Dirt Needs Dirt

Tom Easton

When I was very young, about 1950, my grandparents’ house had an outhouse, even though the house was in town. The house, you see, was owned by my great-grandmother, in her nineties, and she insisted that her late husband (d. 1927) would never have approved of such new-fangled things as indoor plumbing, central heating, and electric lighting.[1]

Yet the amenities did reflect a certain practicality. Once a year, a man would come to clean out the privy and haul the accumulated wastes off to a local farm, where they would be plowed under to enrich the soil. Houses with indoor plumbing routed the wastes to a local river. Today wastes flow from the household to a sewage treatment plant to be digested with the aid of assorted microorganisms and turned into “sludge.” The sludge is then often trucked to a landfill for burial. It can also be incinerated.[2]

It can also be applied to farm fields, but urbanites who have moved to the countryside to be closer to Nature often find that agriculture doesn’t always smell sweet. Cows, y’know. And chickens and pigs. And if you even mention the word “sludge,” those neighbors complain.[3]

If the truth be told, sludge can indeed stink, though composting can reduce this problem, as well as potential contamination by disease-causing bacteria and viruses. So can plowing it promptly into the soil. You can even eat the food grown in that soil, though you might reasonably prefer crops grown above ground, such as tomatoes, rather than root crops such as potatoes, beets, and carrots.

Animal manure—from cows, chickens, horses, pigs—also stinks, but it is more broadly accepted as fertilizer. The hot-button word that upsets people seems to be human manure, as if it were somehow less natural than animal manure.[4] Yet, once upon a time, using human manure was as conventional as using any other kind of manure. It was good for the soil. Dirt needs dirt.

It really doesn’t make much sense to bury perfectly good fertilizer in a landfill. It is much better to put it back in the soil where it came from in the first place, in the form of plant nutrients. Yet organic farmers have long resisted using sludge on their farms. A major reason is chemical contamination, especially by various toxic industrial chemicals. Industries are supposed to clean up their effluent before they route it into a municipal sewer system, and thence into a sewage treatment plant, but they don’t always. If contaminated sludge goes to a farm, chemicals such as lead and mercury can wind up in food or wash off the land into local streams and lakes. It thus behooves any sewage treatment plant to test its sludge for chemical contamination before deciding what to do with it. Landfill the bad stuff. Put the rest to fertile use. Even so, the Environmental Working Group is against using sludge in any food production system.[5]

The liquid that enters a sewage treatment plant is also of interest, for it contains a great many things that have passed through the human body or have been discarded via the flusher. This includes various drugs such as birth control drugs and antibiotics, both of which have been found in the cleaned-up liquids the plant releases to local bodies of water. Birth control drugs in rivers have been shown to affect fish.[6]  Antibiotics can lead to antibiotic-resistant bacteria.[7]  And since downstream communities may take drinking water from these bodies of water, there is a chance for the drugs to affect humans (though they are very much diluted by then). You don’t have to worry about sharing anti-psychotics and other meds. Yes, they’re there too.[8]

Sewage effluent also includes illicit drugs such as cocaine and meth.[9] One study found that if you sampled the sewage flow upstream from the sewage treatment plant, you could track drugs, pipe-branch by pipe-branch, to neighborhoods within a city. The researchers did not try to track the drugs all the way to individual households out of concern for privacy.[10] But not everyone has the same attitude. China, for one, appears ready to include waste monitoring for drugs in its extensive surveillance measures.[11]

Given the modern ability to sequence DNA quickly and cheaply, it is surely worth reflecting that where our poop goes, so goes our DNA as cells slough from the lining of the intestine. So far the technique is being used mostly to detect microorganisms, with an eye on monitoring public health,[12] but the potential is either tantalizing or frightening, depending on how you feel about Big Brother watching you.

Imagine, for example, that you know a dastardly criminal is hiding in a city, but you don’t know where. You have a DNA sample, perhaps as a bit of skin and blood from under the fingernails of a rape victim. So you check the local sewage treatment plant to see if any of the perp’s DNA has made it there. If it has, then you move upstream, sampling the sewage, pipe-branch by pipe-branch, until you are under his toilet. (If the pipes are too small for you, send a pipe-crawling robot,[13] perhaps equipped with its own DNA reader.)  Then you check your GPS for the address and call the SWAT team.[14]

What could go wrong, after all? Yet a savvy criminal, like a wild animal, might prefer to poop as far from home as possible. Perhaps at a bar or restaurant six blocks from the hide-out. That SWAT team could cause a great deal of excitement. Innocent bystanders could even get killed.

Can sewage effluent be cleaned up so it contains no drugs, DNA, viruses, toxic chemicals, or even the fragrance of its origin? This is a question of some concern to many areas already suffering from droughts, and to even more places expecting future drought due to climate change. Few people have an issue with using sewage effluent to irrigate lawns, golf courses, and farms. But what about putting it back in the water supply system? Well, El Paso, Texas, will be drinking recycled toilet water soon.[15] It’s already happening in California, though some of the reuse is “indirect” as cleaned-up effluent is injected into underground aquifers from which it can return to homes.[16] Direct reuse is also being considered in Cape Town, South Africa,[17] and indirect reuse in Australia.[18]

Yes, there’s a yuck factor here. No one wants to drink toilet water! Leave that to the pet dogs and cats.

But we are facing a future in which serious droughts are likely to be both more common and more widespread. If the choice is between drinking cleaned-up toilet water and not drinking at all, I know what I’ll choose.


[1] When great-grammy died, things changed in a hurry.

[2] For a thorough discussion, see https://extension.psu.edu/what-is-sewage-sludge-and-what-can-be-done-with-it.

[3] E.g., https://loudounnow.com/2018/10/05/farm-neighbors-renew-objections-to-use-of-biosolid-fertilizer/

[4] To be fair, the bacteria, viruses, and parasites to be found in human manure are those that infect human beings. (So are some of those in animal manure.) Coming into contact with sludge can pose problems. But these problems can be minimized by composting and prompt plowing.

[5] https://www.ewg.org/research/dumping-sewage-sludge-organic-farms

[6] https://www.sciencedaily.com/releases/2016/03/160304092230.htm

[7] https://www.sciencedaily.com/releases/2015/02/150213112142.htm

[8] https://newrepublic.com/article/115883/drugs-drinking-water-new-epa-study-finds-more-we-knew

[9] https://www.smithsonianmag.com/smart-news/sewage-water-reveals-communitys-illegal-drug-habits-180948197/

[10] https://motherboard.vice.com/en_us/article/z43kk9/the-plan-to-test-cities-sewage-for-drugs-is-a-new-form-of-mass-surveillance-5886b75df1bddf454bd80da8

[11] https://www.scientificamerican.com/article/china-expands-surveillance-of-sewage-to-police-illegal-drug-use/

[12] https://www.wateronline.com/doc/researchers-sequence-sewage-samples-0001

[13] https://cnre.mit.edu/research/development-pipe-crawling-robot-water-pipeline-network-discovery

[14] Might make an interesting CSI show, eh?

[15] https://qz.com/1353825/a-major-us-city-will-start-drinking-its-own-sewage-others-need-to-follow/

[16] https://alumni.berkeley.edu/california-magazine/just-in/2015-07-06/effluent-communities-why-drought-will-mean-learning-drinking

[17] https://www.news24.com/SouthAfrica/News/you-could-be-drinking-your-neighbours-loo-water-city-of-cape-town-may-take-water-saving-to-another-level-20180307

[18] http://theconversation.com/more-of-us-are-drinking-recycled-sewage-water-than-most-people-realise-92420

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