Thermal destruction of wastes containing polychlorinated naphthalenes in an industrial waste incinerator

An updated global overview of the manufacture and unintentional formation of polychlorinated naphthalenes (PCNs)

This review updates information on the historical manufacture and unintentional production of polychlorinated naphthalenes (PCNs). The direct toxicity of PCNs as a result of occupational human exposure and through contaminated feed in livestock was recognised decades ago, making PCNs a precursor chemical for consideration in occupational medicine and occupational safety. This was confirmed by the listing of PCNs by the Stockholm Convention as a persistent organic pollutant in the environment, food, animals and humans. PCNs were manufactured globally between 1910 ∼ 1980, but reliable data on the volumes produced or national outputs are scarce. A total figure for global production would be useful for the purposes of inventory and control and it is clear that combustion related sources such as waste incineration, industrial metallurgy and use of chlorine are current major sources of PCNs to the environment. The upper bound estimate of total global production has been put at 400,000 metric tons but the amounts (at least, many 10 s of tonnes) that are currently emitted unintentionally every year through industrial combustion processes should also be inventoried along with estimates for emissions from bush and forest fires. This would however require considerable national effort, financing and co-operation from source operators. The historical (1910-1970 s) production and resulting emissions through diffusive/evaporative releases through usage, are still reflected in documented occurrence and patterns of PCNs in human milk in Europe and other locations worldwide. More recently, PCN occurrence in human milk from Chinese provinces has been linked to local unintentional emissions from thermal processes.

The toxicological profile of polychlorinated naphthalenes (PCNs)

The legacy of polychlorinated naphthalenes (PCNs) manufactured during the last century continues to persist in the environment, food and humans. Metrological advances have improved characterisation of these occurrences, enabling studies on the effects of exposure to focus on congener groups and individual PCNs. Liver and adipose tissue show the highest retention but significant levels of PCNs are also retained by the brain and nervous system. Molecular configuration appears to influence tissue disposition as well as retention, favouring the higher chlorinated (≥ four chlorines) PCNs while most lower chlorinated molecules readily undergo hydroxylation and excretion through the renal system. Exposure to PCNs reportedly provokes a wide spectrum of adverse effects that range from hepatotoxicity, neurotoxicity and immune response suppression along with endocrine disruption leading to reproductive disorders and embryotoxicity. A number of PCNs, particularly hexachloronaphthalene congeners, elicit AhR mediated responses that are similar to, and occur within similar potency ranges as most dioxin-like polychlorinated biphenyls (PCBs) and some chlorinated dibenzo-p-dioxins and furans (PCDD/Fs), suggesting a relationship based on molecular size and configuration between these contaminants. Most toxicological responses generally appear to be associated with higher chlorinated PCNs. The most profound effects such as serious and sometimes fatal liver disease, chloracne, and wasting syndrome resulted either from earlier episodes of occupational exposure in humans or from acute experimental dosing of animals at levels that reflected these exposures. However, since the restriction of manufacture and controls on inadvertent production (during combustion processes), the principal route of human and animal exposure is likely to be dietary intake. Therefore, further investigations should include the effects of chronic lower level intake of higher chlorinated PCN congeners that persist in the human diet and subsequently in human and animal tissues. PCNs in the diet should be evaluated cumulatively with other similarly occurring dioxin-like contaminants.

Determination of polychlorinated naphthalenes in ambient air by isotope dilution gas chromatography-triple quadrupole mass spectrometry

环境空气中的多氯萘(PCNs)一般为痕量水平(pg/m³),要实现其准确定量必然对分析方法的提取、净化和仪器分析提出较高要求。研究通过考察提取溶剂种类、净化流程和色谱-质谱参数,建立了加速溶剂萃取(ASE)-多层硅胶复合中性氧化铝柱的净化方法,并利用同位素稀释气相色谱-三重四极杆质谱(GC-MS/MS)对环境空气中的多氯萘进行测定。同时,通过在采样、提取和进样分析前分别添加同位素内标,开展质量控制和保证。结果表明,在2~100 ng/mL范围内3~8氯萘的平均相对响应因子(RRF)的相对标准偏差(RSD)均小于16%。PCNs同类物的方法检出限为1~3 pg/m³(以样品体积为288 m³计算)。采用基质加标法评价了方法对环境空气样品中PCNs测定的精密度和准确度,低、中、高加标水平下3 ~8氯萘的平均加标回收率分别为89.0%~119.4%、98.6%~122.5%和93.7%~124.5%,测定结果的平均相对标准偏差分别为1.9%~7.0%、1.6%~6.6%和1.0%~4.8%。整个分析过程中,采样内标和提取内标的平均回收率分别为136.2%~146.0%和42.4%~78.1%, RSD分别为5.6%~7.5%和2.7%~17.5%,满足痕量分析的要求且平行性较好。方法的灵敏度和准确度高,精密度良好,适用于环境空气中3~8氯萘的准确定量测定,可在一定程度上缓解多氯萘监测对高分辨气相色谱-高分辨质谱的依赖,为实现多氯萘的国际履约提供方法支持。

Slaughterhouse and poultry wastes: management practices, feedstocks for renewable energy production, and recovery of value added products

The slaughterhouse and poultry industry is possibly one of the fastest-growing sectors driven by the increasing demand in food availability. Subsequently, the wastes produced from the slaughterhouse and poultry industry are in huge quantities, which could be a promising resource for the recovery of value added products, and bioenergy production to minimize the dependence on fossil fuels. Furthermore, the wastes from slaughterhouses and poultry are a hub of pathogens that is capable of infecting humans and animals. This demands the emerging need for an effective and safe disposal method to reduce the spread of diseases following animal slaughtering. In light of that, the state of the production of slaughterhouse and poultry wastes was presented at first. Following this, the impact of solid waste exposure in terms of air, water, and soil pollution and the associated health challenges due to improper solid waste management practices were presented to highlight the importance of the topic. Secondly, the potency of these solid wastes and the various waste-to-energy technologies that have been employed for effective management and resource utilization of wastes generated from slaughterhouses and poultry were reviewed in detail. Finally, this review also highlights the opportunities and challenges associated with effective solid waste management, future requirements for the development of effective technologies for the recovery of value added products (like keratin, fibreboards), and biofuel production.

Reduction of polychlorinated naphthalenes (PCNs) emission from municipal waste incinerators in Taiwan: Recommendation on control technology

Emission factor and removal efficacy of PCNs are evaluated via the flue gas sampling of two MWIs equipped with different air pollution control devices (APCDs) in Taiwan. MWI-A is equipped with ESP, wet scrubber (WS) and selective catalytic reduction (SCR), while cyclone (CY), semi-dry absorber (SDA), activated carbon injection (ACI) and baghouse (BH) are employed in MWI-B. The average concentrations of PCNs measured at stacks of MWI-A and MWI-B are 2.1 ng Nm^-3 (0.218 pg TEQ Nm^-3) and 23.2 ng Nm^-3 (0.425 pg TEQ Nm^-3), respectively. The emission factors of PCNs calculated from feeding rates of waste and stack sampling results range from 6.7 to 6.95 μg t^-1 (0.790-1.45 ng TEQ t^-1). PCNs are formed in ESP via chlorination, while SCR and SDA + ACI + BH are effective in removing PCNs with the overall efficacies of 97.6% and 94.3%, respectively. PCN removal efficiencies achieved with SCR and SDA + ACI + BH increase as chlorination level increases. Specifically, around 72% and 82% of Mono-CN are removed by SCR and SDA + ACI + BH, respectively. The removal efficacies of other homologues achieved with SCR are consistently high (96-100%). Dominances of Mono-to Tri-CNs in scrubbing liquid collected from WS and higher removal efficacies of these homologues achieved with WS + ESP compared with ESP alone indicate that WS can capture low chlorinated PCNs to some extent. The results suggest that CY + SDA + ACI + BH should be equipped in MWI for effective removal of PCNs, while ESP, WS and SCR should be utilized with precaution to eliminate PCNs formation and enhance the PCNs removal efficiency.

Investigation on pyrolysis and incineration of chrome-tanned solid waste from tanneries for effective treatment and disposal: an experimental study

Chrome-tanned leather solid wastes (leather finished trimmings (LFT) and chrome shavings (CS)) from tanneries were studied using pyrolysis and incineration. Detailed characterization of CS and LFT indicated higher calorific value of 15.77 MJ/kg and 19.97 MJ/kg respectively, which makes it suitable for thermal treatment. Thermal Gravimetric Analysis (TGA) of CS and LFT recorded a weight loss of 79.82% and 68.22% at 800 °C respectively. Energy-dispersive X-ray spectroscopy and scanning electron microscopy analysis for CS and LFT were also carried out. Pyrolysis of CS and LFT was carried out using a fixed bed-type pyrolysis unit at a temperature of 500 ± 10 °C for a reaction time of 30 min and three different by-products (bio-oil, biochar and pyrolytic gas) were obtained as a result of pyrolysis. From pyrolysis process, higher bio-oil yields of 52 wt.% and 49 wt.% from LFT and CS with calorific value of 28.0 and 27.8 MJ/kg respectively were obtained. The calorific values of the biochar obtained from LFT and CS were found to be 20.5 and 23.0 MJ/kg respectively. Incineration was carried out in the existing incineration facility of 150 kg/h capacity at a temperature of 1200 °C. The results of incineration process showed a higher weight reduction (93.0 wt.%) and higher concentration of gaseous emissions, revealing the need for off-gas treatment. Further, FT-IR spectra of residual ash from the incineration process revealed the occurrence of oxidation of trivalent chromium to its hexavalent form, which could be a potential raw material in the metallurgical/chemical industry for the synthesis of sodium chromate or ferrochrome alloy. Comparative experimental investigations of pyrolysis and incineration revealed that incineration could be a potential treatment and disposal option, in developing countries like India, for chrome-tanned leather solid wastes from tanneries, for producing heat energy and the residue with potential utilization viability in another industry paving a way towards circular economy.

Validity of using a relative potency factor approach for the risk management of dioxin-like polychlorinated naphthalenes

Here, we characterized the dioxin-like activities of 42 polychlorinated naphthalenes (PCNs) and 6 technical Halowax formulations by using the DR-CALUX (dioxin-responsive chemically activated luciferase expression) assay with rat hepatoma luciferase-expressing H4IIE cells. Of the 42 PCNs examined, 31 showed dioxin-like activities, for which the mass-based REP-EC_5TCDD (potency relative to that of 2,3,7,8-tetrachlorodibenzo-p-dioxin based on the 5% effective concentration determined from the dose-response curve for 2,3,7,8-TCDD) ranged from 0.00000012 to 0.0051, indicating that some of the PCNs (e.g., 1,2,3,6,7,8-HxCN and 1,2,3,4,6,7-HxCN) had dioxin-like activities that were equal to or higher than the WHO-TEFs and the mass-based REP-EC_5TCDD reported for dioxins such as octachlorodibenzo-p-dioxin, octachlorodibenzofuran, 3,3',4,4'-tetrachlorobiphenyl (PCB-77), 3,4,4',5-tetrachlorobiphenyl (PCB-81), and 3,3',4,4',5,5'-hexachlorobiphenyl (PCB-169). For PeCNs to OCN with high dioxin-like activities, REPs determined in previous studies were comparable to the REP values obtained in the present study. The TCDD-EQs (2,3,7,8-TCDD equivalents) obtained experimentally for the Halowax formulations decreased in the order HW1051 (37 mg/kg) > HW1014 (30 mg/kg) > HW1013 (5.6 mg/kg) > HW1099 (2.9 mg/kg) > HW1001 (0.60 mg/kg) > HW1031 (<0.10 mg/kg) and were comparable to the theoretical TCDD-EQs calculated by multiplying the concentration and REP of each PCN. In addition, the theoretical TCDD-EQs for PCNs in emission gases produced by thermal processes were below the Japanese emission standard of 0.1-10 ng WHO-toxicity equivalent (TEQ)/m³N, and 3 to 4 orders of magnitude lower than the corresponding WHO-TEQ. Based on a comparison of theoretical and experimental TCDD-EQs, we found that our REP-based approach was suitable for the risk management of industrially produced and unintentionally generated dioxin-like PCNs. This approach will be particularly useful for the risk management of unintentionally generated PCNs in emission gases because the contribution of dioxin-like PCNs to the whole dioxin-like toxicity of emission gases can be elucidated.

Concentrations of POPs based wood preservatives in waste timber from demolished buildings and its recycled products in Japan

One of the major proportions of recycled persistent organic pollutants (POPs)-containing waste is timber originating from old buildings, utility poles, and cross-arms because POPs-based treatments were once a common means of preserving wood. In 2016 and 2017, we conducted the first survey in Japan on the residue concentrations of chlordanes (CHLs), pentachlorophenol (PCP), pentachloroanisole (PCA), and polychloronaphthalenes (PCNs) in waste timber (n = 55) and its recycled products (woodchip, n = 42; particle board, n = 3). In the recycled products, the highest concentrations detected were 0.86 mg kg^-1 CHLs, 3.0 mg kg^-1 PCP, 1.1 mg kg^-1 PCA, and 2.6 mg kg^-1 PCNs, which were one to two orders lower than the low POP content (LPC) limits for the environmentally sound management of wastes defined under the Basel Convention (50, 100, and 10 mg kg^-1, respectively). In the waste timber, which included bearers and columns from demolished buildings, the highest concentrations were 15 mg kg^-1 CHLs, 0.20 mg kg^-1 PCP, and 0.036 mg kg^-1 PCNs, no higher than about 30% of the LPC limit. The concentration of CHLs in timber bearer was significantly higher than those in timber column (p < 0.05). Although none of the waste timber or recycled products had concentrations exceeding the LPC limits, one means of ensuring low POP concentrations in recycled products is separating timber bearer from timber column when demolishing wooden buildings, according to the results in Japan. The timber column can be used to produce recycled products and the remaining timber can be used for heat utilization and power generation.