Section III. PRINCIPLES OF OPERATION
1-10. GENERAL. The ROWPU consists of a series of diesel-engine-driven pumps, filters, and a reverse osmosis block
assembly capable of converting 150,000 gpd of brackish or sea water to drinking water. The following paragraphs
describe the operation of the individual functional groups which comprise the ROWPU and their relation to the overall
1-11. FUNCTIONAL GROUPS
Raw Water Pump Assembly. Consists of a skid-mounted diesel engine/centrifugal pump combination. The
engine may be started by a handcrank or with an electric starter. The pump takes water from a remote location up to 95
ft away and pumps it to the boost pump assembly up to 500 ft away.
Boost Pump Assembly. Consists of a skid-mounted diesel engine/centrifugal pump combination. The engine is
started with an electric starter and drives the pump through a belt. This pump provides the pressure to maintain
feedwater flow to the pretreatment assembly, through the multimedia filters back to the pretreatment assembly, and to
the high pressure pump assembly.
Pretreatment Assembly. Consists of skid-mounted gage panel, two chemical metering pumps, cartridge filter,
and interconnecting piping and valves. A manually adjustable chemical metering pump doses the feedwater with a
coagulant aid as it enters the pretreatment assembly. This coagulant aid helps the multimedia filters to remove fine
particles. The feedwater then goes to the multimedia filters where particles are removed. It returns to the pretreatment
assembly where it is dosed with a scale inhibitor by a second manually adjustable chemical metering pump. The scale
inhibitor prevents the formation of scales on the reverse osmosis membranes. The feedwater continues to the cartridge
filter where any remaining fine particles are removed.
Multimedia Filters. Three identical skid-mounted filters with lifting eyes. Water is received from the
pretreatment assembly at the top of the filter, flows downward through the multimedia, and returns from the bottom of the
filter to the pretreatment assembly. Multimedia filters need backwashing when MEDIA FILTER OK light goes out.
High Pressure Pump Assembly. Consists of a skid-mounted diesel engine/Jet pump combination. The pump is
driven by the diesel engine through a series of matched V-belts. The feedwater from the pretreatment assembly is raised
to the high pressure needed to perform the reverse osmosis process.
Reverse Osmosis (RO) Block Assembly. Consists of 16 skid-mounted RO tube assemblies, each of which holds
5 RO membrane elements. Water coming from the high pressure pump enters the tubes, where the membrane elements
separate it into drinkable water and brine concentrate.