Leaching Of Contaminants Research Articles

Fire hazard in coal waste dumps – selected aspects of the environmental impact

In areas of coal basins all over the world, wastes are produced along with the process of coal exploitation. Formerly, the wastes were deposited to waste dumps in large amounts. The presence of coal waste dumps at the surface is strictly related to their environmental impact. One of the more significant problems related to the environmental impact is constituted by spontaneous fires. This paper presents the selected aspects related to the negative impact of spontaneous fires on the environment. Based on own experience and scientific literature, the causes and the mechanism behind the formation of fires as well as the factors impacting the development of fires were presented. The paper also concerns the environmental impact resulting from the process of leaching of contaminants from the wastes to surface and ground water as well as fire-related dust and gas emissions to atmosphere. It has been found that the emission of substances to the atmosphere is the most disturbing to the environment. The emissions include significant amounts of toxic substances and greenhouse gases.

The comparison of Durio Zibethinus seed starch extraction for landfill leachate treatment

The characteristics of Durio Zibethinus seed starch (DSS) that is used for landfill leachate treatment was investigated in this study. The DSS was extracted using dry milling (DM-DSS) and wet milling (WM-DSS) methods. The physico-chemical properties and surface morphology of the extracted starches were examined and analysed. Besides that, the efficiency of the extracted starch to remove colour, COD, suspended solid and turbidity were also evaluated and compared. Based on the results obtained, the WM-DSS showed better starch characteristics with high purity and smooth granule particles compared to DM-DSS. In addition, WM-DSS also recorded better leachate contaminants removal even at low dosage. Nevertheless, the performance of leachate contaminants removal for both extracted starch was very low. Thus, further chemical modification is required in order to improve the coagulation ability of the extracted starch. This finding indicated the potential of WM-DSS to be use as a coagulant aid for landfill leachate treatment.

Comparison of the effectiveness of different binders in solidification/stabilization of a contaminated soil

In the current research, solidification/stabilization (S/S) treatment of the contaminated soil using hydraulic binders and additives was used to (1) reduce the mobility of organic and inorganic contaminants and (2) compare the ability of various binders in fixing contaminants. The samples were collected from Franco-Tunisian Petroleum Company, located in Sidi Litayem, Sfax (Southern Tunisia). Leaching tests were performed on contaminated soil, containing metallic elements, and hydrocarbons. Calcium aluminate cement (CAC), ordinary Portland cement (OPC), and ground-granulated blast-furnace slag (GGBFS), additives especially the bentonite and water, were used for S/S treatment. The obtained standard specimens were subjected for treating after treatment the leachability of pollutants, compressive strength (CS), and XRD analysis. The results of analysis conducted on contaminated soils showed that concentrations of metallic elements were in the range of 9.08–427 mg/kg and 15,520 mg/kg of organic compound. Next, 10% of the used binder improved the immobilization of pollutants and gave a satisfactory CS exceeding 1 MPa. Thus, the CAC is more effective in reducing the leachability of metal contaminants than OPC + GGBFS and produces much higher strength, which was of the order of 2.41 MPa. The mechanical characterization was confirmed by XRD analysis. The lowest values of organic compounds are presented in mixtures treated by 10% of used binder, indicating the effectiveness of those with the presence of 10% of bentonite. This work shows that 10% (OPC + GGBFS) + 10% bentonite improved the immobilization of metallic elements and hydrocarbons, thus proving its efficiency due to its low cost.

Influence of hydrothermal treatment on the mechanical and environmental performances of mortars including MSWI bottom ash

Nowadays, in many countries the household waste is more and more incinerated, converting refuse in municipal solid waste incineration bottom ash (MSWI BA). A main concern related to the reuse of BA is linked to the leaching of contaminants, such as heavy metals and salts, to the surrounding environment. To limit this leaching, BA is applied as aggregate in the construction field, since the hydration products of cement are able to immobilize contaminants. Although not always suitable from an environmental point of view, a hydrothermal treatment (HT) can be applied to further increase the contaminants retention, as it stimulates the formation of tobermorite and it densifies the cement matrix. However, not many studies have investigated the influence of HT on cement based mortars and even less have been conducted concerning the optimization of the HT conditions. This study investigates the minimum HT duration for the maximization of mechanical performances and minimization of the environmental impact, for mortars including 25% BA, as sand replacement. The optimal autoclaving duration is found to be 6 h HT, which increases the compressive strength by 30% and it improves the retention of ions as Ba2+, Zn2+, and Cl− by 90%, 60% and 32%, respectively, compared to the standard cured sample. For longer treatment (8 h), the HT is not beneficial, since the leaching of contaminants increases due to the decomposition of reaction products as AFt and AFm.

Time dependent electrical resistivity tomography and seasonal variation assessment of groundwater around the Olushosun dumpsite Lagos, South-west, Nigeria

Time-lapse electrical resistivity tomography (ERT) and seasonal variation studies of the physicochemical properties of groundwater were carried out on the Olushosun dumpsite in Lagos South-western Nigeria, to monitor, track the depth of leachate contamination, and to investigate the impact of seasonal variation on groundwater quality around the dumpsite. Six 2-D resistivity imaging lines were investigated. The independent inversion of the dipole–dipole and pole-dipole resistivity data indicated that contaminated zones are characterised by resistivity values ranging from 0.63 to 12.5 Ωm, and a maximum depth of 141 m was investigated. The pole-dipole models show clear evidence of vertical migration of contaminant with time, as depth of contamination increased from 106 m in May 2014 to about 120 m in December 2015 around the investigated portion of the dumpsite. Analysis of the seasonal variation of the examined physicochemical properties of the water samples taken from wells and boreholes within and around the site showed that there is increase in concentration of TDS and EC in the dry season study and a corresponding increase in the mean concentration of pH, Ca, Mg, hardness, Cu, Cr, NO3, SO4 and Na from the dry season results. Also, there is reduction in the mean concentration of Fe, Zn, Mn, PO4, Cl, and Ni in the dry season when compared with the wet season analysis. Generally, there is a strong correlation between the ERT results and the physicochemical parameters of ground water quality viz-a-viz the contamination status of the Olushosun dumpsite. This increased trend in the dry season period could be attributed to the increase in concentration of the dissolved metals due to evaporation, and on the other hand, dilution effect of the rainfall during the wet season. South East direction of contaminant flow was established from the water table contour lines produced for the area. The research has clearly shown that the groundwater within the study area has been impacted by the leachate from the decomposed refuse at the dumpsite and may constitute danger to the life of residents living around the dumpsite.

Electromagnetic soundings to detect groundwater contamination produced by intensive livestock farming

Feedlots, a set of corrals where livestock is gathered to be fattened for market, are widely spreading in Buenos Aires Province, Argentina. However, the impact of manure as a consequence of this activity on soil organic matter mineralisation and groundwater is still to be explored. Although previous studies have described contamination in sandy soil environments, there is still little evidence on the effect of leachates in soils with a finer texture. The objective of this work was to assess contamination at a pen and its surroundings, by means of the modelling of electromagnetic induction (EMI) soundings carried out annually during two years of feedlot activity.A multifrequency conductivity meter was used for frequencies from 2 kHz to 16 kHz. For the 1D inversion of experimental data, the quadrature component of the secondary H-field normalized by the primary field expressed in ppm was used. The models of each measurement site were joined and 2D sections were obtained along transects in the pen and its surroundings. Groundwater chemical analysis was also performed annually during four years of feedlot activity.With soil depth, model resistivity decreased, reaching values between 6 and 8 Ω m at the unsaturated and the saturated zone. This decline indicated that the leachates from animal manure had increased soil salinity. In the second year of soundings, the layers below the pen showed an important decrease of resistivity. On the other hand, variation of the concentration of nitrates, chlorides and sulfates remained the same both in the phreatic and in the deep well along the four years of groundwater analysis. The concentration of sulfates and nitrates showed a maximum value in the second and in the third year after the beginning of the animal confinement activity in the pen. The following year, with the increase of precipitations, these concentrations decreased. Thus, the modelling of electromagnetic soundings proved to be a useful tool to determine the effect of leachate contamination in feedlot pens.

Stable isotope insights into the weathering processes of a phosphogypsum disposal area

Highly acidic phosphogypsum wastes with elevated potential for contaminant leaching are stack-piled near coastal areas worldwide, threatening the adjacent environment. Huge phosphogypsum stacks were disposed directly on the marshes of the Estuary of Huelva (SW Spain) without any impermeable barrier to prevent leaching and thus, contributing to the total contamination of the estuarine environment. According to the previous weathering model, the process water ponded on the surface of the stack, initially used to carry the waste, was thought to be the main washing agent through its infiltration and subsequently the main component of the leachates emerging as the edge outflows. Preliminary restorations have been applied to the site and similar ones are planned for the future considering process water as the only pollution agent. Further investigation to validate the pollution pathway was necessary, thus an evaluation of the relationship between leachates and weathering agents of the stack was carried out using stable isotopes (δ18O, δ2H, and δ34S) as geochemical tracers. Quantification of the contribution of all possible end-members to the phosphogypsum leachates was also conducted using ternary mixing via the stable isotopic tracers. The results ruled out ponded process water as main vector of edge outflow pollution and unveiled a continuous infiltration of estuarine waters to the stack implying that is subjected to an open weathering system. The isotopic tracers revealed a progressive contribution downstream from fluvial to marine signatures in the composition of the edge outflows, depending on the location of each disposal zone within the different estuarine morphodynamic domains. Thus, the current study suggests that the access of intertidal water inside the phosphogypsum stack, for instance through secondary tidal channels, is the main responsible for the weathering of the waste in depth, underlying the necessity for new, more effective restorations plans.

Groundwater fluoride contamination, probable release, and containment mechanisms: a review on Indian context.

Fluoride contamination in the groundwater has got great attention in last few decades due to their toxicity, persistent capacity and accumulation in human bodies. There are several sources of fluoride in the environment and different pathways to enter in the drinking water resources, which is responsible for potential effect on human health. Presence of high concentration of fluoride ion in groundwater is a major issue and it makes the water unsuitable for drinking purpose. Availability of fluoride in groundwater indicates various geochemical processes and subsurface contamination of a particular area. Fluoride-bearing aquifers, geological factors, rate of weathering, ion-exchange reaction, residence time and leaching of subsurface contaminants are major responsible factors for availability of fluoride in groundwater. In India, several studies have reported that the groundwater of several states are contaminated with high fluoride. The undesirable level of fluoride in groundwater is one of the most natural groundwater quality problem, which affects large portion of arid and semiarid regions of India. Rajasthan, Andhra Pradesh, Telangana, Tamil Nadu, Gujarat, and West Bengal are the relatively high-fluoride-contaminated states in India. Chronic ingestion of high doses of fluoride-rich water leads to fluorosis on human and animal. Over 66 million Indian populations are at risk due to excess fluoride-contaminated water. Therefore, groundwater contamination subject to undesirable level of fluoride needs urgent attention to understand the role of geochemistry, hydrogeology and climatic factors along with anthropogenic inputs in fluoride pollution.

Utilization of waste products as alternative landfill liner and cover materials – A critical review

ABSTRACTLandfill sealing technologies comprise low hydraulic conductivity engineered layers as part of covers and bottom liners, for which clays and geosynthetic materials are conventionally used. In last decades, an increasing number of diverse wastes have been suggested as alternative landfill barrier materials. A comprehensive critical review on the different wastes proposed in the literature as components of landfills barriers is presented. The geotechnical and hydraulic properties, the advantages and disadvantages of the studied wastes are discussed, while their environmental impact issues are emphasized. Overall, several wastes were identified as technically suitable to be used in landfill barriers, nonetheless it is worth to mention that some of them also show concerning leaching of hazardous contaminants that could restrict their practical application in real landfills.

Integrated geophysical characterisation of Sunyani municipal solid waste disposal site using magnetic gradiometry, magnetic susceptibility survey and electrical resistivity tomography

Non-invasive geophysical investigation using magnetic gradiometry, magnetic susceptibility survey and electrical resistivity tomography (ERT) was carried out on the Sunyani Municipal Assembly (SMA) solid waste disposal (SWD) site. The study was aimed at delineating the physical boundaries and the area extent of the waste deposit, mapping the distribution of the waste at the site, detecting and delineating zones of leachate contamination and its preferential migration pathways beneath the waste deposit and its surroundings. The results of both magnetic susceptibility and gradiometric methods displayed in anomaly maps clearly delineated the physical boundaries of the waste deposit with an approximate area extent of 82,650 m2 that are characterised by high magnetic susceptibilities between 426 × 10−5 SI and 9890 × 10−5 SI. They also revealed high magnetic anomalies erratically distributed within the waste deposit attributable to its heterogeneous and uncontrolled nature. The high magnetic anomalies outside the designated waste boundaries were also attributed to indiscriminate deposition of the waste. Similarly, the ERT sections delineated and characterised zones of leachate contamination beneath the waste body and its close surroundings as well as pathways for leachate migration with low resistivity signatures up to 43.9 Ωm. In spite of the successes reported herein using the ERT, this research also revealed that the ERT is less effective in estimating the thickness of the waste deposit in unlined SWD sites due to leachate infiltration into the ground beneath it that masks the resistivities of the top level ground and makes it indistinguishable from the waste body.

Identification of Groundwater Contamination Sources Using Meshfree RPCM Simulation and Particle Swarm Optimization

In this study, a simulation-optimization (SO) model is presented by coupling a meshfree based simulator using radial point collocation method (RPCM) and particle swarm optimization (PSO) as optimizer to identify the unknown groundwater contaminant sources from the measured/simulated contaminant concentration data in the aquifer. To demonstrate the approach, two case studies have been presented. The first example is a hypothetical case which simulates the contaminant releases from several disposal sites in an aquifer during four years release period. The second case considered is a field study where leaching of contaminant, during their storage, from disposal sites at several locations in the aquifer leads to contamination of the groundwater. The goal in both cases was to reconstruct the contaminant release history from the disposal sites and their magnitudes from the given historical concentration data at a few observation wells in the aquifer. It was observed that the source identification model could reconstruct the release histories from the waste disposal sites in both the cases accurately. This study demonstrated that PSO based optimization model with a meshfree flow and transport simulator can be effectively used for groundwater contaminant source identification problems.

Analysis of Groundwater Quality Surrounding Municipal Solid Waste Landfill: Banyuurip Landfill, Magelang, Indonesia

Banyuurip landfill generates leachate containing suspended and dissolved matter, including some heavy metals, a result of waste degradation and decomposition of organic materials. Leachate can infiltrate the soil then contaminate groundwater. Once the leachate infiltration reaches the soil and groundwater, it will contaminate the surrounding environment. In this study, the contamination of leachate into ground water was investigated by measuring the concentration of Manganese (Mn), Iron (Fe) and Free Ammonia (NH3-N) in leachate and dug wells surrounding the landfill. The concentration of Mn, Fe and NH3-N in leachate was found to be 5.42 mg/L, 6.16 mg/L, and 1652 mg/L, respectively. The concentration in the surrounding dug wells located within 500 m from the landfill varied from 0.00 – 0.86 mg/L for free ammonia, 0.00 – 0.31 mg/L for total Fe, and 0.00 – 0.26 mg/L for total Mn. The concentration of Mn, Fe and NH3-N decrease with increasing distance between the landfill and wells.

Riparian Vadose Zone Preferential Flow: Review of Concepts, Limitations, and Perspectives

Core Ideas Riparian ecosystems are hotspots for macropore flow due to their biogeomorphology. Macropore prevalence can reduce riparian buffer pollution mitigation effectiveness. Characterization of macropore morphology and connectivity is needed in riparian zones. An effect of seasonal shallow water table on macropore flow is proposed. Integration of infiltration–soil moisture–macropore flow model into design tools is needed. The design and analysis of surface water pollution control practices such as vegetative filter strips and riparian buffers typically focus on surface runoff, with limited attention given to subsurface flow and transport. Field evidence suggests a prevalence of macropore flow (MF) in the riparian vadose zone (RVZ) due to abundant biological activity (e.g., fauna and roots) and steep hydraulic gradients created by the adjacent stream and the presence of a seasonally shallow water table (SWT). Because rapid leaching and subsurface transport of contaminants can be significant with MF, their prevalence in riparian buffers can negate the intended benefits of this widely adopted surface runoff pollution control practice. While theories exist for modeling preferential flow processes, experimental and modeling techniques are still lacking to characterize in situ RVZ macropore network morphologies at the soil profile and landscape scales. Importantly, the presence of a seasonal SWT can increase MF and transport processes neglected in current analyses. Additional research is needed to evaluate holistic modeling frameworks that can represent MF from measurable parameters at the riparian field scale. In this work, we review various MF theories and concepts suitable to RVZ conditions and identify current limitations and knowledge gaps. We emphasize the use of dual‐permeability approaches as a compromise between model complexity and parameter identifiability. We also identify the need for well‐controlled experimental studies using the latest monitoring technology and validation studies at the laboratory and field scales. Only then can decision‐support tools realistically predict the influence of preferential flow processes on the performance of riparian buffers as a surface water quality control practice.

Analysis of leaks from geomembrane in a sanitary landfill through models of electrical resistivity tomography in South Brazil

Landfills are the main destination of solid waste generated in Brazil. Based on technical criteria, the construction of a landfill aims to minimize environmental impacts since it can present problems of high complexity. This paper discusses the use of electric resistivity tomography applied in a waste cell of a landfill, and its objective is to evaluate the effectiveness of such tool in the detection of possible leachate’s leakage points in the landfill’s geomembrane. The leachate is a liquid effluent characterized by a high content of dissolved salts produced by the decomposition of organic matter. Therefore, a signature of low electrical resistivity defines the presence of this compound in soil and groundwater. The analysis of 12 sections of electrical resistivity tomography in Schlumberger arrangement allowed the estimation of 47 Ω m as the minimum resistivity value for the natural conditions, in addition to the possibility to provide the identification of the area under the waste cell with lower resistivity values. The integration of a software that compiles 2D data into 3D viewing models enabled isosurface adjustments of 7 and 14 Ω m in resistivity maps to − 4 and − 10 m depth levels at the base of the landfill and the aquifer, respectively. These areas define points of infiltration in soil, by leakage at geomembrane in the bottom of the landfill. The results show the applicability of the method in the diagnosis of leachate contamination in a high-complexity environment. In addition, it is possible to establish an effective system for the remediation in a place where the installation of monitoring wells can increase the environmental impact.

Long-term leaching of nutrients and contaminants from wood combustion ashes

With increasing amounts of woody biomass being combusted for energy purposes worldwide, more wood ash is being generated and needs management. As an alternative to landfilling, residues may be utilised for liming and fertilising purposes on forest soils. Comprehensive evaluations of long-term leaching from these residues are needed in order to assess potential environmental impacts associated with their utilisation. Two Danish wood ash samples, one fly ash and one mixed ash (a combination of fly ash and bottom ash), were evaluated in long-term percolation column tests (up to L/S ∼2000 L/kg), in order to quantify the release of major, minor and trace metal(loid)s. While columns of three different lengths were used, the leaching of individual elements could be described as a function of the L/S ratio – irrespective of the column length. At L/S 1000 L/kg, the cumulative releases of K, S, Na, Ca and Rb were at 40–100% of their respective solid contents, followed by Ba, Cr, Sb, Sr and V at 15–40% and Al, Mg, Zn, Cd, Co, Fe, Pb, Tl, Mn and P at < 5%. Speciation calculations indicated that (i) the observed concentrations of Ca, Mg, Al, Ba, Si and sulphate from both ash types could be described through the dissolution/precipitation of a limited set of minerals and that (ii) leaching of silicates should be included in long-term assessment of alkalinity release from wood ashes. Non-equilibrium conditions were indicated by flow interruptions. However, the presence of non-equilibrium did not have significant effect on the calculated cumulative releases at high L/S ratios. Based on the assessment of cumulative releases at L/S 10 L/kg and L/S 1000 L/kg it is concluded that low L/S-based data may not provide sufficient background for prediction of long-term release from wood ash, in particular for Ba, Cr, Sb and V, and less critically also for As, Cd, Cu, Mo and Ni.

A long-term comparative assessment of human health risk to leachate-contaminated groundwater from heavy metal with different liner systems.

The handling and management of municipal solid waste (MSW) are major challenges for solid waste management in developing countries. Open dumping is still the most common waste disposal method in India. However, landfilling also causes various environmental, social, and human health impacts. The generation of heavily polluted leachate is a major concern to public health. Engineered barrier systems (EBSs) are commonly used to restrict potentially harmful wastes by preventing the leachate percolation to groundwater and overflow to surface water bodies. The EBSs are made of natural (e.g., soil, clay) and/or synthetic materials such as polymeric materials (e.g., geomembranes, geosynthetic clay liners) by arranging them in layers. Various studies have estimated the human health risk from leachate-contaminated groundwater. However, no studies have been reported to compare the human health risks, particularly due to the leachate contamination with different liner systems. The present study endeavors to quantify the human health risk to contamination from MSW landfill leachate using multiple simulations for various EBSs. To quantify the variation in health risks to groundwater consumption to the child and adult populations, the Turbhe landfill of Navi Mumbai in India has been selected. The leachate and groundwater samples were collected continuously throughout January-September in 2015 from the landfill site, and heavy metal concentrations were analyzed using an inductively coupled plasma system. The LandSim 2.5 Model, a landfill simulator, was used to simulate the landfill activities for various time slices, and non-carcinogenic human health risk was determined for selected heavy metals. Further, the uncertainties associated with multiple input parameters in the health risk model were quantified under a Monte Carlo simulation framework.

State-Of-The-Art Review of Geosynthetic Clay Liners

An important component of modern landfills is the liner system for the prevention of leachate contamination of surrounding ground. Among landfill liner systems, geosynthetic clay liner (GCL) has gained widespread popularity across the world because of its lower hydraulic conductivity as well as its ability to self-heal local damage, which is almost unavoidable in the field. Over the past few decades, numerous studies have been conducted to examine the performance of GCLs, particularly in regard to hydraulic conductivity, chemical compatibility, water-swelling, self-healing capacity, diffusion characteristics, gas migration, and mechanical behavior. In this paper, a brief introduction on modern GCL products is firstly given. Subsequently, the main findings of previous publications on the critical properties influencing the long-term performance of GCLs are summarized in a comprehensive manner. Finally, further research perspectives on polymer-treated GCLs are presented. This paper provides general insights that help readers gain a state-of-the-art overview of GCLs and trends for future development.

Occurrence, removal, mass loading and environmental risk assessment of emerging organic contaminants in leachates, groundwaters and wastewaters

A comprehensive study is presented, on the occurrence, removal, mass loading, and environmental risk assessment of 19 multi-class emerging organic contaminants in three Municipal Solid Waste landfills and three Wastewater Treatment Plants located at northeast Poland. The target compounds: methylparaben, ethylparaben, propylparaben, buthylparaben, benzophenone, benzophenone-2, benzophenone-3, 3-(4-methylbenzylidene) camphor, N,N-diethyltoluamide, 4-n-octylphenol, 4-n-nonylphenol, triclosan, bisphenol A, diclofenac, clotrimazole, carbamazepine, estrone, 17β-estradiol, diethylstilbestrol were in a wide range of concentration, from below limit of detection to 116 micrograms per liter in leachates and to 18 micrograms per liter in groundwaters and wastewaters. Benzophenone and bisphenol A were found in all analyzed samples. The highest total content of target chemical classes were registered for pharmaceuticals and phenols, 44% and 41%, respectively. Benzophenone-2 and diethylstilbestrol were not detected in all examined samples. In this study, mass loading of target analytes to aquatic ecosystem was calculated. Finally, environmental risk assessment has been presented as the risk quotient for effluent wastewaters and groundwaters on three trophic levels. Diclofenac was found to be the most critical compound in respect of environmental risk.

Utility of Jatropha for Phytoremediation of Heavy Metals and Emerging Contaminants of Water Resources: A Review

Contamination of water resources by organic and inorganic pollutants emitted from industrial and non‐industrial activities is a global concern. The availability of toxic pollutants in high concentrations may be lethal to humans and the natural ecosystem. Established technologies that range from biological to chemical methods are available to ameliorate polluted environments. Traditional remediation technologies including physical, chemical, and thermal processes have several drawbacks. The key point is that the fate of most of their products is not known. Recently, phytoremediation has gathered momentum and has attracted the interest of many scientists. It has more advantages than traditional methods. Phytoremediation uses plant mechanisms to remodel contaminated environments. The technologies include phytoextraction, rhizofiltration, phytostabilization, phytodegradation, and phytovolatization. These approaches differ in purposes and goals, which can be remediation, detoxification, management of water movement, and leaching of contaminants, containment, and stabilization. Jatropha has now emerged as a plant that can be exploited for phytoremediation. The plant is able to survive on degraded land, often poor and fragile soils. Jatropha has the ability to facilitate sequestration, uptake, translocation, and detoxification of pollutants. The objective of this paper is to provide a review of the utility of Jatropha for phytoremediation of heavy metals and emerging contaminants. Phytoremediation is a new area undergoing extensive scientific research and development. Thus, amalgamation of trends in research and development is essential in order to shape and guide future work.

A risk-based approach for assessing the recycling potential of an alkaline waste material as road sub-base filler material

In this work we present an integrated risk-based approach that can be used to evaluate the recycling potential of an alkaline waste material such as incineration bottom ash (BA) as unbound material for road sub-base construction. This approach, which is aimed at assessing potential risks to the groundwater resource (in terms of drinking water quality) and human health associated to the leaching of contaminants from the BA, couples the results of leaching tests for the estimation of source concentrations with the fate and transport models usually adopted in risk assessment procedures. The effects of weathering and of the type of leaching test employed to evaluate eluate concentrations were assessed by carrying out different simulations using the results of laboratory leaching tests. Specifically, pH-dependence and column percolation leaching tests were performed on freshly collected and 1-year naturally weathered BA samples produced from a grate-fired incineration plant treating Refuse Derived Fuel (RDF). To evaluate a broad span of possible scenario conditions, a Monte Carlo analysis was performed running 5000 simulations, randomly varying the input parameters within the ranges expected in the field. In nearly all the simulated conditions, the concentrations of contaminants in the groundwater for the specific type of BA tested in this work were well below EU and WHO drinking water quality criteria. Nevertheless, some caution should be paid in the case of the establishment of acidic conditions in the field since in this case the concentration of some elements (i.e. Al, Pb and Zn) is expected to exceed threshold values. In terms of risks to human health, for the considered utilization scenario the probability of exceeding the acceptable reference dose for water ingestion was usually less than 1% (except for Cr and Pb for which the probability was lower than 3.5% and 7%, respectively).