The document discusses criteria for sanitary wells and well construction. It provides three key criteria for sanitary wells: location at least 15m from contamination sources and upgradient; brick lining and concrete reinforcement to prevent collapse; and a parapet wall, apron, drain, and cover to protect the well. It also describes disinfecting new wells by scrubbing chlorine solution on the walls and pouring it in overnight. Dangers of well construction mentioned are inadequate ventilation, wall collapse trapping workers, and injuries from subsoil creatures.

1. Water Supply and
Treatment Technology
(EHT 215)
LECTURER: SIR OAK

2. LECTURE 5
 Sanitary Well
Learning objective:
At the end of this topic, students should be able to:
• describe a sanitary well;
• list and explain the criteria for a sanitary well;
• identify steps in disinfecting well;
• mention dangers in well construction.

3. Introduction
• Groundwater is one of the most important water resources on the
planet that can be found in either the aquifers or the water
table.
• After precipitation, most of the water flows into streams and some
of that water percolates into soil.
• As gravity pulls the water deeper into the soil layer, it tends to
pool on top of the bedrock.
• The soil immediately above the bedrock becomes fully saturated
with water, while the soil just beneath the surface is unsaturated.

4. Introduction cont…
• ​The line between saturated soil and unsaturated soil is known as
the ​water table.
• The water below the water table makes up an unconfined
aquifer​.
• Confined aquifers are reservoirs of water that managed to seep
below the confining rock layer (Bedrock)
• Confined aquifers are connected to the unconfined aquifers in
that water from the water table can seep into the confined
aquifer.

5. Well
• A well is a dug hole on the ground which contains water and is
maintained for drinking, domestic and other purposes.
• There are two (2) main types of wells, namely: shallow well and
deep well.
• Shallow wells are dug into soils with pick axe and shovels and
generally not more than 15m deep. They do not penetrate the
bedrock found more deeply in the ground.
• Deep wells are excavated over 30m deep. They also go beyond
the bedrock into the confined aquifer

6. Sanitary Well
• A sanitary well is one that is
properly located,
well constructed, and
well protected from possible locations of contamination so as
to ensure supply of safe water.
• The criteria for a sanitary well are:

7. Criteria for a Sanitary Well
 Location
• A sanitary well should be located at least 15m away from possible
sources of contamination.
• It should be sited up-hill or raised grounds.
• It is suggested that no user should have to carry water for more
than 100m.
• A 1.5m or 1.3m diameter ring is marked on the ground to show
where the well should be dug. Diameter of 1.2m can be use in
rocky areas which do not require lining.

8. Criteria for a Sanitary Well cont…
 Brick-Lining
• The inside of the well should be lined with bricks up to a depth of
at least 6cm to:
ensure that the water enters the well from the bottom and not
from the sides in order to prevent the side walls from
collapsing;
prevent seepage from nearby sanitary sites.
• Also the lining should be continued till about 60-90cm above the
ground level.
• A caisson is used to enable the well to be deeper into the ground
and also prevents caving-in.

9. Criteria for a Sanitary Well cont…
 Reinforced concrete lining:
It prevents brick wall from collapsing.
 Parapet wall:
A sanitary well should have a parapet wall up to a height of at
least 70-75cm.
 Apron/Platform:
• A cement concrete platform should be constructed around the well with
a radius of at least 1m in all directions
• The margin of the platform should have a drain for collecting the spilled
water

10. Criteria for a Sanitary Well cont…
 Drain:
• The spilled water should be channeled away from the well
using a proper drain system.
• It should be connected to the public drain system or to a
drainage pit located outside the cone of filtration of the well.
 Cover
• A proper cement concrete cover is essential for maintaining
the quality of the water of the well
• It increases the bacterial quality of the well water considerably

11. Criteria for a Sanitary Well cont…
 Hand pump:
• A hand pump should be installed to draw water from the well.
• It should be of good quality so as to endure the rough handling
by the people.
• It should be regularly serviced and there should be provision to
repair it quickly if any fault were to arise

12. Criteria for a Sanitary Well cont…
 Consumer responsibility
• The people who use the well should observe certain
precautions to ensure the quality of the water.
• They shouldn’t dump waste materials around the well.
• Washing of clothes and animals in the vicinity of the well should
be prohibited
 Quality:
The physical, chemical and biological parameters of the well
water should conform to acceptable standards

13. Disinfection Of Wells Before Use
• Mix two liters of ordinary bleach (Calcium hypochlorite) in 35liters
of water. Scrub the sides of the wall (shaft) with this solution and
pour the rest into the well.
• Mix similar solution and pour into the well and allow it to stand
overnight.
• Pump the well to waste until the odour of chlorine disappears. The
remaining chlorine disappears slowly with time as it oxidises.
• Nevertheless, chlorination of a rural water source may be a
worthwhile temporally measure during an epidermic which is
suspected to be water-borne.

14. Dangers In Well Construction
• Ventilation may be inadequate as well becomes deeper.
• Walls or Shaft of wells may fall in and trap sinkers.
• Danger of bites from reptiles and other sub-soil creatures eg.
Snakes, scorpions, etc.
• Danger of sinkers injuring themselves.

15. Thank you