Removal efficiency

Mlcrofiltra.tlon, Various membrane filters have been used to remove viral agents from fluids. In some cases, membranes which have pores larger than the viral particle can be used if the filtration is conducted under conditions which allow for the adsorption of the viral particle to the membrane matrix. These are typically single-pass systems having pore sizes of 0.10—0.22 lm. Under situations which allow optimum adsorption, between 10—10 particles of poHovims (28—30 nm) were removed (34—36). The formation of a cake layer enhanced removal (35). The titer reduction when using 0.10—0.22 p.m membrane filters declined under conditions which minimized adsorption. By removal standards, these filters remove vimses at a rate on the low end of the desired titer reduction and the removal efficiency varies with differences in fluid chemistry and surface chemistry of viral agents (26). 

RCRA incinerator regulations include adrninistrative as weU as performance standards. Administrative standards include procedures for waste analysis, inspection of equipment, monitoring, and facihty security. Steps needed to meet adrninistrative standards are outlined ia the permit apphcation performance standards are demonstrated during a trial bum. Trial bum operating conditions are included in the permit to assure ongoing compliance with the performance standards. Performance standards include destmction and removal efficiency (DRE), particulate emissions limits, products of incomplete combustion emission limits, metal emission limits, and HCl and Cl emission limits (see Exhaust CONTROL, INDUSTRIAL). 

Fig. 1. Ink removal effectiveness of unit operations as a function of ink particle size (a) particle size distribution ia pulper (b) unit removal efficiency (4).

Flotation. Flotation (qv) is used alone or in combination with washing and cleaning to deink office paper and mixtures of old newsprint and old magazines (26). An effective flotation process must fulfill four functions. (/) The process must efficiently entrain air. Air bubble diameter is about 1000 p.m. Typically air bubbles occupy 25—60% of the flotation cell volume. Increa sing the airRquid ratio in the flotation cell is said to improve ink removal efficiency (27). (2) Ink must attach to air bubbles. This is primarily a function of surfactant chemistry. Air bubbles must have sufficient residence time in the cell for ink attachment to occur. (3) There must be minimal trapping of cellulose fibers in the froth layer. This depends on both cell design and surfactant chemistry. (4) The froth layer must be separated from the pulp slurry before too many air bubbles coUapse and return ink particles to the pulp slurry. 

Mechanical Gleaning. A cleaner is a hydrocyclone device utilizing fluid pressure to create rotational fluid motion (20). Pulp is introduced tangentially near the top of the cleaner. Contaminants denser than water such as chemically treated toner inks and sand migrate toward the outer wall of the cleaner and exit in a separate (reject) stream. For most forward cleaners, optimal ink removal efficiency is obtained at a pulp consistency of 0.2—0.3%. Most forward cleaners deinking efficiency declines at pulp feed consistencies greater than 0.4%. However, a cleaner said to be efficient at 1.2% pulp consistency has been reported (39). 

Regenerable absorption processes have also been developed. In these processes, the solvent releases the sulfur dioxide in a regenerator and then is reused in the absorber. The WelLman-Lord process is typical of a regenerable process. Figure 11 illustrates the process flow scheme. Sulfur dioxide removal efficiency is from 95—98%. The gas is prescmbbed with water, then contacts a sodium sulfite solution in an absorber. The sulfur dioxide is absorbed into solution by the following reaction ... 

Fig. 8. Illustrative relationships of air stripping removal efficiencies to media height and air-to-water ratios.

Superrate. High BOD removal efficiencies (97%) at hydrauHc loadings of 10.8 m /(has) [1150 gal/(acred)] were obtained ia experimental plants with plastic media. In these plants, much of the microbial mass remains ia the recirculated effluent. This process is, ia effect, a modification of activated sludge. Organic loadings are ca 1.60 kg BOD/(m -s) [6.1 g BOD/(gal-s)]. 

Microstrainers. Microstrainers are rotating steel screens with extremely fine stainless steel mesh (85—170 perforations per square centimeter (13—26/in. )). The flowing Hquid enters the open end of the dmm and passes through the mesh to the effluent end. The mesh traps soHd impurities and rotates with the dmm. A wash-water spray washes the trapped soHds into a hopper for final disposal. The mesh is washed with filtered effluent discharged from jets fitted into the dmm and then exposed to uv radiation to inhibit microbial growth. The mesh is washed with chlorine water at intervals of 7 to 28 days in order to control slime growth removal efficiencies are 30—55% of the appHed BOD and 40—60% of suspended soHds. 

Three commercial processes that use these various hot carbonate flow arrangements are the promoted Benfield process, the Catacarb process, and the Giammarco-Vetrocoke process (26—29). Each uses an additive described as a promoter, activator, or catalyst, which increases the rates of absorption and desorption, improves removal efficiency, and reduces the energy requirement. The processes also use corrosion inhibitors, which aHow use of carbon—steel equipment. The Benfield and Catacarb processes do not specify additives. Vetrocoke uses boric acid, glycine, or arsenic trioxide, which is the most effective. 

The methanation reaction is carried out over a catalyst at operating conditions of 503—723 K, 0.1—10 MPa (1—100 atm), and space velocities of 500—25,000 h . Although many catalysts are suitable for effecting the conversion of synthesis gas to methane, nickel-based catalysts are are used almost exclusively for industrial appHcations. Methanation is extremely exothermic (AT/ qq = —214.6 kJ or —51.3 kcal), and heat must be removed efficiently to minimise loss of catalyst activity from metal sintering or reactor plugging by nickel carbide formation. 

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). 

TABLE 17-11 Comparison of Air Filters by Percent Removal Efficiency for Various Particle Sizes ... 

Group Efficiency Removal efficiency, %, for particle size of... 

All filters require a filter medium to retain solids, whether the filter is for cake filtration or for filter-medium or depth filtration. Specification of a medium is based on retention of some minimum parficle size at good removal efficiency and on acceptable hfe of the medium in the environment of the filter. The selection of the type of filter medium is often the most important decision in success of the operation. For cake filtration, medium selection involves an optimization of the following factors ... 

DRE Destruction and removal efficiency SMART Save money and reduce toxics... 

Relatively low removal efficiency for gaseous contaminants (at concentrations typical of pollution-control applications)... 

Condensation Equipment There are two basic types of condensers used for control contact and surface. In contact condensers, the gaseous stream is brought into direct contact with a cooling medium so that the vapors condense and mix with the coolant (see Fig. 25-15). The more widely used system, however, is the surface condenser (or heat exchanger), in which the vapor and the cooling medium are separated by a wall (see Fig. 25-16). Since high removal efficiencies cannot be obtained with low-condensable vapor concentrations, condensers are typically used for pretreatment prior to some other more efficient control device such as an incinerator, absorber, or adsorber. 

Raw Gas Composition The suitabihty of the raw gas stream must first be determined. The raw gas stream must contain the following in order to ensure both reasonable removal efficiencies and microorganism hfe expectancy ... 

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