From Toilet to Plate: the Unexpected New Trip Your Waste Water is Making

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Have you every wondered where the water we flush down our drains every day really goes? Most of us have the vague idea that the water ends up in lakes, rivers, and oceans. In lots of places, that's right! But for residents of California, the story is a little different. Wastewater from their homes and from nearby factories will soon end up in a completely new place: on their food.

Growing food using treated waste water is hardly a new concept, in fact many desert countries rely heavily on recycled water. In Israel, treated waste water provides over 50% of the water used for irrigation. And for the struggling farmers of California, this new source of water is the difference between scarcity and abundance. Water shortages mean that many farmers have drastically reduced the number of crops planted, while others have been forced to abandon farming altogether. Some farmers have been able to scrape by using groundwater, but it is poor quality, expensive, and supply is never guaranteed. Recycled Waste Water, while unfortunately still pricey, will be reliable and high quality: something most California farmers haven't experienced in years. While the project has received the support of environmental groups like Audubon California and Ducks Unlimited, other environmentalists worry about the possible health consequences of using sewage water on food.

Waste Water refers not only to raw sewage, but also the water from sinks, showers, and bathtubs. While the sanitation process involved in treating grey and black water is very thorough, residue from pharmaceuticals and personal care products (PPCP's) can be nearly impossible to remove completely. Just as growing plants absorb the pesticides sprayed on them, they will also absorb traces of pharmaceuticals. While one recent study shows that the amount of pharmaceutical residue left in plants is not enough to cause harm on their own, scientists are unsure what the cumulative impact of a lifetime of exposure could entail. There is also the worry that antibiotic residue in the food we eat could contribute to the “superbug” epidemic. However irrigating crops with treated waste water, whatever the potential risks, is far preferable to what's happening south of the border in Mexico, and in other developing nations: Severe water shortages are forcing third world farmers to irrigate and fertilize their crops with raw sewage. 

While it may seem odd, feces – even human feces – makes for excellent fertilizer, as it contains essential nutrients that can otherwise be costly or difficult to obtain: nitrogen, phosphorus, and potassium. And while food grown using human poop rarely makes the news, a report done in 2008 estimated that nearly 10% of the world's population depended on food grown using raw sewage. The same report found that over 200 million farmers around the world were using raw sewage to irrigate and fertilize over 49 million acres of farmland. Although sometimes the contamination is accidental, occurring when farmers draw water from contaminated lakes and rivers, in drought ridden areas farmers often re-route sewer pipes to flow through their cropland. Sewage is especially popular for use on fields of grains like wheat or barley, as grains are usually cooked prior to consumption, reducing the risk of illness. Nevertheless, more than 2.2 million people each year die from diarrhea-related diseases, of which 80% are caused by contact with contaminated water.

While the ability to re-use even the filthiest water is incredible, and secures a living for millions of people around the globe, the process is still very new in the developing world, and the possible risks and possible long term side effects can't be overlooked. More research is needed, and until then, focus on buying local produce – or better yet, grow your own!