Recycle grey water

UN-Habitat has commenced a new global consultation to reiterate the crucial role of wastewater management in the water cycle and explore policy options for a sustainable future. These consultations have also become necessary to set a future goal for water use, particularly for the years following 2015, which is the target year for the Millennium Development Goals. For India — a severely water-stressed region — this offers an opportunity to reflect on its policies and draw lessons from best practices across the world. The core challenge facing the country is the yawning gap between demand for water and the severely constrained supply. From 813 billion cubic metres — the figure for 2010 — demand is set to reach 1,093 BCM by 2025. Conventional resources alone cannot meet this steep increase. There is a pressing need to explore alternative sources. In this context, policymakers have done well to promote water harvesting to improve supply. But they have utterly failed when it comes to reusing water. Industrial scale recycling would help, but it could be expensive. On the other hand, the often overlooked building level reuse of grey water — wastewater from kitchen sinks, showers and laundry fixtures — is a more effective strategy to pursue.

According to a Centre for Science and Environment estimate in 2011, kitchen use, shower and laundry consume more than 70 per cent of the 920 litres of water supplied per household per day. Building systems seldom trap this wastewater for non-potable use such as toilet flushing, fire fighting and gardening. Instead, they drain it out along with sewage, burdening the system. More important, the precious water is lost. In contrast, countries such as Japan extensively recycle water and successfully tide over their water deficit. Through a combination of strategies involving small treatment plants and closed loop water supply at building level, Japan reuses more than 53 million litres of water every day. In addition, innovative bathroom fixtures conduct used sink water directly to the flush tank of the toilet and save about 22,000 gallons every year. Recycling needs changes to plumbing arrangements in a building, but it is not hard to implement or monitor. What is missing is the will and regulatory framework. Cities such as Nanded have amended their building rules to make wastewater treatment in large buildings compulsory, but such provisions are present more on paper than in practice. If policymakers are serious about increasing water use efficiency through recycling — a goal set by the National Water Mission — buildings should be compelled to meet most of their non-potable water requirement through grey water reuse.

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Printable version | Jun 12, 2021 11:27:34 PM | https://www.thehindu.com/opinion/editorial/Recycle-grey-water/article12318409.ece

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