Metals In Municipal Solid Waste Research Articles

In-situ measurement of alkali metal concentrations and temperatures during the incineration of municipal solid waste and sludge

The release of alkali metals in municipal solid waste (MSW) incineration caused corrosion of thermal equipment and slagging in incinerator. By using a spectrometer and multispectral camera, the concentrations of Na and K, flame temperatures and emissivities in an industrial incinerator with different proportions of food waste, sludge, waste paper and waste fabric were measured in this study. The flame temperatures on the left wall decreased from 1479.5 K to 1366.2 K as the height increased from 13.4 m to 16.9 m. Flame temperatures near the left side of the incinerator were 8.9 % higher than those near the right side, which were caused by the ununiform distribution of MSW. The concentrations of Na and K increased by 67.16 % and 86.9 % with the primary air flow increased by 3969.35 t/h. The average concentrations of Na and K at 16.9 m of the left wall decreased by 25.87 % and 37.53 % with the decreasing of food waste and increasing of sludge. The Na and K contents in fixed carbon were greater than those in volatile matter and ash in fuels. Compared with waste paper and waste fabric, the blending of sludge with food waste was more effective on reducing the release of Na and K. When the proportion of food waste: sludge was set as 8:2, the lowest releases of Na 20.75 ppm and K 5.30 ppm existed in the incineration of food waste and sludge. The concentrations of Na and K decreased by 17.3 % and 46.9 % with the increasing of waste paper, the waste paper was a better alternative to sludge when mixed with MSW.

Sulfur Transformation and Metals Recovery During Co-Gasification of Municipal Solid Waste and Gypsum

AbstractThe fate of sulfur and conversion of metals during the co-gasification of municipal solid waste (MSW) and gypsum is examined here using aspen plus combined with Thermo-Calc for the process model development. The effect of air ratio, temperature, and MSW-to-gypsum feed mass ratio on the syngas evolution, sulfur transformation, and mineral speciation behavior is investigated. The results showed prevention of gypsum sulfur transformation to sulfur dioxide at temperatures below 1050 °C, air ratio < 0.4, and MSW-to-CaSO4 feed mass ratio < 33 wt%. Approximately 90 wt% of feed was transformed into gas products comprising 22% CO and 19% H2. At approximately 900 °C, major minerals formed were CaS (alabandite), melilite, anorthite, rankinite, nepheline, and wollastonite. Melilite, a calcium silicate of aluminum and magnesium, dominated over all other silicates. At temperatures >1000 °C, these minerals transformed into a more stable calcium orthosilicate (CaSiO4) and molten oxysulfide. At temperatures higher than 1200 °C, all metals in MSW were transformed into molten oxides. The results show that syngas and minerals can be recovered during the co-gasification of MSW and gypsum to directly reveal the synergetic benefits of co-processing MSW and gypsum low-value waste materials.

Impact evaluation with potential ecological risk of dumping sites on soil in Baglung Municipality, Nepal

This study is focused on the analysis of the impact caused by the municipal solid waste (MSW) dumping sites in Baglung Municipality of Nepal. For assessment of pollution level, physicochemical parameters of the dumping site's soil and potential ecological risk (PER) index was determined. The nature of the studied dumping site's soil was weakly acidic with high EC and TDS value. The result evidenced the higher values of available nitrogen (N), phosphorus (P) and potassium (K) which signify disposed waste is with high organic content. The concentration of heavy metals in the soil of dumping sites is ranked as Zn>Cu>Pb>Ni>Cr>Cd for the older sites and Zn>Cu>Pb>Ni>Cd>Cr for newer sites. The correlation matrix visualizes that there are positive correlations between Cr-Cd, Pb-Cd, Cu-Zn and Zn-Cd. PCA analysis shows the strong associations of NPK and heavy metals which depict their common source of contamination. The estimated PER index of each and multiple heavy metals represent older dumping sites have a higher potential for causing risk to the environment than the newer ones. This reflects the prospect of environmental threats due to haphazard disposal of MSW. The major implication of this research outcome is the necessity of monitoring and management of possible source of toxic heavy metals in MSW which may contaminate the nearby source of waterbodies by the runoff and infiltration of leachate produced by the dumping site. Also, it is advised to ensure the intense segregation of the MSW prior to final disposal.

Role of microbes in bioaccumulation of heavy metals in municipal solid waste: Impacts on plant and human being

The presence of heavy metals in municipal solid waste (MSW) is considered as prevalent global pollutants that cause serious risks to the environment and living organisms. Due to industrial and anthropogenic activities, the accumulation of heavy metals in the environmental matrices is increasing alarmingly. MSW causes several adverse environmental impacts, including greenhouse gas (GHG) emissions, river plastic accumulation, and other environmental pollution. Indigenous microorganisms (Pseudomonas, Flavobacterium, Bacillus, Nitrosomonas, etc.) with the help of new pathways and metabolic channels can offer the potential approaches for the treatment of pollutants. Microorganisms, that exhibit the ability of bioaccumulation and sequestration of metal ions in their intracellular spaces, can be utilized further for the cellular processes like enzyme signaling, catalysis, stabilizing charges on biomolecules, etc. Microbiological techniques for the treatment and remediation of heavy metals provide a new prospects for MSW management. This review provides the key insights on profiling of heavy metals in MSW, tolerance of microorganisms, and application of indigenous microorganisms in bioremediation. The literatures revealed that indigenous microbes can be exploited as potential agents for bioremediation.

Ecotoxicological and pre-remedial risk assessment of heavy metals in municipal solid wastes dumpsite impacted soil in morocco

Study related to heavy metal pollution and subsequence health risk assessment adjacent to landfills region is indispensable since landfills are a convergence point for hazardous elements which have adverse impacts on the soil and subsoil in the surrounding area with a threat to human health and ecosystem. In this view, assessing the spatial distribution of heavy metals, and evaluating their associated hazards on public health in the areas surrounding open dumpsites in Morocco using pollution indicators, multivariate statistics, and health risk assessment are the main objectives of the current work. The results of this paper indicated that the average concentrations of Zn, Cd, Fe, Cu, Ni, Pb, and Cr were well above their geochemical background. The enrichment of soils by heavy metals was confirmed by the analysis of available fractions of metals using DPTA and CaCl2. Values of pollution indexes (Geo-accumulation index, Pollution Load Index) indicated that soils in the vicinity of the landfill had moderate to high contamination level (PLI = 1.84), especially due to the enrichment by Cd and Pb. Multivariate statistical analysis and Enrichment Factor showed that heavy metals mainly originated from anthropogenic sources related to disposing practices of Municipal Solid Wastes. As well as, the results of the non-carcinogenic risk showed that daily intake for ingestion pathway was higher than for inhalation and dermal contact. Values of hazard index (HI) for trace elements exceeded the safe level (HI > 1), for children. Likewise, the total carcinogenic risk of Pb and Cd in both groups is less than the EPA threshold (10−6), indicating an acceptable carcinogenic risk. This pre-remedial assessment provides useful tools and guidelines, to propose the appropriate remediation technique for this kind of open dumpsites.

Leaching characteristics of heavy metals in MSW and bottom ash co-disposal landfills

Bottom ash (BA) management is often implemented through its co-disposal with municipal solid waste (MSW) in landfills. However, BA co-disposal may lead to heavy metal leaching in landfills. In this study, the effect of BA co-disposal on heavy metal leaching behavior under different scenarios, specifically, MSW, low BA co-disposal (BA_L), high BA co-disposal (BA_H), and BA monofill were investigated. The heavy metal concentrations in the leachate decreased in landfills over time. The leached metals primarily included Zn, Cu, Mn, Pb, Cr, and Cd. The discharge concentration ratio of heavy metals in the leachates exhibited the following decreasing order: MSW, BA_L, BA_H, and BA. In particular, the discharge concentration ratio of Cu in the MSW, BA_L, BA_H, and BA cases ranged from 7.1 × 10−3 to 8.8 × 10−1 (mean = 3.0 ×10−1), 2.8 × 10−4 to 2.0 × 10−1 (mean = 5.4 ×10−2), 9.1 × 10−5 to 3.0 × 10−2 (mean = 5.9 ×10−3), and 4.4 × 10−4 to 7.9 × 10−3 (mean = 1.8 ×10−3), respectively. Moreover, the leaching of the heavy metals could be attributed to waste contents, properties of the heavy metals, and leachate characteristics, such as the pH, chemical oxygen demand (COD), alkalinity, and Cl- content. The presented findings can help clarify the leaching characteristics of heavy metals in BA co-disposal landfills, thereby facilitating the optimization of practical landfills.

Effects of Co-composting of Municipal Solid Waste and Pigeon Pea Biochar on Heavy Metal Mobility in Soil and Translocation to Leafy Vegetable Spinach.

An experiment was conducted to study the effects of co-composted products of municipal solid waste (MSW) and pigeon pea biochar (PPB) on heavy metal mobility in soil and its uptake by spinach. Application of municipal solid waste biochar co-compost (MSWBC) significantly (p ≤ 0.05) reduced the heavy metal content in spinach leaves and roots compared to municipal solid waste compost (MSWC) amended soil. The percent decrease in spinach leaf following the application of MSWBC-10% PPB compared to MSWC was 20.62%, 28.95%, 36.02%, 41.88%, 41.50%, and 41.23% for Cu, Cd, Pb, Cr, Ni, and Zn, respectively. The dry matter yield of spinach and soil organic carbon (SOC) content in soil amended with MSWBC-10% PPB was significantly increased by 32.75% and 47.73%; and 17.62% and 27.45% relative to control and MSWC amended soil. The study concludes that co-composted product, MSWBC, stabilized heavy metals in MSW, reduced their uptake by spinach and thus making it a viable option for safe disposal of MSW.

Pollution and health risk assessment of toxic metals in solid waste dumping site soil and its impact on groundwater: a case study

ABSTRACT Distribution, sources, level of pollution, and associated human health risk assessment of toxic metals in municipal solid waste (MSW) dumping site soil of Tezpur town, located on the northern side of the river Brahmaputra, Assam were investigated. The extent of metal contamination in the MSW dumping site soil was evaluated using enrichment factor (EF), geoaccumulation index (Igeo), contamination factor (Ci f), degree of contamination (Cd), and pollution load index (PLI). Based on these indices it can be concluded that MSW dumping site soil is highly contaminated with Cd and Pb. Moreover, ecological risk indices demonstrated high and low to moderate potential ecological risk due to Cd and Pb, respectively. Although no significant non-carcinogenic risk was found for the measured metals, potential carcinogenic risks of Cr, Pb, Ni, Cd for both children and adults were observed. Source apportionment study was carried out using principal component analysis (PCA) and it was found that metals were mainly originated from two sources: (1) Cu, Pb, Zn, and Cd were mainly from different components of MSW; (2) Mn, Cr, and Ni were from lithogenic materials. The concentrations of Cd and Pb in groundwater source at a radial distance of 20 m from the dumping site exceeded the prescribed limit for drinking water set by World Health Organization (WHO) and raises serious concern to the people residing near the dumping site.

A componential approach for evaluating the sources of trace metals in municipal solid waste

Trace metals concentrations of 25 elements were determined for 22 subcomponents of biodegradable and non-biodegradable waste samples representing the United States municipal solid waste (MSW) stream collected during three separate waste sorts. The subcomponent trace metal concentrations and estimated composition results were used to predict trace metal concentrations present in the overall MSW stream along with MSW compost and waste to energy (WTE) ash, which were compared to health-based standards (i.e., US EPA regional screening levels) and to values previously reported in the literature. These estimates for potentially problematic elements like As and Sb could be attributed to abundant base materials in MSW, while other elements, such as Pb, were calculated at much lower concentrations than other published studies. This suggests that trace metals measured in actual MSW compost and WTE ash could originate not only from MSW base components but also from other sources, such as highly concentrated low-mass wastes (e.g., e-waste). While the removal of small quantity components with high metal concentrations may reduce concentrations of some potentially problematic metals (e.g., Pb), others (e.g., As and Sb) are likely to persist in quantities that impede reuse and recycling since they are present in the more abundant base MSW components (e.g., papers, plastics, organics). Promoting meaningful reductions in potentially problematic trace metals in MSW-derived materials may require reevaluating their presence in higher-volume, lower-concentrated MSW components such as paper, plastics, and organics.

Stabilization of heavy metals in municipal solid waste circulating fluidized bed incineration fly ash by fusion–hydrothermal method

Municipal solid waste circulating fluidized bed incineration (MSWCFBI) fly ash was a hazardous waste, maintaining challenges for disposal. One effective approach was stabilizing the toxic heavy metal ions in the fly ash structures in situ. This work proposed a fusion–hydrothermal method, including fusion pretreatment in nitrogen atmosphere and microwave-assisted hydrothermal process, to treat three MSWCFBI fly ash samples. Specifically, leaching tests were performed to demonstrate the heavy metal stabilization. Through the treatment of the fusion–hydrothermal process, the concentrations of Cd, Cu, Zn, Pb, Ni, and Cr ions leaching from the fly ashes were obviously less than those of the raw fly ash and the sample only treated by hydrothermal process. Meanwhile, the heavy metal ions migrating from the fly ash to the hydrothermal residual liquid were reduced. Importantly, lots of zeolites formed during the fusion–hydrothermal process, such as to bermorite and sodalite. The fusion pretreatment significantly facilitated the conversion of quartz into amorphous silicon and silicate salts. Then, the silicon dissolution was accelerated and zeolite formation was promoted. Eventually, the heavy metal ions could be trapped in zeolite frameworks, enhancing the stabilization of heavy metal. Moreover, the cation-exchange capability values of the three treated fly ash were 1.099, 1.168, and 1.188 meq g−1, two-folder larger than those of the samples only treated by hydrothermal process. In summary, the fusion–hydrothermal method could facilitate the stabilization of heavy metal ions in the fly ash and the as-obtained solid product with high content of zeolite was promising for future applications.

In-situ measurement of temperature and alkali metal concentration in municipal solid waste incinerators using flame emission spectroscopy

In order to address slagging, fouling and high-temperature corrosion problems caused by alkali metals in Municipal Solid Waste (MSW), in-situ measurement of alkali metal in MSW incinerators is needed. The paper presents experimental measurements of temperatures and alkali metal concentrations in two MSW incinerators based on Flame Emission Spectroscopy (FES). Through the analysis of spontaneous emission spectra and a calibration procedure, the concentration of gas phase sodium (Na) and potassium (K), temperature and thermal radiation in the incinerator were in-situ measured by a portable spectral system simultaneously. Experimental results showed MSW composition has significant effect on the measured gaseous Na and K. Higher volatile content in MSW may enhance the alkali metal emission. Besides that, the released gaseous Na and K in the two incinerators are correlated with temperature in incinerators. The study provided a low cost and effective solution for in-situ measurement of temperature and alkali metal concentration in MSW incinerators.

Source Apportionment and Health Risk Assessment of Heavy Metals in Eastern Guangdong Municipal Solid Waste

This research focused on the contents of the five most bio-toxic heavy metals, As, Cd, Hg, Cr, and Pb of 26 municipal solid waste (MSW) samples from the Eastern Guangdong Area. To investigate the apportion of the heavy metal source, Pearson correlation and principal component analysis (PCA) were introduced as major approaches. The health risks posed to MSW workers exposed to heavy metals in MSW were assessed using a Monte Carlo simulation combined with the US Environmental Protection Agency Health Risk Assessment Model. The As, Cd, Hg, Cr, and Pb contents of the east Guangdong MSW were (0.76 ± 0.75), (2.14 ± 4.44), (0.11 ± 0.14), (55.42 ± 31.88), and (30.67 ± 20.58) mg/kg, respectively. Hg, Cr, and Pb were potentially derived from glass, textile, food waste, and white plastic, while As and Cd were mainly derived from soil and food waste in the MSW. The non-carcinogenic risks of heavy metal in MSW exposure to MSW workers could be ignored. However, the heavy metals in MSW might pose carcinogenic risks, with the probabilities for male and female workers being 35% and 45%, respectively. The non-carcinogenic and carcinogenic risk indices were slightly higher for female workers under the same exposure situations.

Composting of municipal solid waste by different methods improved the growth of vegetables and reduced the health risks of cadmium and lead.

Reutilization of putrescible municipal solid wastes (MSW) in agriculture can provide valuable plant nutrients. However, it may pose serious noncarcinogenic health risks for a human when contaminants, especially the heavy metals in MSW, end up in plants through the waste-soil-plant continuum. This study examined the effects of composting methods viz. aerobically (AC), anaerobically (ANC), and aerobic-anaerobically (AANC) composted MSW material on (i) fertilizer value: vegetable yield, nitrogen (N) mineralization, and apparent N recovery (ANR); and (ii) associated health risks: selected heavy metal concentration, daily intake of metals (DIM), health risk index (HRI), hazard index (HI), and target hazard quotient (THQ) when applied to a loamy soil. All the aforementioned compost materials were incorporated into the sandy loam soil filled in pots and carrot and spinach were cultivated for 85 and 90days, respectively. After soil application, between 51 and 56% of the applied organic N was mineralized from ANC material, while the values in case of AC and AANC were 26-31% and 34-40%, respectively. Consequently, dry matter yield and vegetable N uptake from composts were in the order ANC > AANC > AC (P < 0.05). Further, vegetable ANR was the highest from ANC (56 and 56%) than AANC (42 and 45%), and AC (30 and 33%) for spinach and carrot, respectively (P < 0.05). Interestingly, plant uptake of lead and cadmium was lowest from ANC as compared to AC or AANC (P < 0.05), irrespective of the vegetable type. Consequently, DIM, HRI, and THQ for these metals were substantially lower in the former as compared to the latter compost materials. Further, HI from ANC material was 50% lower over the unfertilized control indicating the absence of noncarcinogenic human health risks via vegetable intake. This all indicates that from viewpoint of sustainable waste recycling in agriculture, anaerobic composting is superior to the other composting methods.

Analysis of physical composition and heavy metals pollution of municipal solid waste (MSW) in Beijing

By using on-site sampling and physical-chemical analysis, the physical composition and the contents of heavy metals in Beijing MSW were researched. The result showed that the main components of MSW in Beijing are mainly kitchen waste, the average content of kitchen waste are more than 60% and 50% in summer and in winter, respectively. The pollution of Cu, Hg and Cr are all more serious for MSW in Haidian and Dongcheng district. The heavy metal pollution of MSW in summer is higher than that in winter in Beijing. Seasonal impacts should be taken into consideration when dealing with MSW. The content of heavy metals in MSW exceeded the background value of soil in Haidian and Dongcheng districts. In order to reduce heavy metal pollution, the MSW should be separated collection and treated.

Assessment of heavy metal contamination from municipal solid waste open dumping sites in Bangladesh

Co-disposal of household hazardous materials with municipal solid wastes (MSW) into the open dumping sites is the usual practice in Bangladesh. In this paper, characterization of heavy metals in MSW in open dumping sites at Matuail, Dhaka and Khulna is presented. MSW samples were collected and analyzed for total metals content (Cd, Co, Cr, Cu, Mn, Ni, Pb and Zn) and metal fractions. The analysis results showed that total metals content in MSW at Matuail dumping site is higher than Khulna dumping site and the metals are predominantly associated with fine soil fraction. Both sites contain higher bio-available fraction of metals. The TCLP analysis result showed that the dumping sites are non-hazardous in nature in context of heavy metals pollution. Runoff leachate also contains insignificant concentration of metals. Under the present condition prevailing at both dumping sites, the dissolution of acid soluble metals and the associate risk is very low.

Dynamic Experimental Investigation on the Volatilization Behavior of Lead and Cadmium in the Simulated Municipal Solid Waste (MSW) Influenced by Sulfur Compounds during Incineration

In China, coal, often with a high level of sulfur, is always mixed with municipal solid waste (MSW) in waste incineration plants due to the low heating value and high moisture content of MSW. The influence of sulfur compounds on the volatilization of heavy metals in MSW is of great concern for China’s waste incineration plants. In this study, the continuous dynamic volatilization process of Pb and Cd is investigated by adding different forms of sulfur compounds, elemental sulfur (S), and sodium sulfate (Na2SO4), to the simulated MSW in a laboratory incinerator, at both 1 and 3 wt %, respectively. The experimental results show that the added S begins to affect the volatilization of Pb and Cd at about 700 °C; adding S can lead up to 49.6% reduction in the volatilization of Pb, as the produced sulfur dioxide is promoting the formation of a condensed sulfate phase, and part of Pb is fixed in the form of PbS in the bottom ash. But for Cd, adding S causes up to 15.9% increase in its volatilization as S seizes part of O2 in the air, which is conducive to forming the reducing atmosphere. In the reducing atmosphere, CdO can be easily reduced to Cd, which volatilizes more easily than CdO at high temperatures. In fact, in the reducing atmosphere, the volatilization of Cd far outweighs the volatilization of Pb at 700–800 °C. On the other hand, adding Na2SO4 almost has no influence on the volatilization of lead and cadmium below 900 °C.

Levels of heavy and essential trace metals and their correlation with antioxidant and health status in individuals occupationally exposed to municipal solid wastes.

Recent studies have indicated an increased incidence of toxic neuropathies among waste management workers (WMW) possibly linked to increased detection of heavy metals in municipal solid wastes. The present study evaluated serum levels of some heavy and essential trace metals in relation to oxidant/antioxidant status of WMW. One hundred and twenty-six WMW and 84 non-WMW (control) were recruited. Metal/element concentration was measured by atomic absorption spectrophotometry and oxidant/antioxidant markers were determined using standard procedures. The WMW exhibited significantly ( p < 0.001) decreased ferric reducing ability of plasma (FRAP) and higher levels of ceruloplasmin (Cp) and malondialdehyde. Iron (Fe) and copper (Cu) levels were significantly lower ( p < 0.05) and higher ( p < 0.001), respectively in WMW when compared with control while levels of other trace elements were not significantly different between these groups. Lead (Pb) and chromium levels were significantly higher ( p < 0.001 and p < 0.05, respectively) in WMW while mercury levels were comparable with those of control subjects. In WMW, Cp ( r = -0.182; p > 0.05) and FRAP ( r = 0.277; p < 0.05) negatively and positively correlated with Pb, respectively, while a positive correlation was observed between zinc ( r = 0.230; p < 0.05) and Pb and between Cu ( r = 0.541; p > 0.001) and Fe. Overall, the decreased antioxidant capacity and increased oxidative stress observed in WMW in this study may be related to their blood levels of heavy and essential trace metals. Conscious efforts are required, therefore, to reduce risk and protect WMW from toxic neuropathies and other adverse health consequences of occupational exposure.

Content of Heal Metals in Incinerated Municipal Solid Waste at Kaohsiung City, Taiwan

Two samplings of municipal solid waste (MSW) were conducted at four MSW incineration plants at Kaohsiung City. Samplings were conducted in April and July of 2013 at different seasons. Physical composition was analyzed to find out the content of heavy metals in combustible and incombustible MSW. In 2013, the weight percentage for combustible MSW in Kaohsiung area was at 95.59%. It means that combustible MSW in Kaohsiung area is above 90%. Incombustible metals and non-metals have less content in terms of percentage. The possible reason might be valuable metals have been recycled. In 2013, the average content of heavy metals in Kaohsiung area from high to low came in this order: Pb&gt;Zn&gt;Cu&gt;Cr&gt;Cd. The average content of Pb was 155.10 mg/kg. Cd was at minimal level with average content lower than 1.00 mg/kg. The average content of Pb was 147.84 mg/kg. Cd was at minimal level in Kaohsiung area with average content lower than 1.00 mg/kg. MSW amount in Kaohsiung area for the first sampling in April 2013 and the second sampling in July 2013 were respectively at 35491 and 36062 tons. According to this research, the content of heavy metals in MSW was respectively 146.88 and 411.56 mg/kg. The content of heavy metals were calculated at 5.21 and 15.92 tons, which equal to 0.01% and 0.04% of the total amounts of MSW. After incinerating, they contain byproducts of heavy metals such as ashes, smoke emission, and dust.

Non-segregated municipal solid waste in an open dumping ground: a potential contaminant in relation to environmental health

The present article discusses an overview on the contamination of non-segregated open municipal solid waste (MSW) in and around a dumping site at Garchuk in Guwahati city, Assam, India. Analysis showed depth-wise variations in the concentrations of selected heavy metals in MSW and their subsequent accumulations with increasing depths. Zinc was the most abundant heavy metal in MSW. Six-step selective sequential extractions revealed that most of the heavy metals in MSW were in the residual phase except zinc. Analysis of the leachate from MSW showed high concentrations of fluoride, chloride, ammonium–nitrogen and the ratio of biological oxygen demand/chemical oxygen demand. Concentrations of all the heavy metals in the leachates were higher than the Indian national effluent standards. High amounts of biological oxygen demand, heavy metals, total and fecal coliforms in water samples from the adjoining water body (Deepor Beel, a Ramsar site) of the MSW dumping site indicated its unsuitability for domestic use. Principle component analysis showed that influence of MSW leachate was the major source of water contamination in Deepor Beel. Though accumulation of heavy metals in different vegetables growing in MSW dumping site did not exceed the recommended maximum intake, it was a significant additional source of heavy metals in cooked human diet.

Effect of biostabilization on the release potential and speciation of heavy metals in municipal solid waste

Biostabilization prior to landfilling of municipal solid waste (MSW) has been developed to reduce leachate pollution and increase landfill capacity and stability. Leaching tests were used in this study to examine the effect of biostabilization on the release potential and fate of heavy metals in MSW. The speciation of heavy metals in leached MSW and leachates, and their distribution in different molecular weight (MW) fractions of organic matter in leachate were studied. The results showed that a 44-day biostabilization period could lower the release potential of Pb, Cr, Cd, Cu, and Zn in MSW by 50 to 84%. With the exception for Zn, biostabilization tended to decrease the percentages of the metals in the leachate organic fraction with MW < 1 kDa, but increase those of metals associated with organic colloids and high-MW fractions. Therefore, the effects of biostabilization on the behaviour and fate of Pb, Cr, Cd and Cu in leachate would vary in treatment facilities that use different methods and in the natural environment. Biostabilization only slightly affected the behaviour and fate of Zn, due to an insignificant variation in the speciation and distribution of Zn in different MW fractions. In addition, the aerobic and hydrolytic-aerobic biostabilization processes showed similar release potential, speciation, and distribution of heavy metals in different MW fractions.