Effects of water washing on removing organic residues in bottom ashes of municipal solid waste incinerators

Due to their potential toxicity and odourous nature, the residual organics in municipal solid waste incinerators are recently gaining attention as an important issue of resources recovery apart from their complex mixture of organic counterpart. Studies of the organic fractions in municipal solid waste incinerator residues have been limited. In this study, extended solid-phase extraction of the water-washed bottom ash and liquid-phase extraction of the washing water were carried out with regard to bottom ash samples from three mass-burning incinerators in Taipei County (Taiwan) during four consecutive seasons of year 2008-2009. Supercritical fluid extraction and Soxtec extraction techniques along with GC-MS were successfully used to characterize the residual organics in weathered and washed bottom ashes. Supercritical fluid extraction provided the quantification of aliphatics and aromatic compounds such as hexanoic acid and benzaldehyde, respectively. Soxtec extraction was useful for qualitative analysis of aromatic and aliphatic groups in the ashes and many of which were odourous and toxic compounds. By mixing one unit weight (g) bottom ash with two unit volume (mL) water for 15 min, total organic carbon in the bottom ash was greatly reduced (e.g., from 4.1 to 1.8 wt.%). Among the removed were foul odour-causing compounds such as pyridine and quinoline derivatives, while some aromatic compounds such as 4-hydroxybenzaldehyde and low-molecular-weight aliphatics such as hexanoic acid remained. The results here suggest that washing with water can be an effective pre-treatment step for removing odour-causing and environmental concerned organics.     

Distribution of polybrominated diphenyl ethers (PBDEs) and polybrominated dibenzo-p-dioxins and dibenzofurans (PBDD/Fs) in municipal solid waste incinerators

The stack flue gases and the ashes in different units of two municipal solid waste incinerators (MSWIs) are sampled to investigate the characteristics of polybrominated diphenyl ethers (PBDEs), polybrominated dibenzo-p-dioxins and dibenzofurans (PBDD/Fs), and polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs). Bottom ashes (BA) exhibited much higher PBDD/F (8.11-52.2 pg TEQ/g) and PBDE contents (20.4-186 ng/g) than those of fly ashes (0.0932-2.02 pg TEQ/g and 0.332-25.5 ng/g), revealing that the PBDD/Fs and PBDEs in the feeding waste may not be completely destroyed. The PBDE concentrations/contents in the stack flue gases (26.1-109 ng/Nm³) and in the BA (20.4-186 ng/g) of the MSWIs could reach three orders higher than those in the atmosphere and reference soils. PBDE contributions to the environment from the stack flue gases or the reutilization of BA of MSWIs should not be ignored from the developing PBDE inventory.     

高COD浓度污水与洁净底泥作用的实验研究

通过底泥吸附和污水有机物降解实验 ,研究了高COD浓度污水与洁净底泥的相互作用。结果表明 ,洁净底泥对高COD浓度污水中的污染物具有吸附作用 ,且在起始段此作用较明显 ,但在后期的作用就下降很多。底泥固相量的增加可显著提高水相有机污染物的吸附去除率 ;但对于不同来源的污水 ,并非按照同一比例增加 ,污水性质显著影响底泥的有机污染物吸附量。污水中的有机污染物的生物降解由于其作用缓慢 ,在开始的阶段 ,对水相有机污染物的减少远没有底泥吸附所起的作用大 ;但在后期其累计的作用将明显显现出来     

粉煤灰的组分特征及其系统分类

利用光学显微镜、X射线衍射及扫描电镜等手段,从岩石学角度对粉煤灰的组分特征进行了详细观察研究。结果表明:粉煤灰的组分可分为有机组分和无机组分两大类。有机组分包括煤粒和残炭2个亚组;而无机组分则可进一步分为玻璃微珠、磁铁微珠、不定形颗粒、碎屑石英和莫来石。在此基础上,首次提出了粉煤灰显微组分分类系统并对显微组分作了定量统计。      

Sulfur organic compounds in bottom sediments of the eastern Gulf of Finland

Background, Aims and Scope Despite the large number of studies on the forms of sulfur in marine deposits, investigations on sulfur organic compounds are still rare. It is known that the processes leading to formation of intermediate and final sulfur compounds (including organic ones) in modern deposits are the results of microbiological transformation of sulfur containing proteins, as well as the microbiological reduction of sulfate ions. The latter are finally reduced by anaerobic sulfate-reducing bacteria to H₂S, HS⁻ and S²⁻; the total sum of these is referred to as ‘hydrogen sulfide’ in chemical oceanography. Further, the formation of reduced sulfur organic derivatives (sulfides and polysulfides) is the result of interaction of the organic substance destruction products with the sulfide ions. In such cases, the main source of organic substances, as well as sulfates for the sulfur reducing processes, is the pore water in the sediments. The choice of the target of our study is based on the fact that the eastern part of the Gulf of Finland water area receives the bulk of the anthropogenic load of the St. Petersburg region. Low vertical intermixing of the water thickness is observed there (thus creating a deficiency of oxygen near the bottom), and the bottom sea current transfers the polluted salty water of the Baltic Sea into the Neva Bay. The whole of the above are the preconditions for the formation of sulfur-bearing organic compounds. A great number of bottom sediment samples for analytical surveys were collected in the Eastern Gulf of Finland during research expeditions in the years of 1997 and 2001. These were screened for structures of sulfur organic microcontaminants, including organic forms of sulfur, using advanced instrumentation and experienced personnel in our two, cooperating laboratories. This work is a part of the research being carried out on organic micro-admixtures present in bottom sediments, and is the summary of our findings on previously unstudied sulfur organic substances there. Materials and Methods A number of sulfur organic compounds present in nineteen bottom sediment samples from the Eastern Gulf of Finland (EGF) were characterized by high performance gas chromatography connected to low and high resolution mass spectrometers (GC/LRMS and GC/HRMS). The structure screening was carried out as compared with literature and library mass spectra, and taking the GC retention times into account. In the cases of an absence of mass spectra not in the literature, interpretation of the most probable structures was performed with the help of high resolution mass-spectrometric data, fragmentation rules for sulfur-bearing organic substances and ICLU simulation of spectra. These data were registered to form a conclusive ‘fingerprint’ for identification and confirmation of the structure of each novel compound found, e.g. by later syntheses of authentic model compounds. The relative contents of sulfur organic compounds were determined from MS response ratios of each compound to 2-fluorine naphthalene (internal standard). Results This paper is a completion of work, which has been published in part as three papers in the European Journal of Mass Spectrometry. As the total study result, 43 sulfur-bearing compounds were characterized. The mass spectra of 20 of them were found in the literature. The most probable structures for the 23 compounds whose mass-spectra were not available in the literature data were proposed. All of those 23 compounds were detected in bottom sediments for the first time, and 5 of them were described as originating from plants or being generated by chemical synthesis products, while the remaining 18 substances were previously unknown. The structures of these were deduced to be most probably the following (in order of their GC retention): dichloromethyl thiylsulfenylchloride, chloromethyl dichloromethyl disulfide, 3,4-dithiacyclohexene, 1,2,4-trithiacycloheptane, 1,2,3-trithiacyclohexane, tetrathiacyclopentane, 3,4,5-trithiacyclohexene, 1,2,4-trithiacyclohexane, cyclopropylhydrotrisulfide, 1,2-dithiane-3-thiol, 1,3-dithiane-2-thiol, bis(trichloromethyl)-tri-sulfide, 1,2,4,5-tetrathiacyclohexane, 1,2,3,4-tetrathiacycloheptane, 1,2,3,4-tetrathiacycloheptane, 1,2,3,4-tetrathia-cyclo-hexane, pentathiacyclohexane, and 1,2,4,6-tetrathiacyclooctane. The highest amounts of sulfur organic compounds were found in the deepest, bottom areas in the open part of the sea, where the salinity was highest, and oxygen deficiency occurred as well. Also, some coastal places with a high solid matter deposition rate had elevated contents of sulfur organic compounds. Discussion From the 43 sulfur organic compounds found, the HRMS data provided the atomic composition of the molecular ions for 16 compounds with a high confidence (see Table 3). The LRMS spectra could be identified with catalogue or literature spectra in 29 cases. The MS information obtained was insufficient in two cases: 1) The obvious molecular ion (at m/z 110) of compound 1 was not visible in LRMS. 2) For compound 43, the HRMS measurement, due to the low intensity (2%) of the molecular ion (m/z 210), could not exclude the presence of 2 oxygen atoms (instead of one sulfur atom) in the molecule. Major fragments, however, of our 43, certainly contained no oxygen atoms according to HRMS. The limited LRMS data in the literature, for an isomer of 43, had m/z values of all fragments different from those of the compound found by us. The retention times (RT) formed one more evidence for identity between compounds in different samples. The use of different non-polar columns in GC and similar, but not identical, temperature programs produced eluted peaks of novel and known compounds in each sample (mixture) in GC/HRMS and GC/LRMS. These gave sets of RTs which were in a very significant linear correlation (measured example R = 0.999866, p = 1.85E-06, N = 5). Therefore, the RTs in the HRMS analysis systems could be converted to values comparable with those from the LRMS device. The RT values, HRMS m/z values, LRMS spectra, and ICLU simulation results for each organic sulfur compound form an identification ‘fingerprint’. The interpretation of these experimental data, with supporting use of fragmentation rules, allow the giving of a provisional name and structure to the ‘suspect’. In this study and in environmental surveys of micropollutants in general, the compounds suspected of anthropogenic or natural origin occur at low levels in complex mixtures. Therefore, no bulk amount of an authentic, pure model substance for the suspect is available quite often. The most probable name and structure from the fingerprint data are very useful in guiding the preparation of the model substance for a conclusive identification. Similarly, the unknown criminal can be identified in advance by forensic science and his fingerprint, DNA, etc. as registered before the arrest. The analogy can be found in the literature and CAS register of organic polysulfides, which in great part consists of the results of sensitive mixture analysis methods. Conclusions Sediment of the Eastern Gulf of Finland is over large areas anaerobic, as indicated by the existence of novel, non-oxygenated sulfur organic microcontaminants. These substances were most abundant in anoxic and saline, deep bottom regions, and, in addition, in one coastal area near industrial discharges. This occurrence, and also the limited information about sulfur organic compounds in scientific literature, is considered evidence for the dominantly natural processes in their formation. Recommendations and Perspectives The importance and necessity of investigating the sulfur organic compounds in the bottom sediments, result from the fact that their presence can be an indicator of stable anaerobic processes. Similarly, the oxygen disappearance (anoxia) in the marine water, due to a high concentration of the sulfate ions and relatively high content of organic matter, is practically always connected with the appearance of hydrogen sulfide and sulfides. The generation of sulfur organic compounds precedes the formation of the new, or expansion of the existing anaerobic (‘hydrogen sulfide’) zones, which lead to such environmental disasters as mass destruction of hydrobionts. Many organic compounds of sulfur, including sulfides and polysulfides, are toxic to the aquatic organisms. Therefore, in addition to the danger of mass wholesale deaths of marine fauna in the bottom sediments region, there exists a probability of secondary pollution of the water thickness as well, due to the entry of those substances from bottom sediments in the water when the environmental conditions are changed (stormy weather, floods, geological activity of the earth’s crust, etc.).     

Pilot scale evaluation of the BABIU process – Upgrading of landfill gas or biogas with the use of MSWI bottom ash

Biogas or landfill gas can be converted to a high-grade gas rich in methane with the use of municipal solid waste incineration bottom ash as a reactant for fixation of CO₂ and H₂S. In order to verify results previously obtained at a laboratory scale with 65–90 kg of bottom ash (BA), several test runs were performed at a pilot scale, using 500–1000 kg of bottom ash and up to 9.2 N m³/h real landfill gas from a landfill in the Tuscany region (Italy). The input flow rate was altered. The best process performance was observed at a input flow rate of 3.7 N m³/(h t_BA). At this flow rate, the removal efficiencies for H₂S were approximately 99.5–99%.     

Quantification of the resource recovery potential of municipal solid waste incineration bottom ashes

Municipal solid waste incineration (MSWI) plays an important role in many European waste management systems. However, increasing focus on resource criticality has raised concern regarding the possible loss of critical resources through MSWI. The primary form of solid output from waste incinerators is bottom ashes (BAs), which also have important resource potential. Based on a full-scale Danish recovery facility, detailed material and substance flow analyses (MFA and SFA) were carried out, in order to characterise the resource recovery potential of Danish BA: (i) based on historical and experimental data, all individual flows (representing different grain size fractions) within the recovery facility were quantified, (ii) the resource potential of ferrous (Fe) and non-ferrous (NFe) metals as well as rare earth elements (REE) was determined, (iii) recovery efficiencies were quantified for scrap metal and (iv) resource potential variability and recovery efficiencies were quantified based on a range of ashes from different incinerators. Recovery efficiencies for Fe and NFe reached 85% and 61%, respectively, with the resource potential of metals in BA before recovery being 7.2%ww for Fe and 2.2%ww for NFe. Considerable non-recovered resource potential was found in fine fraction (below 2 mm), where approximately 12% of the total NFe potential in the BA were left. REEs were detected in the ashes, but the levels were two or three orders of magnitude lower than typical ore concentrations. The lack of REE enrichment in BAs indicated that the post-incineration recovery of these resources may not be a likely option with current technology. Based on these results, it is recommended to focus on limiting REE-containing products in waste for incineration and improving pre-incineration sorting initiatives for these elements.     

Solidification/stabilization of ash from medical waste incineration into geopolymers

In the present work, bottom and fly ash, generated from incinerated medical waste, was used as a raw material for the production of geopolymers. The stabilization (S/S) process studied in this paper has been evaluated by means of the leaching and mechanical properties of the S/S solids obtained. Hospital waste ash, sodium hydroxide, sodium silicate solution and metakaolin were mixed. Geopolymers were cured at 50 °C for 24 h. After a certain aging time of 7 and 28 days, the strength of the geopolymer specimens, the leachability of heavy metals and the mineralogical phase of the produced geopolymers were studied. The effects of the additions of fly ash and calcium compounds were also investigated. The results showed that hospital waste ash can be utilized as source material for the production of geopolymers. The addition of fly ash and calcium compounds considerably improves the strength of the geopolymer specimens (2–8 MPa). Finally, the solidified matrices indicated that geopolymerization process is able to reduce the amount of the heavy metals found in the leachate of the hospital waste ash.     

Fragility assessment of bottom plates in above ground storage tanks during flood events

This study aims to improve the fundamental understanding on the performance of bottom plates in above ground storage tanks (ASTs) during flood events. To this end, fragility models that estimate the probability of material yielding and rupture in the bottom plates were derived. A significant number of ASTs are located in coastal areas and are susceptible to hurricane hazards. Consequently, ASTs have suffered severe damage during past hurricanes resulting in spills with catastrophic environmental and social impacts. Therefore, several failure modes such as flotation, buckling, and sliding have been studied in past research. However, the literature lacks studies that consider the failure of bottom plate due to uplift pressure generated during floods and there are no design guidelines to address this issue. To address this gap, fragility functions that provide the probability of failure as a function of tank geometry, material properties, design parameters, and hazard conditions were developed herein. For this purpose, Latin Hypercube Sampling was performed to span the space of these parameters uniformly. For each parameter combination, maximum stresses in bottom plates were determined using analytical formulations for simply supported and clamped boundary conditions and were compared against two different failure thresholds. The results were used to develop a closed form fragility model using step wise logistic regression. Fragility functions were applied to four case study tanks. Sensitivity analysis were performed to understand the impacts of different probability density functions for various variables on the bottom plates’ fragility. The results provided several insights such as ASTs with larger diameter were vulnerable to bottom plate failure. Comparison with other failure modes revealed that the probability of bottom plate failure was higher than flotation failure for anchored ASTs with clamped boundary condition.     

Mercury leaching characteristics of waste treatment residues generated from various sources in Korea

In this study, mercury (Hg) leaching characteristics of the waste treatment residues (fly ash, bottom ash, sludge, and phosphor powder) generated from various sources (municipal, industrial, medical waste incinerators, sewage sludge incinerator, oil refinery, coal-fired power plant, steel manufacturing plant, fluorescent lamp recycler, and cement kiln) in Korea were investigated. First, both Hg content analysis and toxicity characteristic leaching procedure (TCLP) testing was conducted for 31 collected residue samples. The Hg content analysis showed that fly ash from waste incinerators contained more Hg than the other residue samples. However, the TCLP values of fly ash samples with similar Hg content varied widely based on the residue type. Fly ash samples with low and high Hg leaching ratios (R_L) were further analyzed to identify the major factors that influence the Hg leaching potential. Buffering capacity of the low-R_L fly ash was higher than that of the high-R_L fly ash. The Hg speciation results suggest that the low-R_L fly ashes consisted primarily of low-solubility Hg compounds (Hg₂Cl₂, Hg⁰ or HgS), whereas the high-R_L fly ashes contain more than 20% high-solubility Hg compounds (HgCl₂ or HgSO₄).