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1.
Floor dusts from Vietnamese end-of-life vehicle (ELV)-processing households were investigated to elucidate the contamination levels and exposure risk of polychlorinated biphenyls (PCBs), polybrominated diphenyl ethers (PBDEs) and dioxin-related compounds (DRCs). The concentrations were in order of PBDEs (260–11,000, median 280 ng/g overall) > PCBs (19–2200, median 140 ng/g) > dioxin-like PCBs (8.8–450, median 22 ng/g) ? polybrominated dibenzo-p-dioxin/dibenzofurans (PBDD/Fs, 2000–28,000, median 8500 pg/g) > polychlorinated dibenzo-p-dioxin/dibenzofurans (PCDD/Fs, 440–4100, median 1800 pg/g) > MoBPCDD/Fs (1.9–1200, median 250 pg/g). Concentrations of PCBs and DRCs were higher than those reported for Vietnamese urban houses, indicating ELV processing as a significant source of these contaminants. Higher concentrations of PCBs relative to PBDEs suggest the abundance of old electrical capacitors/transformers in ELVs. The PBDD/F and PCDD/F profiles were indicative of DecaBDE-containing materials and combustion sources, respectively. PBDFs, PCDFs and DL-PCBs were the most important dioxin-like toxic equivalent (TEQ) contributors. The estimated PCB and TEQ intake doses from dust ingestion approached or exceeded the reference doses for children living in some ELV-processing households, indicating potential health risk. More comprehensive risk assessment of the exposure to PCBs and DRCs is required for residents of informal ELV recycling sites.  相似文献   

2.
Sludge as dioxins suppressant in hospital waste incineration   总被引:1,自引:0,他引:1  
Nitrogen containing compounds such as ammonia, urea and amines can effectively inhibit the formation of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs). Sewage sludge accumulates both sulfur and nitrogen during wastewater treatment so it could be used to reduce PCDD/Fs formation. Indeed, it is observed in this study that the gas evolving from the sludge drying process can significantly suppress chlorobenzene (CBz) and PCDD/Fs formation from fly ash collected from a hospital waste incinerator. For instance, the reduction of hexachlorobenzene (HxCBz) and PCDD/Fs amount was 92.1% and 78.7%, respectively, when the drying gas evolving from 2g sludge flew through 2g fly ash. These tests were conducted in the frame of projects devoted to hospital waste incineration. The disposal technology for hospital waste (HW), developed in this institute, features rotary kiln pyrolysis combined with post-combustion followed by flue gas cleaning. Hence, some preliminary tests were devoted to investigate dioxins suppression by co-pyrolysis and co-combustion of polyvinyl chloride (PVC) and sludge in lab scale. More experimental research will be conducted to appropriately assess these effects of sludge on PCDD/Fs emissions during co-pyrolysis/combustion of HW and sludge.  相似文献   

3.
Polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs) are formed during waste incineration and in waste-to-energy boilers. Incomplete combustion, too short residence times at low combustion temperatures (<700 °C), incineration of electronic waste and plastic waste containing chlorine are all factors influencing the formation of PCDD/Fs in boilers. The impact of chlorine and catalysing metals (such as copper and iron) in the fuel on PCDD/F formation was studied in a 12 MWth circulating fluidised bed (CFB) boiler. The PCDD/F concentrations in the raw gas after the convection pass of the boiler and in the fly ashes were compared. The fuel types were a so-called clean biomass with low content of chlorine, biomass with enhanced content of chlorine from supply of PVC, and solid recovered fuel (SRF) which is a waste fuel containing higher concentrations of both chlorine, and catalysing metals. The PCDD/F formation increased for the biomass with enhanced chlorine content and it was significantly reduced in the raw gas as well as in the fly ashes by injection of ammonium sulphate. A link, the alkali chloride track, is demonstrated between the level of alkali chlorides in the gas phase, the chlorine content in the deposits in the convection pass and finally the PCDD/F formation. The formation of PCDD/Fs was also significantly reduced during co-combustion of SRF with municipal sewage sludge (MSS) compared to when SRF was fired without MSS as additional fuel.  相似文献   

4.
Dioxins like polychlorinated dibenzo-p-dioxins (PCSDDs), polychlorinated dibenzofurans (PCDFs) and polychlorinated biphenyls (PCBs) are mainly emitted from waste incinerators (WIs) and have become an international research focus because of its serious concerns over the adverse health effects. The detoxification of PCCDs/Fs and PCBs is very difficult because of their stable chemical structure. A significant hydrodechlorination/detoxification of polychlorinated 1-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs) and polychlorinated biphenyls (PCBs) were achieved in fly ash by using an aqueous mixture of calcium hydroxide and sulfur. Two different fly ashes were studied: originating from municipal waste incinerator (FA1) and industrial waste incinerator (FA2). They were heated with the aqueous mixture at 150 °C for 30 or 60 min with agitation. Higher decomposition (87%) and detoxification (87.7%) of PCDD/Fs and PCBs were achieved at 150 °C with two runs; every run was for 30 min, compared to one run for 60 min. FA2 gave higher decomposition and detoxification as compared to FA1, which might be due to higher metal content that played a catalytic role to decompose and detoxify the PCDDs, PCDFs and PCBs. The decomposition and detoxification of PCDFs in fly ash was higher than PCDDs and was augmented with increasing number of chlorides on aromatic compounds. As the highly significant decomposition and detoxification of higher concentration of PCDD/Fs and PCBs were achieved in 1 hour without additive catalyst and at low temperature of 150 °C, therefore, the developed method is cost effective and most suitable to apply on commercial/industrial level. The detail results of hydrodechlorination/detoxification of PCDD, PCDFs at different conditions are described and its mechanism is discussed.  相似文献   

5.
An efficient catalytic detoxification method for polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans (PCDD/Fs) in fly ash produced by municipal waste incinerator has been studied using palladium on carbon (Pd/C) catalyst. As one of the trace components in fly ash, the detoxification of PCDD/Fs is very difficult because of the interferences of other persistent components with higher concentrations. However, the detoxification reaction of PCDD/Fs shows higher activity in water/isopropanol solution using commercial Pd/C catalyst at 40 degrees C under normal pressure. The results indicated that the catalytic degradation of PCDFs has been found to be easier than that of PCDDs. Moreover, the dechlorination ratios were higher for octa- and hepta-chlorinated congeners than those for tetra- and penta-chlorinated ones. The detoxification process worked well in water. The dechlorination efficiencies of almost all of the PCDD/Fs congeners can reach over 99% within a shorter reaction time.  相似文献   

6.
Open dumping sites in Surabaya and Palembang, Indonesia, have been studied to investigate emissions of polychlorinated dibenzo-para-dioxins and dibenzofurans (PCDD/Fs) and dioxin-like polychlorinated biphenyls (DL-PCBs), as well as the resulting soil contamination that might be caused by open burning of municipal solid waste. The emission factors of the waste residue, accounting for the ratio of waste burned, have also been characterized. The concentrations of PCDD/Fs and DL-PCBs in soil from Palembang were 61–310 pg-TEQ/g (dry weight) and 6.3–32 pg-TEQ/g, respectively. In Surabaya, very low levels of PCDD/Fs and DL-PCBs, ranging from 0.075 to 0.098 and 0.00032 to 0.095 pg-TEQ/g, respectively, were observed in soil for an open dumping site that included a top cover layer of soil above the compacted waste. The large difference in concentrations can be explained by the fact that open burning of waste is the source of PCDD/Fs and DL-PCBs. The emission factors for the residue for PCDD/Fs ranged from 27 to 140 pg-TEQ/g, and a sensitivity analysis found that the maximum emission factor to the residue could be 5600 pg-TEQ/g. Our results indicate that emissions of PCDD/Fs can be controlled by modifying the open dumping process to one that involves depositing soil layers on top of the compacted waste.  相似文献   

7.
The application of activated carbons has become a commonly used emission control protocol for the removal or adsorption of persistent organic pollutants from the flue gas streams of waste incinerators. In this study, the 2378-substituted PCDD/F removal efficiency of three types of activated carbons derived from the pyrolysis of refuse derived fuel, textile waste and scrap tyre was investigated and compared with that of a commercial carbon. Experiments were carried out in a laboratory scale fixed-bed reactor under a simulated flue gas at 275 °C with a reaction period of four days. The PCDD/F in the solid matrices and exhaust gas, were analyzed using gas chromatography coupled with a triple quadrupole mass spectrometer. In the absence of activated carbon adsorbent, there was a significant increase in the concentration of toxic PCDD/F produced in the reacted flyash, reaching up to 6.6 times higher than in the raw flyash. In addition, there was a substantial release of PCDD/F into the gas phase, which was found in the flue gas trapping system. By application of the different commercial, refuse derived fuel, textile and tyre activated carbons the total PCDD/F toxic equivalent removal efficiencies in the exhaust gas stream were 58%, 57%, 64% and 52%, respectively. In general, the removal of the PCDDs was much higher with an average of 85% compared to PCDFs at 41%. Analysis of the reacted activated carbons showed that there was some formation of PCDD/F, for instance, a total of 60.6 μg I-TEQ kg−1 toxic PCDD/F was formed in the refuse derived fuel activated carbon compared to 34 μg I-TEQ kg−1 in the commercial activated carbon. The activated carbons derived from the pyrolysis of waste, therefore, showed good potential as a control material for PCDD/F emissions in waste incinerator flue gases.  相似文献   

8.
The huge amount of medical waste (MW) has caused a tough challenge to environmental protection in China because of its serious infectious potential. At present, incineration is the most common technology for MW disposal. Unfortunately, the medical waste incinerator (MWI) is considered one of the major sources of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs). This study was conducted to investigate the generation and the components of MW; the fingerprint of PCDD/Fs in MWI; and PCDD/F, polychlorinated biphenyl (PCB) and hexachlorobenzene concentrations in residue ash. The estimated annual production of MW was estimated to be 0.97 million tons in China in 2008; in addition, plastic and rubber accounted for 24.5% of MW contents. PCDD/F emissions from MWI could be divided into two main groups according their fingerprints, and the ratio of PCDFs/PCDDs was mostly over 1.5, with a mean value of 3.43. The toxic equivalent of PCDD/Fs was over 30 times that of the value of PCBs in the residue ash, and PCDD/F contents in fly ash accounted for approximately 67% of the total output of PCDD/Fs, which was in line with the UNEP default emission factors for MWI (class 3, 63.7%).  相似文献   

9.
Polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs) are emitted in trace amounts from municipal solid waste (MSW) incinerators. The exposure to PCDD/Fs experienced by an individual is dominated by the food chain pathway, which accounts for over 98% of the total uptake. Defining a target daily intake (the World Health Organization TDI of 10 pg I-TEQ kg.bw−1day−1) exposure assessment algorithms were then applied to arrive at the corresponding PCDD/F levels in air, soil, plants, food products, etc., which would allow the target intake to be met while retaining the balance of intake between the various exposure pathways. These concentrations were converted to an ambient air concentration of PCDD/Fs and ultimately, by defining criteria for acceptability, to a guide value for PCDD/F concentration in emissions from the MSW incinerator. This strategy was applied to PCDD/F emissions from MSW incinerators of various sizes against two illustrative criteria for acceptability: an “insignificant” release and a threshold above which the release may require further assessment for environmental effects and for control. Using the criteria developed in this paper, the current PCDD/F emission limit of 0.1 ng I-TEQ m−3results in an emission that is classed as “insignificant” for all plant sizes. However, higher emission concentrations can also be accommodated below the threshold for further assessment and control.  相似文献   

10.
The characterization of PCDD/Fs and heavy metals in the flue gas and fly ash of Harbin municipal solid waste (MSW) incineration plant, located in the northeast of China, was investigated in this study. The MSW was treated in a twin internal fluidized (TIF) bed incinerator. The results indicate that the emission of PCDD/Fs into the environment is 0.02 ng I-TEQ/m3 and the level of PCDD/Fs in the fabric filter fly ash is 0.7982 ng I-TEQ/g. The leachability levels of Pb, Cd and Hg in the fly ash are below the limits of environmental protection standard in China. However, the contents of Cu, Zn, and Hg are high in the fly ash. This suggests that the fly ash is a hazardous waste that requires special treatment and disposal. The practice of more than four years of operation shows that the TIF bed incinerator is very suitable and practical for China.  相似文献   

11.
Very few data for polybrominated diphenyl ethers (PBDEs) were available in the electronic waste (e-waste) as one of the most PBDEs emission source. This study reported concentrations of PBDEs in e-waste including printer, rice cooker, computer monitor, TV, electric iron and water dispenser, as well as dust from e-waste, e-waste dismantling workshop and surface soil from inside and outside of an e-waste recycling plant in Shanghai, Eastern China. The results showed that PBDEs were detected in the majority of e-waste, and the concentrations of ΣPBDEs ranged from not detected to 175 g/kg, with a mean value of 10.8 g/kg. PBDEs were found in TVs made in China after 1990. The mean concentrations of ΣPBDEs in e-waste made in Korea, Japan, Singapore and China were 1.84 g/kg, 20.5 g/kg, 0.91 g/kg, 4.48 g/kg, respectively. The levels of ΣPBDEs in e-waste made in Japan far exceed the threshold limit of RoHS (1.00 g/kg). BDE-209 dominated in e-waste, accounting for over 93%. The compositional patterns of PBDEs congeners resembled the profile of Saytex 102E, indicating the source of deca-BDE. Among the samples of dust and surface soil from a typical e-waste recycling site, the highest concentrations of Σ18PBDEs and BDE-209 were found in dust in e-waste, ranging from 1960 to 340,710 ng/g and from 910 to 320,400 ng/g, which were 1–2 orders of magnitude higher than other samples. It suggested that PBDEs released from e-waste via dust, and then transferred to surrounding environment.  相似文献   

12.
As part of the NJ Toxics Reduction Workplan for NY-NJ Harbor, ambient water samples were collected at fifteen locations along the tidal portions of the Hackensack, Passaic, Raritan, Rahway and Elizabeth Rivers, and in Newark Bay, the Arthur Kill, and Kill van Kull. A Trace Organics Platform Sampler was used to collect a total of 75 suspended sediment phase samples between June 2000 and May 2002. These samples were analyzed for spatial and wet vs. dry weather trends in the 17 polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs; modified USEPA Method 1613b). Mean total PCDD/F (tPCDD/F) concentrations at the sampling locations ranged between 3.8 and 41.5 ng/g. On average, OCDD accounted for almost 80% of the tPCDD/F concentrations; mean total [PCDD/F – OCDD] concentrations ranged between 0.84 and 5.20 ng/g at the sampling locations. Mean 2,3,7,8-TCDD concentrations ranged between 0.003 and 0.28 ng/g, with the highest concentrations (> 0.10 ng/g) along the tidal Passaic and lower Hackensack Rivers, and in upper Newark Bay. Mean tPCDD/F Toxic Equivalency Quotients (TEQ) ranged between 45 and 344 TEQ pg/g, with the highest levels found in the lower Passaic River. Toxicity was primarily driven by 2,3,7,8-TCDD concentrations in the Passaic and Hackensack Rivers, and in Newark Bay. Examples of congener distribution patterns at some of the sampling locations are also presented.  相似文献   

13.
Hospital solid waste incinerator (HSWI) fly ash contains a large number of carbon constituents including powder activated carbon and unburned carbon, which are the major source of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) in fly ash. Therefore, the removal of carbon constituents could reduce PCDD/Fs in fly ash greatly. In this study, the effects of the main flotation parameters on the removal of carbon constituents were investigated, and the characteristics of the final product were evaluated. The results showed that loss on ignition (LOI) of fly ash increased from 11.1% to 31.6% during conditioning process. By optimizing the flotation parameters at slurry concentration 0.05 kg/l, kerosene dosage 12 kg/t, frother dosage 3 kg/t and air flow rate 0.06 m3/h, 92.7% of the carbon constituents were removed from the raw fly ash. Under these conditions, the froth product has LOI of 56.35% and calorific values of 12.5 MJ/kg, LOI in the tailings was below 5%, and the total toxic equivalent (TEQ) of PCDD/Fs decreased from 5.61 ng-TEQ/g in the raw fly ash to 1.47 ng-TEQ/g in the tailings. The results show that column flotation is a potential technology for simultaneous separation of carbon constituents and PCDD/Fs from HSWI fly ash.  相似文献   

14.
The formation of polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans (PCDDs/Fs) from carbon that was produced by the pyrolysis of paper fibers and from wood charcoal was investigated experimentally. Fibers obtained from filter paper were pyrolyzed at 300° and 800°C to produce low- and high-temperature carbon samples. The two types of carbon and wood charcoal were mixed with silica (SiO2) and trace copper oxide to produce three synthetic fly ash samples. Experiments to measure the formation of PCCDs/Fs from the three ash samples were conducted using a bench-scale reactor. The two carbon samples derived from paper fibers generated more PCDDs/Fs than was generated by the wood charcoal. The PCDDs/Fs generated by the low-temperature carbon and by the wood charcoal were dominated by the lower-chlorinated PCDFs. Such unique homologue distribution patterns are very similar to those generated by the open burning of household waste. The high-temperature carbon generated more highly chlorinated PCDDs/Fs. The effect of pyrolysis temperature on the de novo formation of PCDDs/Fs from residual carbon is discussed. Paper and paper products contained in household waste are likely to be the source of unburned carbon that contributes to high PCDD/F emissions in the open burning of household waste.  相似文献   

15.
Biogas production from anaerobic digestion of chicken feathers with swine manure or slaughterhouse sludge was assessed in two separate experiments. Ground feathers without any pre-treatment were added to 42-L digesters inoculated with swine manure or slaughterhouse sludge, representing 37% and 23% of total solids, respectively and incubated at 25 °C in batch mode. Compared to the control without feather addition, total CH4 production increased by 130% (P < 0.001) and 110% (P = 0.09) in the swine manure and the slaughterhouse sludge digesters, respectively. Mixed liquor NH4N concentration increased (P < 0.001) from 4.8 and 3.1 g/L at the beginning of the digestion to 6.9 and 3.5 g/L at the end of digestion in the swine manure and the slaughterhouse sludge digesters, respectively. The fraction of proteolytic microorganisms increased (P < 0.001) during the digestion from 12.5% to 14.5% and 11.3% to 13.0% in the swine manure and the slaughterhouse sludge digesters with feather addition, respectively, but decreased in the controls. These results are reflective of feather digestion. Feather addition did not affect CH4 yields of the swine manure digesters (P = 0.082) and the slaughterhouse sludge digesters (P = 0.21), indicating that feathers can be digested together with swine manure or slaughterhouse sludge without negatively affecting the digestion of swine manure and slaughterhouse sludge.  相似文献   

16.
The effect of ammonia inhibition was evaluated during the enhanced anaerobic treatment of digested effluent from a 700 m3 chicken-manure continuous stirred tank reactor (CSTR). A 12.3 L internal circulation (IC) reactor inoculated with an anaerobic granular sludge and operated at 35 ± 1 °C was employed for the investigation. With a corresponding organic loading rate of 1.5-3.5 kg-COD/m3 d over a hydraulic retention time of 1.5 d, a maximum volumetric biogas production rate of 1.2 m3/m3 d and TCOD (total COD) removal efficiency ranging from 70% to 80% was achieved. However, the continual increase in the influent TAN content led to ammonia inhibition in the methanogenesis system. The SCOD/TAN (soluble COD/total ammonia nitrogen) ratio was presented to be the key controlling factor for the anaerobic treatment of semi-digested chicken manure, and further validation through shock loading and ammonia inhibition experiments was conducted. The threshold value of the SCOD/TAN ratio was determined to be 2.4 (corresponding to a TAN of 1250 mg/L) at an influent pH of 8.5-9.  相似文献   

17.
The input and output samples from existing large-scale municipal solid waste incinerator (MSWI) were collected and analyzed for polychlorinated dibenzo-р-dioxins and dibenzofurans (PCDD/Fs) in this study, aiming to evaluate PCDD/F characteristic and the corresponding mass balance through the whole system. The grate-type MSWI is equipped with semi-dry scrubber, activated carbon injection, and bag filter as air pollutant control devices (APCDs). Results showed that on the output side, the stack gas, bottom ash and fly ash presented their mean dioxin levels of 0.078 ng I-TEQ/Nm(3), 12.94 ng I-TEQ/kg and 858 ng I-TEQ/kg, respectively, and showed large similarities in congener profiles. Instead, on the input side, the municipal solid waste (MSW) presented a mean dioxin level of 15.56 ng I-TEQ/kg and a remarkable difference in congener profiles compared with those of the output. The dioxin mass balance demonstrated that the annual dioxin input value was around 5.38 g I-TEQ/yr, lower than the total output value (7.62 g I-TEQ/yr), signifying a positive dioxin balance of about 2.25 g I-TEQ/yr.  相似文献   

18.
The biosolids (BS) generated in the wastewater treatment process of a meat processing plant were monitored and the priority pollutant content was characterized. The trace metal and organic pollutant content – polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs) and polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/PCDF) – were determined quantitatively and compared to guideline limits established by the US EPA and EU. PCBs were not detected in the solid samples, while trace metals, PAHs and PCDD/PCDF were detected in concentrations below the limits established by international standards. Toxic equivalent factors were evaluated for the biosolids, and the results proved that these wastes can be safely deposited on land or used in combustion/incineration plants. Since no previous data were found for meat processing waste, comparisons were made using municipal sewage sludge data reported in the literature. Since, this report monitored part of the priority pollutants established by the US EPA for meat and poultry processing wastewater and sludge, the results verified that low pollution loads are generated by the meat processing plant located in the southern part of Brazil. However, the BS generated in the treatment processes are in accordance with the limits established for waste disposal and even for soil fertilizer.  相似文献   

19.
采用化学除油降黏—污泥调理—离心脱水工艺处理某炼油厂废水处理系统的混合污泥,并对工艺条件进行优化。实验结果表明,最佳的工艺条件为:化学除油降黏阶段处理体系的pH=4,反应温度35 ℃,H2O2加入量 2 g/L,m(H2O2)∶ m(Fe2+)=4,反应时间 60 min;污泥调理反应阶段的CaO加入量7.0 g/L;离心脱水阶段在分离因数为1 558时脱水5 min。在此条件下,得到的泥饼的含水率为70.0%~75.0%(w),含油率小于2%(w),污泥比阻约为3.0×107 s2/g。  相似文献   

20.
Effects of carbon concentration and Cu additive in simulated fly ash (SFA) and real fly ash (RFA) on the formation of polychlorinated dibenzofurans (PCDFs), polychlorinated dibenzo-p-dioxins (PCDDs), chlorobenzenes, and polychlorinated biphenyls which were all regarded as persistent chlorinated aromatics in iron ore sintering were investigated. In the annealing process of SFA with various carbon contents, the yield of chlorinated aromatics and the I-TEQ obtained their maximum at 10 wt% carbon content. Active carbon in SFA acted as the carbon source as well as an adsorbent which led to higher production of PCDD/F in solid phase at 10 wt% carbon content. The increase of carbon content will be beneficial on the formation of 2,3,7,8-Chloro-substituted PCDF compared with 2,3,7,8-Chloro-substituted PCDD. In addition, the CuCl2·2H2O was a much more powerful catalyst in the formation of chlorinated aromatic compounds compared with elementary Cu, since it served as both a catalyst and a chlorine donor. However, the RFA behaved similarly with SFA with elementary Cu in the formation of chlorinated aromatic compounds. The effect of carbon content and copper additives on formation of 2,3,7,8-chloro-substituted congeners displayed similar characteristics with the tetra- to octa-PCDD/F isomers and even the total PCDD/Fs.  相似文献   

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