Reverse Osmosis Desalinators

8, 12, 16m3/Day

Ton

Technical Specification

1

System Summary

Production Capability: Model T8- 0.33 m3/Hour (8 m

3/Day)

Model T12- 0.5 m3/Hour (12 m

3/Day)

Model T16- 0.66 m3/Hour (16 m

3/Day)

Electrical Load: 6.25 kW

Standard Voltage: 440V/3-Phase, 50 Hz/60 Hz

Alternative Voltages Available

Noise Level: 85 Db

System Design Parameters

Feed Water Flow: 2-2.3 m3/Hour

Feed water Pressure: 35 PSI (2.4 BAR)

Feed Water P.H. level: 2-11

Feed Water SDI: 5

Feed Water Salinity: 35,000ppm NaCl

Nominal Feed Water Temperature: 25oC

Feed Water Temperature Range: 5-350c

Salt Rejection: 99.4%

Working Pressure: 850PSI (58 BAR)

Product Flow/Membrane Rating: +/-15%

Product Water Quality: <450ppm

Weights (Including Primer Pump): Model T8- 190 kg

Model T12-220 kg

Model T16-250 kg

2

Principles of Reverse Osmosis

Reverse Osmosis (RO) is a low cost method of desalination, and is excellent for both marine and land

based applications.

Osmosis is a naturally occurring process and is defined that when two solutions of different

concentrations are separated by a semi-permeable membrane then the less concentrated (purer) water

will flow towards the saltier (more concentrated) side of the membrane. This will happen until the

pressures and concentrations are equalised.

The Cathelco Seafresh desalination plant reverses this process by pressurising salt water at double the

natural osmosis pressure against the membrane surface, resulting in potable water being produced.

The principal of operation is such that the feed water has passed through a strainer (or similar) to

ensure feed water is free of large debris before entering the system. Sea water is pumped by a priming

pump through a series of pre-filters to extract any free particles to a designed micron size according to

the operating conditions.

The filtered feed water then passes through the high pressure pump which increases the pressure to

800 – 900 PSI (55-62 BAR) prior to entering the membrane(s).

Each membrane is held in the centre of a high pressure casing. The pressurised feed water is fed

through the membranes and discharged through a pressure regulating valve to sea water discharge.

The product water which permeates through the membranes is piped through a salinity sensor to a

solenoid valve which diverts the fresh water either to store or to dump depending on the quality. This

operation is controlled by a temperature compensated controller set to reject water that is not well

within the WHO directive of a maximum 500ppm salinity for potable water.

Although the product water is suitable for potable storage directly from the Cathelco Seafresh plant, it

can be treated in various ways including ultra violet sterilisation, active carbon filtration, re-

mineralisation and chlorination. These are available as optional extras and are detailed later in the

document.

Product water without chlorine treatment tastes better but for long term storage chlorine dosing is

advisable.

Every unit is manufactured to Cathelco Seafresh exacting standards, and is comprehensively tested prior

to despatch to ensure safety and operational excellence.

3

Component Description

The standard system consists of the following components which are housed within one main control

frame. The frames are Aluminium, epoxy powder coated in white. Suitable shock mounts are supplied

with the plant. Only the Primer pump is supplied outside the frame to be installed on or below the

waterline. Other optional items such as Media Filter, Re-Mineralisation and Fresh Water Flush are

supplied separately.

1. PRIMER PUMP

This pump is installed on or below the waterline and forces water through the pre-filter units

and delivers it to the high pressure pump with a positive pressure. The pump also features a

maintenance inlet, used to introduce chemicals into the system.

Type: Single stage centrifugal

Materials: Bronze pump body, Bronze Impeller, 316 SS Shaft

Speed: 2900 RPM

Power: 0.75 kW, 2.3 A

2. PRE-FILTERS

This consists of two disposable cartridge filters mounted in series fitted with bleed buttons for

simple removal of air from the system. A 25 micron filter element followed by 5 micron element

ensures “clean” water passes into the high pressure pump and membranes. Clear filter

housings make it easy to see when the elements are in need of cleaning/replacing, this will be

dependent on the quality of the feed water. Polyester elements are used instead of cotton as

they are a poor host for bacteria and fouling. For systems fitted with a media filter, only a 5

micron element is required.

Size: 4.25” x 20”

3. HIGH PRESSURE (HP) PUMP

The high pressure pump delivers the pre-treated seawater to the membranes and pressurizes it

to working pressure (850 PSI / 58 BAR). The pump is fitted with a vibration dampener for

smoothing of outlet flow water. The pump is belt driven from a four pole T.E.F.C motor. The

assembly includes a mechanism for tightening a loosening of the drive belts.

Type: Triplex plunger

Materials: Nickel Aluminium Bronze pump body, die cast Aluminium crankcase, 316 SS valves

and seats

Speed: 1040 RPM

Power: 5.5 kW, 440v 3ph- 11 A

4

4. PRESSURE VESSELS AND MEMBRANES

The R.O. membranes are housed in GRP pressure vessels sealed with stainless steel reinforced

nylon end plugs. Depending on the model the system will have two, three or four membranes in

series. Interconnecting pipe work is made from super duplex stainless steel joined with Victaulic

couplings.

Membrane type: Dow Filmtec SW30 4040

Sodium Chloride Rejection: 99.4%

Max operating pressure: 1000 PSI (69 BAR)

Vessel Test Pressure: 1500 PSI (103 BAR)

5. CONTROL PANEL / SYSTEM CONTROLS

The system features simple electronic controls for ease of operation. These controls are housed

in an IP55 rated, powder coated steel enclosure. The features include:

• Membrane keypad for operation of system

• Fully automated Salinity Controller showing quality of product water in TDS

• Audible alarm with mute button in addition to LED’s to indicate fault states

• High pressure switch set to shut down system if the pressure exceeds 1000 PSI (69 BAR)

• Low pressure switch to protect HP Pump from cavitations in feed water create by low feed

pressure

• Hour meter

• Fresh water flush switch (optional)

6. WET CONTROLS

• Feed pressure gauge(s) to indicate clogging of pre-filters and media filter

• Restrict valve and high pressure gauge to regulate working pressure

• Inlet flow meter

• Product flow meter

• Product water sample tap

7. CONNECTIONS

Sea inlet: 1” BSP

Brine discharge: 1” BSP

Fresh water: 1/2” BSP

Both sea dump and fresh water lines are fitted with over pressure relief valves. The system also

features a 1” maintenance inlet connection mounted on the Primer pump, and a 1”

maintenance outlet connection within the main frame.

5

6

7

8

9

10

Optional Extras

Media Filter

Commonly referred to as a sand filter because the filter media is borosilicate grit which looks like beach

sand. This is an FRP housing containing specially calibrated filter media. Particles present in the feed

water get caught in the upper layers of the media. The flow through the housing can be reversed to

flush the “dirt” out through the discharge pipe. This unit significantly lowers the consumption of the

cartridge filter elements when the plant is operated in dirty water. For systems using a media filter, only

a 5 Micron pre-filter is supplied.

Oil/Water Separator Element

A pre-treatment option for use with feed water that may contain oil. The unit uses the same type

housing as the standard pre-filters for compatibility and ease of replacement.

UV Sterilizer

The unit sterilises the water to be completely free from bacteria, parasites and algae spores. This can be

used for pre-treatment of feed water when operating in dirty waters and also as a post treatment if the

water has been held in storage for long periods of time.

Fresh Water Flush

Upon system shut down the fresh water flush system allows the user to flush potable water through the

system. This ensures maximum operational efficiency and longevity of the R.O membranes.

The system is plumbed into the vessels pressurized fresh water system and features a carbon filter to

remove any chlorine that may be present.

Re-Mineralization

Used to restore mineral content and restore equilibrium with alkalinity/CO2 levels. Also known as re-

hardening or de-acidification. The unit uses the same type housing as the standard pre-filters for

compatibility and ease of replacement.

Carbon Filter

Removes dissolved gases (including Chlorine), tastes and odours to improve the taste of the product

water. This unit uses the same housing as the pre-filtration cartridges for compatibility and ease of

replacement.

Remote Keypad

This keypad allows the user to control both pumps and assess the running status remotely to the plant.

Chlorine Dosing

The unit sterilises the product water to be completely free from bacteria, parasites and algae spores.

Chlorine is added to the product water (0.2-0.3mg/l in accordance with W.H.O rules on potable water)

to sterilise it for storage for long periods of time.