Fly ash treatment via conventional and microwave-assisted organic acid leaching: kinetics and life cycle assessment.

Heedless disposal of oil-based fly ash contributes to the contamination of the air, water, and soil. Acid leaching of industrial solid wastes is recognized as a versatile, cost-effective, and environmentally friendly solid waste treatment approach. The present study investigated the viability of conventional leaching (CL) and microwave-assisted leaching (MAL) of predominant heavy metals from Mazut-burnt fly ash. For this purpose, the practicality of four organic acids with various specifications (ascorbic, gluconic, citric, and oxalic acids) on the dissolution efficiency of fly ash components was examined. Utilization of oxalic acid led to achieving full V recovery, complete Fe removal, and Ni enrichment in the residue in both CL and MAL setups. The Ni content of the sample was enriched from 6% in the calcinated sample to 23.7% in the oxalic acid leaching residue. Using citric acid resulted in the co-extraction of V, Ni, and Fe with nearly 70% V, 50% Ni, and 89% Fe dissolved in CL. The dissolution efficiencies were slightly lower in MAL. Oxalic acid was selected as the most promising organic acid reagent for fly ash treatment, so its CL kinetics was studied and defined by the shrinking particle model. The model showed that the controlling steps in the leaching of V differ over time, changing from a chemical reaction before 60 min to fluid film diffusion or mixing afterward. The kinetic study proved MAL as an effective technique in overcoming the leaching kinetic barriers. A life cycle assessment study was conducted to determine the environmental impacts of the proposed process. Accordingly, the MAL using oxalic acid was the most environmentally friendly process among the studied ones, and the utilization of microwaves leads to the reduction of the leaching processes' environmental impacts by decreasing the processing time.

Characterization of MSW incineration bottom ash for use as structural fill in reinforced soil structures: Geoenvironmental, geotechnical and economical assessment.

The study presents the geoenvironmental and geotechnical characterization of MSW incineration bottom ash (IBA) and examines its reuse as structural fill in reinforced soil structures (RSS).The suitability of reuse has been assessed with regard to international regulatory standards. The prime focus of the work remains on evaluating the pullout response of geosynthetic reinforcements through IBA fill to determine the interaction coefficient, which has never been addressed in the literature. The economic viability of using IBA instead of locally available river sand for a 12 m high MSE wall is also established. The column leaching test results confirm that IBA can be utilized in RSS with suitable design measures. The geotechnical investigation shows that IBA is a well-graded, non-plastic lightweight material with adequate drainage and high shear strength. The pullout test results demonstrate that the interaction coefficient of polymeric strips and geogrid in IBA (0.73-1.53 and 0.79-1.91, respectively) is comparable or higher to materials conventionally used as structural fill in RSS, indicating adequate bondage between IBA and geosynthetic reinforcement. Further, it is estimated that using IBA as a substitute for available river sand in the vicinity can potentially reduce the overall RSS project cost by 15-20%, even if IBA has to be transported 50 km away from the project site.

Solidification/stabilization and risk assessment of heavy metals in municipal solid waste incineration fly ash: A review.

Incineration is currently the most common method of treating municipal solid waste. Municipal solid waste incineration fly ash (MSWI FA) contains a high concentration of toxic heavy metals (HMs), making it a hazardous waste. A series of detoxification treatments are required to reduce the toxicity of fly ash. Furthermore, the environmental risk of MSWI FA after treatment is becoming a cause of concern. This paper reviews the primary ash properties, pH, liquid-solid ratio, and other factors (microorganism, type of leaching agents, etc.) that affect the leaching of HMs from MSWI FA, compares and summarizes the most widely applied solidification/stabilization (S/S) techniques. In particular, models and methods for the environmental risk assessment and prediction of HMs are classified and described in detail. Finally, the inadequacy of current S/S techniques for MSWI FA is pointed out, which may be useful for upcoming studies on this topic.

Life cycle assessment for the production of MSWI fly-ash based porous glass-ceramics: Scenarios based on the contribution of silica sources, methane aided, and energy recoveries.

Municipal solid waste (MSW) production in the world has increased by 60 % in recent years. Incineration of MSW reduces their volume in conjunction with energy recovery. Incineration produces two residues, namely bottom ash (BA) and fly ash (FA), with high concentration of heavy metals and organic pollutants, especially for FA, making them an environmental concern. Vitrification is a costly, highly safe high temperature treatment, ensuring encapsulation of heavy metals. FA vitrification requires a source of silica to be able to get vitrified. In this study, we have proposed valorizing treated (vitrified) FA through the production of porous glass-ceramics, subsequently to MSWI. The entire process, from incineration to glass-ceramics production, was evaluated for several scenarios by Life Cycle Assessment (LCA) using Sima Pro 9.0. Three main scenarios were analysed; each one considering a different silica source: bottom ash (BA), glass cullet (G) and silica sand (S), and for each scenario, three thermal recovery subscenarios were assumed: no thermal recovery used to heat FA prior to vitrification (N), heating FA prior to vitrification using incineration gases thermal recovery (T) and methane-combustion-aided thermal recovery, which exploits methane combustion to further increase the gases temperature (M). Results proved that vitrification was a technically feasible and environmentally-energetically sustainable technology. The result indicates that the most eco-sustainable scenario was using bottom ashes as a silica source together with methane-combustion-aided recovery: 0.467 kgCO2,eq, 5.83 × 10-8 carcinogenic-CTUh and 9.26 MJ required per kg of glass-ceramics produced.

Combined effect of silica fume and fly ash as cementitious material on strength characteristics, embodied carbon, and cost of autoclave aerated concrete.

Aerated concrete (AAC) or lightweight concrete is primarily used for non-load bearing structures in construction work. Generally, it is produced with cement as a main binding ingredient, and the production of cement is blamed to contribute 7 to 8% of CO2 emission in the environment. In addition, the dumping of industrial wastes is also a great environmental concern. This research is an attempt to produce low-cost and sustainable aerated concrete utilizing silica fume and fly ash as partial substitution to cement without compromising the fundamental properties of aerated concrete. The current study was divided into two phases: in the first phase, the silica fume was substituted up to 20% with a variation of 5% in each mix. In the second phase, the fly ash was replaced with cement in three variations, i.e., 10%, 20%, and 30% containing an optimum proportion of silica fume obtained in phase 1. The aluminum powder was added at 0.4% by weight of binder to introduce aeration in concrete. Before testing, samples of aerated concrete were cured with steam in an autoclaving machine for 9 h at a pressure and temperature of 1.5 bars and 127 °C respectively and oven-dried at a temperature of 105 °C for 24 h after steam curing. From the experimental results, the highest compressive and split tensile strength of AAC was recorded when 15% of the cement was replaced with silica fume and 30% of the cement was replaced with fly ash combined. At this proportion the least density was also recorded which showed the lightweight of AAC without compromising the strength characteristics. In addition, the reduction of 42.64% and 32.4% of embodied carbon and cost was observed respectively.

Environmental damage caused by coal combustion residue disposal: A critical review of risk assessment methodologies.

Coal combustion generates almost 40% of world's electricity. However, it also produces 1.1 billion tons of coal combustion residues (CCR) annually, half of which end up in landfills. Although current regulations require proper lining and monitoring programs, the ubiquitous old, abandoned landfills are often not lined nor included in these programs. In addition, the total number of coal ash disposal sites and their status in the world is unknown. Therefore, this article reviews the environmental damage caused by CCR and three commonly used risk assessment methodologies: leaching assessment, groundwater assessment, and toxicity testing. Leaching methods are usually the first step in coal ash risk assessment, however, a large number of methods with different parameters make a comparison of data difficult. Groundwater pollution is commonly detected near coal ash disposal sites, but other anthropogenic activities may also exist nearby. Therefore, multivariate statistical methods and isotope traces should be used to differentiate between different sources of pollution. So far, both stable (δ18O, δD, δ11B, δ34S, δ7Li) and radiogenic (87Sr/86Sr, 206Pb/207Pb) isotopes have been successfully used as coal ash pollution tracers. Coal ash also negatively affects biota, reduces the diversity of organisms, affects children's health, and increases the risk for developing various diseases. Toxicity studies are great for early screening of coal ash safety; however, they provide no insights into mechanisms causing the adverse effects. Future directions are also proposed, such as the development of new 'low-level' detection methods for coal ash pollution and sustainable and selective method for recovery of critical elements.

Treatment of environmental contamination using sepiolite: current approaches and future potential.

To evaluate the potential of sepiolite-based materials to resolve environmental pollution problems, a study is needed which looks at the whole life cycle of material application, including the residual value of material classified as waste from the exploitation of sepiolite deposits in the region or from its processing and purification. This would also maximize value from the exploitation process and provide new potential for local waste management. We review the geographical distribution of sepiolite, its application in the treatment of potentially toxic elements in soil and across the wider landscape, an assessment of modification and compositional variation of sepiolite-based applications within site remediation and wastewater treatment. The potential of sepiolite-based technologies is widespread and a number of processes utilize sepiolite-derived materials. Along with its intrinsic characteristics, both the long-term durability and the cost-effectiveness of the application need to be considered, making it possible to design ready-to-use products with good market acceptance. From a critical analysis of the literature, the most frequently associated terms associated with sepiolite powder are the use of lime and bentonite, while fly ash ranked in the top ten of the most frequently used material with sepiolite. These add improved performance for the inclusion as a soil or wastewater treatment options, alone or applied in combination with other treatment methods. This approach needs an integrated assessment to establish economic viability and environmental performance. Applications are not commonly evaluated from a cost-benefit perspective, in particular in relation to case studies within geographical regions hosting primary sepiolite deposits and wastes that have the potential for beneficial reuse.

Assessment of strength and leaching characteristics of heavy metal-contaminated soils solidified/stabilized by cement/fly ash.

Solidification/stabilization technique has been widely adopted to remediate the heavy metal-contaminated sites. In the present work, the strength and leaching characteristics of the contaminated soils solidified/stabilized by cement/fly ash were systemically investigated. Electrical resistivity was also measured to establish empirical relationships for assessment of remediation efficacy. Tests results showed that the unconfined compressive strength increased and the leached ion concentration decreased with increasing curing time. In contrast, the unconfined compressive strength decreased and the leached ion concentration increased with increasing initial heavy metal ion concentration in the specimen. For the strength characteristic, the most notable detrimental effect was induced by Cr3+ and the least was induced by Pb2+. For the leaching characteristic, the trend was reversed. The electrical resistivity of the tested specimen increased significantly with increasing curing time and with decreasing initial ion concentration. The electrical resistivity of the Pb-contaminated specimen was higher than that of the Zn-contaminated specimen, which in turn was higher than that of the Cr-contaminated specimen. Empirical relationships between the strength, leaching characteristic, and electrical resistivity were established, which could be adopted to assess the remediation efficacy of heavy metal-contaminated soil solidified/stabilized by cement/fly ash.

Life cycle assessment of autoclaved aerated fly ash and concrete block production: a case study in China.

With the rapid development of construction industry, consumption of concrete block has increased rapidly in China. As a kind of green building material and resource comprehensive utilization product, autoclaved aerated fly ash and concrete block have better performance in terms of heat preservation, sound insulation, and fire resistance. However, some typical issues are associated with autoclaved aerated fly ash and concrete block production process such as energy and material consumption as well as pollutant emissions. To examine the environmental and economic impacts of its production process is imperative. Choosing 1 m3 of autoclaved aerated fly ash and concrete block product as functional unit and "cradle to gate" as system boundary, a life cycle inventory is developed. The key processes and key materials with significant environmental impact are identified. Results show that the top four environmental impact categories are marine ecotoxicity, freshwater ecotoxicity, freshwater eutrophication, and human toxicity. Key processes are fly ash slurry production, lime grinding, and steam curing processes. These processes account for 46.58%, 26.00%, and 19.62% of the total environmental load respectively. The key materials are cement, lime, and natural gas, which account for 44.91%, 22.79%, and 20.61% respectively of overall environmental impact. Sensitivity analysis shows that the fly ash slurry production should be optimized preferentially, followed by lime grinding and steam curing processes. These findings are helpful to facilitate the sustainable production of autoclaved aerated fly ash and concrete block.

Residue concentrations and profiles of PCDD/Fs in ash samples from multiple thermal industrial processes in Vietnam: Formation, emission levels, and risk assessment.

The residue concentrations and congener profiles of polychlorinated dibenzo-p-dioxins/furans (PCDD/Fs) were examined in fly ash and bottom ash released from different thermal industrial processes in Vietnam. PCDD/F concentrations and toxic equivalents (TEQs) in the ash samples varied greatly and decreased in the following order: steel making > aluminum recycling > medical waste incinerator > boilers > municipal waste incinerator > tin production > brick production > coal-fired power plant. Both the precursor and de novo synthesis were estimated as possible formation mechanisms of dioxins in the ash, but the latter pathway was more prevalent. The highest emission factors were estimated for the ash released from some steel-making plants, aluminum-recycling facilities, and a medical waste incinerator. The emission factors of PCDD/Fs in ash released from some steel plants of this study were two to six times higher than the UNEP Toolkit default value. The annual emission amount of ash-bound dioxins produced by 15 facilities in our study was estimated to be 26.2 to 28.4 g TEQ year-1, which mainly contributed by 3 steel plants. Health risk related to the dioxin-containing ash was evaluated for workers at the studied facilities, indicating acceptable risk levels for almost all individuals. More comprehensive studies on the occurrence and impacts of dioxins in waste streams from incineration and industrial processes and receiving environments should be conducted, in order to promote effective waste management and health protection scheme for dioxins and related compounds in this rapidly industrializing country.

Volatilization of toxic elements from coal samples of Thar coal field, after burning at different temperature and their mobility from ash: Risk assessment.

In present study, the volatilization of arsenic (As), cadmium (Cd), mercury (Hg) and lead (Pb) by the burning of coal samples in the electric furnace was evaluated. The coal samples were obtained from different blocks of newly developed Thar coal field, Pakistan. The replicate coal samples were heated/burned in an electric furnace at laboratory scale for three temperature intervals (200, 400 and 900 °C). The ash obtained after each temperature intervals were analyzed for selected toxic elements. The resulted data indicated that the total contents of As, Cd, and Pb in coal samples of block X and XI were found in the range of 16.8-18.5, 4.21-4.72, and 14.2-18.8 mg/kg, respectively. Whereas, 67.8-79.7%, 34.3-36.8% and 9.89-10.8% of As, Cd, and Pb, respectively, were volatized out after combustion of coal samples at 900 °C. The total contents of Hg in selected coal samples of block X and XI were observed in the range of 0.985-1.46 and 0.992-1.41 mg/kg, respectively. The contents of Hg volatilized out via burning in a furnace at 200 °C and 400 °C, were observed in the range of 32.0-36.5% and >91.0% of its total contents, respectively, whereas at 900 °C, it was not detected in ash. The partitioning and mobility of studied toxic elements in residue termed as (laboratory made ash) obtained after burning at 900 °C, was carried out by three-step sequential extraction scheme. The resulted data of present study will give a better knowledge about the quality of coal and its burning product, which may help to take measure to reduce the adverse effects on the environment in future.

Low cost sustainable materials for grey water reclamation.

Grey water reclamation is a sustainable solution for managing water shortages. However, grey water contains high levels of detergents, particularly surfactants, which alongside other chemical constituents can pose a serious risk to human health and the environment. Biological treatments are not effective in the treatment of grey water since the detergents inhibit the activities of microorganisms. Chemical treatment options have an impact on public perception and could be cost prohibitive for domestic and small scale reuse applications. In this paper, we review the characterization of the constituents of grey water and the application of various low cost sustainable materials such as zeolite, activated carbon, mussel shells, tyre granules, fly ash, ground granulated blast furnace slag and silica gel for the treatment and removal of detergent characteristics.

Statistical study on distribution of multiple dissolved elements and a water quality assessment around a simulated stackable fly ash.

This study reports the leaching and transport behaviors of sixteen elements in fly ash taken from coal-fired power plant stations. A total of 480 water samples were collected from 20 simulative monitoring wells at three different times. Concentrations of elements in water samples were detected to know the spatial variability of substance, contamination level and quality of groundwater around stackable fly ash. The results of the water quality index (WQI) indicate that the water around a stackable fly ash is unsuitable for drinking. Sixteen parameters (Al, As, B, Ba, Cd, Co, Cr, Cu, Fe, Mg, Mn, V, Pb, Sb, Ni and Zn) were analyzed using different multivariate statistical approaches to assess the origins of elements in groundwater around stackable fly ash, identified five factor types that accounted for 75.66% of the total variance. Based on drinking water guidelines, As, Sb, Pb, Al and Cd were the dominant contaminants in groundwater around stackable fly ash. The quality of fly ash were considered to contribute much of the Mn, V, Ba and Mg (Cd, Cr and Ni for leaching time; Sb and Pb for leaching intensity; Al and Fe for water depths; B for flow velocity). Co, Cu and Zn had natural and random origins from crustal materials and upper reaches. Cluster analysis (CA) was adopted to classify the 20 simulative monitoring wells into two groups of water pollution, high pollution and low pollution, reflecting influences from leaching solution and upper reaches activities, respectively. The results of Hazard quotient and index (HQ/HI) suggests that As, Sb, Cd, Pb, V and Cr are the largest contributors to health risks in monitoring sites around stackable fly ash.

Litter breakdown as a tool for assessment of the efficiency of afforestation and ash-aided phytostabilization on metal-contaminated soils functioning in Northern France.

The main objective of the study was to assess the efficiency of phytoremediation methods implemented for 14 years on highly metal-contaminated soils. The different experimental strategies were plots planted with a tree mix or with a single tree species coupled or not with the use of fly-ashes as an amendment to limit metals mobility in soil. The breakdown of poplar litter on the four plots was monitored during 10 months. In parallel, colonization of litter bags by functional groups of mesofauna (Collembola and Acari) was followed. Two mesh-sized litter bags were used to allow distinguishing microbial and mesofaunal actions on the litter breakdown. We observed the breakdown of litter in four studied plots. Litter breakdown occurred faster in 3-mm litter bags than 250 µm ones during summer demonstrating the importance of mesofauna. Mixed plantation allowed faster litter breakdown than mono-specific plantation. A higher abundance of mesofauna and/or better abiotic conditions (moisture, shading…) could explain this result. Regarding litter breakdown and mesofauna, no significant difference was observed between the amended plots and those subjected to soil phytomanagement. However, communities of the studied area are disturbed since a low abundance of detritivores was observed. This could explain also the slower litter breakdown than expected in our study. To conclude, among the phytomanagement methods tested, mixed plantations could provide a benefit for the restoration of degraded soils. By contrast, the use of fly-ashes does not seem to have any effect on the functionality of ecosystem neither on the litter breakdown process nor on the abundance of mesofauna.

Heavy-metal speciation redistribution in solid phase and potential environmental risk assessment during the conversion of MSW incineration fly ash into molten slag.

The alkalinity (AKash), BCR sequential extraction method, and principle component analysis (PCA) were adopted to investigate the heavy-metal partitioning and their speciation redistribution in solid phase in ash-melting process. The results indicated that the conversion of Zn-OXI (oxidisable fraction) into Zn-RES (residual fraction) and the decomposition of Cu-OXI fraction were prevailing in solid-phase reaction. Moreover, the alkalinity reduction from AKash = 2.0 to AKash = 1.2 had positive implications for the concentration reduction of As-RED (reducible fraction), Zn-RED, and Pb-RES fractions in slags. The modified synthesis toxicity index (STIM) calculation model was introduced to investigate the potential ecological risk (PEI) of heavy metals in the recycling and utilization of molten slag. Based on STIM calculation model, PEI of heavy metal in hazardous materials was classified into five ranks, such as serious pollution (STIM > 462), heavy pollution (330 < STIM < 462), moderate pollution (132 < STIM < 330), mild pollution (0 < STIM < 132), and no pollution (STIM = 0). The molten slags produced from fly ash can be directly reused as building materials like freestone and ceramics due to the mild PEI.

Research and industrialization progress of recovering alumina from fly ash: A concise review.

Fly ash, a by-product of high temperature combustion of coal in coal-fired power plants, is one of the most complex and largest amount of industrial solid wastes generated in China. Its improper disposal has become an environmental problem. Now it is widely realized that fly ash should be considered as a useful and potential mineral resource. Fly ash is rich in alumina, making it a potential substitute for bauxite. With the diminishing reserves of bauxite resources, as well as the increasing demand for alumina, recovery of alumina from fly ash has attracted extensive attention world-wide. The present review describes, firstly, the generation and physicochemical properties of high alumina fly ash found in northern China and then focuses on the various alumina recovery technologies, the advantages and disadvantages of these processes, and in particular, the latest industrial developments. Finally, the directions for future research are also considered.

Stabilization of fly ash using cementing bacteria. Assessment of cementation and trace element mobilization.

Fly ash from municipal solid waste incineration (MSWI) was treated with microorganisms (Sporosarcina pasteurii and Myxococcus xanthus) to assess their capacity for cementing this waste material. Leaching tests on the samples treated with bacteria were also performed to assess the possibility of recovering and recycling trace elements from the fly ash. Sequential extractions combined with mineralogical studies demonstrated that Pb is mobile in water when associated with portlandite. Also, Cd, Pb, and Zn are primarily associated with carbonates and are mobile in acidic environments (up to 4.8, 13.9 and 248mg/l of Cd, Pb and Zn, respectively, extracted with acetic acid). Microbial treatment of the fly ash, especially with Sporosarcina pasteurii, led to its cementation and stabilization, preventing its dispersion into the environment. But samples treated with bacteria exhibited a higher capacity for trace element leaching than did untreated fly ash. The ability of these bacteria to mobilize metals can be applied to recover those of economic interest. The use of low cost biotechnologies can be an alternative to chemical treatments currently utilized for the recovery and reuse of these wastes.

Sustainability assessment and prioritisation of bottom ash management in Macao.

In Macao, about 7200 t yr-1 of bottom ash (BA) is generated and conventionally landfilled with construction waste. Because the properties of BA are similar to those of natural aggregates, it is suitable to be recycled as construction material. However, pre-treatment processes for BA reuse may require more resource input and may generate additional environmental impacts. Life cycle assessment, multi-media transport model analysis, cost-benefit analysis and the analytical hierarchy process were conducted to evaluate the impacts of current and potential BA management scenarios regarding environmental, economic, social and regulatory aspects. The five analysed scenarios are as follows: (0) BA buried with construction and demolition waste (current system); (1) pre-treated BA used to replace 25% of the natural aggregate in asphalt concrete; (2) pre-treated BA used to replace 25% of the natural aggregate in cement concrete; (3) pre-treated BA used to replace 25% of cement in cement concrete; and (4) pre-treated BA sent to China, blended with municipal solid waste for landfill. The results reveal the following ranking of the scenarios: 3 > 2 > 0 > 1 > 4. Scenario 3 shows the best conditions for BA recycling, because the quantity of cement concrete output is the highest and this brings the greatest economic benefits. Our use of integrated analysis provides multi-aspect investigations for BA management systems, particularly in accounting for site-specific characteristics. This approach is suitable for application in other non-western regions.

Geochemical modeling and assessment of leaching from carbonated municipal solid waste incinerator (MSWI) fly ash.

Municipal solid waste incinerator (MSWI) fly ashes are characterized by high calcium oxide (CaO) content. Carbon dioxide (CO2) adsorption by MSWI fly ash was discussed based on thermogravimetry (TG)/differential thermal analysis (DTA), minerology analysis, and adapting the Stenoir equation. TG/DTA analysis showed that the weight gain of the fly ash below 440 °C was as high as 5.70 %. An adapted Stenoir equation for MSWI fly ash was discussed. The chloride in MSWI fly ash has a major impact on CO2 adsorption by MSWI fly ash or air pollution control (APC) residues. Geochemical modeling of the critical trace elements copper (Cu), cadmium (Cd), zinc (Zn), lead (Pb), and antimony (Sb) before and after carbonation was performed using a thermodynamic equilibrium model for solubility and a surface complexation model for metal sorption. Leaching of critical trace elements was generally found to be strongly dependent on the degree of carbonation attained, and their solubility appeared to be controlled by several minerals. Adsorption on ferrum (Fe) and aluminum (Al) colloids was also responsible for removal of the trace elements Cd, Pb, and Sb. We used Hakanson's potential ecological risk index (HPERI) to evaluate the risk of trace element leaching in general. The results demonstrate that the ecological risk showed a V-shaped dependency on pH; the optimum pH of the carbonated fly ash was found to be 10.3-11, resulting from the optimum carbonation (liquid-to-solid (L/S) ratio = 0.25, carbonation duration = ∼30-48 h). The dataset and modeling results presented here provide a contribution to assessing the leaching behavior of MSWI fly ash under a wide range of conditions.

Polychlorobenzenes and polychlorinated biphenyls in ash and soil from several industrial areas in North Vietnam: residue concentrations, profiles and risk assessment.

Polychlorinated benzenes (PCBzs) including penta- and hexachlorobenzene can be unintentionally formed from thermal processes in different industrial activities, and very little information is available on the contamination and emission characteristics of these new persistent organic pollutants from industries in Vietnam. In this study, contamination of PCBzs (including penta- and hexachlorobenzene, named PeCBz and HCB, respectively) and PCBs (including CB-28, 52, 101, 153, 138, 180) in fly ash, bottom ash and soil from combustion processes of waste incineration, metallurgy (steel making and zinc production) and cement production from several provinces in the Northern Vietnam, including Hai Duong, Hanoi, Bac Ninh, Hai Phong and Thai Nguyen, was preliminary investigated. The PCBzs concentrations in fly ash, bottom ash and soil ranged from 2.7 to 100 ng g(-1), from 2.7 to 159 ng g(-1) and from 0.28 to 33.9 ng g(-1), respectively. Relatively high residues of PeCBz in fly ash and bottom ash from municipal waste incinerators in some provinces from the Northern Vietnam were encountered. Total PCBs concentrations ranged from 18.0 to 8260 ng g(-1), from 1.0 to 10600 ng g(-1) and from 14.5 to 130 ng g(-1) for the fly ash, bottom ash and soil, respectively. Daily intakes of PeCBz, HCB and PCBs through soil ingestion and dermal exposure estimated for children ranged 0.33-9.93 (mean 3.14), 0.39-21.1 (mean 4.9) and 6.09-1530 ng/kg bw/day (mean 346), respectively; and these intakes were about 4.7-5.4 times higher than those estimated for adult. The intakes of PeCBz and HCB were relatively low, while those for PCBs exceeded WHO TDI for some samples.