For most, water is something that is hardly given any thought. It is used to shower, flush the toilet, brush, clean, and for everything else. DNA maps the journey of water in your tap, right from its source
The water’s journey is actually quite impressive. From a lake or a reservoir (the source), to the nearest treatment plant and sometimes also the furthest, to finally reaching a commercial complex or a residential building, the journey is long, tedious and costly. Mumbai’s population has more than doubled since 1991, with the city itself becoming home to 12,478,447 people. The city’s water table has shrunk so drastically that the National Green Tribunal had admitted a Rs 222 crore damage plea over the plundering of two wells in South Mumbai for 11 years. A report prepared by the water supply and sanitation department in October 2018, pointed out that nearly 11,500 of Maharashtra’s 40,000 villages face water scarcity However, citizens and authorities are yet to wake up to the importance of water conservation.
Tweak Of Old With A Nip Of New
- Vihar is the oldest lake of Mumbai. Within the city area, the work on the Vihar waterworks started in January 1856 and completed in 1860. Development of this lake cost Rs 65 lakh then. Its total capacity of water stock is 27,698 million litres (ML). 90 million litre of water is supplied on a daily basis
- Tulsi is a very small lake in comparison to others and is situated in the heart of the Sanjay Gandhi National Park in Borivali. The cost of the development work of the lake, which started in 1872 and completed in 1879, was Rs 40 lakh then. Its capacity is 8,046 ML and the daily water supply is 18 ML
- Tansa The work of this lake started in 1892 and was completed in 1945. The lake is 106 km away from the city. The water storage capacity is 1,45,080 ML and the city gets 500 MLD water from this lake
- Modak Sagar The lake construction completed in 1954. It is on the Vaitarna River in Palghar District, 163 km away from the city. Having a capacity of 1,28,925 ML water, it provides 455 ML to the daily water supply
- Upper Vaitarna This lake was ready in 1972 and is 163 km away on the upper part of Vaitarna River with a capacity of 2,27,047 ML of water. The city gets 635 ML water daily
- Bhatsa The state constructed this dam, in segments, from 1980 to 2007. It is 102 km away from the city in Shahapur district of Thane with a storage capacity of 7,17,037 ML water. Mumbai gets 2,020 MLD of water from the dam, which provides water to other cities as well
- Middle Vaitarna The youngest dam started functioning in 2014. Rs 800 crore were spent on its construction and Rs 3,000 crore were used to tunnel the dam up to Bhandup which is 102 km away from the lake. Among the 550 roller-compacted concrete (RCC) dams built across the world, the Middle Vaitarna dam is the 9th quickest to be built. It has a capacity of 1,93,530 ML water and provides 455 MLD water to the city
A 40 Hour-Journey From Source To Mouth
It takes 40 long hours for the water to reach your home from the Upper Vaitarna Lake, which is the farthest from Mumbai. The water does not require any external push to reach the Bhandup complex or the Panjapor processing unit as the lake is located at a height. The water, which travels at the speed of 1.5 meters per second, takes 30 hours to reach these units. At the complex, detention time is 4 hours. The treated water is stored in the Master Balancing Reservoirs (MBR) located near the plants at Bhandup Complex and Yewai (in Thane). Water from these reservoirs take at least 5 hours to reach the furthest corners of the city. The water then reaches the underground tanks of your building and is then pumped to the overhead tank on the terrace, and then, finally reaches your tap after completing a 40-hour long journey
Strong Network
150-odd-km long pipeline network brings the water to the city
The water from these lakes travels in pipelines and tunnels which are 2,235 mm to 5,500 mm in diameter and reaches the water treatment facilities at Bhandup Complex and Panjrapole. Treatment plants for Tulsi and Vihar are located near the sources. The Bhandup plant processes 2,810 ml and Panjrapole processes 1,365 ml of water every day
100 to 175 km
The water comes from 7 lakes, 5 of which are located outside the city at a distance of 100 to 175 km
What happens at the water treatment plant?
- The Bhandup treatment plant, commissioned in 1980, is the largest treatment plant in Asia, which was awarded an ISO 9000-2001 certificate for a consistent high-quality water treatment. Water treatment is done through various processes like coagulation, flocculation, setting, rapid sand filtration and post-chlorination. The quality is maintained as per the IS 10500:2012 drinking water norms
- Coagulation-flocculation involves addition of polymers that clump the small, destabilised particles together into larger aggregates so that they can be easily separated from the water. Coagulation is a chemical process that involves neutralisation of charge whereas flocculation is a physical process and does not involve neutralisation
- Rapid sand filters use relatively rough sand and other granular media to remove particles and impurities that are trapped in a floc through the use of flocculation chemicals — typically alum. The unfiltered water flows through the medium filter under gravity or under pumped pressure and the floc material is trapped in the sand matrix
- Chlorination refers to a chemical process that is used primarily to disinfect drinking water and spills of microorganisms. The active agent in chlorination is chlorine
- The treated water is stored in the Master Balancing Reservoirs (MBR) located near the treatment plants at Bhandup Complex (in Mumbai) and Yewai (in Thane)
- It is further distributed to 27 service reservoirs located throughout the city with 450 km of supply network. These pipelines contain water 24/7 to eliminate contamination due to groundwater or/and sewage water intrusion
How Water Travels, Step By Step
(Clockwise: The water from these lakes travels through tunnels and pipelines, which are 2,235 mm to 5,500 mm in diameter and reaches the treatment facilities at Bhandup Complex and Panjrapol; The treated water is stored in the Master Balancing Reservoirs (MBR) located near the treatment plants at Bhandup Complex (in Mumbai) and Yewai (in Thane); It is further distributed to 27 service reservoirs located throughout the city with a 450-km of water supply networks; These pipelines contain water 24/7 to eliminate contamination due to groundwater and/or sewage water intrusion ) (Pic: Salman Ansari/dna)
Cleaning agents
- 10 metric tonne of Chlorine on a daily basis
- 75 metric tonne of Alum (aka Turti) required everyday
- Instead of Alum, Poly Aluminium Chloride (PAC), is being used for coagulation and sedimentation since 2008
Storage Projects & Expected Completion
Gargai (2022-2023), Pinjal (2024-2025) and Damanganga (2029-2030) will give additional 2,891 million litre of water per day (MLD) to the city. Gargai and Pinjal are on Kalu river and
180 km and 195 km away from the city
Total Reservoirs: 26
- Borivali East: 2
- Malad east: 2
- Veravali, Andheri east high level: 3
- Bandra pali hill: 2
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Eastern suburb
- Bhandup: 3
- Ghatkopar: 2
- RCF: 2
- Powai: 1
- Trombay -high level, low level: 2
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City
- Rowli: 1
- Phosbary, cotton green: 1
- Bhandarwada: 1
- Malbar hill: 1
- Worli: 2
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Electricity Cost Of Water Treatment & Supply
Rs 286 crore per year or
Rs 71 lakh per day
50% water supply is free as it requires no external push to reach the plant from dams, which are located at a height
3,800 mld water is equal to
3,85,000 water tankers
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