TM 10-4610-232-12
(2) Polyelectrolyle. This chemical is pumped from the polyelectrolyte tank (4) by the polyelectrolyte pump (1). It is
injected under pressure into the feed water at the feed water booster pump(7) inlet. The polyelectrolyte acts to trap the
very fine dirt particles in the media filter(8). These particles, normally will not form larger particles because of electrical
charges within their structures. The polyelectrolyte is a long string like molecule which also has electrical charges
along its length. As a polyelectrolyte string contacts the fine particles, the electrical charges hold them and larger sticky
floe particles are formed. When a floe particle contacts a grain of filter media, it has a good chance of sticking. Some
polyelectrolyte strings will stick to media grains and then trap fine dirt particles as they pass through the media filter.
The amount of polyelectrolyte is very important. If there is not enough polyelectrolyte, too many fine particles escape. If
there is too much polyelectrolyte, the electrical charges interfere with each other and many of the fine particles and
some polyelectrolyte as well escape from the filter. The amount of polyelectrolyte used must be carefully optimized to
give the best removal of fine particles,
(3) Sequestrant. This chemical is pumped from the sequestrant tank(5) by the sequestrant pump (2). Sequestrant
(scale inhibitor) is injected into the feed water after the media filter to minimize or avoid the formation of scale in the RO
elements. The amount of sequestrant (if needed at all) depends on the raw water source.
(4) Hypochlorite. This chemical is pumped from the hypochlorite tank (6) by the hypochlorite backwash pump (9)
and injected into the water flow during media filter backwash. It acts to kill algae and bacteria which can form a sticky
matt on top of the filter media. If hypochlorite is not used, the algae will make the AG media in the media filter so sticky
that backwashing will not remove the suspended solids and algae. The tank and chemical packets are marked with a
circle for easy identification. During operation hypochlorite is pumped by the hypochlorite pump(3) and injected into the
product water, This provides the chlorine residual amount needed to keep the water safe to drink (potable) during
distribution and use.
g. Air Supply(Figure 1- 16). The air compressor(1), mounted in the high pressure pump package(2), is the source of
air pressure to operate automatic valves and aid in media filter backwash. Compressed air is stored in the air reservoir
(3) which provides 1800 psig (12,400 kPa) service air. An inlet air filter is located at the air compressor. A high pressure
outlet air filter (4) is inside the van. An air system low pressure regulator valve (5), reduces the air pressure to 85 psig
(585 kPa) for service use. An air dryer (6) further reduces moisture from the low pressure air used for valves and
instruments. Air manifolds (7) and (8) distribute the process and utility air,
Figure 1-16. Air Supply Components
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