Fecal coliform bacteria such as Escherichia coli (E. coli) are one of the main sources of groundwater pollution. An assessment of the transport and Persistence of E. coli in poultry litter amended Decatur silty Clay s...Fecal coliform bacteria such as Escherichia coli (E. coli) are one of the main sources of groundwater pollution. An assessment of the transport and Persistence of E. coli in poultry litter amended Decatur silty Clay soil and Hartsells Sandy soil was conducted using soil columns and simulated groundwater leaching. Enumeration of initial E. coli was determined to range from 2.851 × 10<sup>3</sup> to 3.044 × 10<sup>3</sup> CFU per gram of soil. These results have been used in a batch study to determine the persistence rate of E. coli in Decatur silty Clay soil and Hartsells Sandy soil. Results prove that E. coli survival growth rate increases for clay soil later than and at a higher rate than sandy soil. The column study has determined that E. coli was transported at a rate of 3.7 × 10<sup>6</sup><sup> </sup>CFU for Decatur silty loam and 6.3 × 10<sup>6</sup><sup> </sup>CFU for Hartsells sandy per gram of soil. Further, linear regression analysis predictions show higher porosity and soil moisture content affect transport, and Hartsells sandy soil has higher transport of E. coli due to its higher porosity and lower volumetric water content.展开更多
The geochemical components of the leachate from loess-paleosol deposits can provide information about climaterelated post-depositional processes.For example,leachate lithium([Li]_(leachate))is a potential paleoclimate...The geochemical components of the leachate from loess-paleosol deposits can provide information about climaterelated post-depositional processes.For example,leachate lithium([Li]_(leachate))is a potential paleoclimate proxy because lithium is a typical lithophile element that is readily adsorbed by clay minerals during weathering and pedogenesis,and thus stratigraphic variations in[Li]leachatecan reflect these processes.We investigated the[Li]leachatevalues of two loess-paleosols profiles(the Luochuan and Weinan sections),on a north-south climatic gradient on the Chinese Loess Plateau.Independent paleoclimate information was provided by measurements of magnetic susceptibility,grain size,Rb/Sr ratios,and clay mineral content.During the last glacial-interglacial period,[Li]leachateincreased from 0.39 to 1.97μg/g at Luochuan and from 0.67 to 2.45μg/g at Weinan,mainly due to increasing pedogenesis.Based on these results we developed a conceptual model to explain the variations in[Li]leachate,Li^(+)within loess layers is mainly derived from dust input and the decomposition of primary minerals,influenced by the East Asian winter monsoon,while in paleosol layers Li is mainly derived from clay mineral adsorption during pedogenic processes,influenced by the East Asian summer monsoon.展开更多
Population growth combined with the rising standard of living of people around the world is the reason for the ever-increasing production of waste which management is costing states a lot of money for its disposal. Am...Population growth combined with the rising standard of living of people around the world is the reason for the ever-increasing production of waste which management is costing states a lot of money for its disposal. Among available waste treatment techniques, landfill is one of the most promoted waste management techniques with the emergence of the bioreactor concept. However, the control of biodegradation parameters in order to accelerate waste stabilization is an important issue. For environmental and economic reasons, the technique of leachate recirculation by injection into the waste is increasingly used to improve the degradation of landfilled waste. The injection of leachate is possible using vertical boreholes, horizontal pipes, infiltration ponds or a combination of these. Indeed, moisture is the main factor in waste degradation and biogas production. The migration of leachate to the bottom of the landfill creates low moisture in the upper areas of the landfill reducing the growth of microbial populations. This results in low or no biogas production. The main objective of the present work is to develop a numerical model of leachate recirculation by injection into the waste to rewet the waste and restart biological activity. The analysis of the results shows that the diffusion of the wet front increases with time and depth. The lateral widening of the wet front is slow in relation to the progression of the wet front towards the bottom of the waste cell. This indicates the predominance of gravity effects over diffusion phenomena. The results reveal that the distributed re-injection is the best mode of leachate recirculation because the moisture distribution on the whole waste mass is totally satisfactory and the biogas generation is more important. Leachate recirculation campaigns should be done periodically to rewet the waste, boost microbial activity and hope for a quicker stabilization of the landfill.展开更多
After washing and curing, P is transported from the phosphogypsum to the leachate during the phosphogypsum detoxification process, providing two ideas for phosphorus recovery from phosphogypsum leachate: 1) preparatio...After washing and curing, P is transported from the phosphogypsum to the leachate during the phosphogypsum detoxification process, providing two ideas for phosphorus recovery from phosphogypsum leachate: 1) preparation of calcium hydrogen phosphate for feed;2) preparation of calcium phosphate. A ready-to-use calcium oxide slurry was used to recover P from phosphogypsum leachate at a slurry concentration of 20% and a quantitative link between calcium to phosphorus ratio and fixation rate was fitted by mixed use batch experiments, reaction kinetics and thermodynamics, and theoretical calculations were used to demonstrate that phosphorus cannot be completely reused in the preparation of calcium hydrogen phosphate. The findings demonstrated that: a) the residual phosphorus concentration was in the range of 1300 - 1500 mg/L for the preparation of type I feed grade calcium hydrogen phosphate from phosphogypsum leachate;b) the P removal effect could reach 99.99% for the preparation of calcium phosphate from phosphogypsum using the theoretical equation: fixation rate = 87.91 - 10.96(Ca/P) + 3.22(Ca/P)<sup>2</sup> (R<sup>2</sup> = 0.9954);c) The procedure follows the suggested secondary kinetics, and according to the Freundlich isothermal model, the reaction process is under the control of the chemical reaction, with a reaction index of 0.7605. This study can be used as a theoretical guide for the recovery of P from phosphogypsum leachate, the preparation of products to bring about economic by-products, and the purification of wastewater for reuse.展开更多
This study was conducted to measure the impact of a municipal solid waste landfill on groundwater quality around Njelianparamba, a solid waste dumping site in Kozhikode district, Kerala state, India. One of the major ...This study was conducted to measure the impact of a municipal solid waste landfill on groundwater quality around Njelianparamba, a solid waste dumping site in Kozhikode district, Kerala state, India. One of the major problems associated with dumping of municipal solid waste landfill is the release of leachate and its impact on surrounding groundwater. In this study, physico-chemical and bacteriological parameters of groundwater samples collected from the region surrounding the leachate area during the pre- and post-monsoon seasons were analysed. The majority of the groundwater samples contained contaminants at a level beyond the permissible limit set by the Bureau of Indian Standards for drinking water quality. The Geographic Information System software of the Environmental Systems Research Institute, (USA) ArcMap 10.1 was used to prepare spatial distribution maps of different parameters and Leachate Pollution Index and Water Quality Index in the study area were applied to assess the overall quality of groundwater. Characterisation of leachate and groundwater samples revealed that, water in the domestic wells has been deteriorated in response to the percolation of leachate. Additionally spatial and correlation analysis revealed that contamination was present maximum within 300 m radius around the landfill site.展开更多
Population development of key groups of anaerobic and aerobic bacteria involved in municipal refuse decomposition under laboratory landfill bioreactors with and without leachate recycle and inoculation was measured si...Population development of key groups of anaerobic and aerobic bacteria involved in municipal refuse decomposition under laboratory landfill bioreactors with and without leachate recycle and inoculation was measured since modeling municipal refuse was landfilled in bioreactors for about 210 days. Hydrolytic fermentative bacteria (HFB), hydrogen producing acetogenic bacteria (HPAB), methane producing bacteria (MPB), sulfate reducing bacteria (SRB), anaerobic and aerobic cellulolytic bacteria and denitrabacteria were enumerated by the most probable number technique. The results showed that the dominant microorganism groups were the methanogenic bacteria including hydrolytic fermentative, hydrogen producing acetogenic and methane producing bacteria. They were present in fresh refuse but at low values and positively affected by leachate recycle and refuse inoculation. The amounts of HFB or HPAB in digesters D4 and D5 operated with inoculation and leachate recycle reached their maximum values of 10 10 -10 12 cells/g dry refuse for HFB or 10 5-10 6 cells/g dry refuse for HPAB on day 60, in digester D3 operated with leachate recycle on day 120 for HFB (10\+9 cells/g dry refuse) or on day 90 for HPAB (10\+5 cells/g dry refuse), and in digesters D1 and D2 on day 210 for HFB (10 9 cells/g dry refuse) or on day 90 for HPAB (10 4-10 6 cells/g dry refuse). The population of methane producing bacteria in digesters D4 and D5 sharply increased on days 60 and 90 respectively, however in digesters D1, D2 and D3 on day 120. Leachate recycle and inoculation changed the cellulolytic microorganisms composition of refuse ecosystem, the higher amounts of anaerobic cellulolytic bacteria were measured in digesters D4 and D5 (10 7 cells/g dry refuse), followed by digesters D3 (10 6 cells/g dry refuse), D2 or D1(10 4 cells/g dry refuse). However, the amounts of aerobic cellulolytic bacteria were much lower than that of anaerobic cellulolytic bacteria. And it was higher in digester D3 than those in digesters D1, D2, D4 and D5 The amounts of SRB and denitrabacteria were also higher in digester D5 than those in digesters D1, D2, D3 and D4 Refuse decomposition could be accelerated by leachate recycle and inoculation in the view of microorganism development.展开更多
Soil microbes may be critical players in determining the allelopathic potential of some plants. Low levels of plant community biodiversity in Eucalyptus plantations have been attributed to the allelopathic potential o...Soil microbes may be critical players in determining the allelopathic potential of some plants. Low levels of plant community biodiversity in Eucalyptus plantations have been attributed to the allelopathic potential of these tree species. The role of soil microbes in the allelopathic effect of leaf leachates of the hybrid tree Eucalyptus grandis×E.urophylla, was tested in Petri dish assays with Brassica chinensis as a receiver plant. Soils were collected from either a local garden(soil A) or a Eucalyptus plantation(soil B) and half of each soil was sterilized to remove microbes.These soils were then treated with E. grandis×E. urophylla leachates for 0–72 h. Seed germination of B. chinensis was significantly inhibited in soils treated with leaf leachates relative to untreated soils. The inhibitory effect of the leaf leachates was more pronounced in sterilized soils. Total phenolic content was obvious lower in nonsterile leachatetreated soils than in sterile soils. Biomass of B. chinensis was negatively correlated with the total phenolic content in soils.Our findings suggest that soil microbes can alleviate the allelopathic potential of Eucalyptus and thereby its negative impact on plant growth.展开更多
Organic micropollutants,with high toxicity and environmental concern,are present in the landfill leachate at much lower levels than total organic constituents (chemical oxygen demand (COD),biochemical oxygen demand (B...Organic micropollutants,with high toxicity and environmental concern,are present in the landfill leachate at much lower levels than total organic constituents (chemical oxygen demand (COD),biochemical oxygen demand (BOD),or total organic carbon (TOC)),and few has been known for their behaviors in different treatment processes.In this study,occurrence and removal of 17 organochlorine pesticides (OCPs),16 polycyclic aromatic hydrocarbons (PAHs),and technical 4-nonylphenol (4-NP) in landfill leachate in a combined anaerobic-membrane bioreactor (MBR) were investigated.Chemical analyses were performed in leachates sampled from different treatment processes,using solid-phase extraction and gas chromatography with electron capture detector and mass spectrometry.Concentrations of OCPs,PAHs,and 4-NP in the raw leachate were detected within the range from ND (not detected) to 595.2 ng/L,which were as low as only 10-7-10-5 percentage of TOC (at the concentration of 2,962 mg/L).The removal of 4-NP was mainly established in the MBR process,in agreement with removals of COD,BOD,and TOC.However,the removals of OCPs and PAHs were different,mainly achieved in the anaerobic process.High removal effciencies of both total organic constituents and organic micropollutants could be achieved by the combined anaerobic-MBR technology.The removal effciencies of total organic constituents were in the order of BOD (99%) > COD (89%) > TOC (87%),whereas the removal effciencies of investigated organic micropollutants were as follows: OCPs (94%) > 4-NP (77%) > PAHs (59%).展开更多
As fouling has always been a major drawback of membrane technology, qualitative and quantitative understanding of membrane fouling mechanisms therefore becomes vital in order to help push membrane separation technolog...As fouling has always been a major drawback of membrane technology, qualitative and quantitative understanding of membrane fouling mechanisms therefore becomes vital in order to help push membrane separation technologies forward. In this study, firstly, self-cleaning Polysulfone(PSf) membranes were synthesized by incorporation of WO_3nanoparticles(0–2 wt%) and subsequent UV irradiation for efficient ultrafiltration(UF)of landfill leachate and dairy wastewater. The membrane surface properties were characterized by scanning electron microscopy(SEM) and contact angle analysis. It was found that UV-irradiated membranes exhibited higher percent COD removals due to the hydrophilicity and photocatalytic properties of nano-WO_3. Subsequently, in order to analyze the fouling behavior of the membranes, a set of experimental data from cross-flow ultrafiltration of municipal landfill leachate and industrial dairy wastewater at 25 °C was obtained. A new model of membrane fouling was proposed based on a resistance in series concept and was fitted well with all experimental data sets.Almost all relative errors of prediction provided by the proposed model were less than 2.5%. In addition, it was revealed that this newly-developed model exhibited smooth transition between the common successive twostep pore blockage-cake filtration phenomena and thus eliminates the need to use separate equations for different mechanisms.展开更多
A comprehensive assessment of heavy metals and organic content was performed for leachates produced from a number of old and new landfills in Jordanover 9 month in efforts to set a framework for treatment regulations....A comprehensive assessment of heavy metals and organic content was performed for leachates produced from a number of old and new landfills in Jordanover 9 month in efforts to set a framework for treatment regulations. All leachates were basic (pH = 7 - 9) and have high electric conductivity and high organic contents (COD = 3000 - 500,000 mg/L, TOC= 500 - 21,000 mg/L). The organic content was inversely proportional to the age of landfill. Heavy metals analysis showed no significant threat of Co, Zn, Pb and Al in any site. Meanwhile, the concentrations of Cr, Mn, Ni, Cd and As were high, exceeding local and international standard limits. Typical physical, chemical and biological treatments can be employed to upgrade the leachates of the active Ghabawi and Akaider sites. Whereas for the high organic strength of Russeifeh, an adsorption treatment by activated carbon is recommended.展开更多
Jatropha curcas L. commonly known as “physic nut” is an exotic species that shows invasive characters. Plantation of Jatropha species is being undertaken at a large scale for biodiesel production. The plants defolia...Jatropha curcas L. commonly known as “physic nut” is an exotic species that shows invasive characters. Plantation of Jatropha species is being undertaken at a large scale for biodiesel production. The plants defoliate their leaves twice a year and have been shown to possess certain antinutritional factors. Seeds of Jatropha are removed from mature dried fruits for oil extraction and ovary walls are discarded. For the present experiments leachates from sun dried leaves and ovary walls of Jatropha curcas L. were used for analyzing their possible allelopathic effects on the growth of wheat (Triticum aestivum L. cultivar, MP-4010). Leachate treatments result in slight decrease in growth in terms of plant height, leaf area, biomass, spike length and 100 seed weight of wheat and increase in total phenols, tannins, phytic acid and free amino acids. Results suggest that the leachates of leaf and ovary wall of Jatropha curcas are slightly inhibitory, however the impact does not last long. Nevertheless, continuous plantation may lead to accumulation of damaging constituents which reflects the need for further analysis and experimentation.展开更多
This study describes the treatment of composting leachate by the combination of coagulation and nanofiltration process.Poly ferric sulfate(PSF) was used as coagulant,and the effect of p H value and PSF dosage on the c...This study describes the treatment of composting leachate by the combination of coagulation and nanofiltration process.Poly ferric sulfate(PSF) was used as coagulant,and the effect of p H value and PSF dosage on the coagulation performance was investigated.The results indicated that the chemical oxidation demand(COD)and turbidity removal efficiency could reach to 62.8% and 75.3%,respectively at an optimum dosage of1200 mg·L^(-1)at p H 6.0.During the nanofiltration process,the operation conditions such as temperature and pressure were optimized,89.7% of COD,78.2% of TOC,72.5% of TN,83.2% of TP,and 78.6% of NH3-N were retained when tested at 0.6 MPa at 25 °C.The final leachate effluent concentration of COD,BOD5,NH3-N,TOC,SS was92 mg·L^(-1),31 mg·L^(-1),21 mg·L^(-1),73 mg·L^(-1)and 23 mg·L^(-1),respectively,which reached the local discharge standard.The combination of coagulation-filtration is useful for composting leachate treatment.展开更多
The generation of highly polluting leachate from Sanitary Landfills has prompted the development of technologies applicable to treatment of these liquids. The aim of this study was to determine the kinetics of adsorpt...The generation of highly polluting leachate from Sanitary Landfills has prompted the development of technologies applicable to treatment of these liquids. The aim of this study was to determine the kinetics of adsorption of organic and inorganic matter contained in pre-treated leachate (by advanced oxidation by the Fenton reaction);after two adsorbents were used, first eggshell and then activated carbon. To determine the content of organic and inorganic matter COD was measured;this was the parameter for monitoring the kinetics. The leachate was subjected to advanced oxidation treatment by the Fenton reaction, then the adsorption process was conducted by batch, in two consecutive steps, the first step was the use of eggshell and the second step activated carbon. Due to the oxidation treatment the pH value decreased to 2, after the adsorption eggshell the pH increased to 6.9 and this was maintained in the treatment with activated carbon. The kinetics of adsorption of organic and inorganic matter on eggshell was evaluated by models pseudo-first-order and pseudo-second-order, the better fitting was the latter. The adsorption process was adjusted to the model of Langmuir. The negative value of △Hads indicated that the adsorption process was exothermic, spontaneous and favorable. The separation factor RL of Langmuir Isotherm values indicated that the adsorption of the matter on the eggshell was favorable at different temperatures. Finally, the activated carbon adsorption of liquid obtained from treatment with eggshell was favored with the kinetic model of pseudo second order. With the oxidation process, eggshell adsorption and activated carbon adsorption, the removal COD was 98.6%. The final COD value was fulfilled with the Mexican standard NOM-001-SEMARNAT-1996.展开更多
The UASB reactor was used to reconstruct leachate treatment project of Beijing Asuwei Waste Sanitary Landfill Site,and the commissioning with the UASB reactor was executed.Water quality indicators were determined in t...The UASB reactor was used to reconstruct leachate treatment project of Beijing Asuwei Waste Sanitary Landfill Site,and the commissioning with the UASB reactor was executed.Water quality indicators were determined in the debugging process,and the results showed that the VFA content in the anaerobic tank was controlled within 600 mg/L,which indicated that the water quality did not have the acidified phenomenon.The COD removal efficiency was 50%approximately and NH_3-N concentration showed as light decline when operation stability in anaerobic system.展开更多
This paper presents a study on the biotic/abiotic conditions of the S?o Giácomo sanitary landfill, located near the city of Caxias do Sul, Brazil, through statistical analysis of fourteen physic-chemical data set...This paper presents a study on the biotic/abiotic conditions of the S?o Giácomo sanitary landfill, located near the city of Caxias do Sul, Brazil, through statistical analysis of fourteen physic-chemical data sets for the leachate, produced in the garbage dump site over a long period of years. Different chemometric methods are used in the statistical analysis. For example, the correlations between the variables, related to the degraded organic matter and biological activity, are determined by means of multivariate methods. The results highlight that BOD, COD, VTS, FTS and TS give information on the anaerobic degradation of the organic matter contained in the cells, and suggest that the greater the contribution of the variables with positive weights in PC1 the greater the level of organic matter degradation. The variables TN, Amon Nit. and alkalinity are related to the biological activity and determine the potency of the variables in relation to time. The greater the contribution of the variables related to organic degradation the greater the values in PC2 and the lesser the potency of these variables, whose influence is greater in the second stage of anaerobic degradation. The variables of PC2 is important plans of the contamination of the leached in the bodies hídrics.展开更多
The furrow irrigation tests were done to estimated the efficiency of the HRT(Hydraulic Retention Time) and landfill leachat collected from Dalian Maoyimgzi Municipal Solid Waste Landfill, which contained high level of...The furrow irrigation tests were done to estimated the efficiency of the HRT(Hydraulic Retention Time) and landfill leachat collected from Dalian Maoyimgzi Municipal Solid Waste Landfill, which contained high level of COD (Chemical Oxygen Demand, 3.8 × 104 mg·L–1), TOC (total carbon, 4.8 × 103 mg·L–1), TN(total nitrogen, 2.9 × 103 mg·L–1) and SS (Suspended Solids, 6.5 × 102 mg·L–1), using the reed (phragmites) cultivated onland located in south area of Dalian Jiaotong University. The results showed that: 1) The TN concentration was decreased from 9.8 × 102 mg·L–1 in the landfill leachate to 7.6 × 102 mg·L–1 in the soil water, and the 22.4% of the removal rate;2) The TOC concentration was decreased from 4.8 × 103 mg·L–1 in the landfill leachate to 1.0 × 103 mg·L–1 in the soil water, and the 79.2% of re- moved rate;3) The water concentration in the soil was no significant difference of irrigation between the water and the landfill leachate;4) ΔHRT was 2.1 hours in irrigation 39 L of the water and landfill leachate and 1.3 hours in the 9 L.展开更多
Investigations were conducted over a six-month period on leachate which continuously egresses from a “natural attenuation” landfill site into a fragile ecosystem in the Accra Metropolis, Ghana. Most physico-chemical...Investigations were conducted over a six-month period on leachate which continuously egresses from a “natural attenuation” landfill site into a fragile ecosystem in the Accra Metropolis, Ghana. Most physico-chemical, oxygen demand parameters and nutrient contents were within permissible limits but Total Dissolved Solids (1124 - 13200 mg/l), conductivity (7960 - 24890 μS/cm), Mn (0.12 - 0.94 mg/l), Ca2+ (160 - 356 mg/l) and, more especially chloride contents (1030 - 2967 mg/l) far exceeded respective World Health Organisation (WHO) limits for effluent discharge into the natural environment. Multivariate statistics using Principal Component Analysis (PCA) and Cluster Analysis (CA) suggest significant concentrations of Ca2+, Cl-, and to a lesser extent Zn, Cd, Mn and PO42- relative to the river water samples. Because the landfill was abandoned recently (in 2009), degradation and other breakdown processes of waste material may only have just began, suggesting that the uncontrolled and continuous discharge of chloride and some heavy metal-laden leachate could, in the long-term, substantially impact negatively on the Ramsar Densu wetland and surrounding water bodies, soil and nearby marine ecosystem.展开更多
To compare the treatment effects and the costs of coagulation/Fenton process and Fenton/coagulation process in leachate treatment,fresh and old leachates were respestively treated with these two techniques.The experim...To compare the treatment effects and the costs of coagulation/Fenton process and Fenton/coagulation process in leachate treatment,fresh and old leachates were respestively treated with these two techniques.The experimental results indicate that the highest chemical oxygen demand(COD)removal rate of Fenton reaction on leachate can be acquired under the conditions of pH=3.5,nH2O2/nFe2+=6,mH2O2/mCOD=3,and reaction time=4 h.Polyaluminium chloride(PAC)coagulation has the highest COD removal rate on leachate under the condition of mPAC/mCOD=0.6.Under the optimum reaction conditions,coagulation/Fenton and Fenton/coagulation processes were respestively adopted to treat raw leachate.The data also show that COD removal rate of coagulation/Fenton process on fresh and old leachates are 90.56% and 86.52% respectively and that of Fenton/coagulation process 89.99% and 85.99%,so there is no obvious difference.But the cost of coagulation/Fenton process for leachate treatment is RMB 62.6,lower than that of Fenton/coagulation process.Therefore,coagulation/Fenton process is more optimized than Fenton/coagulation process for leachate treatment.展开更多
Deep-well injection is a cost-effective alternative for industrial wastewater disposal, given the appropriate geology. Fouling of injection well tubing by biofilm or scale is common and reduces the effective diameter ...Deep-well injection is a cost-effective alternative for industrial wastewater disposal, given the appropriate geology. Fouling of injection well tubing by biofilm or scale is common and reduces the effective diameter of the pipe, which results in increased wellhead pressure and lower injectivity. A detailed microbiological composition of biofilms and abiotic fingerprints use of mineral scale from an injection well has not been reported before. Therefore, biofilm and mineral scale samples from three depth intervals within a deep injection well (surface zone, D1= 0 - 61 m;intermediate zone, D2 = 62 - 457 m;and above the injection zone, D3 = 458 - 884 m) with recurrent biofilm development were collected to characterize the mineral composition and microbial community DNA. X-ray diffraction (XRD) analysis of the solids confirms the composition of the solids collected was mostly calcium carbonate (CaCO3) with minor contributions from common mineral salts. Microbiological fingerprinting suggests that methanogenic archaea and sulfate-reducing bacteria both of which are anaerobic biofilm producers were the most prevalent members of the prokaryotic community at all sampled depths. Methanosarcinae spp. increased with increasing depths, unlike other archaea. A non-pathogenic biofilm-producing Entamoeba dispar was the most prevalent member of the microbial domain (>30%) in all samples but was highest at the middle depth. The Chao alpha diversity indices for bacteria, viruses, and protozoans were highest at the shallow depth and gradually declined with increasing depth. The prevalent species above the injection zone depth are not barophilic organisms that thrive at high pressures, rather they are sulfate-reducing bacteria involved in anaerobic dissimilatory sulfate metabolism.展开更多
Leachate pollution from landfills is a major source of environmental hazard in many Nigerian municipalities and there is the need to mitigate its effects. The aim of this study is to examine the leachate pollution and...Leachate pollution from landfills is a major source of environmental hazard in many Nigerian municipalities and there is the need to mitigate its effects. The aim of this study is to examine the leachate pollution and determine the effectiveness of liner system in leachate management of dumpsites in Ogbomosoland. The method of modeling us ing principles of system dynamics was employed to determine the interrelationships of leachate generation components for 50 years. Causal loops indicating the linkage of population, economic status, waste generation per capita and weather conditions to wastes and leachate generation were developed. A set of state model equations for Gas Produced (Gp), Precipitation (Pt), Degradation water-loss (Wg), Leachate Quantity (LQn), were formulated. Leachate management strategies of liner systems were studied, and the effectiveness of Compacted Clay (CC), High Density Polyethylene (HDPE), Low Density Polyethylene (LDPE), Geosynthetic Clay (GC), Silt (SI), Sandy loam (SL), and Sand (SA) liners were examined. A user-friendly computer program for estimating leachate generation per time and breakthrough time for liners was then developed. The results showed that a direct relationship exists between leachate and Gp, Pt, Wg and LQn. Average leachate breakthrough times for the liners, in years, were CC (41.5), HDPE (14.0), LDPE (10.0), GC (1.1), SI (0.1), SL (0.01), and SA (0.00002). In conclusion, dumpsite leachate pollution was established as having negative effects on the groundwater resource. Compacted Clay liner is therefore recommended for use in curtailing its menace.展开更多
文摘Fecal coliform bacteria such as Escherichia coli (E. coli) are one of the main sources of groundwater pollution. An assessment of the transport and Persistence of E. coli in poultry litter amended Decatur silty Clay soil and Hartsells Sandy soil was conducted using soil columns and simulated groundwater leaching. Enumeration of initial E. coli was determined to range from 2.851 × 10<sup>3</sup> to 3.044 × 10<sup>3</sup> CFU per gram of soil. These results have been used in a batch study to determine the persistence rate of E. coli in Decatur silty Clay soil and Hartsells Sandy soil. Results prove that E. coli survival growth rate increases for clay soil later than and at a higher rate than sandy soil. The column study has determined that E. coli was transported at a rate of 3.7 × 10<sup>6</sup><sup> </sup>CFU for Decatur silty loam and 6.3 × 10<sup>6</sup><sup> </sup>CFU for Hartsells sandy per gram of soil. Further, linear regression analysis predictions show higher porosity and soil moisture content affect transport, and Hartsells sandy soil has higher transport of E. coli due to its higher porosity and lower volumetric water content.
基金supported by the National Natural Science Foundation of China(NSFC)(Grant Nos.42272221,41930863)the Fundamental Research Funds for the Central Universities(Grant No.300102272901)+1 种基金the Foundation of the State Key Laboratory of Loess and Quaternary Geology(Institute of Earth and Environment,CAS)(SKLLQG1905,SKLLQGPY2006)the Second Tibet Plateau Scientific Expedition and Research Program(STEP)(2019QZKK0704,2019QZKK0101)。
文摘The geochemical components of the leachate from loess-paleosol deposits can provide information about climaterelated post-depositional processes.For example,leachate lithium([Li]_(leachate))is a potential paleoclimate proxy because lithium is a typical lithophile element that is readily adsorbed by clay minerals during weathering and pedogenesis,and thus stratigraphic variations in[Li]leachatecan reflect these processes.We investigated the[Li]leachatevalues of two loess-paleosols profiles(the Luochuan and Weinan sections),on a north-south climatic gradient on the Chinese Loess Plateau.Independent paleoclimate information was provided by measurements of magnetic susceptibility,grain size,Rb/Sr ratios,and clay mineral content.During the last glacial-interglacial period,[Li]leachateincreased from 0.39 to 1.97μg/g at Luochuan and from 0.67 to 2.45μg/g at Weinan,mainly due to increasing pedogenesis.Based on these results we developed a conceptual model to explain the variations in[Li]leachate,Li^(+)within loess layers is mainly derived from dust input and the decomposition of primary minerals,influenced by the East Asian winter monsoon,while in paleosol layers Li is mainly derived from clay mineral adsorption during pedogenic processes,influenced by the East Asian summer monsoon.
文摘Population growth combined with the rising standard of living of people around the world is the reason for the ever-increasing production of waste which management is costing states a lot of money for its disposal. Among available waste treatment techniques, landfill is one of the most promoted waste management techniques with the emergence of the bioreactor concept. However, the control of biodegradation parameters in order to accelerate waste stabilization is an important issue. For environmental and economic reasons, the technique of leachate recirculation by injection into the waste is increasingly used to improve the degradation of landfilled waste. The injection of leachate is possible using vertical boreholes, horizontal pipes, infiltration ponds or a combination of these. Indeed, moisture is the main factor in waste degradation and biogas production. The migration of leachate to the bottom of the landfill creates low moisture in the upper areas of the landfill reducing the growth of microbial populations. This results in low or no biogas production. The main objective of the present work is to develop a numerical model of leachate recirculation by injection into the waste to rewet the waste and restart biological activity. The analysis of the results shows that the diffusion of the wet front increases with time and depth. The lateral widening of the wet front is slow in relation to the progression of the wet front towards the bottom of the waste cell. This indicates the predominance of gravity effects over diffusion phenomena. The results reveal that the distributed re-injection is the best mode of leachate recirculation because the moisture distribution on the whole waste mass is totally satisfactory and the biogas generation is more important. Leachate recirculation campaigns should be done periodically to rewet the waste, boost microbial activity and hope for a quicker stabilization of the landfill.
文摘After washing and curing, P is transported from the phosphogypsum to the leachate during the phosphogypsum detoxification process, providing two ideas for phosphorus recovery from phosphogypsum leachate: 1) preparation of calcium hydrogen phosphate for feed;2) preparation of calcium phosphate. A ready-to-use calcium oxide slurry was used to recover P from phosphogypsum leachate at a slurry concentration of 20% and a quantitative link between calcium to phosphorus ratio and fixation rate was fitted by mixed use batch experiments, reaction kinetics and thermodynamics, and theoretical calculations were used to demonstrate that phosphorus cannot be completely reused in the preparation of calcium hydrogen phosphate. The findings demonstrated that: a) the residual phosphorus concentration was in the range of 1300 - 1500 mg/L for the preparation of type I feed grade calcium hydrogen phosphate from phosphogypsum leachate;b) the P removal effect could reach 99.99% for the preparation of calcium phosphate from phosphogypsum using the theoretical equation: fixation rate = 87.91 - 10.96(Ca/P) + 3.22(Ca/P)<sup>2</sup> (R<sup>2</sup> = 0.9954);c) The procedure follows the suggested secondary kinetics, and according to the Freundlich isothermal model, the reaction process is under the control of the chemical reaction, with a reaction index of 0.7605. This study can be used as a theoretical guide for the recovery of P from phosphogypsum leachate, the preparation of products to bring about economic by-products, and the purification of wastewater for reuse.
文摘This study was conducted to measure the impact of a municipal solid waste landfill on groundwater quality around Njelianparamba, a solid waste dumping site in Kozhikode district, Kerala state, India. One of the major problems associated with dumping of municipal solid waste landfill is the release of leachate and its impact on surrounding groundwater. In this study, physico-chemical and bacteriological parameters of groundwater samples collected from the region surrounding the leachate area during the pre- and post-monsoon seasons were analysed. The majority of the groundwater samples contained contaminants at a level beyond the permissible limit set by the Bureau of Indian Standards for drinking water quality. The Geographic Information System software of the Environmental Systems Research Institute, (USA) ArcMap 10.1 was used to prepare spatial distribution maps of different parameters and Leachate Pollution Index and Water Quality Index in the study area were applied to assess the overall quality of groundwater. Characterisation of leachate and groundwater samples revealed that, water in the domestic wells has been deteriorated in response to the percolation of leachate. Additionally spatial and correlation analysis revealed that contamination was present maximum within 300 m radius around the landfill site.
基金TheNationalNaturalScienceFoundationofChina (No .5 980 80 12 )andZhejiangProvince (No .5 9912 7)
文摘Population development of key groups of anaerobic and aerobic bacteria involved in municipal refuse decomposition under laboratory landfill bioreactors with and without leachate recycle and inoculation was measured since modeling municipal refuse was landfilled in bioreactors for about 210 days. Hydrolytic fermentative bacteria (HFB), hydrogen producing acetogenic bacteria (HPAB), methane producing bacteria (MPB), sulfate reducing bacteria (SRB), anaerobic and aerobic cellulolytic bacteria and denitrabacteria were enumerated by the most probable number technique. The results showed that the dominant microorganism groups were the methanogenic bacteria including hydrolytic fermentative, hydrogen producing acetogenic and methane producing bacteria. They were present in fresh refuse but at low values and positively affected by leachate recycle and refuse inoculation. The amounts of HFB or HPAB in digesters D4 and D5 operated with inoculation and leachate recycle reached their maximum values of 10 10 -10 12 cells/g dry refuse for HFB or 10 5-10 6 cells/g dry refuse for HPAB on day 60, in digester D3 operated with leachate recycle on day 120 for HFB (10\+9 cells/g dry refuse) or on day 90 for HPAB (10\+5 cells/g dry refuse), and in digesters D1 and D2 on day 210 for HFB (10 9 cells/g dry refuse) or on day 90 for HPAB (10 4-10 6 cells/g dry refuse). The population of methane producing bacteria in digesters D4 and D5 sharply increased on days 60 and 90 respectively, however in digesters D1, D2 and D3 on day 120. Leachate recycle and inoculation changed the cellulolytic microorganisms composition of refuse ecosystem, the higher amounts of anaerobic cellulolytic bacteria were measured in digesters D4 and D5 (10 7 cells/g dry refuse), followed by digesters D3 (10 6 cells/g dry refuse), D2 or D1(10 4 cells/g dry refuse). However, the amounts of aerobic cellulolytic bacteria were much lower than that of anaerobic cellulolytic bacteria. And it was higher in digester D3 than those in digesters D1, D2, D4 and D5 The amounts of SRB and denitrabacteria were also higher in digester D5 than those in digesters D1, D2, D3 and D4 Refuse decomposition could be accelerated by leachate recycle and inoculation in the view of microorganism development.
基金supported by the Sci-technology program of Guangxi Province(No.Guikezhong 1347001)
文摘Soil microbes may be critical players in determining the allelopathic potential of some plants. Low levels of plant community biodiversity in Eucalyptus plantations have been attributed to the allelopathic potential of these tree species. The role of soil microbes in the allelopathic effect of leaf leachates of the hybrid tree Eucalyptus grandis×E.urophylla, was tested in Petri dish assays with Brassica chinensis as a receiver plant. Soils were collected from either a local garden(soil A) or a Eucalyptus plantation(soil B) and half of each soil was sterilized to remove microbes.These soils were then treated with E. grandis×E. urophylla leachates for 0–72 h. Seed germination of B. chinensis was significantly inhibited in soils treated with leaf leachates relative to untreated soils. The inhibitory effect of the leaf leachates was more pronounced in sterilized soils. Total phenolic content was obvious lower in nonsterile leachatetreated soils than in sterile soils. Biomass of B. chinensis was negatively correlated with the total phenolic content in soils.Our findings suggest that soil microbes can alleviate the allelopathic potential of Eucalyptus and thereby its negative impact on plant growth.
基金the National Natural Science Foundation of China (No.50538090)the National Basic Research Program (973) of China (No.2007CB407301)ST Program of Beijing Municipality (No.D0706007040291-01).
文摘Organic micropollutants,with high toxicity and environmental concern,are present in the landfill leachate at much lower levels than total organic constituents (chemical oxygen demand (COD),biochemical oxygen demand (BOD),or total organic carbon (TOC)),and few has been known for their behaviors in different treatment processes.In this study,occurrence and removal of 17 organochlorine pesticides (OCPs),16 polycyclic aromatic hydrocarbons (PAHs),and technical 4-nonylphenol (4-NP) in landfill leachate in a combined anaerobic-membrane bioreactor (MBR) were investigated.Chemical analyses were performed in leachates sampled from different treatment processes,using solid-phase extraction and gas chromatography with electron capture detector and mass spectrometry.Concentrations of OCPs,PAHs,and 4-NP in the raw leachate were detected within the range from ND (not detected) to 595.2 ng/L,which were as low as only 10-7-10-5 percentage of TOC (at the concentration of 2,962 mg/L).The removal of 4-NP was mainly established in the MBR process,in agreement with removals of COD,BOD,and TOC.However,the removals of OCPs and PAHs were different,mainly achieved in the anaerobic process.High removal effciencies of both total organic constituents and organic micropollutants could be achieved by the combined anaerobic-MBR technology.The removal effciencies of total organic constituents were in the order of BOD (99%) > COD (89%) > TOC (87%),whereas the removal effciencies of investigated organic micropollutants were as follows: OCPs (94%) > 4-NP (77%) > PAHs (59%).
基金Supported by Iran Nanotechnology Initiative Council grant to the Nanotechnology Research Institute(NIR)at Babol University of Technology,Iran
文摘As fouling has always been a major drawback of membrane technology, qualitative and quantitative understanding of membrane fouling mechanisms therefore becomes vital in order to help push membrane separation technologies forward. In this study, firstly, self-cleaning Polysulfone(PSf) membranes were synthesized by incorporation of WO_3nanoparticles(0–2 wt%) and subsequent UV irradiation for efficient ultrafiltration(UF)of landfill leachate and dairy wastewater. The membrane surface properties were characterized by scanning electron microscopy(SEM) and contact angle analysis. It was found that UV-irradiated membranes exhibited higher percent COD removals due to the hydrophilicity and photocatalytic properties of nano-WO_3. Subsequently, in order to analyze the fouling behavior of the membranes, a set of experimental data from cross-flow ultrafiltration of municipal landfill leachate and industrial dairy wastewater at 25 °C was obtained. A new model of membrane fouling was proposed based on a resistance in series concept and was fitted well with all experimental data sets.Almost all relative errors of prediction provided by the proposed model were less than 2.5%. In addition, it was revealed that this newly-developed model exhibited smooth transition between the common successive twostep pore blockage-cake filtration phenomena and thus eliminates the need to use separate equations for different mechanisms.
文摘A comprehensive assessment of heavy metals and organic content was performed for leachates produced from a number of old and new landfills in Jordanover 9 month in efforts to set a framework for treatment regulations. All leachates were basic (pH = 7 - 9) and have high electric conductivity and high organic contents (COD = 3000 - 500,000 mg/L, TOC= 500 - 21,000 mg/L). The organic content was inversely proportional to the age of landfill. Heavy metals analysis showed no significant threat of Co, Zn, Pb and Al in any site. Meanwhile, the concentrations of Cr, Mn, Ni, Cd and As were high, exceeding local and international standard limits. Typical physical, chemical and biological treatments can be employed to upgrade the leachates of the active Ghabawi and Akaider sites. Whereas for the high organic strength of Russeifeh, an adsorption treatment by activated carbon is recommended.
文摘Jatropha curcas L. commonly known as “physic nut” is an exotic species that shows invasive characters. Plantation of Jatropha species is being undertaken at a large scale for biodiesel production. The plants defoliate their leaves twice a year and have been shown to possess certain antinutritional factors. Seeds of Jatropha are removed from mature dried fruits for oil extraction and ovary walls are discarded. For the present experiments leachates from sun dried leaves and ovary walls of Jatropha curcas L. were used for analyzing their possible allelopathic effects on the growth of wheat (Triticum aestivum L. cultivar, MP-4010). Leachate treatments result in slight decrease in growth in terms of plant height, leaf area, biomass, spike length and 100 seed weight of wheat and increase in total phenols, tannins, phytic acid and free amino acids. Results suggest that the leachates of leaf and ovary wall of Jatropha curcas are slightly inhibitory, however the impact does not last long. Nevertheless, continuous plantation may lead to accumulation of damaging constituents which reflects the need for further analysis and experimentation.
基金Supported by the Natural Science Foundation of Zhejiang Province(LQ14B060001,Y14F030005)Foundation of Science and Technology Department of Zhejiang Province of China(2013C33019,2015C33232)Science and Technology Project of Lishui City(2015RC23)
文摘This study describes the treatment of composting leachate by the combination of coagulation and nanofiltration process.Poly ferric sulfate(PSF) was used as coagulant,and the effect of p H value and PSF dosage on the coagulation performance was investigated.The results indicated that the chemical oxidation demand(COD)and turbidity removal efficiency could reach to 62.8% and 75.3%,respectively at an optimum dosage of1200 mg·L^(-1)at p H 6.0.During the nanofiltration process,the operation conditions such as temperature and pressure were optimized,89.7% of COD,78.2% of TOC,72.5% of TN,83.2% of TP,and 78.6% of NH3-N were retained when tested at 0.6 MPa at 25 °C.The final leachate effluent concentration of COD,BOD5,NH3-N,TOC,SS was92 mg·L^(-1),31 mg·L^(-1),21 mg·L^(-1),73 mg·L^(-1)and 23 mg·L^(-1),respectively,which reached the local discharge standard.The combination of coagulation-filtration is useful for composting leachate treatment.
文摘The generation of highly polluting leachate from Sanitary Landfills has prompted the development of technologies applicable to treatment of these liquids. The aim of this study was to determine the kinetics of adsorption of organic and inorganic matter contained in pre-treated leachate (by advanced oxidation by the Fenton reaction);after two adsorbents were used, first eggshell and then activated carbon. To determine the content of organic and inorganic matter COD was measured;this was the parameter for monitoring the kinetics. The leachate was subjected to advanced oxidation treatment by the Fenton reaction, then the adsorption process was conducted by batch, in two consecutive steps, the first step was the use of eggshell and the second step activated carbon. Due to the oxidation treatment the pH value decreased to 2, after the adsorption eggshell the pH increased to 6.9 and this was maintained in the treatment with activated carbon. The kinetics of adsorption of organic and inorganic matter on eggshell was evaluated by models pseudo-first-order and pseudo-second-order, the better fitting was the latter. The adsorption process was adjusted to the model of Langmuir. The negative value of △Hads indicated that the adsorption process was exothermic, spontaneous and favorable. The separation factor RL of Langmuir Isotherm values indicated that the adsorption of the matter on the eggshell was favorable at different temperatures. Finally, the activated carbon adsorption of liquid obtained from treatment with eggshell was favored with the kinetic model of pseudo second order. With the oxidation process, eggshell adsorption and activated carbon adsorption, the removal COD was 98.6%. The final COD value was fulfilled with the Mexican standard NOM-001-SEMARNAT-1996.
文摘The UASB reactor was used to reconstruct leachate treatment project of Beijing Asuwei Waste Sanitary Landfill Site,and the commissioning with the UASB reactor was executed.Water quality indicators were determined in the debugging process,and the results showed that the VFA content in the anaerobic tank was controlled within 600 mg/L,which indicated that the water quality did not have the acidified phenomenon.The COD removal efficiency was 50%approximately and NH_3-N concentration showed as light decline when operation stability in anaerobic system.
文摘This paper presents a study on the biotic/abiotic conditions of the S?o Giácomo sanitary landfill, located near the city of Caxias do Sul, Brazil, through statistical analysis of fourteen physic-chemical data sets for the leachate, produced in the garbage dump site over a long period of years. Different chemometric methods are used in the statistical analysis. For example, the correlations between the variables, related to the degraded organic matter and biological activity, are determined by means of multivariate methods. The results highlight that BOD, COD, VTS, FTS and TS give information on the anaerobic degradation of the organic matter contained in the cells, and suggest that the greater the contribution of the variables with positive weights in PC1 the greater the level of organic matter degradation. The variables TN, Amon Nit. and alkalinity are related to the biological activity and determine the potency of the variables in relation to time. The greater the contribution of the variables related to organic degradation the greater the values in PC2 and the lesser the potency of these variables, whose influence is greater in the second stage of anaerobic degradation. The variables of PC2 is important plans of the contamination of the leached in the bodies hídrics.
文摘The furrow irrigation tests were done to estimated the efficiency of the HRT(Hydraulic Retention Time) and landfill leachat collected from Dalian Maoyimgzi Municipal Solid Waste Landfill, which contained high level of COD (Chemical Oxygen Demand, 3.8 × 104 mg·L–1), TOC (total carbon, 4.8 × 103 mg·L–1), TN(total nitrogen, 2.9 × 103 mg·L–1) and SS (Suspended Solids, 6.5 × 102 mg·L–1), using the reed (phragmites) cultivated onland located in south area of Dalian Jiaotong University. The results showed that: 1) The TN concentration was decreased from 9.8 × 102 mg·L–1 in the landfill leachate to 7.6 × 102 mg·L–1 in the soil water, and the 22.4% of the removal rate;2) The TOC concentration was decreased from 4.8 × 103 mg·L–1 in the landfill leachate to 1.0 × 103 mg·L–1 in the soil water, and the 79.2% of re- moved rate;3) The water concentration in the soil was no significant difference of irrigation between the water and the landfill leachate;4) ΔHRT was 2.1 hours in irrigation 39 L of the water and landfill leachate and 1.3 hours in the 9 L.
文摘Investigations were conducted over a six-month period on leachate which continuously egresses from a “natural attenuation” landfill site into a fragile ecosystem in the Accra Metropolis, Ghana. Most physico-chemical, oxygen demand parameters and nutrient contents were within permissible limits but Total Dissolved Solids (1124 - 13200 mg/l), conductivity (7960 - 24890 μS/cm), Mn (0.12 - 0.94 mg/l), Ca2+ (160 - 356 mg/l) and, more especially chloride contents (1030 - 2967 mg/l) far exceeded respective World Health Organisation (WHO) limits for effluent discharge into the natural environment. Multivariate statistics using Principal Component Analysis (PCA) and Cluster Analysis (CA) suggest significant concentrations of Ca2+, Cl-, and to a lesser extent Zn, Cd, Mn and PO42- relative to the river water samples. Because the landfill was abandoned recently (in 2009), degradation and other breakdown processes of waste material may only have just began, suggesting that the uncontrolled and continuous discharge of chloride and some heavy metal-laden leachate could, in the long-term, substantially impact negatively on the Ramsar Densu wetland and surrounding water bodies, soil and nearby marine ecosystem.
基金National Key Project of Water Pollution Control and Treatment Technology,China(No.2008ZX0720700902)
文摘To compare the treatment effects and the costs of coagulation/Fenton process and Fenton/coagulation process in leachate treatment,fresh and old leachates were respestively treated with these two techniques.The experimental results indicate that the highest chemical oxygen demand(COD)removal rate of Fenton reaction on leachate can be acquired under the conditions of pH=3.5,nH2O2/nFe2+=6,mH2O2/mCOD=3,and reaction time=4 h.Polyaluminium chloride(PAC)coagulation has the highest COD removal rate on leachate under the condition of mPAC/mCOD=0.6.Under the optimum reaction conditions,coagulation/Fenton and Fenton/coagulation processes were respestively adopted to treat raw leachate.The data also show that COD removal rate of coagulation/Fenton process on fresh and old leachates are 90.56% and 86.52% respectively and that of Fenton/coagulation process 89.99% and 85.99%,so there is no obvious difference.But the cost of coagulation/Fenton process for leachate treatment is RMB 62.6,lower than that of Fenton/coagulation process.Therefore,coagulation/Fenton process is more optimized than Fenton/coagulation process for leachate treatment.
文摘Deep-well injection is a cost-effective alternative for industrial wastewater disposal, given the appropriate geology. Fouling of injection well tubing by biofilm or scale is common and reduces the effective diameter of the pipe, which results in increased wellhead pressure and lower injectivity. A detailed microbiological composition of biofilms and abiotic fingerprints use of mineral scale from an injection well has not been reported before. Therefore, biofilm and mineral scale samples from three depth intervals within a deep injection well (surface zone, D1= 0 - 61 m;intermediate zone, D2 = 62 - 457 m;and above the injection zone, D3 = 458 - 884 m) with recurrent biofilm development were collected to characterize the mineral composition and microbial community DNA. X-ray diffraction (XRD) analysis of the solids confirms the composition of the solids collected was mostly calcium carbonate (CaCO3) with minor contributions from common mineral salts. Microbiological fingerprinting suggests that methanogenic archaea and sulfate-reducing bacteria both of which are anaerobic biofilm producers were the most prevalent members of the prokaryotic community at all sampled depths. Methanosarcinae spp. increased with increasing depths, unlike other archaea. A non-pathogenic biofilm-producing Entamoeba dispar was the most prevalent member of the microbial domain (>30%) in all samples but was highest at the middle depth. The Chao alpha diversity indices for bacteria, viruses, and protozoans were highest at the shallow depth and gradually declined with increasing depth. The prevalent species above the injection zone depth are not barophilic organisms that thrive at high pressures, rather they are sulfate-reducing bacteria involved in anaerobic dissimilatory sulfate metabolism.
文摘Leachate pollution from landfills is a major source of environmental hazard in many Nigerian municipalities and there is the need to mitigate its effects. The aim of this study is to examine the leachate pollution and determine the effectiveness of liner system in leachate management of dumpsites in Ogbomosoland. The method of modeling us ing principles of system dynamics was employed to determine the interrelationships of leachate generation components for 50 years. Causal loops indicating the linkage of population, economic status, waste generation per capita and weather conditions to wastes and leachate generation were developed. A set of state model equations for Gas Produced (Gp), Precipitation (Pt), Degradation water-loss (Wg), Leachate Quantity (LQn), were formulated. Leachate management strategies of liner systems were studied, and the effectiveness of Compacted Clay (CC), High Density Polyethylene (HDPE), Low Density Polyethylene (LDPE), Geosynthetic Clay (GC), Silt (SI), Sandy loam (SL), and Sand (SA) liners were examined. A user-friendly computer program for estimating leachate generation per time and breakthrough time for liners was then developed. The results showed that a direct relationship exists between leachate and Gp, Pt, Wg and LQn. Average leachate breakthrough times for the liners, in years, were CC (41.5), HDPE (14.0), LDPE (10.0), GC (1.1), SI (0.1), SL (0.01), and SA (0.00002). In conclusion, dumpsite leachate pollution was established as having negative effects on the groundwater resource. Compacted Clay liner is therefore recommended for use in curtailing its menace.
