2. When do we need each type of filter?
Septic Tank/ Used for
Soak Pit irrigation
• Contains • All used
human water Water
Black Grey White
FILTER
FILTER
waste without suitable for
water • Needs pre Water sewage. Water drinking
treatment
Municipal waste Grey water recycling:
treatment Used to flush toilets, etc.
4. Bio-filter
• Developed by ‘Practical Action’ in Peru and
Bangladesh. First used in Haiti in 1999.
• 30-60 litres of water per hour (family of 5-10
members).
• Advantages:
– Removal of turbidity, colour and odour
– Good microbial removal
– High flow rate
– Can be constructed with local materials
– Income generation
– Durable
– Minimal maintence
5.
6. • Disadvantages:
– Not 100% microbial removal; may require post-
disinfection
– Limited transportation due to weight (not portable)
– Turbiity should not exceed 100NTU
• Cost:
– Around 990-1300 Rupees
– Cost may vary depending on the availability of
materials and labour.
7. Municipal definition
• Municipal Water refers to a water supply
provided from a central point and piped to
individual users under pressure. It may be
from a central well or be treated surface
water. This is as opposed to each user having
a separate water source and pressure system.
10. UV Water Purification
• Prevents enzymes in water
from reproducing
• Water turbidity (i.e., the
amount of suspended &
colloidal solids contained in
the water to be treated) must
be low, such that the water is
clear, for UV purification to
work well. Also, water treated
with UV still has the microbes
present in the water, only
with their means for
reproduction turned "off".
12. Slow sand filtration
• First used in the U.S.A in 1872. Slow sand
filters are the oldest type of municipal water
filtration.
• Municipal Water refers to a water supply
provided from a central point and piped to
individual users under pressure. It may be
from a central well or be treated surface
water. This is as opposed to each user having
a separate water source and pressure system.
13. • Suitable for small systems with low turbidity or
algae containing waters.
• SSF does not require pretreatment
• Simple and reliable process, inexpensive but does
require some highly skilled operators
• No chemicals are added to aid the filtration
process.
• Can remove suspended organic and inorganic
matter. Also may remove pathogenic organisms.
14. • SSF reduces bacteria, cloudiness and organic
levels.
• Sludge handling problems are minimal
• Close operator or supervision is not necessary
• Can use local materials and labor.
15.
16. • Can use granular activated carbon (GAC) layer.
• Water is only applied to filters when the
turbidity level is lower than 10 NTU.
• Less effective with cold water.
• Filtration rate: 0.15 gallons per minute per
square foot of bed area.
• Biological matter forms on sand surface and
helps strain particals.
17. • Models are always nessessary to design SSF.
• Operation of a small model filter, preferably
over several seasons of the year, will insure
adequate performance of the full-scale plant.
• Parameters
– Plant filtration rate
– Bed depth
– Sand size
18. • Monitoring:
– Head loss
– Flow rate
– Water temperatire
– Turbidity
• Filters should operate at constant rate of
water.
• Storage of filtered water is essential.
19. Roughing filters
Advantages:
Built by local and local materials
Reduce turbidity and suspended solids
Reduce organice matter
No chemicals neded
They are appropriate and economical for rural
water treatment
21. Roughing filters
• Filtration rate depends on:
– Type of filter
– Water characteristics
– Desired turbidity reduction
– No of filter layers
– Height and width of filter bed.
– PARTICLE SIZE AND DISTRUBTION OF FILTER
MATERIAL.
– Most filters have 3 layers.
22. Filter size
• Is it better to build a water filtration system
for one house or a bigger one for lots of
homes?
• Small scale home filtration systems are not as
reliable as ‘municipal’ ones.
