Other waste treatment applications

A system for the disinfection of swimming pools based on hypobromite is available. This is a modification of a hypochlorite generator system marketed by Olin, called the Lectranator [44]. 

Electrochemical methods can be used in the destruction of nitrate [34], which may arise as part of ion exchange operations. Regeneration of the effluent from ion exchange resin beds can be achieved by a combined process of cathodic reduction and anodic oxidation. 

Nitrate is first cathodically reduced to ammonia which is stripped from the catholyte and passed to the anolyte for oxidation. 

---

Pyrometallurgical treatment The use of heat in furnaces or incinerators to volatilize and remove arsenic or other inorganic contaminants from solid wastes. For millennia prior to waste treatment applications, this smelting technology was used to extract and concentrate valuable elements from ore deposits. 

Whether the radiation source is a machine-generated e-beam, isotopic gamma rays, or machine-generated x-rays (bremsstrahlung), a continuum of x-rays and electrons is produced as the initial event dissipates its energy in the irradiated medium. This chapter will focus on an e-beam source, as this is the most likely source to be used in a waste-treatment application. It should be noted that most of the comments made here are equally applicable to other sources of radiation. 

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. 

Other plant-scale applications to pollution control include the flotation of suspended sewage particles by depressurizing so as to release dissolved air [Jenkins, Scherfig, and Eckhoff, Applications of Adsorptive Bubble Separation Techniques to Wastewater Treatment, in Lemlich (ed.). Adsorptive Bubble Separation Techniques, Academic, New York, 1972, chap. 14 and Richter, Internat. Chem. Eng, 16,614 (1976)]. Dissolved-air flotation is also employed in treating waste-water from pulp and paper mills [Coertze, Prog. Water TechnoL, 10, 449(1978) and Severeid, TAPPl 62(2), 61, 1979]. In addition, there is the flotation, with electrolytically released bubbles [Chambers and Cottrell, Chem. Eng, 83(16), 95 (1976)], of oily iron dust [Ellwood, Chem. Eng, 75(16), 82 (1968)] and of a variety of wastes from surface-treatment processes at the maintenance and overhaul base of an airline [Roth and Ferguson, Desalination, 23, 49 (1977)]. 

Pollutant parameters and their concentrations found in the oily waste subcategory streams are shown in Table 9.9. The oily waste subcategory for the metal finishing industry is characterized by both concentrated and dilute oily waste streams that consist of a mixture of free oils, emulsified oils, greases, and other assorted organics. Applicable treatment of oily waste streams is dependent on the concentration levels of the wastes, but oily wastes normally receive specific treatment for oil removal prior to solids removal waste treatment. 

After the separation of the actinides from the high-level waste, it is desirable to remove certain other fission products from the nuclear wastes. Some Cs and Sr are low-charged cations that react well with macro-cyclic ligands (e.g., crown ethers, calixarenes). Research to synthesize and investigate the properties of macrocyclic ligands for application in nuclear waste treatment has been an active effort internationally. Some of the results obtained are discussed in section 12.7. 

Sxploratory studies were also undertaken to examine the technical feasibility of application of RO/UF in industrial processes such as waste treatment for recovery of chemicals and/or reuse of water, and in pollution control. Some of the typical problems which were investigated earlier have already been reported (3). Other applications which were studied further are briefly described here ... 

Carbon also is produced and used in other forms namely, activated carbon, carbon black, and coke, that have many commercial applications. Structurally they are amorphous forms of carbon belonging to the graphites. Activated carbon or activated charcoal has a highly porous honeycomb-like internal structure and adsorbs many gases, vapors, and colloidal solids over its very large internal surface area. Some of its major applications include purification of water and air, air analysis, waste treatment, removal of subur dioxide from stack gases, and decolorization of sugar. 

Potential applications for CA-CDI technology include the purification of boiler water for fossil and nuclear power plants, volume reduction of liquid radioactive waste, treatment of agricultural wastewater containing pesticides and other toxic compounds, creation of ultrapure water for semiconductor processing, treatment of wastewater from electroplating operations, desalination of seawater, and removal of salt from water for agricultural irrigation. 

Water has an unusually high (374°C) critical temperature owing to its polarity. At supercritical conditions water can dissolve gases such as 02 and nonpolar organic compounds as well as salts. This phenomenon is of interest for oxidation of toxic wastewater (see Waste treatments, hazardous waste). Many of the other more commonly used supercritical fluids are listed in Table 1, which is useful as an initial screening for a potential supercritical solvent. The ultimate choice for a specific application, however, is likely to depend on additional factors such as safety, flammability, phase behavior, solubility, and expense. 

Since the disclosure by Mobil of Micelle-Templated Silicate structures called MCM-41 (hexagonal symmetry) or MCM-48 (cubic symmetry) [1,2] many other structures have been synthesized using different surfactants and different synthesis conditions. All of these Micelle-Templated Silicas (MTS) have attracted much interest in fields as diverse as catalysis, adsorption, waste treatment and nanotechnology. MTS materials possess a high surface area ( 1000 m2/g), high pore volume ( 1 mL/g), tunable pore size (18-150 A), narrow pore size distribution, adjustable wall thickness (5-20 A). The silica walls can be doped with different metals for catalytic applications, like Al orTi, for acidic or oxydation reactions, respectively. 

At NSF, a great deal of work is done on the development and implementation of NSF standards and criteria for health-related equipment. The majority of NSF standards relate to water treatment and purification equipment, products for swimming pool applications, plastic pipe for potable water as well as drain, waste, and vent (DWV) uses, plumbing components for mobil homes and recreational vehicles, laboratory furniture, hospital cabinets, polyethylene refuse bags and containers, aerobic waste treatment plants, and other products related to environmental quality. 

Because of the need to avoid mutations and maintain the superior qualities of the genetically developed strain, batch or fed-batch operations are used in most applications. Continuous culture operations, however, provide a time-invariant environment that facilitates greatly the study of a biological process in research laboratories. Moreover, some industrial operations employ continuous reactors, such as the single-cell protein facility of ICI in Billingham, England (total reactor volume of about 2,300 m3), all waste treatment processes, and others. It should be noted that it is relatively common to follow a batch process with a period of fed-batch or continuous operation. Also, in most cases batch cultivation is the optimal start-up procedure for continuous or fed-batch cultivation (Yamane et al, 1977). 

We must recognize, however, that our abilities may be limited by a lack of other types of data and by the limitations of the rapidly evolving science of risk assessment. In an effort to minimize these limitations, the Office of Solid Waste is investigating the best available risk assessment techniques. These include estimation of the movement of pollutants through soil, air, and water prediction of adverse human health and environmental effects on the basis of available toxicity data and prediction of the effects of simultaneous exposures to numerous toxic substances. OSW is, in addition, actively compiling data relative to the cost, applicability, and effectiveness of currently available waste treatment, storage, and disposal technologies. 

---