Reclaiming water through recycling the best way ahead
We use six to 12 litres of water every time we pull the flush. But ever spared a thought for what happens to the water that goes down the drain after bathing, washing clothes, cleaning kitchenware, cars and floors?
We use six to 12 litres of water every time we pull the flush. But ever spared a thought for what happens to the water that goes down the drain after bathing, washing clothes, cleaning kitchenware, cars and floors? Why is good, clean water used just once? Why are we struggling to source water from tankers and borewells that are dying or drying up by the day?
City dwellers get away with the government getting fresh water from pristine areas at long distances. Today, however, with river water supply covering only about half of our daily needs together with a population growth which will double in the next decade, it’s time for some radical thinking.
Every Bengalurean gets about 75-80 litres of Cauvery water and the city in total gets 132 crore litres of river water, Pune gets 120 crore litres, Mumbai about 260 crore and Delhi gets a whopping 320 crore litres. The four cities planned for about 130 litres to a person but lose about 40% to leaks and thefts or what is called euphemistically ‘non-revenue’ water.
Related news | Despite rains, bad water management may put TN in a spot
We have relied for over a century on the use of piped supply. This has been around since Roman times and makes little sense that in the future when we won’t have long distance water sources. Every city has stretched its limits on sources of water from rivers or lakes built and nurtured a century ago. Urban planners of the past who rooted for supply side solutions are at a complete loss and find themselves professionally irrelevant.
Making fresh water available to our dwellings after treating it for reuse is where the new engineering challenge of the 2020s. Things are set to change soon. Singapore showed the way, on October 8, 2008 the country’s Prime Minister went on national television to tell citizens about NuWater, which was fresh water treated from out of waste water.
China in the last five years has moved about 60 cities into treating their waste water into high grade, potable drinking water.
Generally, no more than two litres of water is consumed by a person and in an average another five litres is used for cooking.
What this last decade has seen in Singapore and China is reinventing of the basic idea — you cannot use fresh water only once.
A composite water treatment system takes the tertiary Sewage Treatment Plants (STP) treated water to a fourth level with a Health Grade Water treatment system which offers high quality water for use.
Aversion to drinking this water is the major behavioural hurdle. Bottled water that we pay up to Rs 20 has groundwater from a farm zones where the chemical contamination is high, yet because it is packaged well, we accept it ‘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 science of water treatment
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 the technologies that are low on energy use. Apartments and other buildings can have these compact decentralised Health Grade Water systems with no more than the space of a garage needed.
The conventional engineer of the past argued for long – and they were 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 of the waste water – the under 1% 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.
Easy on the pocket too
The cost of installing these waste water to health grade drinking water systems is recovered in under three years if you assume the 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.
Making the best of it
There are apartments in Bengaluru, which 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%.
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.
(The writer is a pioneer in green buildings and a Senior Fellow of the Indian Green Building Council.)