Water Systems for Pharmaceutical Facilities 595 60 MULTIMEDIA FILTRATION Multimedia filtration(also called prefiltration, sand filtration or multilayered filtration)is mainly aimed at removing sediments and suspended matter. Suspended contaminants are trapped in small crevices and, as a result, water turbidity is improved. A number of media are distinctly layered with the coarsest on top so the suspended matter is collected throughout the according to siz The filter beds need to be backwashed periodically as the back pressure increases; however, backwashing removes the filter from use. To avoid downtime, often a dual filter bed system is installed During construction, the filtration unit should be installed before all the walls are erected so it can be kept upright, in which case the filters can be charged by the vendor before shipping. This would reduce chances of damage to the internals during loading. The unit, of course, should be inspe thoroughly upon receiving. Before shipping, the vendor will often disconnect controls to minimize potential damage. Sufficient time should be allowed to reconnect all of these. Finally, to avoid bacteria building up, start-up should be delayed until a constant water flow is assuredWater Systems for Pharmaceutical Facilities 595 Figure 2. Water pretreatment 6.0 MULTIMEDIA FILTRATION Multimedia filtration (also called prefiltration, sand filtration or multilayered filtration) is mainly aimed at removing sediments and suspended matter. Suspended contaminants are trapped in small crevices and, as a result, water turbidity is improved. A number of media are distinctly layered with the coarsest on top so the suspended matter is collected throughout the depth of the filter according to size. The filter beds need to be backwashed periodically as the back pressure increases; however, backwashing removes the filter from use. To avoid downtime, often a dual filter bed system is installed. During construction, the filtration unit should be installed before all the walls are erected so it can be kept upright, in which case the filters can be charged by the vendor before shipping. This would reduce chances ofdamage to the internals during loading. The unit, of course, should be inspected thoroughly upon receiving. Before shipping, the vendor will often disconnect controls to minimize potential damage. Sufficient time should be allowed to reconnect all of these. Finally, to avoid bacteria building up, start-up should be delayed until a constant water flow is assured