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February 27, 2009

Treating human waste

I was surprised to learn that it is easier to reuse and to make harmless human waste when urine and solid waste are separated before they are sent to the waste processing facility.

Sewage, according to the United Nations Environment Program, is the biggest marine pollutant there is. Wastewater-treatment plants work to extract the nutrients before discharging sewage into water courses, but they can’t remove them all. ...When a rainstorm suddenly sends millions of gallons of water into an already overloaded system, the extra must be stored or — if storage is lacking — discharged, untreated, into the nearest river or harbor. Each week, New York City sends about 800 Olympic-size swimming pools’ worth of sewage-polluted water into nearby waters because there’s nowhere else for it to go.

Research by Jac Wilsenach, now a civil engineer in South Africa, found that removing even half of the nutrient-rich urine enables the bacteria in the aeration tanks to munch all the nitrogen and phosphate matter in solid waste in a single day rather than the usual 30. Urine diversion also makes for richer sludge and produces more methane, which can be turned into gas or electricity, Mr. Wilsenach said. In short, separating urine turns a guzzler of energy into a net producer.

I was also surprised to learn that urine contains more nutrients than solid waste does:

In Sweden, some of the collected urine — which contains 80 percent of the nutrients in excrement — is given to farmers, with little objection

All and all it is an interesting article on our waste processing future. I once read a science fiction story where households had salt water and fresh water taps in their sinks so that the didn't wast precious fresh water cleaning themselves when abundant salt water would do. That seemed impossibly impoverished to me as a kid, but a future where there are multiple pipes into and out of the house seems increasingly plausible in a world where fresh water is expensive and so is disposing of human waste.

Posted by OneEyedMan at February 27, 2009 7:25 AM

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