Bioremediation
0 (0 Likes / 0 Dislikes)
Bioremediation, a term which we commonly use
basically means; detoxification of waste using biological systems
So, it could be plants... it could be microbes
Now to tell a little more about the process of purification that is taking place in the Bheri:
The raw sewage has to pass through a sieving procedure where the core suspended material is released
The water moves into a flat basin which is there -
which in created in such a way that the water depth should be between 50-150 cm
A flat bottom which has been treated with alkali – lime
ensures that there is an alkaline pH
which is a must for decreasing the coliform count
Now the water which is rich in organic content, is released there
There is a manual aeration which takes place
and because of that the dissolved oxygen concentration is kept pretty high
Now with sunlight penetrating till the bottom- as it's a flat surface
- through and through aeration and sunlight ensures that plankton grows there
Well, if plankton is allowed to grow for indefinite time, it results in plankton bloom
and that's a problem - nutrification. But that doesn't happen
So before it reaches a plankton bloom, fishlets are released there
and they consume or feed upon the plankton
So it's the initial planktons - the phytoplanktons and the zooplanktons which consume them
Again the phytoplankton is growing and now the fishlets are released, which feed on the phytoplankton as well as the zooplankton
Thus, the entire organic matter in the raw sewage which came here is consumed by these planktons
and that in turn becomes fish feed
So you do not need to actually add additional feed
Whereas the water which is there is purified
When you check the quality in terms of coliform count
-when you compare the raw sewage water to the water in the Bheri post growth (of fish)
there is a 96-99% decrease in the coliform count
There is immense decrease in the metal content.
Now the water which is left after the fish growth,
is good enough to be used for irrigation in the surrounding fields
Each Bheri has surrounding fields
Not only that- it's not just the water which is being used
After every round of cultivation each year
there is a period when the Bheri is dried
The silt which deposits at the bottom-which is absolutely fertile
is picked up and spread on these surrounding farms
As a result it's a fertile soil which is there
and the depth of the Bheri is maintained at 50-150cm
So that's the kind of purification which takes place
As a result, the wastewater is purified
Fish is produced
Environmental damage is prevented
And there is water, as well as fertile soil for irrigation
In addition, it also generates a lot of human resource
that is, in terms of employment
So this leads to production of one third of the fish that is required
And also a major portion of the vegetables that is required for the entire city
So, it is one of the best examples of integrated resource recovery in the world.
And what I have been or my entire group has been able to do till now
we can say for sure that this is a boon to the city of Calcutta
and it absolutely needs to be preserved
without which the detoxification or bioremediation activity
will be severely hampered
Since we do not have formal wastewater treatment plants
This is the natural system which purifies the entire waste