Mixed media

Neither rapid sand nor mixed-media filters remove appreciable quantities of coUoidal particles without adequate pretreatment. Although it is widely beheved that filters are an effective barrier against unsafe water, the effluent may be as colored, as turbid, or as bacteriologicaHy unsafe as the water appHed. In contrast, slow sand filters requite no pretreatment, as the slow passage through the bed allows the particles to contact and attach to the schmut ecke. 

Energy losses become high, and short circuiting passage of dirty water. Sand, mixed media, and diatomaceous earth are the most common filter materials. 

Various rules of thumb exist for standard water filtration rates and cycle time before backwashing. Higher filtration rates may appear to be economically justified, however, when the filter loading is within conventional limits. In this example, we examine the issues involved for constant-rate filtration for a dual-media bed. Dual- and mixed-media beds result in increased production of water in a filter for two reasons. First, the larger grains (say charcoal approximately 1-mm size) as a top layer help reduce cake formation and deposition within the small (150-mm) top layer of the bed. Second, the head loss in the region of significant filtration is reduced. 

Unfolding Square, 2006 01, Mischtechnik auf Leinwand, Oil and mixed media on canvas 240x240cm... 

Technical drawing Mixed media on paper 61x97cm... 

Pulsating membrane Mixed media on paper 97x61cm... 

Acryl, mischtechnik auf Leinwand 3 teilig Oil, acryllic, mixed media on canvas - 3 parts 240x600cm... 

Mischtechnik auf Papier Mixed media on paper 98x62cm... 

Similar fractionation factors can be defined for other species. These are ordinarily given the symbol

solvent fractionation. Thus for an acid dissociation in mixed media, ALj + L20 = L30+ + ALj i ... 

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