STP And Ventillation

Question 1

What are the effects of pollution due to raw sewage?

Answer 1

The biological oxygen demand (BOD) of the organisms will de-oxygenate the water
Suspended solids level in the water will increase
Possibility of the disease producing organisms entering the food chain, particularly via shell fish
Potential health hazard

Question 2

Under current regulations when is the discharge of sewage allowed?

Answer 2

Within 3 miles of coast providing IMO approved STP is in operation, no visible floating solids or discolouration of the water
Between 3-12 miles if an IMO approved system to comminute and disinfect the sewage is in operation
Over 12 miles no treatment necessary, ship must be moving more than 4 knots

Question 3

What are the 3 types of sewage plants?

Answer 3

Biological
Collect, hold and transfer
Membrane bio reactor

Question 4

What is released if the plant has become anaerobic?

Answer 4

Hydrogen sulphide and methane

Question 5

What gas is release from an aerobic plant?

Answer 5

CO2
Smells earthy

Question 6

What should be done before working on an STP?

Answer 6

Plant fully isolated
Flushed through for 30 minutes with water
Check there’s no sludge still in the tank
Tank is force ventilated to the outside, ships ventilation should not be used

Question 7

If there is a blockage in the STP before defect rectification what should be done?

Answer 7

Should be stated on the WRF or defect report form

Question 8

Where does methane sit in the compartment and why is it bad?

Answer 8

Highly flammable
Sits at top of compartment

Question 9

Where does hydrogen sulphide sit in the compartment and why is it bad?

Answer 9

Toxic, and can cause death in high quantities
Sits low down in compartment.

Question 10

What is the ventilation designed to do

Answer 10

Cool certain electrical equipment
Provide fresh air
Tolerable working conditions
Tolerable living conditions

Question 11

What is the ventilation system used to exhaust?

Answer 11

Wild heat
Noxious fumes
Odours
Stale air

Question 12

What does the ventilation system ensure?

Answer 12

In event of fire smoke migration is restricted to specific zones, post fire contamination is cleared with minimal loss of operational effectiveness
When closed down a positive pressure can be achieved to be maintained with in the citadel and machinery spaces when required

Question 13

What are centrifugal fans used for?

Answer 13

General use, supply or exhaust fans in a trimmed system

Question 14

How do centrifugal fans work?

Answer 14

Air drawn into the centre of the fan is expelled outwards to the tips of the blades by centrifugal force and into delivery trunk

Question 15

What are axial fans used for?

Answer 15

Fitted in machinery spaces and large centralised ventilation supply and exhaust systems

Question 16

How does the axial fan work?

Answer 16

The body of the fan being in line with the trunking takes up less space
moves large quantities of air against low resistance

Question 17

What do filters remove?

Answer 17

Impurities from ventilation and air conditioning systems
Such as dust, oily soot, salt, sand, and bacteria
Filters stop impurities quickly clog inlets heaters and coolers which reduce the overall efficiency and performance of the system, equipment of personnel.

Question 18

Where are odour filters fitted

Answer 18

Bathrooms, toilets and galley

Question 19

What’s the filter medium in odour filters

Answer 19

Carbon granules or cloth or a combination of chemicals

Question 20

When does a filter cartridge in an odour filter need replacing?

Answer 20

At least every 6 months, however humidity in compartment shouldn’t exceed 90% as this will impair filter’s efficiency