The Eco club arranged a trip to the V Valley on Mysore Road. We were a group of 55 enthusiastic students accompanied by 2 teachers. It was a one hour journey to the V Valley from our college. We reached there by 11.15 a.m. As we entered in Ms. Mamatha, a chemist guided us and explained about the complete Sewage Water Treatment Process. She told that the water first goes through three types of screening process. They were: coarse screen, medium screen and fine screen. She also told they were cleaning 180 million litres per day. These screening processes consist of a grit chamber, classifier and a grit remover. In grit chamber 60 to 80 % of the stone particles are removed. The classifier consists of a mixer blade which rotates at low RPM and it has a pit where the waste is been collected and stored. Later this is removed by a ladder like grit remover.
Then the water is diverted to the Primary Sedimentation Tank
In primary sedimentation tank, the water that overflows is controlled by valves .There were five sedimentation tanks but now only two are working. It works for around two –three hours per day. The minute solid particles are removed in this stage. It consists of scrapers at the bottom to remove the scud particles.
It also has a rotating channel and a skimmer blade at the top. This skimmer blade removes the oil and grease that is in the particles and later the in the scum box the scum is being dumped.
Primary Bio Filters (Trickling Filters)
Here, about 30-40% of the organic waste is removed. The dimensions of the filter are:
Diameter: 61.8 m
Volume: 5009 m cube
The water is being uniformly distributed with the help of sprinklers on the rough surface of the rocks
to remove the waste particles. It is a natural process that is happening due to gravity. On these rocks the
microbes are attached to eat the remaining organic waste on the surface aerobically causing formation of a bio film which is later removed.
Then usually it is sent to the secondary plant but now it is directly diverted to the tertiary unit. Out of the 180 mld only 60 mld is sent to the tertiary unit.
The tertiary unit was explained to us using the mimic of the whole setup. The water undergoes chemical treatments to make it fit for other domestic purposes (except drinking). We could not see the original unit due to cleaning processes which were taking place.. we were told that this water is used for garden maintenance and was also bought of road and flyover construction works by various corporations.
Varshitha Muniraju and Pravalika B
I PCMB G