1-13. SYSTEM TECHNICAL PRINCIPLES OF OPERATION - continued.
a. Raw water is drawn through a strainer, which keeps large particles of trash from entering the system.
Depending on the distance between the ROWPU and water source, one or two raw water pumps are used to
move the raw water As water enters the ROWPU, the chemical feed pump assembly adds two chemicals to it
The polymer drive unit adds polyelectrolyte (polymer) solution and the sodium hex drive unit adds sodium
hexameta- phosphate (sodium hex) The polymer material collects small pieces of floating solid matter into
particles large enough to be removed by the multimedia filter Sodium hex prevents scaling
b The raw water, containing the added chemicals, flows through the multimedia filter which performs first stage
filtration Second stage filtration is performed by the cartridge filter Water from the cartridge filter is supplied to
the inlet side of the R O pump The R O pump then raises the pressure to that needed to force water through the
membranes of the R O elements. Since the R.O pump output pulsates, it is passed through the pulse dampener
which smooths the flow before the water reaches the R 0. elements The R.O elements are connected in series
and the waste water (brine) from all elements is sent out of the ROWPU to the backwash water tank When that
tank is full, any additional brine is discharged to the ground downstream of the suction hose strainer.
c. The chlorine drive unit adds chlorine to the filtered output of the R 0. elements to kill any bacteria present in
the water. The chlorinated water is then carried out of the ROWPU through a hose for storage in two product
water tanks connected in series When water is needed, the distribution pump sends the stored potable
(drinkable) water through the distribution nozzle to a container provided by the user.
d. There are two cleaning procedures performed after 20 operating hours and one cleaning procedure performed
whenever water flow rate or water pressure exceed certain limits After 20 operating hours, citric acid is injected
into the system by the chemical feed pump before ROWPU shutdown After shutdown, the multimedia filter is
backwashed When system conditions require it, an R 0. element cleaning procedure is performed.
e In the first procedure, the citric acid drive unit injects citric acid into the multimedia filter output The citric acid
removes scaling that accumulated in the system during operation. When the procedure is complete, the ROWPU
is shut down.
f. After shutdown, the multimedia filter backwash cycle is manually activated then controlled by a solid-state
timer. Brine stored in the backwash tank is forced backward through the multimedia filter by the backwash pump
Flow is in the direction opposite to that followed by the raw water during filtration, so trapped particles are forced
from the filter and are discharged through a drain connected to the top of the multimedia filter
g A brine and citric acid solution or detergent solution is circulated through the R O elements to clean them Citric
acid or detergent is added to brine that remains in the backwash water tank after backwash is complete The
backwash pump is then connected to the input of the R 0. elements. This routes the solution through the
elements, then back to the backwash water tank. When repeated recirculation has cleaned the R O elements,
the ROWPU is operated normally to remove residue and drain it outside the product water tank