Sewage treatment

Question 1

What are the health hazards from raw sewage?

Answer 1

1. Typhoid
2. Hepatitis
3. Gastro-enteritis

Question 2

What are the advantages of using a sewage treatment plant?

Answer 2

1. To reduce number of ship side openings
2. To simplify pipe runs
3. Heads and bathrooms can be lower in ship
4. Heads and bathrooms can be used in dry dock
5. The ship can operate in anti-pollution areas
6. It is easier to close down in CBRN conditions

Question 3

During Anaerobic digestion what gas is given off?

Answer 3

Hydrogen sulphide (H2S)

Question 4

What does Hydrogen sulphide smell of?

Answer 4

Rotten eggs

Question 5

What are the hazards associated with operating a sewage treatment plant (STP)

Answer 5

1. Dangerous chemicals - calcium hypochlorite (chlorine)
2. Raw sewage - typhoid, hepatitis
3. Dangerous gases - hydrogen sulphide (H2S) and methane

Question 6

What does 70-150ppm of hydrogen sulphide do?

Answer 6

It will kill sense of smell in 3-15 minutes, irritates eyes, throat and lungs.

Question 7

What does 700-1000ppm of hydrogen sulphide do?

Answer 7

Causes an immediate threat to life. instantaneous unconsciousness and permanent brain damage is possible.

Question 8

What does more than 1000ppm of hydrogen sulphide do?

Answer 8

Immediate unconsciousness and death within seconds.

Question 9

What is the risk with methane?

Answer 9

Methane is flammable and is therefore an explosion risk.

Question 10

What is the risk with chlorine?

Answer 10

If inhaled it will burn the lungs and can be fatal.

Question 11

What precautions should be taken when working in the STP?

Answer 11

1. Personnel should have up to date inoculations. Any injury whilst working on the plant must be treated immediately.
2. No hand to mouth contact before thoroughly washing your hands.
3. Wear adequate PPE
4. Monitor the atmosphere using The H2S monitor