Dioxin destruction

The destruction of dioxins by biological, chemical or thermal means is costly, not least because their low (but highly significant) concentrations are dispersed in large volumes of other (benign) material. Thus large volumes of material must be treated in dioxin destruction processes. 

Selecting, field testing, demonstrating, and evaluating different dioxin destruction technologies. 

The Portable Unit has successfully demonstrated its capability for thermal treatment of hazardous wastes at the source of the material. This type of on-site treatment would eliminate the need of transportation of hazardous materials to a distant site of stationary treatment equipment. The Portable Unit also has demonstrated that it can be moved to a site and be ready to treat material very quickly, a capability which will be very important in operation of full scale equipment. The on-site treatment of the Times Beach dioxin contaminated soil resulted in no dioxin detected in any of the incinerator effluent streams. The product of the testing activity was soil with no detectable level of dioxin. Dioxin contaminated soil thermally treated in this manner will yield soil which can be disposed as non-hazardous material. The decontamination was performed without exceeding RCRA requirements for particulate emissions and with dioxin destruction efficiencies surpassing the required percentage. The overall conclusion was that the infrared incinerator can very effectively remove dioxin from contaminated... 

The principal PIC for penta and penta-treated wood would include volatile organic compounds (VOCs), semivolatile organic compounds (SVOCs), dioxins and furans, as well as SOj, COj, NO, and HCl. Penta would be expected to have undergone a very high destruction efficiency (DRE) during the fire (> 99.99%). Among the VOC emissions, the following chemicals likely contributed to air pollution problems benzene, bromobenzene, chloromethane, 1,3-butadiene, iodomethane, acetone, chloroform, and 1,2-dichloroethane. 

Thermal processes are typically used for highly toxic waste or highly concentrated organic wastes. If the waste contains PCB, dioxins, or other toxic substances, incineration should be chosen in order to assure destruction. If the wastes contain greater than 1000 parts per million of halogens (chlorinated materials), it would probably be desirable to select incineration of these wastes, after consideration of other options. In any case, a material may be incinerated or used as a fuel if the heat content is greater than 8500 BTUs per pound or, if between 2500 and 8500, it may be incinerated with auxiliary fuel. The waste components of concern are halogens, alkali metals and heavy metals. 

Mere destruction of the original hazardous material is not, however, an adequate measure of the performance of an incinerator. Products of incomplete combustion can be as toxic as, or even more toxic than, the materials from which they evolve. Indeed, highly mutagenic PAHs are readily generated along with soot in fuel-rich regions of most hydrocarbon flames. Formation of dioxins in the combustion of chlorinated hydrocarbons has also been reported. We need to understand the entire sequence of reactions involved in incineration in order to assess the effectiveness and risks of hazardous waste incineration. 

Emissions from hazardous waste combustors are regulated under two statutory authorities RCRA and the CAA. The MACT standards set emission limitations for dioxins, furans, metals, particulate matter, total chlorine, hydrocarbons/carbon monoxide, and destruction and removal efficiency (DRE) for organics. Once a facility has demonstrated compliance with the MACT standards by conducting its comprehensive performance test (CPT) and submitting its notification of compliance (NOC), it is no longer subject to the RCRA emission requirements with a few exceptions. RCRA-permitted facilities, however, must continue to comply with their permitted emissions requirements until they obtain modifications to remove any duplicative emissions conditions from their RCRA... 

The disposal and destruction of chlorinated compounds is a subject of great importance. In fact, in 1993, some environmental groups had proposed the need for a chlorine-free economy. The cost of complete elimination of chlorinated compounds is quite staggering with the latest estimate as high as 160 billion/year.46 The most common method to destroy chlorocarbons is by high-temperature thermal oxidation (incineration).47 The toxic chlorinated compounds seem to be completely destroyed at high temperatures however, there is concern about the formation of toxic by-products such as dioxins and furans.48... 

Minimum and maximum operating temperature —CO destruction efficiency continuously or at set intervals —Confirmatory dioxin tests... 

Hilarides and others (1994) investigated the destruction of TCDD on artificially contaminated soils using °Co y radiation. It appeared that TCDD underwent stepwise reduction dechlorination from tetra- to tri-, then di- to chlorodioxin, and then to presumably nonchlorinated dioxins and phenols. The investigators discovered that the greatest amount of TCDD destruction (92%) occurred when soils were amended with 25% water and 2% nonionic surfactant [alkoxylated fatty alcohol (Plurafac RA-40)]. Replicate experiments conducted without the surfactant lowered the rate of TCDD destruction. 

Since 1974, the USEPA has conducted many incineration tests for pesticide destruction. Most pesticides tested were capable of being destroyed to an efficiency of more than 99.99%. The only exception was Mirex, with 98-99% destruction. However, investigators felt that destruction could be improved to the 99.99% level with a somewhat more effective incinerator design. Incineration has become very controversial in recent years because of the potential to generate dioxin under high temperature conditions. 

Alzeta states that their TPUs can achieve 99.99% destruction with emissions of nitrogen oxides and carbon monoxide of <10 parts per million (ppm) corrected for 3% oxygen emissions. They also state the Alzeta systems prevent the formation of dioxins and furans, and are available with several different operating systems and capacities for different site requirements. 

Complete destruction of principle organic contaminants without the production of dioxin and dibenzofuran. 

Destruction of hazardous organic materials, without the production of dioxin... 

The in vitro bioassay for dioxins with cleaned sediment extracts (DR-CALUX) proved to comply with the QA/QC criteria needed to guarantee the reliability of data in an inter- and intralaboratory study (Besselink et al., 2004). The chemical stability of dioxins makes it possible to apply destructive clean-up procedures which remove all matrix factors. Sample extraction and cleanup for other in vitro bioassays for specific mechanisms of toxicity require further development to make sure that the chemicals of interest are not lost or unwanted chemicals included in the sediment extract to be tested. Table 4 summarizes possible bioassays that could be performed in addition to chemical analyses with the dredged sediment in a licensing system. 

The proposed mechanism by which chlorinated dioxins and furans form has shifted from one of incomplete destruction of the waste to one of low temperature, downstream formation on fly ash particles (33). Two mechanisms are proposed, a de novo synthesis, in which PCDD and PCDF are formed from organic carbon sources and Cl in the presence of metal catalysts, and a more direct synthesis from chlorinated oiganic precursors, again involving heterogeneous catalysis. Bench-scale tests suggest that the optimum temperature for PCDD and PCDF formation in the presence of fly ash is roughly 300°C. 

Dehalogenation occurs by either the replacement of halogen molecules or the destruction of the contaminant. Soil and sediment that are contaminated with chlorinated organic compounds, especially PCBs, dioxins, and furans, can be remediated through dehalogenation. The contaminated soil is screened, processed with a crusher and pug mill, and mixed with sodium bicarbonate. The mixture is heated to above 330°C (630°F) in a reactor to partially decompose and volatilize the contaminants. The volatilized contaminants are captured, condensed, and treated separately. 

Dioxins 0.00001- 0.05 0.5 90-99.9 Dechlorination, soil washing, thermal destruction... 

Dioxins are now ubiquitous, thanks to the widespread popularity of 2,4-D and 2,4,5-T herbicides for weed control in agriculture and the massive use of Agent Orange in a defoliation and crop destruction program in Vietnam. Between 1966-81 farm use of herbicides had increased 280)6 to 625M, exceeding total insecticide use. 

There is a lack of effective reduction technologies. Fundamental research on dioxins emission control needs to be effectively promoted. The best available techniques (BAT) and best environmental practices (BEP) for the destruction of the existing PCB wastes need to be implemented. More environmentally benign alternatives to PBDEs are to be sought to meet the demand for FRs. 

Based on the activities that were initially conducted for the enabling activity project (Bravante and Medina, 2004), it was reported that little is known about POPs in the country and that even the users have minimal understanding of their hazards. As no comprehensive data on POPs is available for use as baseline information, a more comprehensive inventory is needed for the Philippines to have an actual measure of the risks that must be managed and addressed in the NIP. The Initial National Inventory conducted showed that POPs have already been banned in the country except HCB and mirex, which have no recorded use, importation or production in the country. Significant amounts of PCBs mainly come from electric transformers and capacitors. Dioxins and Source Inventory by DOST showed that there are numerous sources of dioxins and furans in the country, which emit significant quantities of dioxins and furans into the environment. No treatment facility in the country that deals with the destruction of POPs and other toxic hazardous wastes are present in the country (Bravante and Moreno, 2005). 

Palauschek, N., Scholz, S. (1987) Destruction of polychlorinated dibenzo-p-dioxins and dibenzofurans in contaminated water samples using ozone. Chemosphere 16, 1857-1863. 

Kahr G, Pauliny I, Fercher E. 1990. Destruction of dioxins and furans adsorbed on fly ash in a rotary kiln furnace. Chemosphere 20 1855-1858. 

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