Corrosivity of waste

Corrosivity of waste is determined by measuring the pH of the waste to identify its relative acidity or alkalinity. In this test, waste is corrosive, and therefore hazardous, if its pH is less than 2.0 or greater than 12.5. (Several currently used throwaway sulfur recovery systems, such as fluidized bed combustion and sorbent injection, have problems meeting the RCRA corrosivity classification because of high pH levels due to large amounts of free lime in their waste.)... 

As will be discussed in more detail later, most evidence suggests that the chemical nature of the colloids and the immobile phases is similar (e.g., McCarthy Deguelder, 1993), at least for most natural systems. Similarity of colloids and immobile phase sorptive properties in a three-phase system we define here as a symmetrical system. It is likely, though, that processes occurring in a waste repository (e.g., corrosion of waste containers) will result in the generation of colloids with physicochemical properties markedly different from those of the immobile phase. Such a system is defined accordingly an asymmetrical system. 

Because of its antimicrobial activity, acrolein has found use as an agent to control the growth of microbes in process feed lines, thereby controlling the rates of plugging and corrosion (see Wastes, industrial). 

The capacity of any specific tank configuration, in terms of metric ton equivalents, is deterrnined by one of three parameters. (/) The solubiHty of waste salts. Precipitates can settle and cause thermal hot spots, which in turn can result in accelerated corrosion rates. Thus it is important to maintain the... 

Water as coolant in a nuclear reactor is rendered radioactive by neutron irradiation of corrosion products of materials used in reactor constmction. Key nucHdes and the half-Hves in addition to cobalt-60 are nickel-63 [13981 -37-8] (100 yr), niobium-94 [14681-63-1] (2.4 x 10 yr), and nickel-59 [14336-70-0] (7.6 x lO" yr). Occasionally small leaks in fuel rods allow fission products to enter the cooling water. Cleanup of the water results in LLW. Another source of waste is the residue from appHcations of radionucHdes in medical diagnosis, treatment, research, and industry. Many of these radionucHdes are produced in nuclear reactors, especially in Canada. 

For many waste streams, electrical efficiencies are compromised owing to the corrosivity of the solution toward the precipitated metals and/or the low concentrations of metals that must be removed. The presence of chloride in the solution is particularly troublesome because of the formation of elemental chlorine at the anode. Several commercial cells have become available that attempt to address certain of these problems (19). 

The level of natural versus man-made emissions to the environment are of a similar magnitude. SoH erosion is the major contributor of natural emissions with zinc mining, zinc production facHities, iron and steel production, corrosion of galvanized stmctures, coal and fuel combustion, waste disposal and incineration, and the use of zinc fertilizers and pesticides being the principal anthropogenic contributors. 

Due to both carbonization and penetration of chloride ions, steel will pass from a passive to an active condition and (consequently) may corrode. If the mortar is completely surrounded by water, oxygen diffusion in wet mortar is extremely low so that the situation is corrosion resistant because the cathodic partial reaction according to Eq. (2-17) scarcely occurs. For this reason the mortar lining of waste pipes remains protective against corrosion even if it is completely carbonated or if it is penetrated by chloride ions. 

In sulfuric acid production involving heat recovery and recovery of waste sulfuric acid, acids of various concentrations at high temperatures can be dealt with. Corrosion damage has been observed, for example, in sulfuric acid coolers, which seriously impairs the availability of such installations. The use of anodic protection can prevent such damage. 

Cadmium 0.005 0.005 Kidney damage Corrosion of galvanized pipes erosion of natural deposits discharge from metal refineries runoff fiom waste batteries and paints... 

At other times the burning of waste products in furnaces to save fuel and reduce pollution has caused corrosion and tube failure. 

Because systems are normally not designed for use with this type of fluid, certain aspects should be reviewed with the equipment and fluid suppliers before a decision to use such fluids can be taken. These are compatibility with filters, seals, gaskets, hoses, paints and any non-ferrous metals used in the equipment. Condensation corrosion effect on ferrous metals, fluid-mixing equipment needed, control of microbial infection together with overall maintaining and control of fluid dilution and the disposal of waste fluid must also be considered. Provided such attention is paid to these designs and operating features, the cost reductions have proved very beneficial to the overall plant cost effectiveness. 

Condensate from boiler warmup steam should be wasted or sent for secondary applications to avoid corrosion of the line feeding the deaerator. 

METALWORKING FLUID Eluid applied to a tool and workpiece to cool, lubricate, carry away particles of waste and provide corrosion protection. Generally comprising neat mineral oils, or water-based materials, or a mixture of the two. Eluids may also contain emulsifiers, stabilizers, biocides, corrosion inhibitors, fragrances and extreme pressure additives. 

Corrosive wastes are acidic or alkaline (basic) wastes which can readily corrode or dissolve flesh, metal, or other materials. They are also among the most common hazardous wastestreams. Waste sulfuric acid from automotive batteries is an example of a corrosive waste. U.S. EPA uses two criteria to identify corrosive hazardous wastes. The first is a pH test. Aqueous wastes with a pH greater than or equal to 12.5, or less than or equal to 2 are corrosive under U.S. EPA s rules. A waste may also be corrosive if it has the ability to corrode steel in a specific U.S. EPA-approved test protocol. 

Injection pump. An injection pump is used to force the waste into the injection zone, although in very porous formations, such as cavernous limestone, the hydrostatic pressure of the waste column in the well is sufficient. The type of pump is determined primarily by the well-head pressures required, the volume of liquid to be injected, and the corrosiveness of the waste. Single-stage centrifugal pumps are used in systems that require well-head pressures up to about 10.5 kg/cm2 (150 psi), and multiplex piston pumps are used to achieve higher injection pressures. 

Interactions between corrosive wastes and casing and packing can threaten the integrity of a well if proper materials have not been used in construction. Of equal concern is the potential for failure of the confining zone due to physical or chemical effects. For example, dissolution of an overlying carbonate confining layer may allow upward migration of wastes. This process was observed when hot acidic wastes were injected in a Florida well. 

Potential environmental hazards from wastewater sludges are associated with trace constituents (e.g., chlorinated organic compounds) that partition from the effluent into the sludge. It should be noted, however, that recent trends away from elemental chlorine bleaching have reduced these hazards. A continuing concern is the very high pH (>12.5) of most residual wastes. When these wastes are disposed of in an aqueous form, they may meet the RCRA definition of a corrosive hazardous waste.24... 

The corrosion of iron represents an electrochemical reaction of huge economic significance, accounting literally for billions of dollars of waste every year. The phenomenon has been investigated since the time of Faraday and still presents many controversial and puzzling aspects which only the arrival of in situ spectroscopic techniques has begun to clarify. 

Parker, C.D. (1951), Mechanics of corrosion of concrete sewers by hydrogen sulfide, Sewage Ind. Wastes, 23, 1477-1485. 

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