Hydration properties of eco-cement pastes from waste sludge ash clinkers

Three types of hydraulic cements have been developed by incorporating sludge ash from a primary sewage treatment plant and a water purification plant, as well as slag from steelworks (ferrate), as a partial replacement for clay, silica, alumina, and iron oxide in raw cement meal. The raw meal for the pre-determined recipes was prepared by heating it to 1400 degrees C for 6 hr in a clinkerization process, using a simulated incinerator and smelter. The major components of ordinary Portland cement, C3S, C2S, C3A, and C4AF, were all found in the clinkers. Of the three types of eco-cements, the eco-cement A paste was most similar to ordinary Portland cement in terms of composition and compressive strength development, while the eco-cement B paste showed early strength development. The differential thermal analysis species analyses indicated that the hydrates in the eco-cement pastes were mainly calcium hydroxide and CSH gels, like those found in ordinary Portland cement paste. Moreover, the degree of hydration, as determined by nuclear magnetic resonance, increased in all eco-cement pastes with an increasing curing age. The results indicate that it indeed is feasible to use sludge ash and ferrate to replace up to 20% of the mineral components of raw materials for cement.     

Hydration Properties of Eco-Cement Pastes from Waste Sludge Ash Clinkers

Abstract

Three types of hydraulic cements have been developed by incorporating sludge ash from a primary sewage treatment plant and a water purification plant, as well as slag from steelworks (ferrate), as a partial replacement for clay, silica, alumina, and iron oxide in raw cement meal. The raw meal for the pre-determined recipes was prepared by heating it to 1400 °C for 6 hr in a clinkerization process, using a simulated incinerator and smelter. The major components of ordinary Portland cement, C₃S, C₂S, C₃A, and C₄AF, were all found in the clinkers. Of the three types of eco-cements, the eco-cement A paste was most similar to ordinary Portland cement in terms of composition and compressive strength development, while the eco-cement B paste showed early strength development. The differential thermal analysis species analyses indicated that the hydrates in the eco-cement pastes were mainly calcium hydroxide and CSH gels, like those found in ordinary Portland cement paste. Moreover, the degree of hydration, as determined by nuclear magnetic resonance, increased in all eco-cement pastes with an increasing curing age. The results indicate that it indeed is feasible to use sludge ash and ferrate to replace up to 20% of the mineral components of raw materials for cement.     

Latent Hydraulic Reactivity of Blended Cement Incorporating Slag Made from Municipal Solid Waste Incinerator Fly Ash

Abstract

The reactivity of cement pastes made by blending Portland cement with slag from municipal solid waste incinerator (MSWI) fly ash was investigated to assess the potential of recycling MSWI fly ash slag. The slag, prepared by melting MSWI fly ash at 1400 °C for 30 min, was pulverized and ground, then blended with ordinary Portland cement (OPC), using various substitution levels to make slag-blended cement (SBC). The pozzolanic reactivity of the ecocement was then characterized by determining variations in the compressive strength, degree of hydration, microstructure, speciation, and mineralogical crystalline phases. The results suggest that the strength of the pastes at an early age decreased with increasing substitution levels, whereas the strength at a later age of the tested pastes (with substitution levels less than 10%) outperformed OPC paste because of typical SBC properties. The development of strength at a later age was also confirmed by X-ray diffraction and scanning electron microscopy techniques. This implies that active silica (Si) and alumina (Al) react with the hydration product, calcium hydroxide (Ca(OH)₂), to form calcium silicate hydrate (C-S-H), which contributed to strength development at a later age by the filling up of pores in the SBC pastes. The pozzolanic activity of the SBC pastes indicates that it is suitable for use as a substitute for OPC in blended cement.     

Latent hydraulic reactivity of blended cement incorporating slag made from municipal solid waste incinerator fly ash

The reactivity of cement pastes made by blending Portland cement with slag from municipal solid waste incinerator (MSWI) fly ash was investigated to assess the potential of recycling MSWI fly ash slag. The slag, prepared by melting MSWI fly ash at 1400 degrees C for 30 min, was pulverized and ground, then blended with ordinary Portland cement (OPC), using various substitution levels to make slag-blended cement (SBC). The pozzolanic reactivity of the ecocement was then characterized by determining variations in the compressive strength, degree of hydration, microstructure, speciation, and mineralogical crystalline phases. The results suggest that the strength of the pastes at an early age decreased with increasing substitution levels, whereas the strength at a later age of the tested pastes (with substitution levels less than 10%) outperformed OPC paste because of typical SBC properties. The development of strength at a later age was also confirmed by X-ray diffraction and scanning electron microscopy techniques. This implies that active silica (Si) and alumina (Al) react with the hydration product, calcium hydroxide (Ca(OH)2), to form calcium silicate hydrate (C-S-H), which contributed to strength development at a later age by the filling up of pores in the SBC pastes. The pozzolanic activity of the SBC pastes indicates that it is suitable for use as a substitute for OPC in blended cement.     

Characterization of eco-cement paste produced from waste sludges

In this study, marble sludge, sewage sludge, drinking water treatment plant sludge, and basic oxygen furnace sludge were used as replacements for limestone, sand, clay, and iron slag, respectively, as the raw materials for the production of cement in order to produce eco-cement. It was found that it is feasible to use marble sludge to replace up to 50% of the limestone and also that other materials can serve as total replacements for the raw materials typically used in the production of cement. The major components of Portland cement were all found in eco-cement clinkers. The eco-cement was confirmed to produce calcium hydroxide and calcium silicate hydrates during the hydration process, increasing densification with the curing age. The compressive strength (S_c) and microstructural evaluations conducted at 28 d revealed the usefulness of eco-cement. It was observed that the S_c data correlated linearly with the pore volume (P) data at 28 d. The proposed model equation could be represented as S_c = 178-461P (correlation coefficient, R² = 0.96). Two parameters, the large capillary pore volume and the medium capillary pore volume, were evaluated using multiple regression analysis.     

染料废水混凝污泥免烧砖浸出毒性的研究

染料废水混凝污泥处理处置及资源化利用对环境保护和染料生产企业的可持续发展有重要意义。依据《固体废物浸出毒性浸出方法水平振荡法》(HJ 557—2009)和《固体废物浸出毒性浸出方法硫酸硝酸法》(HJ/T 299—2007)对污泥和污泥免烧砖制备浸出液,用分光光度法和化学滴定法测定了浸出液中主要有机污染物(对硝基苯胺、苯胺、间苯二胺和丙烯腈)的含量。结果表明:(1)硅酸盐水泥(样品标记为42.5R、水泥1、水泥2)和铝酸盐水泥(样品标记为CA)对苯胺和间苯二胺的固化效果差别不大;水泥2对对硝基苯胺的固化效果最好;42.5R对丙烯腈的固化效果不如其他3种水泥。(2)对硝基苯胺、苯胺、间苯二胺、丙烯腈经水泥固化后,其浸出毒性均降低。     

基于响应面法的污泥快速固化效能综合影响简

针对现有污泥固化技术存在的固化养护时间长、低温条件下固化效能低等问题。研究提出污泥快速（3 d）固化技术,采用响应曲面分析方法,重点考察了石灰、组分A、硅酸盐水泥、粉煤灰和温度等5因素对固化效能的综合影响,研究结果表明,石灰、组分A、硅酸盐水泥、粉煤灰和养护温度等因素对3 d固化体的无侧限抗压强度和含水率的线性效应显著,石灰和组分A、石灰和养护温度对无侧限抗压强度的交互影响显著,石灰和粉煤灰、组分A和养护温度、硅酸盐水泥和粉煤灰对含水率的交互影响显著;得出了5因素对固化体3 d无侧限抗压强度和含水率影响的定量模型,可对污泥快速固化进行优化和预测;并利用XRD和SED对污泥固化块的化学成分和微观结构进行了分析。     

基于响应面法的污泥快速固化效能综合影响

针对现有污泥固化技术存在的固化养护时间长、低温条件下固化效能低等问题。研究提出污泥快速（3d）固化技术,采用响应曲面分析方法,重点考察了石灰、组分A、硅酸盐水泥、粉煤灰和温度等5因素对固化效能的综合影响,研究结果表明,石灰、组分A、硅酸盐水泥、粉煤灰和养护温度等因素对3d固化体的无侧限抗压强度和含水率的线性效应显著,石灰和组分A、石灰和养护温度对无侧限抗压强度的交互影响显著,石灰和粉煤灰、组分A和养护温度、硅酸盐水泥和粉煤灰对含水率的交互影响显著;得出了5因素对固化体3d无侧限抗压强度和含水率影响的定量模型,可对污泥快速固化进行优化和预测;并利用XRD和SED对污泥固化块的化学成分和微观结构进行了分析。     

Mechanisms of phosphorus removal by cement-bound ochre pellets

Hydrous ferric oxide (here termed ‘ochre’) sludge, an abundant waste product produced from the treatment of acid mine drainage (AMD), was used in this study for the removal of phosphorus (in the form of phosphate ions) from contaminated waters. The phosphorus uptake capacities of both raw and pelletized AMD solids were compared using batch and column tests. Addition of a cement binder to the AMD solids during pellet production led to significantly increased P-loading of the resultant solids compared to the raw sludge. Additionally, the pellets were found to continue to remove P in tests up to 7 d in duration whereas the unbound AMD sludge appeared to approach equilibrium with phosphate solution after approximately 60 min of contact time. In line with previous studies P uptake by the AMD solids was found to be primarily via adsorption. By contrast calcium phosphate precipitation was found to be the dominant removal mechanism for the cement-bound ochre pellets with a relatively small proportion of removal attributable to the AMD solids. SEM–EDX analysis of the surface of used pellets showed a Ca:P molar ratio close to that of hydroxyapatite (HAP). Continuous column tests on these pellets showed a rapid decrease in P removal capacity by the pellets over time, attributable to the formation of a passivating HAP surface layer.     

Study on substrate metabolism process of saline waste sludge and its biological hydrogen production potential

With the increasing of high saline waste sludge production, the treatment and utilization of saline waste sludge attracted more and more attention. In this study, the biological hydrogen production from saline waste sludge after heating pretreatment was studied. The substrate metabolism process at different salinity condition was analyzed by the changes of soluble chemical oxygen demand (SCOD), carbohydrate and protein in extracellular polymeric substances (EPS), and dissolved organic matters (DOM). The excitation-emission matrix (EEM) with fluorescence regional integration (FRI) was also used to investigate the effect of salinity on EPS and DOM composition during hydrogen fermentation. The highest hydrogen yield of 23.6 mL H₂/g VSS and hydrogen content of 77.6% were obtained at 0.0% salinity condition. The salinity could influence the hydrogen production and substrate metabolism of waste sludge.

     

ESTROM—a Romanian–Swiss research programme

Background, aim, and scope  Composting is an effective treatment process to realize sludge land application. However, nitrogen loss could result in the reduction of nutrient value of the compost products and the stabilization effect of composting on heavy metal concentration and mobility in sludge has been shown to be very limited. Materials and methods  Laboratory-scale experiments were carried out to investigate the effects of bamboo charcoal (BC) on nitrogen conservation and mobility of Cu and Zn during sludge composting. Results  The result indicated that the incorporation of BC into the sludge composting material could significantly reduce nitrogen loss. With 9% BC amendment, total nitrogen loss at the end of composting decreased 64.1% compared with no BC amendment (control treatment). Mobility of Cu and Zn in the sludge may also have been lessened, based on the decline in diethylenetriaminepentaacetic acid-extractable Cu and Zn contents of composted sludge by 44.4% and 19.3%, respectively, compared to metal extractability in the original material. Discussion  Ammonia adsorption capability of BC might be the main reason for the retention of nitrogen in sludge composting materials. Decrease of extractable Cu²⁺ and Zn²⁺ in the composting material mainly resulted from the adsorption of both metals by BC. Conclusions  Incorporation of BC into composting material could significantly lessen the total nitrogen loss during sludge composting. Mobility of heavy metals in the sludge composting material could also be reduced by the addition of BC. Recommendations and perspectives  Bamboo charcoal could be an effective amendment for nitrogen conservation and heavy metal stabilization in sludge composts. Further research into the effect of BC-amended sludge compost material on soil properties, bioavailability of heavy metals, and nutrient turnover in soil needs to be carried out prior to the application of BC-sludge compost in agriculture.     

Pozzolanic reactivity of the synthetic slag from municipal solid waste incinerator cyclone ash and scrubber ash

This study investigates the pozzolanic reactions and compressive strength of the blended cement manufactured using synthetic slag obtained from municipal solid waste incinerator (MSWI) cyclone ash and scrubber ash as partial replacement of portland cement. The synthetic slag was made by co-melting the MSWI scrubber ash and cyclone ash mixtures at 1400 degrees C for 30 min. Following pulverization, the different types of slag were blended with cement as cement replacement at ratios ranging from 10 to 40 wt %. The synthetic slag thus obtained was quantified, and the characteristics of the slag-blended cement pastes were examined. These characteristics included the pozzolanic activity, compressive strength, hydration activity, crystal phases, species, and microstructure at various ages. The 90-day compressive strength developed by slag-blended cement pastes with 10 and 20 wt % of the cement replaced by the synthetic slag outperformed ordinary portland cement by 1-7 MPa. X-ray diffraction species analyses indicated that the hydrates in the slag-blended cement pastes were mainly portlandite, the calcium silicate hydrate gels, and calcium aluminate hydrate salts, similar to those found in ordinary portland cement paste. Differential thermal and thermogravimetric analysis also indicated that the slag reacted with portlandite to form calcium silicate hydrate gels.     

Strength development of solidified/stabilized organic waste and optimum treatment design

Artificially contaminated (spiked) natural soils were solidified/stabilized using various combinations of commonly used additives, such as lime, cement, fly ash, activated carbon, and silica fume. The effectiveness of the solidification/stabilization (S/S) processes was evaluated based on experimental findings from compaction testing, unconfined compressive shear strength, and X-ray diffraction (XRD). Correlations of limited reliability between unconfined compressive strength and penetrometer and torvane measurements were derived. Results from XRD experiments indicated that certain organic contaminants (i.e., naphthalene and pyrene) might impact the S/S processes for a given combination of additives. The type and amount of organic contaminants also affected the pozzolanic reactions. Specifically, the absence or small peak intensity of pozzolanic product XRD patterns for a given combination of additives was a good indication that the type and the amount of organic contaminant present inhibited pozzolanic reactions. This phenomenon was tested and confirmed for actual field-contaminated samples.     

Conditioning of sewage sludge by Fenton's reagent combined with skeleton builders

Physical conditioners, often known as skeleton builders, are commonly used to improve the dewaterability of sewage sludge. This study evaluated a novel joint usage of Fenton’s reagent and skeleton builders, referred to as the F-S inorganic composite conditioner, focusing on their efficacies and the optimization of the major operational parameters. The results demonstrate that the F-S composite conditioner for conditioning sewage sludge is a viable alternative to conventional organic polymers, especially when ordinary Portland cement (OPC) and lime are used as the skeleton builders. Experimental investigations confirmed that Fenton reaction required sufficient time (80 min in this study) to degrade organics in the sludge. The optimal condition of this process was at pH = 5, Fe²⁺ = 40 mg g⁻¹ (dry solids), H₂O₂ = 32 mg g⁻¹, OPC = 300 mg g⁻¹ and lime = 400 mg g⁻¹, in which the specific resistance to filtration reduction efficiency of 95% was achieved.     

Removal of antibiotics and non-steroidal anti-inflammatory drugs by extended sludge age biological process

Removal of four antibiotics (sulfamethoxazole, sulfadimethoxine, sulfamethazine and trimethoprim) and four non-steroidal anti-inflammatory drugs (acetaminophen, ibuprofen, ketoprofen and naproxen) using extended sludge age biological process was investigated. The sludge age of the biological system was greater than 200 d. Hydraulic retention time of 12 h was maintained throughout the experiment. The extended sludge age biological process is able to treat pharmaceuticals with good and steady removal efficiencies: 64–93% removal for antibiotics over 1–5 μg L⁻¹ influent concentrations and 94% to complete removal for acetaminophen and ibuprofen with a wide range of influent concentrations 1–100 μg L⁻¹. For ketoprofen and naproxen the removal efficiencies are 79–96% over a range of 1–15 μg L⁻¹ influent concentrations. The removal efficiency decreases with increasing initial concentrations for all target compounds except for ibuprofen. This indicates that the initial influent concentration is an important parameter for the studies of fate of pharmaceuticals. The amount of bio-mass and size of the reactor required to achieve good and steady removal efficiencies for known influent pharmaceutical concentrations are also suggested in this study.     

Cost–benefit analysis of using sewage sludge as alternative fuel in a cement plant: a case study

Background, aim, and scope  To enforce the implementation of the Kyoto Protocol targets, a number of governmental/international institutions have launched emission trade schemes as an approach to specify CO₂ caps and to regulate the emission trade in recent years. These schemes have been basically applied for large industrial sectors, including energy producers and energy-intensive users. Among them, cement plants are included among the big greenhouse gas (GHG) emitters. The use of waste as secondary fuel in clinker kilns is currently an intensive practice worldwide. However, people living in the vicinity of cement plants, where alternative fuels are being used, are frequently concerned about the potential increase in health risks. In the present study, a cost–benefit analysis was applied after substituting classical fuel for sewage sludge as an alternative fuel in a clinker kiln in Catalonia, Spain. Materials and methods  The economical benefits resulting in the reduction of CO₂ emissions were compared with the changes in human health risks due to exposure to polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) and carcinogenic metals (As, Cd, Co, and Cr) before and after using sewage sludge to generate 20% of the thermal energy needed for pyro-processing. The exposure to PCDD/Fs and metals through air inhalation, soil ingestion and dermal absorption was calculated according to the environmental levels in soil. The carcinogenic risks were assessed, and the associated cost for the population was estimated by considering the DG Environment’s recommended value for preventing a statistical fatality (VPF). In turn, the amount of CO₂ emitted was calculated, and the economical saving, according to the market prices, was evaluated. Results  The use of sewage sludge as a substitute of conventional energy meant a probability cancer decrease of 4.60 for metals and a cancer risk increase of 0.04 for PCDD/Fs. Overall, a net reduction of 4.56 cancers for one million people can be estimated. The associated economical evaluation due to the decreasing cancer for 60,000 people, the current population living near the cement plant, would be of 0.56 million euros (US$ 0.83 million). In turn, a reduction of 144,000 tons of CO₂ emitted between 2003 and 2006 was estimated. Considering a cost of 20 euros per ton of CO₂, the global saving would be 2.88 million euros (US$ 4.26 million). Discussion  After the partial substitution of the fuel, the current environmental exposure to metals and PCDD/Fs would even mean a potential decrease of health risks for the individuals living in the vicinity of the cement plant. The total benefit of using sewage sludge as an alternative fuel was calculated in 3.44 million euros (US$ 5.09 million). Environmental economics is becoming an interesting research field to convert environmental benefits (i.e., reduction of health risks, emission of pollutants, etc.) into economical value. Conclusions  The results show, that while the use of sewage sludge as secondary fuel is beneficial for the reduction in GHG emissions, no additional health risks for the population derived from PCDD/F and metal emissions are estimated. Recommendations and perspectives  Cost–benefit analysis seems to be a suitable tool to estimate the environmental damage and benefit associated to industrial processes. Therefore, this should become a generalized practice, mainly for those more impacting sectors such as power industries. On the other hand, the extension of the study could vastly be enlarged by taking into account other potentially emitted GHGs, such as CH₄ and N₂O, as well as other carcinogenic and non-carcinogenic micropollutants.     

Environmental monitoring of PCDD/Fs and metals in the vicinity of a cement plant after using sewage sludge as a secondary fuel

In 2005, the partial substitution (20%) of fossil fuel by sewage sludge was tested in a Spanish cement plant. In order to establish the environmental impact for the surroundings, in 2006, the levels of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) and heavy metals (As, Cd, Co, Cr, Cu, Hg, Mn, Ni, Pb, Sn, Tl, V, and Zn) were monitored in soil and vegetation samples collected near the cement plant. The temporal trends in the pollutant levels were studied by comparing the concentrations with those obtained in a previous survey (2003) in the same sampling sites. Very slight changes of the PCDD/F concentrations in both monitors were registered in the period 2003–2006 (0.17–0.15 and 0.94–1.10 ng I-TEQ kg⁻¹ dw in herbage and soil, respectively). In turn, there was a notable heterogeneity in the evolution of metal levels, which varied according to each particular element. Anyhow, the current levels of organic and inorganic pollutants are in the low part of the range in comparison with other zones impacted by cement plants, as well as industrial and urban areas worldwide. The human health risks derived from the exposure to PCDD/Fs and metals were also assessed. Although the cancer risks due to PCDD/Fs slightly increased, a reduction of the total carcinogenic risks, including metals, was noted. In conclusion, there were not observed impact changes for the environmental and the local population as a consequence of using sewage sludge as secondary fuel.     

Role of casting and curing conditions on the strength and drying shrinkage of greener concrete

The shrinkage of cement-based materials is a critical dimensional property that needs proper attention as it can influence the corresponding characteristics especially when the preparation of such cement-based material is done in hot weather. Studies have shown that the casting or curing conditions influence the performance of concrete. However, there is limited understanding of the combined role of casting temperature and curing conditions, especially for concrete made with unconventional binders. In this study, five supplementary cementitious materials (SCMs) were utilized as the substitute of the ordinary Portland cement (OPC) at different ratios to produce greener concrete and improve its characteristics and sustainability. The influence of four casting temperatures (i.e., 25 °C, 32 °C, 38 °C, and 45 °C) and two curing regimes (i.e., covering of samples using wet burlap and applying curing compound on the surface of samples) on the corresponding compressive strength and drying shrinkage at various ages was studied. The outcomes of this research revealed that the composition of the binders has a substantial impact on the characteristics of concrete. In addition, the casting temperature and curing regimes also have a huge role on the compressive strength of concrete produced with binary binders. For example, the compressive strength at 3 days of concrete made at 25 °C made with binary binders was reduced up to 31% compared to that made with only OPC as the binder when cured using wet burlap. Nonetheless, less than 38 ℃ was suitable to minimize the durability issues in the studied blended cement mixes.

     

Fluidized-bed-combustion ash for the solidification and stabilization of a metal-hydroxide sludge

Fluidized-bed-combustion (FBC) ash is a by-product from a developing technology for coal-fired power plants that will economically reduce air emissions to meet requirements of the Clean Air Act. FBC ash has physical and chemical properties similar to Portland cement, but only has moderate success as a pozzolan in concrete applications due to low compressive strengths. However, FBC ash has proven effective for use as a binder for the solidification and stabilization (S/S) of metal-bearing sludges. Physical and chemical characterization procedures were used to analyze FBC ash and a metal-bearing sludge obtained from a hazardous waste treatment facility to develop 12 different S/S mix designs. The mix designs consist of four binder designs to evaluate sludge-to-binder ratios of approximately 0, 0.5, and 1. Portland cement is used as a control binder to compare unconfined compressive strengths and Toxicity Characteristic Leaching Procedure (TCLP) analyses from different ratios of the FBC ash streams: fly ash, char, and spent bed material (SBM). Compressive strengths ranging from 84 lbs per square inch (psi) to 298 psi were obtained from various mix designs containing different sludge-to-ash ratios cured for 28 days. All the mix designs passed the TCLP. Recoveries from leaching for each metal were less than 5% for most mix designs. Results of unconfined compressive strengths, TCLP, and percent recovery calculations indicate that the mix design containing approximately a 1:1 ratio of fly ash to char-and-sludge is the best mix design for the S/S of the metal-bearing sludge.     

Anthropogenic mercury emission inventory with emission factors and total emission in Korea

Mercury emissions concentrations, emission factors, and the total national emission from major anthropogenic sources in Korea for the year 2007 were estimated. Uncontrolled and controlled mercury emission factors and the total emission from each source types are presented. The annual national mercury emission from major anthropogenic sources for the year 2007, on average was 12.8 ton which ranged from 6.5 to 20.2 ton. Averaged emissions of elemental, oxidized, and particulate mercury were estimated at 8.25 ton, 3.69 ton, and 0.87 ton, respectively. Due to the removal of a major portion of particulate and oxidized mercury species, elemental mercury was dominant in stack emission. About 54.8% of mercury emission was contributed by industrial sources, 45.0% by stationary combustion sources and 0.02% by mobile sources. Thermal power plants, oil refineries, cement kilns and incinerators (municipal, industrial, medical, sewage sludge) were the major mercury emitters, contributing about 26%, 25%, 21% and 20%, respectively to the total mercury emission. Other sources (crematory, pulp and paper manufacturing, nonferrous metals manufacturing, glass manufacturing) contributed about 8% of the total emission. Priority should be given in controlling mercury emissions from coal-fired power plants, oil refineries, cement kilns and waste incinerators. More measurements including natural and re-emission sources are to be carried out in the future in order to have a clear scenario of mercury emission from the country and to apply effective control measures.