Fresh water Flashcards
State the uses of fresh water.
- Drinking
- Washing
- Cooking
- Cleaning
What services are provided by the fresh water system?
- Laundries
- Galleys
- Showers and sinks
- Water heaters
- Medical use
- bridge window washers
- Fresh water hose reels
- Machinery cooling
What is osmosis?
The transfer of pure water through a semi-permeable membrane into salt water.
What is reverse osmosis?
Is the transfer of water from salt water through a semi-permeable membrane into pure water.
Define TDS
Total dissolved solids
What is TDS the measurement of?
The measurement of water purity
What is the TDS of sea water?
34,000ppm
What is the TDS of water after desalination?
Between 250 and 300ppm
What percentage of sea water is ejected after fresh water is produced?
80%
What is desalinated water called?
Permeate or made water.
What is the waste water called after desalination?
Concentrate
What does CCV stand for?
Concentration control valve.
What happens if the CCV is closed?
Back pressure increases and permeate production increases.
What happens if the CCV is opened?
Back pressure is reduced and permeate production is reduced.
What will happen to the RO plant if the water passing through it contains too much chlorine.
Chlorine will cause irreversible damage to the membranes.
How are the cushion membranes joined together at the edge?
Using ultrasonic welding
What is the pressure of the water supplied by the piston pump in the RO plant?
65 bar
What does the bag filter in the first stage of filtration within the RO plant filter down to?
60 microns
What does the bank of cartridge filters in the second stage of filtration within the RO plant filter down to?
10 microns
Why is chlorine added to the permeate?
To kill off any harmful bacteria.
How often are chlorine levels checked in the fresh water tanks?
Daily and before embarkation.
What level are chlorine levels maintained at?
0.2ppm
Who authorises and supervises the addition of chlorine?
The section head
State the 3 fresh water tests that are carried out?
- CHEMets
- Visual
- Taste
How often is fresh water testing carried out?
Daily and prior to embarking
What is used to heat water on board ?
Calorifiers
What causes a ‘‘water hammer’’?
Air in the fresh water system
What colour are fresh water hoses?
Blue
What should be done to the fresh water hoses before they are used?
They should be flushed with fresh water.
