Levels of Polycyclic Aromatic Hydrocarbons (PAHs) in Healthcare Waste Incinerators’ Bottom Ash from Five County Hospitals in Kenya

Health-care waste contains potentially harmful microorganisms and compounds which can infect and affect hospital patients, healthcare workers, the general public and environment. Therefore, management of health care waste requires safe handling, treatment and disposal procedures. While incineration reduces the volume and quantity of waste for final disposal, it leads to the production of fly and bottom ashes laden with toxic incomplete combustion products such as Polycyclic Aromatic Hydrocarbons (PAHs), dioxins, furans and heavy metals. This exposes workers who handle and dispose the bottom ashes, hospital patients, the general public and environment. The goal of this study was to determine the total and individual levels of 16 most prevalent and toxic PAHs. Bottom ash samples were collected from incinerators in five county hospitals in Kenya, namely;Moi-Voi, Narok, Kitale, Makindu and Isiolo. Bottom ash samples were collected over a period of six months from the five hospitals. The samples were then sieved, homogenised and stored at 4°C in amber coloured glass containers. The PAHs were extracted using 30 ml of a hexane-acetone solvent (1:1) mixture by ultrasonication at room temperature (23°C) for 45 minutes. The PAHs were then analyzed with a GC-MS spectrophotometer model (Shimadzu GCMS-QP2010 SE) connected to a computer work station was used for the PAHs analysis. The GC-MS was equipped with an SGE BPX5 GC capillary column (30 m × 0.25 mm × 0.25 μm) for the separation of compounds. Helium was used as the carrier gas at a flow rate of 15.5 ml/minute and 14.5 psi. 1 μl of the sample was injected at 280°C, split mode (10:1). The oven programming was set for a total runtime of 40 minutes, which included: 100°C (2-minute hold);10°C /min rise to 200°C;7°C /min rise to 249°C;3°C /min rise to 300°C (2-minute hold). The interface temperature was set at 290°C. Analysis was done in Selected Ion Monitoring (SIM) mode and the peak areas of each of the PAHs were collected from the chromatograph and used for quantification of the 16 PAHs listed by the U.S. Environmental Protection Agency (EPA) which included, BaA (benz[a]anthracene: 4 rings), BaP (benzo[a]pyrene: 5 rings), BbF (benzo [b]fluoranthene: 5 rings), BkF (benzo[k]fluoranthene: 5 rings), Chr (chrysene: 4 rings), DbA (dibenz[a,h]anthracene: 5 rings), InP (indeno[1,2,3 - cd] pyrene: 6 rings) and Acp (acenaphthene: 3 rings), Acpy (acenaphthylene: 3 rings), Ant (anthracene: 3 rings), BghiP (benzo[g,h,i]perylene: 6 rings), Flu (fluorene: 3 rings), FluA (fluoranthene: 4 rings), Nap (naphthalene: 2 rings), PhA (phenanthrene: 3 rings) and Pyr (pyrene: 4 rings). Ion source-interface temperature was set at 200°C - 250°C. Internal standards from Sigma Aldrich were used in the analysis and the acquired mass spectra data were then matched against the NIST 2014 library [1] [2]. The mean PAHs concentration in the bottom ashes of each hospital varied broadly from 0.001 mg/kg to 0.4845 mg/kg, and the mean total concentration levels of individual PAHs ranged from 0.0072 mg/kg to 1.171 mg/kg. Low molecular weight PAHs (Phenanthrene, Naphthalene and Fluorene) were predominant in all the hospital wastes whereas Kitale and Narok presented the lowest PAHs concentrations and the lowest number of individual PAHs. Moi/Voi recorded the highest total PAHs concentration at 1.3129 ± 0.0023 mg/kg from a total of 11 PAHs being detected from the bottom ash samples. Narok had only three PAHs being detected at very low concentrations of 0.0041 ± 0.00 mg/kg, 0.0076 ± 0.00 mg/kg and 0.012 ± 0.00 mg/kg for phenanthrene, anthracene and chrysene respectively. This study presents hospital incinerator bottom ash as containing detectable levels of both carcinogenic and non-carcinogenic PAHs. Continued unprotected exposure of hospital workers (waste handlers) to the bottom ash PAHs could be hazardous to their health because of their cumulative effect. Preventive measures e.g. the use of Personal protective equipment (PPE) should be prioritised to minimise direct contact with the bottom ash. The study recommends an upgrade on incinerator technology for efficient combustion processes thus for better pollution control.

Concentration of Copper, Zinc, Lead, Cadmium, and Nickel in the Incinerator Bottom Ash in Five County Hospitals in Kenya

Healthcare wastes contain potentially harmful microorganisms, inorganic and organic compounds that pose a risk to human health and the environment. Incineration is a common method employed in healthcare waste management to reduce volume, quantity, toxicity as well as elimination of microorganisms. However, some of the substances remain unchanged during incineration and become part of bottom ash, such as heavy metals and persistent organic pollutants. Monitoring of pollution by heavy metals is important since their concentrations in the environment affect public health. The goal of this study was to determine the levels of Copper (Cu), Zinc (Zn) Lead (Pb), Cadmium (Cd) and Nickel (Ni) in the incinerator bottom ash in five selected County hospitals in Kenya. Bottom ash samples were collected over a period of six months. Sample preparation and treatment were done using standard methods. Analysis of the heavy metals were done using atomic absorption spectrophotometer, model AA-6200. One-Way Analysis of Variance (ANOVA) was performed to determine whether there were significant differences on the mean levels of Cu, Zn, Pd, Cd and Ni in incinerator bottom ash from the five sampling locations. A post-hoc Tukey’s Test (HSD) was used to determine if there were significant differences between and within samples. The significant differences were accepted at p ≤ 0.05. To standardize the results, overall mean of each metal from each site was calculated. The metal mean concentration values were compared with existing permissible levels set by the WHO. The concentrations (mg/kg) were in the range of 102.27 - 192.53 for Cu, Zn (131.68 - 2840.85), Pb (41.06 - 303.96), Cd (1.92 - 20.49) whereas Ni was (13.83 - 38.27) with a mean of 150.76 ± 77.88 for Copper, 131.66 ± 1598.95 for Zinc, 234.60 ± 262.76 for Lead, 12.256 ± 10.86 for Cadmium and 29.45 ± 18.24 for Nickel across the five sampling locations. There were significant differences between levels determined by one-way ANOVA of Zn (F (4, 25) = 6.893, p = 0.001, p ≤ 0.05) and Cd (F (4, 25) = 5.641, p = 0.02) and none with Cu (F (4, 25) = 1.405, p = 0.261, p ≤ 0.05), Pb (F (4, 25) = 1.073, p = 0.391, p ≤ 0.05) and Ni (F (4, 25) = 2.492, p = 0.069). Results reveal that metal content in all samples exceed the WHO permissible levels for Cu (100 mg/kg), while those for Ni were below the WHO set standards of 50 mg/kg. Levels of Zn in three hospitals exceeded permissible level of 300 mg/kg while level of Pb exceeded WHO set standards of 100 mg/kg in two hospitals. Samples from four hospitals exceeded permissible level for Cd of 3 mg/kg. This study provides evidence that incinerator bottom ash is contaminated with toxic heavy metals to human health and the environment. This study recommends that hospitals should handle the bottom ash as hazardous wastes and there is need to train and provide appropriate personal protective equipment to healthcare workers, waste handlers, and incinerator operators and enforce compliance to existing regulation and guidelines on healthcare waste management to safeguard the environment and human health.

Investigation of basic properties of fly ash from urban waste incinerators in China

Basic properties of fly ash samples from different urban waste combustion facilities in China were analyzed using as X-ray fluorescence （XRF）, scanning electron microscopy （SEM）, X-ray diffraction （XRD）. The leaching toxicity procedure and some factors influencing heavy metals distribution in fly ash were further investigated. Experimental results indicate that the fly ash structures are complex and its properties are variable. The results of XRF and SEM revealed that the major elements （〉10000 mg/kg, listed in decreasing order of abundance） in fly ash are O, Ca, Cl, Si, S, K, Na, Al, Fe and Zn. These elements account for 93% to 97%, and the content of Cl ranges from 6.93% to 29.18 %, while that of SiO2 does from 4.48% to 24.84%. The minor elements （1000 to 10000 mg/kg） include Cr, Cu and Pb. Primary heavy metals in fly ash include Zn, Pb, Cr, Cu etc. According to standard leaching test, heavy metal leaching levels vary from 0 to 163.10 mg/L （Pb） and from 0.049 to 164.90 mg/L （Zn）, mostly exceeding the Chinese Identification Standard for hazardous wastes. Morphology of fly ash is irregular, with both amorphous structures and polycrystalline aggregates. Further research showed that heavy metals were volatilized at a high furnace temperature, condensed when cooling down during the post-furnace system and captured at air pollution control systems. Generally, heavy metals are mainly present in the forms of aerosol particulates or tiny particulates enriched on surfaces of fly ash particles. The properties of fly ash are greatly influenced by the treatment capacities of incinerators or the variation of waste retention time in chamber. Fly ash from combustors of larger capacities generally has higher contents of volatile component and higher leaching toxicity, while those of smaller capacities often produce fly ash containing higher levels of nonvolatile components and has lower toxicity. The content of heavy metals and leaching toxicity maybe have no convincing correlation, and high alkali content of CaO greatly contribute to leaching toxicity of heavy metal and acid neutralization capacity against acid rain.

Chemical speciation and mobility of heavy metals in municipal solid waste incinerator fly ash

Chemical speciation is a significant factor that governs the toxicity and mobility of heavy metals in municipal solid waste incinerator fly ash. Sequential extraction procedure is applied to fractionate heavy metals(Pb, Zn, Cd, Cu, and Cr) into five defined groups: exchangeable, carbonate, Fe-Mn oxide, organic, and residual fractions. The mobility of heavy metals is also investigated with the aid of toxicity characteristic leaching procedure. In the fly ash sample, Pb is primarily presented in the carbonate(51%) and exchangeable(20%) fractions; Cd and Zn mainly exist as the exchangeable(83% and 49% respectively); Cu is mostly contained in the last three fractions(totally 87%); and Cr is mainly contained in the residual fraction(62%). Pb, Zn and Cd showed the high mobility in the investigation, thus might be of risk to the natural environment when municipal solid waste incinerator fly ash is landfilled or reutilized.

Polychlorinated dibenzo-p-dioxins and dibenzofurans in flue gas emissions from municipal solid waste incinerators in China

Polychlorinated dibenzo-p-dioxins and furans （PCDD/Fs） emissions in flue gas from two types of municipal solid waste incinerators （MSWIs） most commonly used in China were investigated in this study. The selected incinerators include two grate-type MSWIs： MSWI-A （350 t/d） and MSWI-B 050 t/d）, and two fluidized bed MSWIs： MSWI-C （400 t/d） and MSWI-D （400 t/d）, which are all equipped with semi-dry lime scrubber and bag filter except MSWI-D equipped with cyclone and wet scrubber （WS） as air pollutant control device （APCD）. Results indicated that the emission concentration and the international toxic equivalents （I-TEQs） of the PCDD/Fs from the stacks were in the range of 1.210-10.273 ng/Nm^3 and 0.019-0.201 ng I-TEQ/Nm^3, respectively. They were greatly lower than the emission regulation standard of PCDD/Fs in China （1.0 ng I-TEQ/Nm^3）. However, only the PCDD/Fs emission level from MSWI-C was below 0.1 ng I-TEQ/Nm^3. Although the homologue profiles were distinct, the contributions of the 2,3,7,8-subsituted congeners to the total I-TEQ were similar among all the investigated MSWIs. Two major 2,3,7,8-substituted congeners, 2,3,4,7,8-PeCDF and 1,2,3,7,8-PeCDD, account for 47% and 9% （average values） of the total I-TEQ values, respectively. The correlation between PCDD/Fs levels and composition of flue gas was also discussed.

Effective incineration technology with a new-type rotary waste incinerator

The technology of steady combustion in a new type of rotary incinerator is firstly discussed. The formation and control of HCl,NOx and SO_(2) during the incineration of sampled municipal organic solid waste are studied with the incinerator. Results showed that the new model of rotary incinerator can effectively control and reduce the pollutant formations by post combustion.

Analysis of Medical Waste Incinerator Performance Based on Fuel Consumption and Cycle Times

A detailed assessment of an incinerator based on fuel consumption and cycle time data is presented in this paper. The study was conducted at Temeke district hospital for 22 months consecutively covering 654 days of daily data collection on fuel consumption and cycle times. The composition for the medical waste incinerated varied between 15% and 35% for sharps waste and between 65% and 85% for other waste, with mean values of 25% and 75%, respectively. The results revealed poor performance of the incinerator due to higher fuel consumption (above 30 L/cycle). The incineration cycle times were observed to range between 2 and 4 hours, all of which were too high for the loading rates observed (55 - 214 kg). A strong dependency of diesel oil consumption on cycle time was observed due to lack of temperature control leading to continuous fuel flow into the burners. The incineration capacity was very low compared to other incinerators in terms of tons per year. This paper gives an insight on the factors affecting incinerator performance assessed based on diesel oil consumption and cycle times. It can be generalized that the incinerator performance was poor due to several factors ranging from poor incinerator design, operator skills, waste management practices, waste storage practices, etc. The hospital was advised to install a new incinerator with short incineration cycle time (30 - 40 minutes) and lower fuel consumption (10 L/cycle) at a loading rate of 200 kg/cycle.

Steam Oxidation Resistance of Nitride Bonded Silicon Carbide Refractories for Waste Incinerators at Elevated Temperatures

Steam oxidation resistance of Si3N4 and Si2N2O as well as SiAlON bonded SiC refractories at 900℃was tested according to ASTM-C863.Phase composition and microstructure before and after oxidation were analyzed by XRD and SEM.The results show that Si3N4 and Si2N2O bonded SiC refractory presents better steam oxidation resistance than SiAlON bonded SiC.For Si3N4 and Si2N2O bonded SiC,the oxidation speed is higher with more pronounced volume expansion in the early 100 h;afterwards,the volume expansion slows down gradually and starts to level off after 300 h.It is considered that the high silica glass phase formed during the oxidation covers Si3N4 and Si2N2O,and SiC as a protective layer and fills the open pores.But for SiAlON bonded SiC,the volume expands gradually and constantly with the increasing oxidation duration even after 500 h,due to the continuous formation of mullite transformed from oxidation products and Al2O3 in SiAlON.

INCINERATOR FOR FIAMMABLE RADIOACTIVE WASTES

An incinerator was built up in 1987 in Shanghai. In this paper, the devices of the incinerator, main parameters of the process, the results of combustion tests for nonradioactive waste and simulated radwaste are given. The instructive information for radwaste treatment were provided.

Determination of thermal parameters for waste liquid and gas fluidized-bed incinerator

Equations are established for calculation of dense and dilute phase zone combustion temperatures, quantity of auxiliary fuel and thermal efficiency for a fluidized bed incinerator with coal burnt as auxiliary fuel, waste liquid burnt in dense phase zone and waste gas burnt in dilute phase zone while there is a heat transfer, thereby providing theoretical basis for design of waste liquid and gas fluidized bed incinerators.

Geo-environmental application of municipal solid waste incinerator ash stabilized with cement

The behavior of soluble salts contained in the municipal solid waste incinerator(MSWI) ash significantly affects the strength development and hardening reaction when stabilized with cement.The present study focuses on the compaction and strength behavior of mixed specimens of cement and MSWI ash.A series of indices such as unconfined compressive strength,split tensile strength,California bearing ratio(CBR) and pH value was examined.Prior to this,the specimens were cured for 7 d,14 d,and 28 d.The test results depict that the maximum dry density(MDD) decreases and the optimum moisture content(OMC)increases with the addition of cement.The test results also reveal that the cement increases the strength of the mixed specimens.Thus,the combination of MSWI ash and cement can be used as a lightweight filling material in different structures like embankment and road construction.

Effects of Nucleating Agents on Crystallization of Arc-Molten Slag from Incinerator Fly Ash

Glass-ceramics obtained from the electric arc furnace molten slag of incinerator fly ash was produced by applying nucleation and crystallization through heat treatment process. The effects of nucleating agent （TiO2 and Cr2O3） on the crystallization kinetics and heat treatment schedule of the slag were investigated. The results show that the nucleating agents changed the crystallization phase and morphology of the obtained glass-ceramics. The optimum heat treatment schedule of the glass with TiO2 was determined as nucleation at 952 K for 1.5 h and crystal growth at 1 258 K for 1.5 h, while those values with Cr203 were estimated at 971 K for 2 h and at 1 238 K for 2 h. TiO2 acting as nucleating agent could decrease the activation energy of the slag and shorten the total thermal treatment time in comparison with Cr2O3. The glass-ceramics obtained under the optimum heat treatment condition was environmentfriendly and had remarkable physical/mechanical properties and chemical durability.

Effects on Strengths of Cement Mortar When Using Incinerator Bottom Ash as Fine Aggregate

The main purpose of this paper is to study the feasibility of using the Incinerator bottom ash fine aggregate to replace natural fine aggregate in the cement mortar products. The research adopts high cement content mortar to conduct the experiment, in which the weight ratio of cement/aggregate is 1/2. The experiment uses Incinerator bottom ash fine aggregates, which passes through #16 sieve, and natural sand of the same size as the aggregate, and separates mortar specimens in- to two main categories based on different W/C ratio. Moreover, different proportions of furnace slag and F-class are used to replace a portion of cement so as to explore the influence on strength of Incinerator bottom ash aggregates mortar by adding the two admixtures. The study shows that, based on the 1:2 cement/aggregate weight ratio, Incinerator bottom ash fine aggregates mortar, unit weight around 1.8 g/cm3, is 20% lighter natural fine aggregate mortar, unit weight around 2.2 g/cm3. The Incinerator bottom ash fine aggregates mortar can only reach 60%-70% the compressive strength of natural fine aggregates mortar. Direct tensile strength and flexural tensile strength tests are 15% and 30% of compressive strength respectively, due to the irregular strength development, which does not follow general concepts, such as low W/C ratio and mineral admixtures will not necessarily help in strength development in Incinerator bottom ash fine aggregates mortar.

Elemental Analysis of Fly and Bottom Ash from Burners/Incinerators in Selected Health Care Facilities in Kiambu County, Kenya

Medical waste incinerators emit a wide range of pollutants like heavy metals, dioxins and furans. These include Pb （lead）, Hg （mercury）, Cd （cadmium）, fine dust particles and PICs （products of incomplete combustion）. The objective was to determine the elemental composition of medical waste residue after incineration in selected hospitals in Kiambu County, Kenya. Bottom/fly ash samples were collected from the burners/incinerators in the selected health care facilities visited. The concentrations of the metals in the fly ash and bottom ash were determined using an XRF （X-ray fluorescence） spectrometer after acid digestion. The concentrations of heavy metals in the fly and bottom ash were as follows： Ti （titanium） 62-839 mg·kg^-1 and a mean of 202 mg·kg^-1 and 344 mg·kg^-1 in fly ash and bottom ash, respectively. Ca （calcium） was 37,753-204,475 mg.kg1 with means of 27,132 mg.kg-1 in fly ash and 131,185 mgg·kg^-1 in bottom ash. Zn （zinc） was 297-6,605 mg·kg^-1 with means （2,307 mg·kg^-1 in fly ash, 4,359 mg·kg^-1 in bottom ash）, Pb （13-1,819 mg·kg^-1） had means of 280 mg·kg^-1 in fly ash and 291 mg-kg-1 in bottom ash. Cu （copper） （9.5-250 mg·kg^-1） had means of 83.47 mg·kg^-1 in fly ash and 98.8 mg·kg^-1 in bottom ash. The wide variations in results can be attributed to the different burners/incinerators used and different segregation methods of the medical waste. The results show that the reported levels of heavy metals could pose a health risk due to possible leaching after disposal.

Performance of a Large-Scale Medical Waste Incinerator in a Referral Hospital

The aim of the study was to analyze the performance of large scale incinerator installed in a referral hospital. The study involved weighing and loading infectious waste of different composition (sharps and other waste), recording temperatures in the primary and secondary chamber with time, fuel used and collecting and weighing the bottom ash for 65 days. The analysis shows that the incinerator on average uses 362 L/day (45 L/h) to incinerate 945 kg of medical waste (40.8 kg/day of sharps waste and 904 kg/day of other waste), generating 51.2 kg of ash daily. The observed fuel consumption rate was too high necessitating corrective action. The average weight reduction was 94.6%. The study shows that the average sharps waste composition for medical waste incinerated was 4.3% and other waste was 95.7%. The incinerator capacity ranged between 100 and 130 kg/h. The fuel effectiveness ranged between 2.0 and 3.0 liters of diesel per kg of waste incinerated. The fuel effectiveness increased linearly with total waste incinerated and incinerator capacity, respectively, depending on the fuel consumption rate.

Application and Hydration Resistance of SiC Refractories for Water-cooled Wall of Waste Incinerators

According to the dual needs of heat transfer and thermal insulation in incinerators,different parts of the incinerators are designed with refractories of different SiC contents.Water vapor is mainly concentrated in the zones of feeding,drying and combustion,and the main damage factors of SiC refractories include high temperature and hydration.The results of hydration resistance of typical SiC-containing refractories show that the higher the SiC content,the worse the hydration resistance.Si_(3)N_(4)-SiC refractories after oxidation treatment have good hydration corrosion resistance,which are appropriate for water-cooled wall of waste incinerators.

Assessment of Medical Waste Incinerator Performance Based on Physical Characteristics of Ashes

The aim of this study was to assess the performance of the combustion process during medical waste incineration by studying physical properties of the ashes produced. Combustion characteristics data including maximum temperatures, total weight of waste loaded, weight of ashes, weight reduction, sieve analysis and particle size distribution were determined experimentally. The test runs were conducted in a newly installed incinerator at Temeke district hospital. The average maximum temperatures achieved in the primary chamber was 397.8℃and 839℃ for secondary chamber with average incineration cycle time of 99 minutes. These temperatures were lower compared to the design temperatures of 650℃ and 950℃ as a result of loading wet waste. The ash samples were collected under the incinerator grate by randomly sampling the ashes for each run after weighing the total ash. The particle size distribution of ashes observed was not uniform due to presence of non-combustible materials in the sharps waste. However, the fineness modulus ranged between 2.0 and 4.0, which is in the acceptable range. From the above results it was concluded that, the incinerator performance was high in terms of the parameters assessed. To improve the incinerator performance further, it was recommended that the medical waste should be stored in a dry place away from rain.

Diagnostic Analysis of Mechanical Conditions of Small-Scale Incinerators in the Healthcare Facilities in Tanzania

This paper provides analytical diagnosis of mechanical conditions of medical waste incinerators used for healthcare waste (HCW) treatment in Tanzania. The main features assessed were types of incinerators, features of incinerators and incinerator house. The assessment was conducted in three levels of health care facilities (HCFs), that is, Regional, district hospitals and health centers, existed in 26 regions of Tanzania. Questionnaires, interview and checklists were used as tools for data collection. It was observed that High-Tech incinerators are mainly used in regional hospitals, while district hospital and health center use both High-Tech and De-Montfort incinerators. About 60% of the incinerators have defective doors. More than 55% of incinerators are corroded in regional and district hospitals. The chimney, top plates and grate which are good condition are 55.6% and 60% in regional hospitals and health centers, respectively. The situation is below 50% in district hospitals. The leakage of the roof and loose structures were observed in district hospitals and health center to be more than 50% of the incinerator houses. On other hand, the performance of burners and incinerator housing cleanliness are generally good. It was concluded that the incinerators in the HCFs are in bad conditions, necessitating maintenance.

Particulate Matter Concentrations in the Vicinity of an Incinerator

Incineration is an effective way of health care waste management, but it is also a source of air pollution. Thermal decomposition of organic and inorganic waste during incineration releases a large concentration of air pollutants such as CO, SO2, NOx, CO2 and particulate matter (PM). A cross sectional-descriptive study was conducted to determine the short-term variations in PM concentrations across various areas in the vicinity of a local incinerator in Windhoek, Namibia. XRF Qualitative analysis method was used to determine the elemental composition of fallout dust concentration from six study areas/stations in the vicinity of a local incinerator. Single bucket fallout monitors were deployed following the American Society for Testing and Materials standard method for collection and analysis of dust fallout to determine the elemental composition of fallout dust. Real-time PM concentration trends were also recorded using a portable Micro dust Pro Real-time Dust Monitor for PM10 at a height of 2.2 m above the ground. High PM concentration peaks were observed in the morning and afternoon hours at varying points. The fallout dust rate ranged between highest 1839.3 mg/m2/day at sampling Point 4 and lowest 711 mg/m2/day at sampling Point 2. The XRF analysis revealed the presence of toxic elements and crustal elements in order of decreasing abundance: Mn > Zn > Cr > V > Zr > Sr > Pb > Ni and SI > K > Fe > Ti > Ca > Al > P respectively. Highest elemental composition concentrations were found at sampling location in the vicinity of the incinerator and in industrial area.

Effects of Sulfur Compounds on Cd Partitioning in a Simulated Municipal Solid Waste Incinerator

The effect of sulfur compounds （including sulfur, sulfide, sulfite and sulfate）, initial concentration of heavy metal and operating conditions on Cd emission in municipal solid waste （MSW） incineration were investi-gated using a simulated tubular furnace and simulated MSW spiked with Cd. The concentration of Cd was meas-ured by inductively coupled plasma-atomic emission spectrometry （ICP-AES） after digesting the samples including bottom ash, fly ash and flue gas according to related USEPA methods. The results show that S and Na2S tend to in- crease Cd partitioning in bottom ash, whereas Na2SO3 and Na2SO4 tend to reduce Cd partitioning in bottom ash. The effect of sulfur compounds on Cd partitioning in bottom ash was in the sequence of Na2S〉S〉Na2SO3〉 Na2SO4. chemical equilibrium analysis is also performed to determine the effect of sorbents on Cd adsorption. The calculations show that S presents strong affinity for Cd and restrains Cd adsorption by SiO2, whereas when temperature rises to between 830℃ and 1030℃, Cd adsorption efficiency of SiO2 is over 80% and the efficiency of Al2O3 is up to 85%.