Sewage Treatment

Preface. Before sewage treatment, cities were hell-holes of foul smells from rotting human waste, industrial effluent, and garbage.  Few people lived beyond 50 because of the many waterborne diseases.  In fact, sewage and water treatment systems are the main reason lifespans nearly doubled (Garrett 2001).  Here are just a few of the diseases possible from drinking untreated water: Adenovirus infection, Amebiasis, Campylobacteriosis, Cryptosporidiosis, Cholera, E. Coli 0157:H7, Giardiasis, Hepatitis A, Legioellosis, Salmonellosis, Vibrio infection, Viral gastroenteritis, free living amoebae (ADHS).  For the full list of waterborne diseases, see post Water-borne diseases will increase as energy declines.

Nearly all sewage infrastructure is past its life-time, a good way to spend the remaining cheap oil before it becomes scarce.

Sewage is also a way to return nutrients back to the soil, especially finite phosphorus, which is eaten and excreted, treated, and lost to oceans and other waterways.

Today moving sludge from city sewage treatment farms works because of cheap energy. In the future energy crisis, that won’t be possible.

There are two articles below, one about sewage sludge for crops, and the other about sewage corrosion.

Alice Friedemann  author of “When Trucks Stop Running: Energy and the Future of Transportation”, 2015, Springer, Barriers to Making Algal Biofuels, and “Crunch! Whole Grain Artisan Chips and Crackers”. Podcasts: Collapse Chronicles, Derrick Jensen, Practical Prepping, KunstlerCast 253, KunstlerCast278, Peak Prosperity , XX2 report


Perkins, T. 2020. Questions remain about using treated sewage on farms. Use of biosolids in agriculture is increasingly coming under fire as a potential health and environmental threat. Salon.

Human waste is a nutrient-rich substance that farmers around the world have spread on cropland for centuries.  Every day, about 20 million gallons of sewage flows into the city of Tacoma’s wastewater treatment plants. The water is separated, treated, and discharged into the Puget Sound, which leaves behind sludge — a mix of human excrement, industrial waste, and everything else that ends up in sewers. The plants further treat the product to reduce pathogens, bacteria, heavy metals, and odors, and convert it into a fertilizer called biosolids, which is high in phosphorus, nitrogen, and other nutrients that help plants grow.

Over 50 percent of the approximately 130 million wet tons of sludge produced nationally each year is treated and applied to less than 1% of cropland. As a fertilizer, it’s popular because most wastewater treatment plants give it away for free or at prices less than the cost of synthetic fertilizers.

The Sierra club notes that it can contain up to 90,000 man-made chemicals and we don’t know what new chemicals are made synergistically by combining them. It’s not certain that biosolids are safe.

One of the most controversial piece of the sewage puzzle is the fact that factories, slaughterhouses, and other industrial facilities are allowed to discharge their waste into the taxpayer-funded sewer system.

Increased testing is consistently finding levels of per- and polyfluoroalkyl substances (PFAS) that are alarming health officials and the public.

Before the 1972 Clean Water Act, the waste industry largely burned it, but that often violates the Clean Air Act, Lewis said. Municipalities also tried dumping it in the ocean, but that created large dead zones. Then, in 1993, the EPA approved a proposal to spread it on land after it was treated. Sludge that isn’t turned into biosolids is landfilled or incinerated — both of which are expensive compared to spreading it on farmland.

The EPA only requires nine pollutants — all heavy metals — to be removed from biosolids, as well as living pathogens such as E. coli and Salmonella. Sludge may be treated by air drying, pasteurization, or composting. Lime is often used to raise the pH level to eliminate odors, and about 95 percent of pathogens, viruses, and other organisms are killed in the process, according to waste management industry officials.

Pikaar, I. et al. 2014. Reducing sewer corrosion through integrated urban water management. Science 345: 812-814  

Sewer systems are among the most critical infrastructure assets for modern urban societies and provide essential human health protection. Sulfide-induced concrete sewer corrosion costs billions of dollars annually and has been identified as a main cause of global sewer deterioration. Aluminum sulfate addition during drinking water production contributes substantially to the sulfate load in sewage and indirectly serves as the primary source of sulfide. This unintended consequence of urban water management structures could be avoided by switching to sulfate-free coagulants, with no or only marginal additional expenses compared with the large potential savings in sewer corrosion costs.

Sewer systems are corroding at an alarming rate, costing governments billions of dollars to replace. Differences among water treatment systems make it difficult to track down the source of corrosive sulfide responsible for this damage.

Urban sewer networks collect and transport domestic and industrial waste waters through underground pipelines to wastewater treatment plants for pollutant removal before environmental discharge. They protect our urban society against sewage-borne diseases, unhygienic conditions, and noxious odors and so allow us to live in ever larger and more densely populated cities. Today’s underground sewer infrastructure is the result of an enormous investment over the last 100+ years with, for example, an estimated asset value of one trillion dollars in the USA (Brongers). This equates to ~7% of its current gross domestic product. However, these assets are under serious threat with an estimated annual asset loss of around $14 billion in the United States alone. Sulfide-induced concrete corrosion is recognized as a main cause of sewer deterioration in most cases.

Many water utilities will need to upgrade both their water supply and wastewater service infrastructure over the next 10 to 15 years, which will require enormous capital investments.


ADHS. Waterborne diseases. Arizona Department of Health Services.

Brongers, M. P. H., et al. 2002. “Drinking water and sewer systems in corrosion costs and preventative strategies in the United States”.  Federal Highway Administration Publication FHWA-RD-01-156, U.S. Department of Transportation, Washington, DC.

Garrett, L. 2001. Betrayal of Trust: The Collapse of Global Public Health. Hatchette Books.

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5 Responses to Sewage Treatment

  1. Hamish McGregor says:

    Regarding “Nearly all sewage infrastructure is past its life-time, a good way to spend the remaining cheap oil before it becomes scarce.” Your sentence (and paragraph) is incomplete – does the spending rebuild what was there before, or build something better? If the answer is implied, I must apologize for not seeing it. The extant implementation is definitively flawed – in may places sewage and storm water use the same infrastructure. Municipal water bills have become obscene – Water Consumption, Water Fixed Charge, Sewage Consumption, Sewage Fixed Charge, Low Income, Storm water fees and taxes. Suddenly it is $100 a month and up, to use something that falls out of the sky!

    Regarding “Today moving sludge from city sewage treatment farms works because of cheap energy. In the future energy crisis, that won’t be possible.” As opposed to the ‘current’ energy crisis where crude oil is circa $40 a barrel, but it costs an average of $60’ish to produce (apologies for no citation) leaving the Fracking industry in tatters (a good thing in my opinion).

  2. Hamish McGregor says:

    Regarding “…the remaining cheap oil before it becomes scarce” this sort of writing cannot be excused. Cheap? Scarce?

    Cheap : lets destroy the global economy and send the price of crude oil negative, then we can talk about “cheap oil”, lets ignore the significant portion of the population that is now unemployed and (for example) cannot afford to run a car at any price. A strong argument can be made that the current price of oil is an aberration that is actually more harmful than good and does not represent an opportunity to rebuild infrastructure.

    Scarce : The price of crude oil did not climb above $145 a barrel in 2008 because it was the opposite of scarce.

  3. Thomas Reis says:

    I favor dry toilettes especially because rising sea levels will ultimate destroy our infrastructure beneath the ground? Also Phosphor is precious, i wrote about this many years ago, also the high energy costs of up to 200kWh per m³ sewage is huge.

  4. Mark Robinowitz says:

    I recommend The Humanure Handbook for advice on how to safely compost our poop for agriculture. Not dumping countless toxic poisons down the drain would be an important shift (and not making them in the first place).

    Composted poop is good.
    Sewage with added poisons is not.

    Also recommended is the sewage system in Arcata, California, which uses constructed wetlands to neutralize sewage. It’s not a perfect system but much better than the standard approach in the rest of the country.

    • Peachtree says:

      The Humanure Handbook is a great resource.

      Of all the civilisational challenges we face, sewage disposal is one of the easier ones to tackle. It has never made a great deal of sense to use five or ten litres of drinkable water to flush away nutrient rich wee and poo that could instead fertilise plants. Obviously the poo needs to be safely composted first, but the wee is fine to use straight away, and many sensible gardeners and farmers do just that. Joe Jenkins (the author of The Humanure Handbook) has been fertilising his fruit and vegetable gardens with his household’s composted wee and poo for more than three decades without any problems.