Non-sanitary Landfill Research Articles

Dynamic processes in conjunction with microbial response to unveil the attenuation mechanisms of tris (2-chloroethyl) phosphate (TCEP) in non-sanitary landfill soils

Although the environmental and health risks of chlorinated organophosphate esters (OPEs-Cl) have drawn much attention, its environmental behaviors have been insufficiently characterized. As a notable sink of this emerging contaminant, non-sanitary landfills, which may decompose/accumulate OPEs-Cl, is of particular concern. In the present study, the dynamic processes of the typical OPEs-Cl, tris(2-chloroethyl) phosphate (TCEP), in non-sanitary landfill soils were analyzed under anaerobic condition, and the microbial taxa involved in these processes were explored. Our results showed that TCEP could be simultaneously reduced by abiotic and biotic processes, as it was reduced by 73.9% and 65.5% over the 120-day experiment in landfill humus and subsoil, respectively. Notably, the degradation of TCEP was significantly (p < 0.05) enhanced under the stress of a high TCEP concentration (10 μg g−1), while its ecological consequences were found insignificant regarding the microbial diversity and community structure and the typical soil redox processes, including Fe(III)/SO42− reduction and methanogenesis, in both soils. The microbial diversity of subsoil was significantly lower, and acetate was an important factor in changing microbial communities in landfill soils. The microbes in the family Nocardioidaceae and genus Pseudomonas might contribute to in the degradation of TCEP in landfill humus and subsoil, respectively. The metabolism related to sulfur and sulfate respiration were significantly (p < 0.05) correlated with TCEP reduction, and Desulfosporosinus were found as a potentially functional microbial taxon in TCEP degradation in both soils. The results could advance our understanding of the environmental behavior of OPEs-Cl in landfill-like complex environments.

Effects of Environmental Factors on the Spatial Succession of the Bacterial Community in Municipal Solid-Waste Landfills

Secondary pollution control and rapid stabilization of municipal solid waste (MSW) landfills are closely associated with bacterial communities. The spatial variations in bacterial community structure and the environmental factors controlling it were studied by the 16S rRNA gene sequencing of MSW sampled at different depths in a large sanitary landfill (LSL) and a medium non-sanitary landfill (MNSL), respectively. The total nitrogen (TN) and total phosphorus (TP) content in the LSL and MNSL samples displayed a downward trend as the depth increased. However, the organic matter (OM) content followed the opposite trend. Diversity of microbes was highest in the middle layer of both the LSL and MNSL. Firmicutes and Proteobacteria were the dominant phylum both in the LSL and MNSL. In the LSL, the dominant bacteria genera succeeded from Psychrobacter, Pseudomonas to Clostridium, Savagea. However, in the MNSL, the genera succeeded from Uncultured, Pleomorphomonas to Hydrogenispora, Acetomicrobium. The type of landfill and the different environmental factors control the succession of the bacterial community in LSL and MNSL. The pH, OM, TN, and TP will change in the landfill as the landfill depth increased. The impact degree of landfill depth on pH, OM, TN, and TP content in the LSL was 15.3%, 16.1%, 4.9%, and 4.2%, respectively. These values were lower than those in the MNSL. In addition, depth and OM had the strongest correlations but no significance with the dominant bacteria both in the LSL (|Rdepth|average=0.48;|ROM|average=0.36) and MNSL (|Rdepth|average=0.51;|ROM|average=0.36). This indicated that bacterial community succession was mainly dependent on space, time, and MSW characteristics in different types of landfills.

Microplastics spatiotemporal distribution and plastic-degrading bacteria identification in the sanitary and non-sanitary municipal solid waste landfills

The municipal solid waste landfill (MSWL) is an important source of microplastics (MPs) and a huge bioreactor for plastic-degrading microorganisms (PDM). However, the spatiotemporal distribution and degradation mechanisms of MPs in MSWLs are unclear. Therefore, they were studied using the samples drilled in a sanitary landfill (SL) and an non-sanitary landfill (NSL). The results showed that there were a lot of polyethylene (PE), polypropylene (PP), polystyrene (PS), polyurethane (PU), Polyamide (PA), Polyethylene terephthalate (PET) and Polyvinyl chloride (PVC) in the landfill, and their abundance ranged from 0 to 80 items/g. The MPs surface gradually faded, became rough and even yielded cracks and holes with the landfill depth and age increase. The tiny-size MPs (< 100 µm) were the most abundant and their amount significantly increased from 28.14% to 49.13% in SL and from 24.54% to 59.51% in NSL, respectively, while large-size MPs were significantly reduced from the top to the bottom. Lysinibacillus (0.21%~67.87%) and Bacillus (0.10%~67.00%) were the dominate PDMs in SL and Candidatus_Caldatribacterium (5.06%~73.48%) was the dominate in NSL. The PE degradation was closely related to Candidatus_Cloacimonas (r = 0.688*) and Candidatus_Caldatribacterium (r = 0.680*); PS and PA were closely related to Candidatus_Contubernalis (r = 0.595*~0.705*) and PVC was closely related to Candidatus_Caldatribacterium (r = 0.547*). In addition to physical and chemical effects, biological effects can also promote the MPs formation in MSWLs.

Pyrolysis and in-line catalytic decomposition of excavated landfill waste to produce carbon nanotubes and hydrogen over Fe- and Ni-based catalysts – Investigation of the catalyst type and process temperature

Undeniably, non-sanitary landfills existing worldwide pose considerable environmental risks related to air, water and soil pollution. Despite that, the landfill mining concept does not spread swiftly around the world. To prevent its fading into oblivion, it is necessary to transform the perception of landfills as waste to seeing them as stocks of valuable materials. Guided by this idea, this novel study investigates the possibility of producing carbon nanotubes (CNTs) and hydrogen-rich gas, materials crucial for our transition towards a more sustainable future, from excavated waste as these. To the best of our knowledge, this is the first study on catalytic pyrolysis of excavated waste. For this purpose, excavated waste was subjected to pyrolysis followed by in-line catalytic decomposition of the produced pyrovapours. The impact of the catalyst type and catalyst bed temperature on the process performance was analysed. Six types of monometallic and bimetallic Ni- and Fe- based catalysts, synthesised using two methods (the sol–gel and the impregnation method), were considered. Three catalyst bed temperatures were taken into account, namely 700 °C, 800 °C, and 900 °C. The results showed that the bimetallic catalyst prepared by using the sol–gel method (FeNi/Al_Sg) outperformed the other analysed catalysts, yielding 9 mmol/gsample_daf of H2 and 76 mg/gsample_daf of CNTs at 800 °C. The product yields and quality were comparable to those reported in the open literature for homogeneous plastic waste pyrolysis. Eventually, the future research directions were discussed.

Occurrence and spatial distribution of heavy metals in landfill leachates and impacted freshwater ecosystem: An environmental and human health threat.

Municipal landfill leachates are a source of toxic heavy metals that have been shown to have a detrimental effect on human health and the environment. This study aimed to assess heavy metal contamination in leachates, surface water, and sediments from non-sanitary landfills in Uyo, Nigeria, and to identify potential health and environmental effects of leachate contamination. Over the wet and dry seasons, surface water and sediment samples were collected from an impacted freshwater ecosystem, and leachates samples from six monitoring wells. Elemental analyses of samples were conducted following standard analytical procedures and methods. The results indicated that leachate, surface water, and sediment samples all had elevated levels of heavy metals, implying a significant impact from landfills. Pollution indices such as the potential ecological risk index (PERI), pollution load index (PLI), degree of contamination (Cd), modified degree of contamination (mCd), enrichment factor (EF), geoaccumulation index (Igeo), and Nemerov pollution index (NPI) were used to assess the ecological impacts of landfill leachates. The following values were derived: PERI (29.09), PLI (1.96E-07), Cd (0.13), mCd (0.16), EF (0.97–1.79E-03), Igeo (0), and NPI (0.74). Pollution indicators suggested that the sediment samples were low to moderately polluted by chemical contaminants from the non-sanitary landfills, and may pose negative risks due to bioaccumulation. Human health risks were also assessed using standard risk models. For adults, children, and kids, the incremental lifetime cancer rate (ILCR) values were within the acceptable range of 1.00E-06–1.00E-04. The lifetime carcinogenicity risks associated with oral ingestion exposure to heavy metals were 9.09E-05, 1.21E-05, and 3.60 E-05 for kids, adults, and children, respectively. The mean cumulative risk values for dermal exposures were 3.24E-07, 1.89E-06, and 1.17E-05 for adults, children, and kids, respectively. These findings emphasized the risks of human and biota exposure to contaminants from landfills.

Environmental risk assessment and factors influencing heavy metal concentrations in the soil of municipal solid waste landfills.

The environmental risk assessment and the factors influencing heavy metals (HM) in the soil at the municipal solid waste landfill sites (MSWLs) were studied by literature review, field survey, and statistical methods. The results indicated that the dominant HM contamination in the soil at the MSWLs was caused by chromium (Cr) with the Nemero index values (PI) from 22.7 to 44.3 and zinc (Zn) with the PI from 0.7 to 9.8. There were significant differences in the Cr, mercury (Hg), lead (Pb), Zn, and arsenic (As) concentrations between soil samples from sanitary and non-sanitary landfills (NSLs) where HM contamination (PI=10.9) was more obvious. As (CRAAs=2.35×10-4) and cadmium (Cd) (CRACd=1.45×10-4) posed potential carcinogenic health effects. The soil Cd concentration had a significant negative correlation (r=-0.476**) with the landfill age. The soil As concentration had a significant positive correlation (r=0.472**) with rainfall in NSLs. There were significant differences in the As (P=0.042) and copper (Cu) (P=0.042) concentrations between soil samples from the surrounding areas of MSWLs and the base where soil had higher HM concentrations. For the efficient prevention of HM ecological risk, a scientific site selection, undamaged coverage and anti-seepage systems, standardized management, and ongoing monitoring are required.

Pollution threat to water and soil quality by dumpsites and non-sanitary landfills in Brazil: A review

This work presents an overview of environmental studies performed in areas affected by dumpsites and non-sanitary landfills in Brazil, focusing on physicochemical analysis of surface water, groundwater, and soils, as well as geophysical surveys. The objective was to identify the main contaminants found in these areas and to assess their environmental impact, guiding possible intervention measures, indicating the priority areas, and showing whether post-closure activities are mandatory. The results should support governmental actions, especially considering the recent approval of Brazil’s new sanitation framework. The present review assessed 162 publications, which described 104 different municipal solid waste (MSW) disposal sites. The physicochemical parameters of analyzed surface water, groundwater, and soil samples were above Brazilian legislation levels in 74%, 70%, and 24% of the studies, respectively. The parameters more frequently above permissible levels were coliforms, biochemical oxygen demand, dissolved oxygen, and phosphorus for surface water; lead, coliforms, and iron for groundwater; copper, cadmium, lead, and zinc for soil. The results indicated that Brazilian dumpsites are causing negative impacts in surrounding soils and water resources, posing ecological and public health risks that persist even after the site’s closure. Considering that this study provides only a reduced scenario, the dimension of this environmental problem in Brazil is noteworthy. Therefore, it is suggested that not only inadequate disposal is prohibited, but also efficient enforcement methods are adopted and aftercare is appropriately regulated in the country, making it obligatory to establish monitoring plans and implement mitigation techniques to avoid abandoning potentially contaminated areas.

Degradation of the Pharmaceutical and Medical Waste on Landfills Due to Rainwater Infiltration

In Bosnia and Herzegovina, there is a large number of non-sanitary landfills and landfills where pharmaceutical waste from households is being disposed, as well as the medical waste from different health institutions. Expired pharmaceuticals are mostly being disposed there, because there is very little attention paid on waste sorting at the place of its origin. Now days, there are thousands of different medicine, and mainly, along with the other household waste, expired antibiotics are disposed of too. Degradation of expired pharmaceuticals in the environment very often leads to formation of products with completely different properties in regards to the original compound, but also it is not uncommon for those newly formed products to be more toxic than the original ones. This paper analyses the impact of rainwater infiltration on the body of the landfill where expired pharmaceuticals are being disposed of, as well as other medical waste at municipal landfills in Bosnia and Herzegovina. Field studies on the size of the rainwater infiltration as a function of different parameters have been conducted, and also degradation analysis of different expired drugs that are being disposed of in landfills has been performed.

Analiza i mere zaštite od deponijskih požara

Large quantities of solid municipal waste containing a variety of flammable substances, that are disposed of in sanitary and non-sanitary landfills and even illegal dump sites, usually entail a high risk of fire. The level of risk is increased by the presence of methane which is released by municipal waste decomposition. The number of landfill fires varies depending on the morphological composition of the waste, ignition sources, meteorological conditions, time of year, as well as fire protection measures. The paper describes the impact of flammable waste on landfill fires, as well as causes, frequency and procedures in preventing and extinguishing landfill fires.

Heavy metals in leachate, impacted soils and natural soils of different landfills in Malaysia: An alarming threat

Landfills are a potential threat to human health and the environment, especially from the detrimental and toxic heavy metals. This study focuses on the assessment of heavy metals contamination in leachate and surface soils from different landfills in Malaysia. Maximum quality rating scale (QRS) values of As (787) and Cr (552) denotes progressive deterioration of leachate contamination in landfill. The impacted soils showed high heavy metal concentrations especially at non-sanitary unlined landfills, as compared to background values, and natural soil nearby the landfills. In addition, to examine the environmental impacts of the landfill area (soil) in more detail, specific indexes; geo-accumulation index (Igeo), pollution index (PI) and integrated pollution index (IPI) were determined. Maximum As (3.122) and Cd (2.633) for Igeo and As (34.037) and Cd (20.881) for PI revealed that the soil samples in non-sanitary landfills were moderate to strongly polluted. The difference in range of IPI values for sanitary (0.294–0.322) and non-sanitary landfill soils (1.263–1.956) confirmed advanced decline of the soil quality in non-sanitary landfills. Arsenic concentrations were found to be statistically significant (ANOVA) for leachate and impacted soil in landfills investigated. It is also important to realize that rise in metal contents in landfill environments were not only caused by anthropogenic sources such as from the waste disposed, but also some other factors such as redox conditions, anoxic environments, pH, oxidation state of metals and microbial activities. Those conditions will actively promotes leaching of metals from waste and also natural soils in the landfill.

Innovative device to assay leachate production in non-sanitary landfills

Improper landfills (waste dumps) are common waste disposal systems in developing countries and represent sources of environmental pollution. These sites defy researchers and managers because they lack structures to collect liquid, solid and gaseous samples, which make it challenging to monitor local environmental quality. In this work, we show one device for sample collection to monitor leachate quality in a closed waste dump in Brazil. During the installation of this device (Leachate Monitoring Station, LMS), interesting facts about the structural, physical, and chemical composition of an old dump could be visualized. Two different kinds of leachate were found: the accumulated leachate (AL), a thick dark fluid entrapped above non-degraded material, and the mobile leachate (ML), a lighter liquid which flowed into the LMS, and thus was not stagnant like AL. In the AL, the chemical oxygen demand and total ammoniacal nitrogen average concentrations were about 21,500 mg/L and 1000 mg/L, respectively, which were considerably higher than the ML concentrations, of about 1100 mg/L and 200 mg/L, respectively, for the same parameters. Thus, despite the lower concentrations of hazardous substances in the ML, the waste body stores pockets of leachate (AL) with significant concentrations of hazardous compounds, even after 15 years of the dumpsite closure. Moreover, waste solubilization assays showed that the solid material could not be considered inert according to the Brazilian Standard Norm NBR 10004/2004. The installation of the LMS enabled a new understanding about pollutant accumulation inside waste deposits and provided an effective, low-cost tool to monitor leachate production in non-sanitary landfills. The results warn about the risks that old dumpsites still pose to the environment and reinforce the need for a post-care action plan for managing uncontrolled waste deposits.

Microbial structure and diversity in non-sanitary landfills and association with physicochemical parameters.

This study assessed the bacterial populations in a non-sanitary landfill around Guarani Aquifer recharge zone in Brazil. Samples from two different positions (sites 1 and 2) at three different depths were evaluated, totaling six solid waste samples; two samples from an impacted stream were also collected. 16S rRNA sequencing was performed using the Ion S5TM XL platform; 3113 operational taxonomic units (OTUs) and 52 phyla were identified. Proteobacteria (37%) and Firmicutes (28%) were the most abundant phyla in the landfill, whereas Proteobacteria (~ 50%) and Bacteroidetes (~ 10%) were more profuse in surface water samples. Canonical correlation analysis (CCA) enabled us to clearly separate the samples according to their spatial location (site 1 or 2) or environmental matrix (surface water or solid waste samples), showing that microbiological populations are strongly associated with site-specific conditions and the kind of environmental matrix they come from. Environmental factors that mostly influenced the microbial communities were organic matter, oxidation-reduction potential, moisture, alkalinity, nitrogen (TKN), sodium, potassium, and zinc. Exiguobacterium (phylum Firmicutes) was overwhelmingly dominant at site 1 and was associated with higher concentrations of organic matter and potassium. Differently, site 2 did not present such dominant genera and was more diverse having lower concentrations of organic matter and nutrients. Distinct environments co-exist inside the same waste deposit, including zones which are representative of active and closed landfills and the occurrence of considerable physicochemical and microbiological shifts within short distances. Those shifts indicate that microbial populations are well adapted to the heterogeneity typical of urban solid waste, which is possibly beneficial to contaminant degradation. Graphical abstract.

Persistent impacts of an abandoned non-sanitary landfill in its surroundings.

The inadequate disposal of solid waste, a common practice in developing countries, can represent an important pollution source since the closure of these deposits typically does not include the adoption of monitoring, isolation, or remediation techniques. Even so, several disposal areas are abandoned, without performing long-term monitoring in order to evaluate the depletion of contaminants' concentrations. This research aimed at comparing current and historical physicochemical data of water resources surrounding a non-sanitary landfill situated in a Guarani Aquifer recharge zone. The primary objective was to recognize whether significant changes in contaminants concentrations occurred, as well as if the area still poses a significant threat to the environment, 20years after ending disposing activities. Samples from eight monitoring wells and three surface water points (upstream and downstream to the deposit) were evaluated in the periods of 1996-1997 and 2016-2019. The parameters pH, electrical conductivity (EC), alkalinity, chemical oxygen demand (COD), oxidation-reduction potential (ORP), chloride, nitrate, iron, manganese, calcium, and magnesium were investigated. Contamination has been detected in the landfill surroundings since the ending of the waste disposal (1996-1997), even though its intensity reduced within short distances from the waste mass. Nevertheless, no statistical variation occurred in 20years' time considering COD, chloride, calcium, magnesium, and ORP. Moreover, increases of EC, pH, alkalinity, iron, and manganese concentrations were observed for the years of 2016-2019. The results indicate that the evaluated contaminants do not suffer depletion in the surroundings of non-sanitary landfills in sandy aquifers, considering a time span of 20years. This study also suggests that those areas need to be adequately remediated to permit other future land uses.

Sanitary landfill improved CNPS microbial functional gene abundance compared to non-sanitary landfill

The landfill soil microbes related to nutrient cycling, such as carbon (C), nitrogen (N), phosphorus (P), and sulfur (S) cycling, are changed by continuous waste decomposition. Monitoring the changes that occur in CNPS functional genes in different types of landfill cover soils as a whole is vital to our understanding of microbial function in element cycling. The high-throughput quantitative polymerase chain reaction–based chip (HT-Q-PCR) method was used to explore differences in the abundance of 71 CNPS functional genes in cover soils (0–20 cm, 20–40 cm, and 40–60 cm) from two types of landfills (sanitary and non-sanitary) and to examine the soil pH and the concentrations of C, N, P, S, and 6 heavy metals. The absolute abundances of CNPS functional genes varied greatly, with the highest gene abundance reaching 5.28 × 109 copies per gram of soil, and 11% (8/71) of the genes not detected. Among the detected genes, there was a much higher functional gene abundance in the sanitary landfill than in the non-sanitary landfill cover soils, and the difference in gene abundance became more significant with increasing sampling depth. In addition to landfill type and sampling depth, the soil pH, soil dissolved organic carbon (DOC), available N (AN), and available S (AS) correlated significantly to functional gene abundance. Conversely, soil heavy metals, such as Cu, Cd, Cr, Zn, and Ni, had no effects on functional gene abundance, which might be due to their low contents. Our results suggest that sanitary landfill increases soil CNPS gene abundance compared to that of non-sanitary landfill. The findings provide suggestions for landfill treatment and ecological protection, especially regarding vegetation restoration.

Assessment of municipal opened landfill and its impact on environmental and human health in central Thailand

Purpose: Non-sanitary landfill or open dumping stored both non-hazardous and hazardous waste disposed from households, restaurants, agricultural activities, and industrial sectors that could contaminated to the environment. This study aimed to assess the environmental status and its impact of opened solid waste landfill located nearby agriculture and natural resources in municipal area of central Thailand. Methods & Materials: Soil and water samples were collected from six locations of landfill and surrounding areas such as paddy field and water reservoir at two-month interval for six consecutive months. Heavy metal contamination and quality of soil and water including physical, chemical, biological parameters were analyzed by using standard methods. Agricultural activities of the land nearby the landfill and practice behavior of workers in the landfill have been observed. Results: We found Salmonella spp. and Clostridium perfringens contaminated in soil samples collected from both inside and outside of landfill. Heavy metals such as Iron (Fe), Magnesium (Mg) and Aluminum (Al) were found in high level, additionally, contamination of Copper (Cu) in soil collected inside the landfill was presented. Water collected from leachate and natural resource was contaminated by coliform bacteria and Salmonella spp. Level of Fe in all water samples was high, however this amount was not above limited value. Inappropriate self-protective and non-hygienic behavior of workers in the landfill was also found. Conclusion: Soil and water samples collected from the opened landfill were contaminated with bacteria. Occupational hazard, protective awareness and protective measure of people who exposed to the landfill such as garbage collectors and farmers should be concerned. Level of heavy metals in soil and water, especially in paddy fields around the landfill should be periodically monitored.

Toxicological Characteristics of Leachate from Non-Sanitary Municipal Solid Waste Landfill

This research evaluated the toxicity and hepatotoxic effects of non-sanitary MSW landfill leachates on freshwater fish, Oreochromis niloticus. Toxicity test was conducted based on the OECD Guidelines for Testing of Chemicals. Fish was exposed to different leachate concentrations for 96 hours under static method. Acute mortality was closely monitored and analyzed using the Probit method. During the toxicity test, observations of fish test samples were performed on behaviour, mortality, and anatomical pathology. Results showed the content of ammonia, nitrate, sulphate, BOD, COD, and Zn in non-sanitary landfill leachate of Cot Padang Nila was found in high concentration. Against the leachate, freshwater fish, Oreochromis niloticus has acute mortality, LC50 for 96 hours at the value of 20.172%. High mortality rate of fish was strongly influenced by the concentration level given (P<0.05). During the toxicity test, observations of fish behavioural changes showed symptoms of acute and sub-acute poison, including acceleration of operculum motion, hyperactivity, sudden jerks and loss of swimming power, and hyperpigmentation. Some fish organs undergo pathologic changes in the eyes, fins, scales, gills, and spleen. Histopathologically, gill tissue changes include epithelial release of lamella, hyperplasia, lamella fusion, and necrosis. The histopathologic features of liver show changes including fat degeneration, congestion, haemorrhage, inflammatory cell infiltration, and hepatocyte cell necrosis.

INTEGRATION OF RESOURCE RECOVERY INTO CURRENT WASTE MANAGEMENT THROUGH (ENHANCED) LANDFILL MINING

Europe has somewhere between 150,000 and 500,000 landfill sites, with an estimated 90% of them being non-sanitary landfills, predating the EU Landfill Directive of 1999/31/EC. These older landfil ...

Adsorptive removal of noxious cadmium from aqueous solutions using poly urea-formaldehyde: A novel polymer adsorbent

Cadmium is a heavy metal toxic that enters water resources through industrial, household, agricultural waste and non-sanitary landfill of urban and industrial wastes. Pollution of water resources by cadmium increases incidence of diseases including Itai-Itai, kidney disorders, cancer, chromosome effects and kidney tubular damages in low exposures. The aim of this study is to study the efficiency of a new poly urea-formaldehyde adsorbent in the removal cadmium ions from aqueous solutions. The effect of different variables such as initial pH, contact time, initial concentration of cadmium and test of real wastewater samples were evaluated. In addition, laboratory data of cadmium adsorption by urea-formaldehyde adsorbent were matched to Langmuir, Freundlich and Temkin isotherm models. The results of the study showed that maximum adsorption capacity obtained by Langmuir model was 76.3?mg/g at pH?=?5.5. Laboratory adsorption data matched mostly by Freundlich isotherm model (R2 =0.999) which indicates that adsorption of cadmium ions on heterogenic surfaces of poly urea-formaldehyde happens by chemical adsorption mechanism. Generally, the results of the study showed that new poly urea-formaldehyde adsorbent can be efficiently used to remove highly concentrated cadmium ions from aqueous solutions.

Characterization of induced metal responses of bacteria isolates from active non-sanitary landfill in Malaysia

Microorganisms have specific genetic mechanisms towards their resistance to heavy metals, and may exhibit tolerance by immobilizing metal on cell surfaces or transforming them into less toxic forms. Unfortunately, selecting microbes that are metal-specific is a problem in remediation processes, and require identification of a process/strategy for evaluating metal interaction and bioreduction potential of microbial species before utilization for biodegradation/reduction in polluted soils. The study aimed to express the metal tolerance and interaction within the microbial abundance in an active non-sanitary landfill soil in Malaysia, as a developmental strategy for selecting bacterial species important for future remediation of metal-polluted soil. The characterized soil exposed the contamination level from heavy metals at the selected active non-sanitary landfill. Further assessment on the microbial community identified and typed the bacterial diversity in the contaminated area. Exposure to varying metal solutions showed the sensitivity of the bacteria species. Microbiological media infused with Pb, Al and Mn solutions demonstrated absolute heavy growth for all the six microbes studied at metal concentrations of 5–20 ppm. Comparison between the microbes indicates that Burkholderia vietnaminesis expressed higher metal resistance. In general all the isolated microbes demonstrated the ability to tolerate and resist metals at different concentrations. Bacterial isolates, mainly the gram-positives are metal-specific and may act as potential agent for remediation of heavy metal in contaminated sites.

Selected microbial diversity of contaminated landfill soil of Peninsular Malaysia and the behavior towards heavy metal exposure

Microbes function normally and effectively when the site of action or immediate environment is intact and unpolluted. Given that microbes can significantly improve the bio-geochemical cycling of toxic heavy metals or the remediation of metal-contaminated environments, understanding the effect of microbe diversity on heavy metal pollution caused by leachate seepage is imperative. This study focused on the difference in the distribution of microbial species in non-sanitary landfill soil of Peninsular Malaysia (operational and non-operational status) regarding the heavy metal tolerance of the bacterial species. Soil and leachate characterization identified the level of pollutants in the landfill environment. Hence, microbial isolation and identification generated the microbial diversity of the contaminated landfill soils of Peninsular Malaysia. Exposure to Hg concentrations (5–20ppm) showed that all the organisms survived with a heavy growth pattern. All strains showed varied resistance to the heavy metals. Pseudomonas mendocina demonstrated the highest resistance to metal exposure. Bacillus pumilus was absolutely resistant to the heavy metals used in the study, except Ni. A comparison of isolates from operational and non-operational landfill sites in Peninsular Malaysia suggests higher susceptibility to chromium ions than to other highly toxic metals, especially lead and mercuric ions. The behavior/response of the isolated microbes suggests suitability for enhanced bioremediation of heavy-metal-polluted environments.