Chemical treatment processes

Adsorption This is the most widely used of the physical-chemical treatment processes. It is used primarily for the removal of soluble organics with activated carbon serving as the adsorbent. Most liquid-phase-activated carbon adsorption reactions follow a Freundlich Isotherm [Eq. (25-21)]. 

The cellulose fiber in paper is attacked and weakened by sulfur dioxide. Paper made before about 1750 is not significantly affected by sulfur dioxide (11). At about that time, the manufacture of paper changed to a chemical treatment process that broke down the wood fiber more rapidly. It is thought that this process introduces trace quantities of metals, which catalyze the conversion of sulfur dioxide to sulfuric add. Sulfuric acid causes the paper to become brittle and more subject to cracking and tearing. New papers have become available to minimize the interaction with SO2. 

To understand chemical treatment processes, it must be remembered that a reaction is not a process. A reaction involves the chemical transformation of a material, whether this is carried out on a lab-scale or an industrial-scale. A process, on tbe other hand, is a series of actions or operations needed to make such a reaction occur in a controlled manner. Thus, the development of a process requires the design of the... 

Chemical treatment processes rely on the intimate mixing of reagents with the waste. Thus, the wastes generally treated by chemical means must be in an aqueous or slurry form. 

Figure 13. Flow diagram of a generic chemical treatment process.

Models typically range from 10 to over 1000 square feet of effective flotation area for raw wastewater flows to over 1000 gallons per minute. Complete systems often include chemical treatment processes. A dissolved air... 

This treatment process involves the use of chemical compounds to initiate a chemical reaction in the wastewater stream, which ends up neutralizing negatively charged colloids and thus, causing changes that would alter the nature of the wastewater, particularly to conform to the standard of wastewater discharge.4 The treatment process possesses an inherent disadvantage, especially net increase in the dissolved constituents of the wastewater, which can hinder reuse of the wastewater.2 Common chemical treatment processes are discussed below. 

Due to the high content of SS and FOG, pretreatment is always necessary for the food industry. It can decrease contaminant loading for subsequent biological and/or chemical treatment processes as well as protect process equipment. In addition, pretreatment is economical in the total process view as it is not as expensive as biological and chemical treatment. 

Knowledge about chemical conversion processes which take place in aquatic and terrestic systems. Also the knowledge and experience of the chemical industry may be of interest in the development of new chemical treatment processes. 

With respect to physical/chemical treatment processes for industrial wastewater we can expect the following innovative developments11,16 17,19,20,... 

In many production processes the process water is used at a relatively high temperature. Also the wastewater which comes free may have an elevated temperature. To treat this wastewater with standard physical/chemical treatment processes at present this wastewater is cooled down to ambient temperatures. In case the treated water can be reused as process water it would be more efficient if the wastewater could be treated at higher temperatures, for example at 60 to 80 °C. However experience with the use of physical/chemical processes in this temperature range is lacking. It can be expected that in future more attention will be paid to this knowledge... 

In its 1977 survey, the U.S. Environmental Protection Agency (USEPA) identified over 150 separate processes being used in refineries [5]. A refinery may employ any number or a combination of these processes, depending upon the type of cmde processed, the type of product being produced, and the characteristics of the particular refinery. The refining processes can generally be classified as separation, conversion, and chemical treatment processes [1]. 

Chemical treatment processes are used to remove impurities from the fractions. The method of treatment depends on the type of cmde oil and on the intended use of the petroleum product. Treatment with hydrogen is a widely used method of removing sulfur compounds. Blending with other products or additives may be carried out to achieve certain special properties. 

T0709 Sevenson Environmental Services, Inc., MAECTITE Chemical Treatment Process T0726 S olidific ation/S tabilization—General... 

T0664 RKK-SoilFreeze Technologies, L.L.C., CRYOCELL T0682 Sandia National Laboratories, Electrokinetic Remediation T0696 Science Applications International Corporation, Plasma Hearth Process T0709 Sevenson Environmental Services, Inc., MAECTITE Chemical Treatment Process... 

Sevenson Environmental Services, Inc. (Sevenson), is the owner of the MAECTITE chemical treatment process for the precipitation and stabilization of toxic heavy metals. Chemical treatment by the MAECTITE process converts teachable lead, hexavalent chromium, or other heavy metals into insoluble minerals and mixed mineral forms within the material or waste matrix. The technology can be used as an in situ or an ex situ method and does not use pozzolanic or siliceous binders to stabilize the treated material. 

EO could be used as an alternative technology for remediation of contaminants in low permeability clay-rich soils, and represents an in situ, abiotic physical and chemical treatment process which utilizes the Eh-pH gradients established in the subsurface as a result of electrolysis reactions at... 

Chemical/physical treatment processes are those in which a chemical reaction is used to alter or destroy a hazardous waste component. Chemical treatment techniques can be applied to both organic and inorganic wastes, and may be formulated to address specific target compounds in a mixed waste. Typical chemical treatment processes include oxidation-reduction reactions such as ozonation, alkaline chlorination, electrolytic oxidation and chemical dechlorination. Physical treatment processes separate waste component by either applying physical force or changing the physical form of the waste. Various physical processes include adsorption, distillation, or filtration. Physical treatment is applicable to a wide variety of waste streams but further treatment is usually required. 

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