A presentation on Potential Technology for Water Treatment by Romeo Afrin Upama, Department of Geography & Environmental Studies, University of Chittagong. The presentation is on the available and potential water treatment technologies.

1. A presentation on
Rome Afrin Upama
Department of Geography & Environmental Studies
University of Chittagong

2. Water Pollution, A Social Concern
• Water is a source of life and the most essential
natural resource.
• Only 0.036% of the planet’s total water supply
is accessible .
• A growing number of contaminants are
entering water supplies from industrialization
and human activity.
• It is causing various health hazards, natural
disasters, drinking water scarcity.
So it is necessary to prevent water
pollution.

3. Water pollution
Water Pollution is the alternation of physical, chemical and
biological characteristics of water which may cause harmful
effects on human and aquatic life.

4. Though Bangladesh is a riverine country, groundwater is the main source
of water for domestic, industrial and irrigation supplies considering the
relatively uncontaminated nature of water, compared with surface water,
which usually is polluted, and often bearing waterborne diseases. A total
of 95% of the domestic and industrial water supplies and 70% of the
irrigation supplies are drawn from groundwater. So by this, water is being
polluted as well, at different sources. And to reduce this water pollution
we have to treat each source in a different manner.

5. Water pollution abatement technologies are
used to reduce the harmful effects of
polluted water before it is discharged into
the natural water sources. It mainly includes
wastewater treatment that uses physical,
chemical and biological methods to remove
contaminants.

6. Why Potential Technology?
More effective, lower-cost, robust
methods for wastewater treatment
without further stressing the
environment or endangering human
health by the treatment itself, we
must use potential technology.

7. At Domestic Level
So for domestic waste, in order to prevent water
pollution we need to construct septic tanks.
These septic tanks are underground tanks which
treat the sewage before it is discharges into the
water body. So in these septic tanks sewage is
discomposed by bacterial action. When it is no
longer harmful, it is then discharged into the
water bodies.

9. At Industrial Level
We know at industrial level the waste and sewage is more
harmful as compared to that the domestic level. So for
industrial
waste we need better set up to treat the waste. In this case
treatment of wastewater is mainly carried out in 3 stages.
• Primary Treatment
• Secondary Treatment
• Tertiary Treatment

10. Primary Treatment
• Remove solids that are suspended in the waste
water via physical settling or filtration.
• The major steps are:
» Wastewater is screened to remove larger
objects;
» Then the grit is removed;
» The rest of the solids are finally extracted using
gravity in large sediment tanks.

11. Bar Screen
• Wastewater first passes through bar screens or bar
racks.
• It removes coarse solids like solids like
sticks, stones and other larger objects.
• Screens of various size and shapes are
used depending on the nature of solids to
be removed.

12. Grit Chamber
• After getting through the bar screen the waste water flow to the grit
chamber.
• Grit chamber are narrow tanks that
are designed to slow down the flow
of waste water.
• When the velocity of wastewater is reduced
at a point, the denser grit and small materials like
sand, dirt, broken glass, eggshell et cetera get
settled out but organic solids remain suspended.

13. Sedimentation Tank
• From grit chamber the effluent is passed into a primary settling tank.
• The rest of the suspended solids are removed by gravitational settling
under motionless condition.
• Flocculants which means chemicals
used to precipitate insoluble substances
are added to water to promote sedimentation.
• This process results in the removal of 50%-65%
of suspended solids.
• The settled solids are called
primary sludge.

14. Secondary Treatment
After primary treatment the effluent undergoes a
secondary treatment which degrades the
biological contents of the sewage by using
biological process. This is mainly done by
activated sludge process, trickling filters, aerated
lagoons and oxidation ponds.

15. Activated Sludge
• Activated sludge process use aeration and biological floc
composed of bacteria and protozoa.
• In an aeration tank where air
(mainly oxygen) is injected in the
mixed liquor.
• This is followed by a settling tank
which is called clarifier settler to allow
biological flocs to settle, thus separating the biological sludge.

16. Oxidation Pond
• Oxidation ponds are large, shallow ponds designed to treat
wastewater through the interaction of sunlight, bacteria and
algae.
• Algae grow within the pond and
produce oxygen by utilizing sunlight
during photosynthesis.
• This O2 is used by aerobic bacteria in
the oxidation pond to breakdown the
organic waste.

17. Aerated Lagoon
• This is a treatment pond with aeration to promote
the biological oxidation of wastewater.
• In a constructed aerated lagoon air is pumped into
the lagoon to turn the whole pond into an aerobic
zone.
• Adding air to the water speeds up the natural
process that breaks down organic waste.

18. Aerated Lagoon

19. Trickling Filter
• Wastewater is sprayed to the air then allowed to
trickle through the media.
• Microorganisms attached to the media break down
the organic matter in wastewater.
• A settling tank after the tricking filter, removes the
detached bacterial film and some suspended
matters.

20. Tertiary
• It is the final treatment the wastewater undergoes
before it is discharged into the environment. It is
also referred to as Effluent Polishing.
• The major processes done are:
1. Filtration
2. Nutrient Removal
3. Disinfection

21. Filtration
• Either sand or activated charcoal is used to filter
treated effluent.

22. Nutrient Removal
High level of nutrient such as N2 & P must be removed.
 Phosphorous Removal
• Phosphorous can be removed by Polyphosphate Accumulating Organisms (PAOs)
• It can be also removed by chemical precipitation, usually with salts of Fe, Al or Lime.
 Nitrogen Removal
 In wastewater much of the nitrogen is found in the form of ammonia.
 Bacteria can utilize the ammonia as an energy source and convert ammonia into nitrite
and nitrate.

23. Disinfection
• To kill microorganisms present in water
• Chlorination is the most common method
• UV light & Ozone can also be used for
disinfection.

24. Industrial Wastewater Treatment

25. Institutional Framework of Water Treatment of Bangladesh
• Ministry of Water Resources (MoWR);
• Water Resources Planning Organisation (WRPO);
• Institute of Water Modelling;
• Bangladesh Water Development Board;
• Local Government Engineering Development (LGED);
• Water Supply and Sewerage Authority(WASA);

26. Water treatment Plants in Economic Zone of
Bangladesh

27. Presented by
Romeo Afrin
ID: 18603049