Waste detoxification

It is not currently feasible to achieve a zero discharge of chemical pollutants from metal finishing operations. However, substantial reductions in the type and volume of hazardous chemicals wasted from most metal finishing operations are possible.8 Because end-of-pipe waste detoxification is costly for small- and medium-sized metal finishers, and the cost and liability of residuals disposal have increased for all metal finishers, management and production personnel may be more willing to consider production process modifications to reduce the amount of chemicals lost to waste. 

This section provides guidance for reducing waterborne wastes from metal finishing operations in order to avoid or reduce the need for waste detoxification and the subsequent off-site disposal of detoxification residuals. Waste reduction practices may take the form of5 ... 

Supercritical technology, 23 242,13 449 Supercritical water (SCW) properties, waste detoxification and, 14 108 Supercritical water oxidation (SCWO), 24 16-17... 

Soil has physical, chemical, and biological characteristics that can enable waste detoxification, biodegradation, chemical decomposition, and physical and chemical fixation. Therefore, land treatment of wastes can be accomplished by mixing the wastes with soil under appropriate conditions. 

It has been suggested that cesium may be useflil in the fixation of radioactive waste in a cesium-based glass and in detoxification procedures for fugitive Cs emissions, such as at Chernobyl, Ukraine. 

Also, wet air oxidation offers an alternative to conventional incineration for the destmction and detoxification of dilute ha2ardous and toxic waste waters. A 98% removal efficiency of dyehouse effluent has been claimed by wet air oxidation (203). 

Chemical treatment is a class of processes in which specific chemicals are added to wastes or to contaminated media in order to achieve detoxification. Depending on the nature of the contaminants, the chemical processes required will include pH adjustment, lysis, oxidation, reduction or a combination of these. Thus, chemical treatment is used to effect a chemical transformation of the waste to an innocuous or less toxic form. In addition, chemical treatment is often used to prepare for or facilitate the treatment of wastes by other technologies. Figure 12 identifies specific treatment processes which perform these functions. 

Solidification/Stabilization technologies are techniques designed to be used as final waste treatment. A major role of these processes is posttreatment of residuals produced by other processes such as incineration or chemical treatment. In some cases, solidification/ stabilization processes can serve as the principal treatment of hazardous wastes for which other detoxification techniques are not appropriate. High volume, low toxicity wastes (such as contaminated soils) are an example of this application. 

Livingston, A.G., Brookes, P.R., Detoxification of chemical industry wastewaters using an extractive membrane bioreactor, 49th Annual Purdue Industrial Waste Conference, May 9-11, 1994. 

Oxidation is a process in which one or more electrons are transferred from the chemical being oxidized to the chemical initiating the transfer. The main purpose of treating wastes by oxidation is detoxification. Oxidation can also aid in the precipitation of ions in cases of oxidized ions that have a solubility lower than that of the original ions. 

Destruction, detoxification, neutralization, etc. of wastes into less harmful substances... 

Aprill W, RC Sims, JL Sims, JE Mattews (1990) Assessing detoxification and degradation of wood preserving and petroleum wastes in contaminated soil. Waste Manag Res 8 45-65. 

Oxidation can be an effective way of pretreating waste prior to biological treatment either by detoxification or by rendering refractory compounds to be more amenable to biological treatment. 

Table 20.5 lists the partition and transformation processes applicable in the deep-well environment and indicates whether they significantly affect the toxicity or mobility of hazardous wastes. None of the partition processes results in detoxification (decomposition to harmless inorganic constituents), but all affect mobility in some way. All transformation processes except complexation can result in detoxification however, because transformation processes can create new toxic substances, the mobility of the waste can be critical in all processes except neutralization. 

Polymerization is the formation of large molecules (polymers) by the bonding together of many smaller molecules. For example, styrene polymerizes to form polystyrene. Polymerization can enhance the tendency of a substance to be adsorbed on mineral surfaces by increasing the molecular weight, but is not likely to result in detoxification of hazardous wastes. 

In a separate study, Igwe and Abia46 determined the equilibrium adsorption isotherms of Cd(II), Pb(II), and Zn(II) ions and detoxification of wastewater using unmodified and ethylenediamine tetraacetic acid (EDTA)-modified maize husks as a biosorbent. This study established that maize husks are excellent adsorbents for the removal of these metal ions, with the amount of metal ions adsorbed increasing as the initial concentrations increased. The study further established that EDTA modification of maize husks enhances the adsorption capacity of maize husks, which is attributed to the chelating ability of EDTA. Therefore, this study demonstrates that maize husks, which are generally considered as biomass waste, may be used as adsorbents for heavy metal removal from wastewater streams from various industries and would therefore find application in various parts of the world where development is closely tied to affordable cost as well as environmental cleanliness.46... 

Four courses of action now seem warranted. First, toxic mercurials in agriculture and industry should be replaced by less toxic substitutes. Second, controls should be applied at the point of origin to prevent the discharge of potentially harmful mercury wastes. Third, continued periodic monitoring of mercury in fish and wildlife is needed for identification of potential problem areas, and for evaluation of ongoing mercury curtailment programs. And fourth, additional research is merited on mechanisms of mercury accumulation and detoxification in comparatively pristine ecosystems. 

Deglor [Detoxification and glassification of residues] A process for vitrifying wastes, such as fly ash, by heating to 1,400°C in an electric furnace. Some of the heat is provided by radiant heaters, some by passage of electricity through the melt. Developed and piloted by ABB in Switzerland from the 1980s, commercialized in Japan in 1996. 

Exner, J.H. Detoxification of Hazardous Waste, Ann Arbor Science Michigan, 1982. 

In addition to the common pathways, glycolysis and the TCA cycle, the liver is involved with the pentose phosphate pathway regulation of blood glucose concentration via glycogen turnover and gluconeogenesis interconversion of monosaccharides lipid syntheses lipoprotein formation ketogenesis bile acid and bile salt formation phase I and phase II reactions for detoxification of waste compounds haem synthesis and degradation synthesis of non-essential amino acids and urea synthesis. 

MFO). Similar MFO microsomal redox systems operate for the metabolic detoxification of drugs and some waste products (Section 6.4). 

All tissues except mature red blood cells are able to manufacture haem for use in the respiratory cytochrome proteins of the electron transport chain. However, the liver is an especially important site of haem synthesis because it (a) is a major organ of erythropoiesis in utero and (b) haem-containing cytochrome-P450 (CYP-450) enzymes play significant roles in hepatic detoxification of drugs, toxins and endogenous waste products (Section 6.4). 

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