Fresh water

Question 1

What are the 4 uses for fresh water

Answer 1

Drinking
Washing
Cooking
Cleaning

Question 2

What services are provided with fresh water

Answer 2

The laundry
The galley
Showers and sinks
Water heaters
Medical use
Bridge window washers
Fresh water hose reals
Machinery cooling

Question 3

What is osmosis

Answer 3

Is the transfer of pure water through a semi-permeable membrane into salt water

Question 4

What is reverse osmosis

Answer 4

Is the transfer of water from salt water through a semi-permeable membrane into pure water

Question 5

What does TDS stand for and what does it measure

Answer 5

Total dissolved solids and it is the measurement of water purity

Question 6

What is the TDS of sea water

Answer 6

34,000 PPM

Question 7

What is the TDS of water after desalination

Answer 7

Between 250-300 PPM

Question 8

How much of the supplied sea water is ejected in regards to TDS

Answer 8

Approximately 80%

Question 9

What is desalination called and referred to as

Answer 9

Desalination water is called “Permeate” and sometimes referred to as “Made water”

Question 10

What is the waste water called after desalination

Answer 10

“Concentrate”

Question 11

Describe the desalination in the reverse osmosis plant

Answer 11

• The RO plant has two filtration stages, the first stage comprises of a bag filter which filters down to 60 microns
• The second filter stage comprises of a bank of two cartridge filters which filter down to 10 microns
• The RO plant has a high pressure, 3 piston positive displacement pump, providing 65 bar
• The salt water passes to the cushioned membranes that have ultrasonically wedged edges
• The anti-scalant dosing unit prevents precipitation of calcium salts directly forming on the membrane surfaces, hypersperse, anti scalant is added at a rate of 5ppm

Question 12

What does CCV stand for and what does it do

Answer 12

Concentration control valve
Controls the BACK PRESSURE of the sea water acting on the MEMBRANE CUSHIONS. By CLOSING the valve, the back pressure is INCREASED and the amount of PERMEATE is INCREASED. Therefore OPENING the valve REDUCES the back pressure and the PERMEATE is REDUCED

Question 13

What chemical cannot pass through the reverse osmosis plant and why

Answer 13

Water passing through the reverse osmosis plant cannot contain chlorine as it causes irreversible damage to the membranes

Question 14

What is used to kill off bacteria after it passes through the membranes

Answer 14

Chlorine

Question 15

How often are chlorine levels in fresh water tanks checked and what level is it maintained at

Answer 15

Daily and before embarkment, maintained at 0.2ppm

Question 16

When should desalination stop

Answer 16

If the source of water is likely to be contaminated
I.E Harbour waters and Estuary waters

Question 17

Who authorises and supervisors the addition of chlorine to fresh water

Answer 17

The section head

Question 18

What are the 3 fresh water tests

Answer 18

CHEMets
Visual
Taste

Question 19

What is used to heat water onboard ship

Answer 19

Calorifiers

Question 20

What is water hammer

Answer 20

Air in the fresh water system, which is a loud and repetitive banging noise inside the pipes

Question 21

What is used to bring on fresh water

Answer 21

Fresh water hoses which are blue in colour
They should be flushed with fresh water before use

Question 22

What is used to prevent water hammer and how

Answer 22

Air eliminator is fitted to a high point because as the air rises in the water it will naturally accumulate in any high point