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Should water be used just once?

There is a clear need in our cities for understanding why we use fresh water only once when technology has transformed to turn used water into pure drinking water.

When you flush down the poop every day consider this. To each of us there’s no more than 130 grams we put out daily. We use 6 to 12 litres to flush down the stuff. What happens to the ‘dirty’ water after you are done with using it for washing your bodies, clothes, kitchenware, cars and floors? You need less than 20 percent for drinking and cooking.

Why would you use good clean water just once and wrestle with sourcing water from tankers and from borewells that are dying or drying up by the day? Until now as city dwellers we got away with governments getting us fresh water from pristine areas at long distances. Today, with river water supply to each of us at about half our daily need and the number of us doubling in the city in just the next ten years, we need disruptive thinking.

The per head statistic in Bangalore of Kaveri water supply is about 75-80 litres with a lot lost (50 crore litres a day at ₹ 100 for every thousand litres of leakages and theft that are subsidised — every day). Bangalore gets 132 Cr litres of river waters, Pune gets 120 Cr litres, Mumbai about 260 Cr and Delhi gets a whopping 320 Cr litres. All of them planned for about 130 litres to a head in their cities but lose about 40 percent to leaks and thefts or what is called euphemistically ‘non-revenue’ water.

We have relied for a century on the ‘modern technology’ of using piped supply for getting fresh water for consumption. This has been around from the Roman times and makes no sense at all into a future where we have no more long-distance water sources. Every city has stretched its limits on sources of water from rivers, or lakes last built and nurtured a century ago. Those urban planners of the past who rooted for supply side solutions are at a complete loss and find themselves professionally irrelevant.

Solutions to make our buildings net zero on water with all fresh water, once used, being treated for drinking again, is where the new engineering challenge of the 2020s lies. Things are set to change. It was Singapore that first showed the way in 2008 when in October 8, their national day, the Prime Minister went on national television drinking what they called NuWater which was fresh water treated from out of waste water. China in the last 5 years has moved about 60 cities quietly without fanfare into treating their waste water into high grade, potable drinking water.

No more than two litres to a person is used for drinking, with another 5 litres per person for cooking at a generous estimate. So much fresh water for all the rest of the use that don't need high hygiene, high-cost water. As someone said graphically, this is like using your new BMW to take chickens from a farm to the marketplace.

What this last decade has seen in Singapore and China is a reinventing of the very basic idea — you cannot use fresh water only once.

A composite water treatment system takes the tertiary STP treated water to a fourth level with a Health Grade Water treatment system that offers high quality water that the apartment can use. Aversion to drinking this water whose source is your own apartment’s waste water is the major behavioural hurdle. Bottled water that we pay up to Rs 20 has as source groundwater in farm zones where the chemical contamination is high, yet because it is packaged well, we accept it has water that is ‘safe’ to drink. Water that is supplied from tankers again comes from borewells in areas of the city’s periphery suffer the same risk of contamination.

The water treatment business has changed dramatically thanks to advancement in human genomics and its impact on environment engineering. Water treatment systems now understand the structure and function of microbes in biological treatment systems. These are sequentially managed systems that essentially modify the operating conditions in a way that they infuse more powerful bacteria to cleanse water of organic content. These are technologies that are low on energy use. Apartments and other buildings can have these compact decentralised Health Grade Watersystems with no more than the space of a garage needed. The conventional engineer of the past argued for long -- and he was right -- that the scale of economy offers better costs if centralised. That has changed over the last five years, both in terms of thinking and in the delivery of such treatment options.

The organic portion in the waste water -- the under 1 per cent part of waste water -- contains more energy than you need to treat this used water, about 2 KW per cubic meter that can be captured from the organic matter once you get this to settle down. There are technologies that are already available to recover this energy, with digesters that produce a variety of gas you can use in your kitchens. If the quantities of waste water and the organic matter are large -- over 300,000 litres a day in a building, it becomes viable to convert sludge to energy. In smaller quantities this organic matter becomes good rich compost that can help vegetation and gardens.

The cost of installing these waste water to health grade drinking water systems is recovered in under three years if you assume cost of fresh water purchased by tankers to be about Rs 15 per kilo litre. About 20,000 units of power is saved every year at 300 kilolitres a day of water use. This major disruption in costs of such technology has been possible thanks to deep end research in human genomes. The commercialising of such products has already succeeded. Many companies in India have taken to such Health Grade Water treatment systems but have not brought themselves to drink it — they have used them for chiller plants for centrally air conditioned buildings: a challenge of behavioural acceptance and not of the water-grade itself.

There are apartments in Bangalore who have swung into action. Some pioneering builders have shown the way ten years ago. It’s only a matter of a couple more years before more such solutions hit the marketplace with used water becoming drinking water with the loop closed right at the point of use. Produce-consume as Alvin Toffler said ‘prosume’ is now going to be the norm. The burdensome legacy of the past, of water from rivers at a long distance will reduce dramatically as our need for water from pristine sources falls by 90 per cent.

If there’s a certainty in this scenario playing out over the next half decade it is because it doesn’t need the government to step. The compelling logic of price and the proven quality of water will alone be enough to make our cities sustainable water if all stakeholders and users simply helped in educating the end water user to see good sense in this financially viable approach that will sustain the future of our cities.

Hariharan Chandra

The writer is a founder-mentor at AltTech. You can connect with us at

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