Filter performance

Filtration is employed when the suspended soUds concentration is less than 100 mg/L and high effluent clarity is required. Finely dispersed suspended soUds require the addition of a coagulant prior to filtration. Filters most commonly used in wastewater treatment are a dual media (anthrafUt and sand) or a moving bed or continuous-backwash sand filter. Performance data for the tertiary filtration of municipal and industrial wastewater are shown in Table 10. 

The two steps in the removal of a particle from the Hquid phase by the filter medium are the transport of the suspended particle to the surface of the medium and interaction with the surface to form a bond strong enough to withstand the hydraulic stresses imposed on it by the passage of water over the surface. The transport step is influenced by such physical factors as concentration of the suspension, medium particle size, medium particle-size distribution, temperature, flow rate, and flow time. These parameters have been considered in various empirical relationships that help predict filter performance based on physical factors only (8,9). Attention has also been placed on the interaction between the particles and the filter surface. The mechanisms postulated are based on adsorption (qv) or specific chemical interactions (10). 

Process Concept The application of a direct elec tric field of appropriate polarity when filtering should cause a net charged-particle migration away from the filter medium. This electrophoretic migration will prevent filter-cake formation and the subsequent reduction of filter performance. An additional benefit derived from the imposed electric field is an electroosmotic flux. The presence of this flux in the membrane and in any particulate accumulation may further enhance the filtration rate. 

Gustavsson, J. Cabin air filters Performances and requirements. SAE Conference, Detroit, Feb-ruary 1996. 

Dennis, R., R. W. Cass, and R. S. Hall. Dust Dislodgement from Woven Fabrics Versus Filter Performance. ]. Air Pollution Control Assoc. 28, no. 1 (Jan. 1978), pp. 47-52. 

Air filter performance An overall assessment ot the collection efficiency, pressure drop, flow rate, fire rating, health aspects, and behavior of a filter in the environment in which it is used. 

Filter class A certain range of filter performance characteristics as specified by international standards. 

Lawton, D.J. and T. Constanuno, What Makes Gartridge Filters Perform Effectively, Chemical Engineering Progress, V. 83, No. 11, 1987, p. 20. 

Many other filter functions can be designed, e.g. an exponential or a trapezoidal function, or a band pass filter. As a rule exponential and trapezoidal filters perform better than cut-off filters, because an abrupt truncation of the Fourier coefficients may introduce artifacts, such as the annoying appearance of periodicities on the signal. The problem of choosing filter shapes is discussed in more detail by Lam and Isenhour [11] with references to a more thorough mathematical treatment of the subject. The expression for a band-pass filter is H v) = 1 for v j < v < else... 

Substituting Eq. (13-34) into Eq. (13-32) and rearranging results in the basic equation governing the filter performance ... 

It is evident that the filter performance is governed by the system constants C and C2 regardless of whether the operation is at constant pressure or constant flow rate and that these constants can be evaluated from laboratory data taken under either type of operation and used to analyze the performance of the plant filter for either type of operation. 

In case 4, the increasing pressure compresses the cake to such as extent that it actually squeezes off the flow so that as the pressure increases the flow rate decreases. This situation can be compensated for by adding a filter aid to the slurry. This is a rigid dispersed solid that forms an incompressible cake (diatomaceous earth, sand, etc.). This provides rigidity to the cake and enhances its permeability, thus increasing the filter capacity (it may seem like a paradox that adding more solids to the slurry feed actually increases the filter performance, but it works ). 

The analysis is based on the matched filtering performed at the receiver. Before proceeding to the mathematical background, it is necessary to state the assumptions made when modeling the system. These are ... 

Filtration, 11 321-397 75 824—825. See also Filter cycles Filter performance Filters Microfiltration Nanofiltration membranes Ultrafiltration as advanced wastewater treatment, 25 908-909... 

Perforate basket centrifuges, 16 660 operation, 5 529, 543-545 Perforated bowl centrifuge, theory of performance, 5 515 Perforated-drum dryers, 9 120 Perforated-plate columns, 10 772-774 Perforated plates, 11 810 Performance. See also Filter performance of BJTs, 22 248-249 of FETs, 22 165... 

Fluorescein Sodium Dissolve 50 mg in 20 ml DW, and 2.5 ml dil. HC1 and filter. Perform the test with the filtrate. Complies with the limit test for Sulphates. 

Phthalylsulphathiazole Heat 4.0 g with 200 ml DW at 70°C for 5 minutes, cool and filter Perform test with 50 ml of filtrate. -do-... 

Extensive work has been carried out in the US regarding the use of soil filters for odour reduction. (6) It was shown that the filter performance depended on filter loading, type of soil, soil moisture, temperature and concentration of odourous components. The US study also concluded that both chemical and biological processes were responsible for the odour reduction. 

In Tonsberg, Norway, an iron oxide filter was constructed to reduce odours from a pumping station close to the municipal treatment plant. The filter is shown in Figure 6. The filter treats odours caused by evacuation of air from a pressure main. The air enters the filter through a perforated pipe at the bottom and flows through the filter media into the atmosphere. The filter has been in operation since the Summer of 1978. Tests of the filter performance have been carried out regularly since then. 

Gibson, J.R. Taylor, S. Prediction of Quadrupole Mass Filter Performance for Hyperbolic and Circular Cross Section Electrodes. Rapid Commun. Mass Spectrom. 2000,14, 1669-1673. 

Besides fouling, cell retention efficiency is another important factor regarding spin-filter performance. A poor retention capacity of a spin-filter leads to a low apparent growth rate of the cell culture due to cell leakage (Eq. 10). 

Combining these techniques, they carried out cultivations for 250-350 h, and were able to repeatedly use the same cartridge (four times at least) without measurable deterioration in filtration efficiency. However, when perfusion rate and cell concentration in the bioreactor increased, fouling eventually occurred. Van Reis et al. [92] provided backpressure on the filtrate line to control filtrate rates and so to avoid too high initial filtration rates, which can cause rapid fouling. De la Broise et al. [99] compared the filter performance using membranes of different pore sizes (2 and 10 pm). In both cases partial retention of the produced IgM was observed and membranes had to be changed every 5 days, the... 

The CFPP was developed in 1965-66 to predict the low-temperature filterability performance of diesel fuels. This method is commonly used throughout the world to quickly determine low-temperature fuel filterability characteristics. In more recent... 

Perform a pressure hold test with the sterilized filter. Perform the filtration of the product to be sterile filtered using normal production conditions. After the filtration step, the filter should be tested again with the bubble point test. 

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