TM 55-1930-209-14&P-1
Table 13-1. ROWPU System Components (continued)
Component
Quantity
Function
Location
RO block assembly
1 per
Processes chemically
Inboard of media filters
ROWPU
treated seawater from HP
pump
Hydrakleen-20
1 per
Cleans RO membrane
Inboard of Hydrapol-50 drum
(55-gallon cleaning
ROWPU
elements
agent drum)
Chemical meter-
2 per
Adds measured amounts of
On top of pretreatment skid
ing pumps
ROWPU
chemicals (coagulant aid and
inhibitor) to feedwater
Hydrapol-50
1 per
Added to seawater as
Forward of pretreatment skid
(55-gallon
ROWPU
a coagulant aid before
coagulant drum)
entering media filters
Hydrapol-100
1 per
Added to seawater as
Outboard of Hydrapol-50 drum
(55-gallon
ROWPU
a scale Inhibitor before
Inhibitor drum)
entering cartridge
filter assembly
* See Table 13-3 for listing of ROWPU system valves.
13-3.2 Media filters. Three identical media filters are provided for each ROWPU. Each filter has a capacity of 120 gpm
and all filters are used constantly during water processing. Inlet water is pumped into the top of the filters where it is
spread out across the filter media and forced downward through four different kinds of media to the outlet. The top layer
consists of a layer of relatively coarse, high density anthracite coal. Below the anthracite is a layer of medium fine silica
sand. The next layer is fine garnet and below that Is a layer of coarse garnet which covers the radial laterals of the
bottom distributor. These four media rest upon a supporting bed of gravel placed in the bottom of the filter body. Media
filters require periodic backwashing to remove minute particles collected from the seawater during normal operation. The
need for backwashing is indicated when the difference between pressure gauges P1 and P2 exceeds 35 psi or when
green MEDIA FILTER OK light on control panel goes out. Valves on the pretreatment skid control backwashing and
flushing Drinking water production must be stopped while backwashing media filters. Because media materials are
progressively denser from top to bottom, they rearrange themselves after backwashing to the original layers for correct
filtering.
13-3
