What happens to the Cauvery Water in Bangalore before it reaches you?
We use water every day for various uses. Survival without water is impossible. But have you ever wondered what happens to the water before it reaches you? How and from where does it come?
Sourced from Krishnarajasagara and Kabini dams, the Cauvery water that Bangalore receives, was once drawn to Thorekadanahalli (T.K. Halli) from T.Narsipur e-pumping station for the treatment and purification in Bengaluru Water Supply and Sewerage Board (BWSSB), which is said to be Asia’s biggest water purification plant.
Standards of potable water (indicating the physical, chemical and bacteriological factors) set by Bureau of Indian Standards (BIS) has been updated twice since it was first published in 1983, the latest version in India being BIS 10500:2012, to meet international specifications set by WHO.
Bangalore draws 1450 MLD of water per day from Cauvery for about 8.5 million Bangaloreans (2018 data).
Overview
The first 4 stages of the treatment take place in T.K. Halli water treatment plant. The treatment that follows this is for the purpose of treating almost pure water since most contaminants are removed in the T.K. Halli plant. Fully treated water then enters steel pipes (preventing leakages) to reach the city and finally individual households.
The water in BWSSB undergoes five stages of purification and pumping with both traditional and modern technologies. This capital-intensive plant operates at various level and uses automation.
The Treatment Process
Physical impurities form majority of the contaminants in water which in turn impact factors like colour, odour, taste, pH, turbidity and total dissolved solids (TDS).
Oxygen is absorbed by water falling in thin sheets over various steps in the cascade aerators killing bacteria.
Chlorination
The next step is chlorination. Huge amounts of chlorine are injected via pipes; about 300kg is used in a day to kill harmful organisms in water. Due to huge amounts being handled, major safety precautions need to be taken to prevent chlorination’s impact on humans.
According to BIS, factor bacteria, i.e., faecal and total coliform which shouldn’t exist in potable water at all, is common in water sources in India. Biological and bacteriological pollution can be treated with 2 ppm chlorination that kills new microbes that enter water. Hence, even household treatment systems use simple filters with chlorine tablets to remove these bacteria.
Next, Alum Dosing takes place. Aluminum Sulphate is mixed with the water ensuring right turbidity levels. Hence, if the municipal water supply is from Cauvery and water gets treated at the source before getting piped, chemical contamination stays low.
Filtration
Filtration is the next step. Firstly, sedimentation is allowed to occur. Chemicals like alum are added to accelerate its speed and also help smaller, finer, particles to settle. The water Is filtered by passing it through beds of sand filters (or other granular materials). The rapid speed helps remove pathogenic bacteria. Backwashing (or forced upward movement) is used for cleaning filters using wash water and compressed air.
Finally…
Water from T.K. Halli flows to Tataguni, Kanakpura Road via three pumping stations. Water is first drawn to Harohalli and then pulled for 25 km by gravity, without being pumped. Following this, water goes to Tataguni via underground pipelines (with 1200 mm width) working against gravity as water is pulled up 1500 feet.
2000 samples are then taken to BWSSB labs for testing where the Cauvery water is mostly contaminant free.
So that’s the little roller-coaster ride that the water resting in your house underwent before reaching you.
