Unit water supply, responsibilities and the 6 principles of water purification

Question 1

What are the formation Staff’s Responsibilities?

Answer 1

Scales of use for personnel, vehicles and animals

Notify units of WP locations and routes of waterpoint and opening times

General distribution policy including transportation and policing

Water for fire fighting.

Question 2

What are the EH Responsibilities?

Answer 2

Advise on suitability of water for drinking and methods of treatment

Initial and routine, bacterial and chemical testing of sources and supply

Training of CHA and CHD personnel

Advise of scale of issue in particular for climatic conditions.

Question 3

What are the Royal Engineers Responsibilities?

Answer 3

Recce, initial field testing and development of water point

Collection of water, treatment and storage of water including protection from CBRN contamination

Construction, operation and maintenance of bulk water supply equipment

Advising formation staff on locations, availability and policy of water supply.

Question 4

What are the RLC’s Responsibilities?

Answer 4

Transport of bulk supplies

Provision of equipment and chemicals.

Question 5

What are the 6 principles of water purification?

Answer 5

1. selection of source
2. clarification
3. disinfection
4. contact period
5. test
6. de-taste

Question 6

What different sources of surface water are there?

Answer 6

Lakes
Ponds
Reservoirs
Rivers
Streams
Canals

Question 7

What are the vulnerabilities of surface water?

Answer 7

Surface water can be deliberately or accidentally contaminated.

Question 8

What considerations are considered when looking at a potential source of surface water?

Answer 8

Quality
Yield
Seasonal variation
Development required (cutting back vegetation, fencing, bank/damn integrity ect.)

Question 9

What different sources of ground water are there?

Answer 9

Artesian wells

Artesian springs (deep springs)

Land springs

Deep wells or boreholes

Shallow wells or boreholes.

Question 10

What are other notable sources of water?

Answer 10

Source Water (Local Water Treatment Facilities)
Bottled Water
Sea Water

Question 11

What are the characteristics of an ideal source?

Answer 11

Fast flowing large river

Oxygenated

Mountain filtered

Greater yield

Easy access

Question 12

Why can flooding affect certain surface water sources?

Answer 12

Creates access issues to water points.

Surface runoff can cause contamination to the water source.

Damage to equipment.

Question 13

What are the 2 main sources of pollution and give examples of each?

Answer 13

Dissolved:

Poisons
Detergents
Salts
Heavy metals
War agents

Suspended:

Leaves/twigs
Sand
Sewage, refuse
Worms
Disease causing organisms.

Question 14

Why would we carry out multiple recce’s prior to identifying a water source?

Answer 14

Identify all potential sources in operating area

Establish suitability of potential sources

Identify sources of contamination & Identify already contaminated sources

Establish tactical/logistical suitability

Identify requirements for source development and treatment.

Question 15

What are the 3 stages of carrying out a water recce?

Answer 15

Stage 1: Planning (Information gathering)

Stage 2: Conducting the recce

Stage 3: Testing

Question 16

What is clarification?

Answer 16

The physical removal of suspended contaminants through filtration, settling (often aided by some form of chemical addition) or biological removal of micro-organisms.

Question 17

What are the two principle methods of water clarification?

Answer 17

Sedimentation
Filtration

Question 18

What is sedimentation?

Answer 18

The removal of suspended matter by gravitational action or the use of a coagulant, flocculant (flocculation) Aluminium sulphate (Alum)

Question 19

What is filtration and an example?

Answer 19

Passing water through a filtering membrane or substance.

Millbank Bags
Stelmet Filters
Improvised Filters

Question 20

What chemical can we add to increase the speed of the sedimentation process?

What does this chemical do?

Answer 20

Commonly Aluminium Sulphate (Alum)

Particles destabilize, aggregate and form ‘flocs’

Flocs reach a critical mass and sink to the bottom of the settler

Question 21

What are the two types of sand filtration and what distinguishes them?

Answer 21

Slow sand filtration:

Biological process, gravity fed.
Top Schmutzdecke Layer
Fine sand
Couse sand
Gravel

Rapid sand filtration: Physical process, pressure forced

Activated charcoal
Fine sand
Gravel

Question 22

What method of disinfection do we adopt and using what chemical?

Answer 22

Fixed Dose Chlorination: Adding a known quantity of disinfectant, to a known quantity of water, to produce a known residual content on testing after a contact period.
Calcium Hypochlorite.

Question 23

What ratio do we fixed dose chlorinate?

Answer 23

4 grams per 50 gallons or 225 litres

Question 24

What is the aimed initial dose in ppm and the ideal residual test figure in ppm?

Answer 24

8 initial, 5 residual.

Question 25

What are the 2 contact periods and what circumstances would determine the time value to be extended?

Answer 25

In the military, circumstances may dictate that the contact period should be extended from 15 mins to 30 mins

30 Mins for:

Cold water (>0oC <4oC)
Suspected schistosomiases present
No check kit available.

Question 26

What do we use to test the chlorination level of disinfected water?

Answer 26

Lovibond checkit

Question 27

What do we do if the result is below 5 ppm? what could cause this?

Answer 27

If the result of the test indicates that there is less than 5ppm of chlorine present:
Add half the original dose
Wait a further contact period.
Test again

What could be causing the failure?
Calcium hypochlorite – out of date / incorrectly stored
Dirty water treatment equipment

Question 28

What do we do if the test value is above 5 ppm?

Answer 28

Dilute with clarified water, wait the contact period and re-test.

Question 29

When and why do we de-taste disinfected water and what do we use?

Answer 29

To neutralise remaining chlorine prior to consumption.
Remove unpleasant taste of chlorine.
Sodium thiosulphate pentahydrate crystals

Question 30

Why do we de-taste as close to consumption as possible?

Answer 30

to ensure sufficient levels of chlorine are present to protect the integrity of the water from further contamination.

Question 31

Like the addition of calcium hypochlorite we add the de-taste (de-chlorination) as a fixed dose, what is the ratio?

Answer 31

2 grams of sodium thiosulphate pentahydrate crystals per 225 litres/50 gallons of water.