic substances (humic acid, fulvic acid, and non-humic substance), aromaticity and toxicity. Results show that the active landfills B and C had the significant higher concentration of COD, VSS, TS, PtCo, TOC and conductivity. The mixed landfill B had the higher DS, TS, Na, Ca, Mg and conductivity than that of direct MSW landfill C. Direct MSW landfill C had the highest contents of Fe, Cr, Ni and acute toxicity among these landfills. A significant degree of variation was encountered and factors which may influence leachate quality were identified and discussed.

Aliivibrio fischeri↗
PubMed2004

Influence of landfill leachate suspended solids on clog (biorock) formation.

Laboratory column tests were performed to evaluate the role of leachate-suspended-solids in clogging a granular material permeated with Keele Valley Landfill leachate. The development of the clog material was a result of biological, chemical, and physical processes occurring within the column. The increase in volatile solids, which contributed to clog development over time, was primarily due to the retention of volatile suspended solids and growth of a biofilm capable of removing acetate, propionate, and butyrate from the leachate. Acetate fermentation was primarily responsible for precipitation of calcium within the column. The precipitated calcium and retention of inorganic suspended solids contributed to the increase in clog inorganic solids. Over the duration of the experiment, 3.7 times more calcium was precipitated in the column (due to acid fermentation) than was retained with inorganic suspended solids. Clogging resulted in a greater than 60% reduction in drainable porosity and a six-order magnitude decrease in hydraulic conductivity. The potential practical implications with respect to pipe cleaning and leachate recirculation were discussed.

Calcium↗
PubMed2004

Parametric sensitivity analysis of leachate transport simulations at landfills.

This paper presents a case study in simulating leachate generation and transport at a 2000 ton/day landfill facility and assesses leachate migration away from the landfill in order to control associated environmental impacts, particularly on groundwater wells down gradient of the site. The site offers unique characteristics in that it is a former quarry converted to a landfill and is planned to have refuse depths that could reach 100 m, making it one of the deepest in the world. Leachate quantity and potential percolation into the subsurface are estimated using the Hydrologic Evaluation of Landfill Performance (HELP) model. A three-dimensional subsurface model (PORFLOW) was adopted to simulate ground water flow and contaminant transport away from the site. A comprehensive sensitivity analysis to leachate transport control parameters was also conducted. Sensitivity analysis suggests that changes in partition coefficient, source strength, aquifer hydraulic conductivity, and dispersivity have the most significant impact on model output indicating that these parameters should be carefully selected when similar modeling studies are performed.

Geological Phenomena↗
PubMed2004

Effect of an uncontrolled fire and the subsequent fire fight on the chemical composition of landfill leachate.

Landfill leachates sampled during and after an accidental landfill fire were analysed and the levels of selected metals and chemical compounds compared to those occurring in the leachate under normal conditions. The fire at the landfill site was put out by excavation and cooling by use of water. The investigation during the fire and fire fight revealed a moderate increase in the level of nitrogen and also in pH and conductivity. Heavy metals and COD in the leachate showed considerably increased levels. In general, the determined variables appeared to normalise within one week after the fire was extinguished. It can be concluded that landfill fires extinguished by excavation may lead to elevated leachate levels of especially COD and heavy metals, but that this is only a short-term effect.

Fires↗
PubMed2005

Leachate quality from landfilled MBT waste.

A research project recently completed on behalf of the UK Environment Agency, has collected data and sampled leachates from EU landfills that have received imports of MSOR and MBT wastes. Results are presented for sanitary analyses, heavy metals, and an extensive range of trace organic substances, from sites containing MBT wastes that have received different degrees of composting pre-treatment. Leachates produced from MSOR wastes have a very high polluting potential, but biological pre-treatment of these wastes can avoid the peak acetogenic phase of decomposition, and produce leachates similar to, or weaker than, those from conventional methanogenic landfills. Effective MBT processes can also significantly reduce concentrations of trace organics, and of ammoniacal-N in leachates. However, further research is needed to examine the relative importance of nitrification/denitrification processes, generation of stable, organically based nitrogen forms, and other routes during MBT processing, in order that appropriate reactions to remove nitrogen can be encouraged and optimised.

Biodegradation, Environmental↗
PubMed2006

Removal of manganese and zinc from Kahrizak landfill leachate using daily cover soil and lime.

The possibility of in situ removal of heavy metals found in leachate generated at municipal solid waste landfills was studied through amendment of daily cover soil. Kahrizak landfill, which receives the waste generated at Tehran, was selected as the source of leachate and soil samples. Manganese and zinc were selected in this study. The soil sample taken from the Kahrizak site contained about 17% clay, which was presumed to have significant capability for removing manganese and zinc. This capability was assumed to be enhanced further through the addition of lime and consequently to improve the potential for chemical precipitation of the selected metals. The in situ removal experiment was accomplished through a set of seven columns filled with the sampled soil with varying contents of lime (i.e., from 0% to 6% by dry weight). Fresh leachate of low pH was added to the columns on a daily basis. Concentrations of manganese and zinc were measured in the influent and effluent during 40 days when biological clogging resulted in a condition of almost no outflow in the columns. The results indicated a substantial increase in removal efficiency through the addition of lime to the daily cover soil. Desorption resulting from the low pH of fresh leachate occurs at later stages compared to the column with no lime addition.

Calcium Compounds↗
PubMed2004

Estimation of the mass-balance of selected metals in four sanitary landfills in Western Norway, with emphasis on the heavy metal content of the deposited waste and the leachate.

A worst-case simulation of the mass-balance for metals in the waste deposited during 1 year and the levels of cadmium (Cd), lead (Pb), mercury (Hg), chromium (Cr) and iron (Fe) in the leachate was calculated for four sanitary landfills in Western Norway. Estimates of the levels of metal content in mixed municipal solid waste (MSW) were found by using recent literature values calculated in a mass-balance study at a Norwegian waste incinerator plant. Leachate from the landfills were sampled and analyzed monthly during 1 year, and from these measurements the total annual discharge of the selected metals through the leachate was determined. The levels of the measured heavy metals in the leachate were low. For Cd less than 0.06%, for Pb less than 0.01% and for Hg less than 0.02% of the estimated year's deposited mass of metals were leached from the landfills during the year of investigation. The high retention of these metals are most likely due to sulfide precipitation, but also due to the immobile condition of the metals in their original deposited solid state (plastics, ceramics, etc.). The percentage of Cr leached was relatively higher, but less than 1.0% per year. The mass balance of Fe suggests that this element is more mobile under the prevailing conditions. The percentage of Fe leached varied and was estimated to be between 1.9% and 18%. The present study clearly supports the theory that MSW only to a small extent will lead to discharge of metals if deposited at well-constructed sanitary landfills with top layers.

Chromium↗
PubMed2006

Size charge fractionation of metals in municipal solid waste landfill leachate.

Municipal solid waste landfill leachates from 9 Norwegian sites were size charge fractionated in the field, to obtain three fractions: particulate and colloidal matter >0.45microm, free anions/non-labile complexes <0.45microm and free cations/labile complexes <0.45microm. The fractionation showed that Cd and Zn, and especially Cu and Pb, were present to a large degree (63-98%) as particulate and colloidal matter >0.45microm. Cr, Co and Ni were on the contrary present mostly as non-labile complexes (69-79%) <0.45microm. The major cations Ca, Mg, K, and Mn were present mainly as free cations/labile complexes <0.45microm, while As and Mo were present to a large degree (70-90%) as free anions/non-labile complexes <0.45microm. Aluminium was present mainly as particulate and colloidal matter >0.45microm. The particulate and colloidal matter >0.45microm was mainly inorganic; indicating that the metals present in this fraction were bound as inorganic compounds. The fractionation gives important information on the mobility and potential bioavailability of the metals investigated, in contrast to the total metal concentrations usually reported. To study possible changes in respective metal species in leachate in aerated sedimentation tanks, freshly sampled leachate was stored for 48h, and subsequently fractionated. This showed that the free heavy metals are partly immobilized during storage of leachate with oxygen available. The largest effects were found for Cd and Zn. The proportion of As and Cr present as particulate matter or colloids >0.45microm also increased.

Chemical Fractionation↗
PubMed2002

Determination of phenols in landfill leachate-contaminated groundwaters by solid-phase extraction.

A solid-phase extraction method for phenols in landfill leachates was developed and optimized in order to solve the expected and observed problems associated with an anaerobic matrix containing high concentrations of salts and organic matter. Isolute ENV+ cartridges exhibited the best retention of phenols of the four sorbents examined, and was the only cartridge which a 1 L leachate sample could pass through. With the other cartridges, clogging made this impossible. The final method, which included 27 different phenols, gave detection limits of <0.1 microg/L (drinking water concentration limit for pesticides) for most phenols (25), and for 12 phenols <0.01 microg/L. Recovery rates (determined for four concentrations in the range 1-25 microg/L, two replicates of each) were in the range 79-104% (SD 1-12%), except for phenol (26+/-1.3%) and 2-methoxyphenol (62+/-4.2%). Up to 12 different phenols could be identified in leachates from three Danish landfills, ranging in concentration from 0.01 to 29 microg/L, which is at the lower end of the concentration range usually found for phenols in landfill leachates (sub-microg/L to mg/L).

Phenols↗
PubMed2001

Stabilized landfill leachate treatment by combined physicochemical-nanofiltration processes.

Landfill leachate is a complex wastewater which the composition and concentration of contaminants are influenced by the type of waste deposited and the age of landfill. In the last years, several processes or process combinations were developed and tested to reach requirements for the discharge of leachate. Among the new processes, membrane processes are considered as promising: reverse osmosis is one of the most widely used treatment in the Northwestern European countries and nanofiltration is gained in popularity during the last 5 years. Successful application of membrane technology for the treatment of landfill leachates, requires efficient control of membrane fouling. Two organic membranes of nanofiltration were used for pilot-scale testing. Leachates were subject to several pretreatments (pH modification, prefiltration and coagulation with FeCl3) to remove potential foulants including dissolved organic and inorganic substances, colloidal and suspended particles. These pretreatments do not enhance the performances (retention and permeation flux) of membranes because the pH range and the presence of Fe3+ ions contribute greatly to change the characteristics of organic matter and the surface charges of membranes. However, the results show that nanofiltration is sufficient to eliminate refractory COD, the permeates have a COD lower than the requirements for discharge.

Adsorption↗
PubMed2002

Removal of ammoniacal nitrogen from landfill leachate by irrigation onto vegetated treatment planes.

Leachate is a contaminated liquor resulting from the disposal of solid and liquid wastes at landfill sites that must be treated before discharge. Vegetated leachate treatment planes have been used at landfill sites in the UK but have received little scientific attention. This paper describes studies of model leachate treatment planes with a focus on the removal of ammoniacal nitrogen (NH3-N). Small-scale and field-scale experimental treatment planes were constructed. filled with clay loam soil and vegetated with grass (Agrostis stolonifera). Landfill leachate was applied at hydraulic loading rates ranging from 17-217l/m2/d. An exponential relationship was used to characterise the pattern of NH3-N removal. No relationship was observed between the hydraulic loading rate and the NH3-N removal rate constants (R2 = 0.0039). The daily specific NH3-N mass removal rate was found to be linearly related to the NH3-N concentration at the start of that day of treatment (R2 = 0.35). Possible causes of variation in the rate of NH3-N removal between experiments are discussed. A simple inorganic nitrogen balance indicated that the mass of N-H3-N and NO2-N removed was not accounted for by NO3-N production. Explanations for this apparent nitrogen deficit are discussed.

Ammonia↗
PubMed2001

Bisphenol A in hazardous waste landfill leachates.

The levels of bisphenol A in hazardous waste landfill leachates collected in Japan in 1996 were determined by gas chromatograph/mass spectrometer (GC/MS). Bisphenol A was found in seven of 10 sites investigated. All the hazardous waste landfills with leachates contaminated by bisphenol A were controlled. The concentrations of bisphenol A ranged from 1.3 to 17,200 microg/l with a median concentration of 269 microg/l. The source of bisphenol A in landfill leachates may be the waste plastics in waste landfill. The concentrations of bisphenol A in some samples exceeded the EC50 or LC50 levels for aquatic biota. Landfill leachates may be a significant source of bisphenol A found in the environment.

Air Pollutants, Occupational↗
PubMed2001

Efficiency of biological treatment affected by high strength of ammonium-nitrogen in leachate and chemical precipitation of ammonium-nitrogen as pretreatment.

Leachate samples with a high strength of ammonium-nitrogen (NH4+-N) were collected from a local landfill site in Hong Kong. Two experiments were carried out to study (1) the inhibition of microbial activity of activated sludge by NH4+-N and (2) the chemical precipitation of NH4+-N from leachate as a preliminary treatment prior to the activated sludge process. The experimental results demonstrated that the efficiency of COD removal decreased from 97.7% to 78.1%, and the dehydrogenase activity of activated sludge decreased from 9.29 to 4.93 microg TF/mg MLSS, respectively, when the NH4+-N concentration increased from 53 to 800 mg/l. The experiment also demonstrated that the NH4+-N in the leachate can be quickly precipitated as MgNH4PO4 x 6H2O after addition of MgCl2 x 6H2O + Na2HPO4 x 12H2O. The NH4+-N concentration was reduced from 5618 to 112 mg/l within 15 min when a molar ratio of Mg2+:NH+:PO4(3-) = 1:1:1 was used. The optimum pH to reach the minimum solubility of MgNH4PO4 x 6H2O was found to be in the range of 8.5-9.0. Attention should be given to the high salinity formed in the treated leachate by using MgCl2 x 6H2O + Na2HPO4 x 12H2O, which may affect microbial activity in the following biological treatment processes. Using two other combinations of chemicals [MgO + 85%H3PO4 and Ca(H2PO4)2 x H2O + MgSO4 x 7H2O] could minimise salinity generation after precipitation, while they were less efficient for NH4+-N removal.

Hydrogen-Ion Concentration↗