At a time when the word “organic” defines responsible living and municipalities wring their hands over soil contamination, stormwater management, and the overtaxed sewer system, how do we put two and two together and harvest the rich minerals and organisms present in our waste streams? Working with waste challenges cultural taboos, as well as presenting as an environmental risk. But sane, safe, low-tech systems for processing waste also present a real solution to reconnecting our bodies to earth. All we have to do is first pull out the thorn of ingrained prejudice.
Our environment is shaped by what we choose to observe. But while our most abundant products are waste, these by-products of our activities are so plentiful and often so strangely formed it is either difficult or impossible to contemplate them, let alone safely hold or fold them into a substrate that is able or willing to digest them.
From drain to faucet (or river or lake) and back again: our current water cycling pattern
Many industrial cities worldwide operate combined sewage-stormwater systems, largely built at the tail end of the 19th century in response to outbreaks of cholera and dysentery.*
Large connected sewage systems in Chicago, Paris, and Hanover, Germany, were some of the first built, and therefore are some of the modern world’s oldest and most in need of repair. Folding in additional infrastructure for expanding populations, repairing tunnels, and/or replacing more than 150-year-old pipes (many of them lead) and tunnels is an expensive and complicated operation. Chicago has been at work on its plumbing infrastructure for decades—repair, expansion, and maintenance is an ongoing process.
Black water from toilets, gray water from bathtubs, showers, and sinks, stormwater (including everything it catches as it flows over streets, parking lots, roofs, lawns, and sidewalks), as well as contaminated water from factories where manufacturing or material processing happens—it all ends up at the wastewater treatment plant at some point. In fact, sewers were designed to receive and treat stormwater first and foremost, and are referred to as “stormwater conveyance systems” by professionals, as the volume of stormwater processed is many times of that which we flush.
The primary treatment is mechanical by nature. Water passes through slotted grates where coarse materials over several inches are caught, collected, and landfilled. The water then rests in large settling tanks for several hours until light solids (including grease) float and are skimmed off and landfilled. Heavy solids sink and become primary sludge, which is then sent to a centrifuge where extra water is spun out and sand, gravel, coffee grounds, etc, are landfilled.
The water from the settling tank then enters secondary treatment, in which air is pumped into the tank to stimulate aerobic bacteria to consume the remaining organic matter suspended in the mixture. Over several hours, as the bacteria eat, more sediment falls out and settles into the tank. The water is then disinfected, usually by adding chlorine, then discharged as “effluent” into a natural waterway. Some of this secondary sludge is used as an inoculant to “seed” the next batch of wastewater with a population of aerobic bacteria. But most of it passes to a biodigester where it produces both oxygen and methane, which is then used for heat and electricity. The effluent from this digestion is then “dewatered” by another centrifugal process to create biosolids, and the resulting water is then returned to the treatment plant for reprocessing and discharged.
The biosolids are mixed with waste carbon (usually wood pulp) and are windrowed to be thermophilically composted and made available as soil amendment or mulch. As recently as a few years ago in Chicago, these biosolids did not enter a composting process. Instead they were heat dried or pasteurized to remove moisture and kill off pathogens, then amended with organic polymers to improve their consistency. There has been both celebration and uproar around the use of biosolids to help revegetate mining tailings, remediate a brownfield into a park, a golf course, or a housing development, etc. The Clintons had them spread in the White House garden; the Obamas had them removed.**
Annually, the city of Chicago sends out an extended water report to every mailbox in the city. Over the years I have noticed that contamination rates in the water supply have increased, though we are assured that they are still within safe levels by EPA standards—as these standards continue to be incrementally increased so we can clear the limbo bar as our systems age. With every human-designed energy system there is entropy or a downcycling that occurs and a need for a discharge of liquid and solid material that can’t be treated any further. Combined sewer overflows usually occur in wet weather when treatment plants fill to capacity. To relieve pressure, excess flow is released into open waters that we share with every citizen and the rest of life’s creatures.
The by-products of human living have great potential for reuse as soil amendment or biogas creation resulting in healthier water, air, and, yes, soil for us all. But whether because that potential is invisible or simply too unpalatable, that potential remains largely untapped. Maybe it doesn’t have a profit margin, is seen to be dangerous, or would require us to unhinge our brains to allow some new impulses to fire. Regardless, we will stay in these nongenerative, damaging, disconnective patterns we have designed and encoded into our lives unless we recognize the gold that lies in the dung heap.***
*At the end of 2018, it was reported that 40 percent of deaths in Pakistan are due to dysentery.
**There are different rules for different classes of biosolids. Class A biosolids contain no detectable levels of pathogens. Class B biosolids are treated but still contain detectable levels of pathogens. Meaning class A biosolids have passed through a thermophilic composting process that kills off pathogens where class B biosolids have not. The use of grade of biosolid, whether A or B, brings with it rules of amount that can be used, type of use of the site it is used on (capping a landfill or mine tailings, to fertilize crop land or community garden, as a turf amendment in a public park or residential backyard). Pathogens aside, many of these biosolids contain various heavy metals and dioxins that escape the treatment of the municipal wastewater facility. Only recently has it been proposed to limit the concentration of dioxin and dioxinlike compounds.
***While mining sewage sludge is being looked at to grab the precious metals—namely nickel, copper, platinum, iron, zinc, silver, and, yes, gold (from electroplating, electronics manufacturing and automotive catalysts)—the economics have not proven worth the hassle. v
Nance Klehm’s The Soil Keepers: Interviews With Practitioners on the Ground Beneath Our Feet (Terra Fluxus Publishing) is available for purchase at spontaneousvegetation.net as well as locally at Women and Children First and Marz Community Brewing Co.