This PowerPoint contains information about Pre treatment/ Grey water process in which it explains the phase’s abstraction, storage, sedimentation, aeration, roughing filtration etc......

1. Day 4
Props: perforated pipe and ceramic
pot
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2. Sand
Large stone
Soil Gravel
Or rice husk...
Broken Bricks Coconut shaving Pebbles

3. Conclusions:
• Did you record the experiment?
• What were your conclusions about the various
materials?

4. Layering
• The different materials depends on the
PURPOSE of the filter.
• We are now going to look in detail at the
filtration process.

5. Pre treatment/ Grey water process
Abstraction
Storage
Sedimentation
Aeration
Roughing
filtration
Coagulation To make white water this is the
with settlement pre treatment process

6. Abstraction
• When finding water – try to remove level of
suspended solids.
• E.g. Take water to treat from A or B?

7. Storage and Sedimentation
• Natural settlement of solids
• Natural die off of pathogenic
bacteria.
• Maximise settlement time
• Sunlight can reduce bacteria
in open storage tanks.
However in the presence of
organic matter it can
encourage growth of algae.

8. Aeration
• Tastes and smells are commonly due
to the presence of hydrogen
sulphide in the groundwater or
decaying organic and bacterial
matter in surface water.
• These tastes and smells can be
reduced by aeration.
• Maximise air/water contact area.
• Discharge in a spray into tank.
• If space let water fall down steps of
perforated tiles or steps.

9. Coagulation
• Some particles in water are quite small and do not
settle to the bottom of the tank during sedimentation.
• These particles must be encouraged to combine
together to create heavier particles and then they can
settle.
• This process is called coagulation (and flocculation)
• Chemicals: Most common coagulant is alum
(aluminimum suphate)
• Natural: Alum rock, crushed seedsof some plants but
may provide organic matter for the growth of bacteria.
• Stages: Rapid mixing and Flocculation

10. Roughing Filters

11. Infiltration rate
(Rate which water will
filter into soil)
Clay Sand
Clay is Sand is Permeable
Impermeable

12. Infiltration time
• Do you think rock has a longer or shorter
infiltration rate?
• Water will flow through rock quicker than
both sand and clay.

13. Soil infiltration rate for white and dirty
water
Soil Type Infiltration Rate (l/m2/day) Infiltration Rate (l/m2/day)
Clean Water Dirty Water
Sand 2000 50
Clay 100 Not suitable
Clay is Sand is Permeable
Impermeable

17. Extras
• For storage of non-
• Special iron fillings to
chlorinated water for filter
filter our arsenic
rinsing and use in bio carbon
tank.

18. Roughing filters
• For pre-treatment removal of
iron, parasites, colour, cysts,manganese, arse
nic, lead, mercury and turbidity.
• Can be used as a pre treatment for a slow
sand filration
• Can be used for grey water treatment as long
as not near a water source and is not going to
be drunk directly.

19. Roughing filter: Layers
• Horizontal roughing • Vertical roughing filter
filter • In series or separate tanks

20. We used the Vertical roughing filter
• But how well it filters the material also
depends on the size of the filter.
• Today we are going to look at volumes of
materials we could use as filter.
1) Ceramic pot
2) Barrel
Can you think of any other materials?

21. Calculating Volume
• There are two methods to do this.
• But first we need to agree on the Units to use.
(e.g. Feet, inches, centimetre and meters)
• We are going to use meters.
• Therefore our final volume will be in m 3
3

22. Method 1
• First: Calculations
– Step 1: Measure the dimensions of the object.
– Step 2: Work out the cross sectional area
– Step 3: Times the cross sectional area by the
height of the object.
– How do you calculate the cross sectional area of
a) Rectangle and b) Circle?

23. Method 1
• Area of cross
section is LxB.
Breadth
Height • What if it is a
square?
Length

25. • Diameter is 2m, what is
the area?
• Height is 1m, what is
the volume of this
cylinder?

26. Method 2
• Work out how many litres of water you can fit
into the object.
• 1Litre = 0.001 m 3

27. Question
• Volume of
– A) Ceramic pot
– B) One barrel
– C) Half a barrel