World Water Day 2020 Homes and gardens

Every drop counts: why grey water recycling is a must

Approximately 50-70% of the water used in your house results in grey water generation   | Photo Credit: Getty Images/iStock

While we are all washing our hands regularly to stay safe from the coronavirus pandemic, we cannot afford to take water for granted by leaving taps on for the 20-second cleansing routine. And since you are now spending a lot more time indoors, how about looking at setting up a grey water system at home?

Approximately 50-70% of the water used in your house results in grey water generation and not even 5% of this is recycled in urban households. This water is suitable for in-situ recycling using simple, low-cost technologies, and it is rather unfortunate that the concept is not commonplace in a water-starved country like India.

With World Water Day being observed tomorrow, and a harsh summer upon us, it’s time we look at not just using water judiciously, but also recycling what we can. Dr. P.Venkateswaran, Deputy General Manager — Operations & Maintenance, at Sri City in Andhra Pradesh, says that traditional in-built practices like landscaping with grey water and rainwater harvesting have diminished due to rapid urbanisation and the commercialisation of land. “Scientists and technocrats are working hard to find alternative ways to source fresh water, like desalination, cloud precipitation technologies, etc. But these advanced technologies are resulting in making water more expensive, artificial and unaffordable for the common man. So when we have simple, reliable, eco-friendly and cost-effective methods like recycling, why should we opt for costly technologies?”

Rising awareness

The Chennai Metro Water Supply and Sewerage Board is championing the use of treated water (grey and black) for supply to industries, thereby reducing the pressure on freshwater demand, says Venkateswaran. Thermal power plants and industries like Chennai Petrochemical Ltd., Madras Fertilizers Ltd. and Madras Petrochemicals Ltd. are already using treated sewage for industrial purposes. “Residential apartments are using reclaimed water for flushing and landscaping applications due to a statutory compulsion, but the availability of open space for disposal is a major constraint,” he says.

To the point
  • In his 2005 book, Self Reliance in Water, Chennai-based environmentalist Indukanth Ragade breaks down the recycling process. He classifies used water into three categories: sewage (black water), kitchen outflow and bath water (grey water).
  • ‘Good building practice requires that these three streams of water be taken out of our homes into three different pipelines,’ he writes, and elaborates on ways to treat wastewater using soil and plants, with installation and maintenance tips, and ways to integrate rainwater harvesting and grey water systems.
  • The author can be contacted at isragade@yahoo.com

Venkateswaran explains that if grey water is utilised at source, additional costs of treatment, disposal, etc. can be avoided. “India’s urban areas generate 61,948 million litres (MLD) of sewage a day, of which about 35% is collected and treated in sewage treatment plants. In Chennai, 1,200 MLD of water is utilised every day, a minimum of 600 MLD of grey water is generated, which gets microbially contaminated after mixing with black water.”

Going by these numbers, it is evident that there is immense scope and need to recycle grey water. Luckily, there has been a lot of awareness of late, especially in urban areas, says Abhijit Sathe, who founded JalSevak Solutions (jalsevak.in) in 2016. The Navi Mumbai-based start-up was founded with the objective of providing compact, onsite greywater recycling solutions to residential customers. “We perform filtration using dual stage fabric filters and chemical treatment through a controlled dosage of chlorine. The system is low-maintenance; only the periodic cleaning of filters and refilling of chemicals in the chamber is required,” says Sathe, who developed the solution with support from IIT Kanpur’s Startup Incubation and Innovation Centre.

(left) Abhijit Sathe of JalSevak Solutions and (right) an septic system being cleaned and unblocked

(left) Abhijit Sathe of JalSevak Solutions and (right) an septic system being cleaned and unblocked   | Photo Credit: Special Arrangement and GettyImages/iStock

Taking me through his water-saving system, he explains how an average Indian residing in an urban area utilises approximately 180 litres of water every day, of which 45-50 litres (25%) is spent on toilet flushing. “For a family of four, the total amount of grey water generated is approximately 400 litres per day. Using our solutions, this water can be recycled for gardening and toilet flushing, saving 400 litres of fresh water every day,” says Sathe, adding that a small family can potentially conserve 12,000 litres of fresh water every month.

Quoting the example of Kanpur’s Jai Narayan School, he explains that with the new recycling system, the school is saving approximately 3,000 litres of fresh water every day. “They are reusing laundry wastewater to flush toilets in the boys’ hostel. The school is thus saving 3,000 litres of groundwater which would otherwise be used in flushing.”

Cost matters

While awareness has increased, consumers are not open to installing costly solutions. “There is huge demand for cost-effective and compact solutions that require minimum re-plumbing,” says Sathe, who has installed recycling systems in Navi Mumbai, New Delhi, Coimbatore, Hyderabad and Bengaluru. For an individual house under construction, installing the solution will cost anywhere between ₹45,000 and ₹65,000. “The price includes the cost of filters, chemical chambers, storage tanks, pump and supporting controls, and plumbing. For an existing individual home, this cost can go up depending on the level of re-plumbing necessary.”

In the absence of automated solutions, people need to manually recycle grey water by using wastewater from the washing machine to wash toilets. “A few customers have also developed a primitive piping mechanism to send kitchen wastewater to their gardens. However, such systems do not function in the long run and suffer from lack of maintenance,” warns Sathe.

Keep in mind
  • Do
  • 1. Consult a professional to design and install the system
  • 2. Segregate light and dark grey water
  • 3. Install sub-surface or covered drains for irrigating landscape areas
  • 4. Disinfect treated grey water to use for purposes other than for gardening/ landscaping
  • 5. Ensure there is no stagnation of grey water and redirect the surplus to sewerage lines / ground water recharging.
  • Don’t
  • 1. Store untreated grey water for more than 24 hours
  • 2. Discard concentrated liquids such as used oil and left-over food in grey water pipes.
  • 3. Allow excess treated grey water to mix with any water body.

Highlighting the benefits at a commercial level, Eshwar N, Chief Marketing Officer at Casagrand, says the STPs (set up by Green Earth Systems) at their various projects in Chennai, Bengaluru and Coimbatore have worked to bring down water consumption. “Water from these plants is used to flush toilets and water landscaped areas. The average estimated water conserved [on a daily basis] is 25 litres per head, for flushing, and 1.5 litres per sq. ft for landscaping,” he says, “The approximate cost to set up a grey water treatment system for an apartment complex of 10 units is ₹3 lakh.”

Eshwar adds that while water recycling as a concept is widespread, there is limited knowledge on the collection and use of grey water. “With modern apartments using STPs integrated with grey water, awareness is gradually increasing.”

What you can do

What people need to do is incorporate recycling systems during construction. Venkateswaran of Sri City advises people to install a ‘dual plumbing’ mechanism to use grey water / STP treated water.

An aerial view of a water treatment tank

An aerial view of a water treatment tank   | Photo Credit: Getty Images/iStock

Light grey water sources are bathrooms, showers, hand basins, laundry rinses and RO rejects, whereas dark grey water sources are dish washing, the first wash from the washing machine and kitchen sinks. “At an economical level, every citizen can divert the bathroom wastewater to a small sump followed by a root zone treatment and gravity sand filters. This method doesn’t require power, chemical, or maintenance. Post filtration, this water can be pumped and used for flushing toilets. A minimum of 2.5 sq. ft space per person is adequate,” he explains.

A complete grey (light + dark) water reusing system, including kitchen waste, requires an oil/ grease trap and a sedimentation facility in addition to the system. “A four member family can reuse 360 litres of water a day. An area of about 50-75 sq.ft. is required and the investment will range from ₹50,000 to ₹1.5 lakh, and will vary on a case-by-case basis. You can recover this amount in 2-3 years by saving on buying fresh water. Such a treatment facility can also be set up on an open terrace,” concludes Venkateswaran.

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Printable version | Feb 27, 2021 1:16:49 AM | https://www.thehindu.com/life-and-style/homes-and-gardens/grey-water-recycling-is-a-must-for-a-water-starved-country-like-india/article31117504.ece

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