Treatment system, physical/chemical

The process is designed from a knowledge of physical concentrations, whereas aqueous effluent treatment systems are designed from a knowledge of BOD and COD. Thus we need to somehow establish the relationship between BOD, COD, and the concentration of waste streams leaving the process. Without measurements, relationships can only be established approximately. The relationship between BOD and COD is not easy to establish, since different materials will oxidize at different rates. To compound the problem, many wastes contain complex mixtures of oxidizable materials, perhaps together with chemicals that inhibit the oxidation reactions. 

A typical physical-chemical treatment system incorporates three "dual" medial (sand anthracite) filters connected in parallel in its treatment train. The major maintenance consideration with granular medial filtration is the handling of the backwash. The backwash will generally contain a high concentration of contaminants and require subsequent treatment. 

There are two principal chemical concepts we will cover that are important for studying the natural environment. The first is thermodynamics, which describes whether a system is at equilibrium or if it can spontaneously change by undergoing chemical reaction. We review the main first principles and extend the discussion to electrochemistry. The second main concept is how fast chemical reactions take place if they start. This study of the rate of chemical change is called chemical kinetics. We examine selected natural systems in which the rate of change helps determine the state of the system. Finally, we briefly go over some natural examples where both thermodynamic and kinetic factors are important. This brief chapter cannot provide the depth of treatment found in a textbook fully devoted to these physical chemical subjects. Those who wish a more detailed discussion of these concepts might turn to one of the following texts Atkins (1994), Levine (1995), Alberty and Silbey (1997). 

Various treatment technologies are used at the iron and steel plant for recycle system water treatment prior to recycle and reuse, or end-of-pipe wastewater treatment prior to discharge to surface water or a POTW. The physical/chemical treatment technologies extensively used include equalization, tar removal, free and fixed ammonia stripping, cooling technologies, cyanide treatment technologies,... 

The specific purpose of this chapter is to describe the chemical and physical pretreatment methods required for nickel-chromium plating wastewater, to describe the upgrades needed by a municipal wastewater treatment system to manage this waste, and to relate the methods and upgrades to the operation of the total treatment system. Special emphasis is placed on presentation of the following ... 

Chemical and physical properties of the contaminant should also be investigated. Solubility in water (or other washing fluids) is one of the most important physical characteristics. Hydrophobic contaminants can be difficult to separate from the soil particles and into the aqueous washing fluid. Reactivity with wash fluids may, in some cases, be another important characteristic to consider. Other contaminant characteristics such as volatility and density may be important for the design of remedy screening studies and related residuals treatment systems. Speciation is important in metal-contaminated sites. 

Wang, L.K., Yoo, S.H., and Hong, Y.N., Development of Two-Stage Physical-Chemical Process System for Treatment of Pulp Mill Wastewater, Lenox Institute of Water Technology, Lenox, M A, Technical Report LIR/05-84/2, 1984, 64 p. 

To meet the specified standard,4 wastewaters are often subjected to a series of treatment processes before they are discharged into the environment, particularly, water bodies. The treatment processes include physical, chemical, and biological processes that may be applied singly or collectively. The collective application of the processes can be employed in a variety of systems classified as primary, secondary, and tertiary wastewater treatment, to achieve different levels of contaminants removal.2... 

The competitive physical/chemical system that is being installed at Rosemount, Minn., consists of primary treatment followed by coagulation, sand filtration, activated carbon adsorption, another filtration step, ion exchange, and oxidation. This can produce a highly purified water at less cost than a system involving primary, secondary, and tertiary treatment.30... 

An industrial treatment system may require some chemical pretreatment before biological treatment even some physical treatment may be desirable. Also, smce the concentrations of the pollutants are usually greater and more predictable than those in municipal wastes, the engineer can design a more specific system than is possible for municipal treatment plants.64 In this case all possibilities must be carefully evaluated by the process engineer. 

Very often the use of process water and/or the treatment of wastewater requires the use of inorganic or organic additives. Sometimes these additives have to be considered later on as pollutants, sometimes as compounds of which the concentration in the process water should not be too high. It is therefor not allowed that the concentration of these additives exceeds a maximal admissible value. This means that in case of a continuous closed loop system, the physical/chemical treatment step has to remove an amount of these compounds corresponding to the amount of these compounds added elsewhere in the closed loop water system, minus the amount consumed in the production process. Often the consequence is that only relatively low removal efficiency in the treatment step is necessary. 

One difference between these systems and the biological treatment of nonhazardous wastewater is that the exhaust air may contain volatile hazardous substances or intermediate biodegradation products. Therefore, the air must be treated as secondary hazardous wastes by physical, chemical, physico-chemical, or biological methods. Other secondary hazardous wastes may include the biomass of microorganisms that may accumulate volatile hazardous substances or intermediate products of their biodegradation. This hazardous liquid or semisolid waste must be properly treated, incinerated, or disposed. 

Constructed wetlands are engineered systems designed to mimic the physical, chemical, and biological mechanisms of a natural wetland. Wetlands may be constructed above ground to resemble natural wetlands such as swamps, bogs, and marshes or they may treat contaminated water below the surface. Constructed wetlands have been used for the ex situ treatment of groundwater contaminated with explosives. 

IT Corporation s thermal desorption system is a commercially available, ex situ technology for the treatment of soils and sludges contaminated with organics. The process drives volatile and semivolatile organic compounds (VOCs and SVOCs) from the soil by heating the soil to temperatures greater than the boiling point temperature of the contaminants. Volatized vapors are oxidized in a secondary combustion chamber or collected for physical/chemical treatment. 

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