Solving Cities

Is growing vegetables from sewer water the next big thing in re-use?

Is growing vegetables from sewer water the next big thing in re-use?

Posting in Cities

All over the world, the inhabitants of cities are figuring out how to recycle their water supply ad infinitum

Brinjal, papaya, snake-gourd and black sugarcane are just a few of the crops Keshav Tavre grows on his suburban plot on the outskirts of Mumbai -- all of it from a supply of untreated sewage that snakes past his land.

After complaining for years about the stench, Tavre realized that what he'd seen as waste was in fact a source of wealth. By re-directing the sewage through a series of earthen dykes, each one filtering a bit more than the last, he was able to ultimately channel reasonably clean "greywater" into ponds for growing crops and enriching his soil.

In the developed world, we take it for granted that we have the technology and the resources to recycle sewage until it's as pure as our drinking water -- a process known as "toilet to tap." It's already in use in Orange County, California (yes, that OC) and it's been proposed for drought-stricken Texas towns like Big Springs.

But it's important to remember, when we speak of cities, that one in three city dwellers lives in a slum -- that's 1 billion people -- and that's unlikely to change anytime soon. Therefore, many of the most impactful technologies on earth right now are the simplest and least expensive.

Using nothing but soil, Tavre was able to redirect and purify so much water that he began re-selling it to local factories for dyeing texties for industrial use. This illustrates a second principle of water re-use: most of the water we use, for irrigation and industry, doesn't need to be nearly as clean as the stuff we drink.

You don't have to be a farmer in India to commit to conservation via so-called "greywater recycling" -- many homeowners practice it already. Unfortunately, conventional plumbing, conceived in an era of seemingly endless resources, doesn't distinguish between the "greywater" in our homes (the stuff that doesn't come from the toilet) and "blackwater" (the stuff that does). Homes have to be outfitted with a different sort of equipment to allow re-use of greywater for landscape irrigation and other purposes, but the savings can be substantial.

[via MIT CoLab Radio]

Photo: Simply CVR

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Christopher Mims

Contributing Editor

Contributing Editor Christopher Mims has written for Scientific American, WIRED, Popular Science, Fast Company, Good, Discover, Slate, Technology Review, Nature and the Nicholas Institute for Environmental Policy Solutions at Duke University. Formerly, he was an editor at Scientific American, Grist and Seed. He is based in Washington, D.C. Follow him on Twitter. Disclosure