250+ TOP MCQs on Design of Septic Tanks and Answers

By engineer / May 26, 2024

Answer: c
Clarification: The World Health Organization recommends they be built a reasonable distance from the house balancing issues of easy access versus that of smell. The distance from groundwater and surface water should be as large as possible to decrease the risk of groundwater pollution. The hole in the slab should not be larger than 25 cm (9.8 inches) to prevent children falling in. Light should be prevented from entering the pit to reduce access by flies. This may require the use of a lid to cover the hole in the floor when not in use.

9. The size of the faeces drop hole in the floor or slab should not be larger than ____________
a) 5m
b) 25 cm
c) 45 cm
d) 250 mm
Answer: b
Clarification: The user positions themself over the small drop hole during use. The size of the feces drop hole in the floor or slab should not be larger than 25 centimeters (9.8 inches) to prevent children falling in. Light should be prevented from entering the pit to reduce access by flies. This requires the use of a lid to cover the hole in the floor when not in use. However, in practice, such a lid is not commonly used as it is easy to lose it or for the lid to get very filthy.

10. As of 2013 pit latrines are used by an estimated ____________ people.
a) 1.77 billion
b) 2.77 million
c) 1.77 billion
d) 4.66 billion
Answer: c
Clarification: This is mostly in the developing world as well as in rural and wilderness areas. In 2011 about 2.5 billion people did not have access to a proper toilet and one billion resort to open defecation in their surroundings. Southern Asia and Sub-Saharan Africa have the poorest access to toilets. In developing countries the cost of a simple pit toilet is typically between 25 and 60 USD. Ongoing maintenance costs are between 1.5 and 4 USD per person per year which are often not taken into consideration.

11. As a very general guideline it is recommended that the bottom of the pit should be at least _______ above groundwater level.
a) 0.5 m
b) 2 m
c) 12 m
d) 20 m
Answer: b
Clarification: As a very general guideline it is recommended that the bottom of the pit should be at least 2 m above groundwater level, and a minimum horizontal distance of 30 m between a pit and a water source is normally recommended to limit exposure to microbial contamination.[1]However, no general statement should be made regarding the minimum lateral separation distances required to prevent contamination of a well from a pit latrine. For example, even 50 m lateral separation distance might not be sufficient in a strongly karstified system with a down gradient supply well or spring, while 10 m lateral separation distance is completely sufficient if there is a well developed clay cover layer and the annular space of the groundwater well is well sealed.

12. A _____________ houses the squatting pan or toilet seat and provides privacy and protection from the weather for the user.
a) roof
b) terrace
c) shade
d) shelter
Answer: d
Clarification: A shelter, shed, small building or “super-structure” houses the squatting pan or toilet seat and provides privacy and protection from the weather for the user. Ideally, the shelter or small building should have hand washing facilities available inside or on the outside (e.g. supplied with water from a rainwater harvesting tank on the roof of the shelter) although this is unfortunately rarely the case in practice. In the shelter, anal cleansing materials (e.g. toilet paper) and a solid waste bin should also be available. A more substantial structure may also be built, commonly known as an outhouse.