Do you ever give thought to what goes down your sink, shower, laundry, and toilet drains? If you don’t I don’t blame you one bit. The first three are yucky enough; thinking about the fourth one is only for weirdos like me, right? Well, no. Wastewater treatment is a huge science and industry and utterly necessary for living in a modern world.
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When we humans transitioned from being nomadic hunter-gatherers and started living in denser stay-put conglomerations, what to do with our human bodily waste became a real problem. It would seem evolution put the stink in for a purpose — it being a signal to us that this stuff, solid human waste, feces in particular, was nasty. From pit latrines to cesspools to just letting it float away down a river, we’ve tried through the ages to separate it away from us. Many “advanced” civilizations of the past had rudimentary septic sewer systems for their cities — just look at the ancient Romans for one example. When nineteenth and twentieth-century modern man began living in large cities where the poop wouldn’t just float quickly down and out to the ocean, however, deadly epidemics like typhoid and cholera became all too frequent. Our sewage was contaminating our drinking water. Something had to be done. It was. We created the modern, scientific, sewage treatment plant. But it has its limitations:
Imagine visiting bustling San Francisco at the dawn of the twentieth century. You walk down towards the wharves and can smell the bay long before you see the marshes, which have become festering pits of sewage. Smells like we’re back in the Middle Ages. As cities grew, health officials realized that transporting sewage beyond the city limits was not enough and began building sewage treatment plants. As these systems evolved, engineers developed a two-tiered process comprising primary and secondary treatment.
Until the passage of the Clean Water Act in 1972, most cities only performed primary treatment, which mechanically screens out the trash and debris that float in sewage, then settles out the solid sludge. The resulting effluent was sent into a nearby watercourse.
Secondary treatment was developed to remove the polluting organic materials and nutrients that damage rivers and estuaries. This damage occurs when aquatic microorganisms proliferate in the glut of nitrates and phosphates in sewer effluent. When they die, their decomposition robs the water of oxygen, sometimes creating lethal “dead zones.”
Wastewater plants also chlorinate treated wastewater in a last-ditch attempt to kill off any surviving bacteria. The new treatment plants’ pumps, digesters, clarifiers, and conveyor belts consume massive amounts of energy, and are therefore very expensive to operate.
Billions of dollars later, upgraded and expanded plants employ sewage treatment methods that combine nutrients and toxins, creating a new by-product to be disposed of: sludge — 1.6 billion dry pounds of it in the U.S. every year. Sludge is the de-watered, sticky black cake created by the truckload in modern sewage treatment plants. It consists of the indigestible solid remnants of everything that goes down household and industrial drains, including any number of the seventy thousand different chemicals produced in commercial quantities in the U.S.
--greywateraction.org
If you’re fortunate enough to live somewhere that you can have an alternate to the modern sewage system, like a composting toilet and grey water recycling, then good on you. I wish I did, but I don’t and can’t change the fact that what goes down my drains goes to a place somewhat similar to this (in the video below), except that my local sewer plant is much smaller in scale and doesn’t produce activated sludge (but maybe that is going to change with the rebuild that’s happening).
Trigger warning: this ain’t pretty. In fact, much of it is rather gross. But it is reality.
The sewage treatment plant that serves my town of Quincy, CA, and the entire American Valley area has been undergoing a massive, complete renovation and rebuild for the past two years. This doesn’t show much, but you can get an idea.
I visited Quincy’s sewer plant on a college class field trip back in 2011. We got to see how our wastewater gets processed, start to finish. The wetland filtration area is a major component of this system, allowing the final treated water to flow directly into Spanish Creek with all contaminants filtered out, at potable water quality. I was shown a sample flask of the final water that was collected for analysis and was told that it could be safely consumed, although of course we weren’t allowed to drink it. But I did believe it. The point is that the treated water that flows into Spanish Creek is as clear, if not clearer, than the water that flows out of my kitchen tap. Here’s a fuller size image of the wetland filtration area:
Still, I worry about a lot of the things that we put down our drains, like cleaning chemicals and pharmaceuticals, and so I only clean my toilet with a scrub sponge and brush, no chemicals, and I NEVER flush unused medications down the toilet. That’s my little contribution to trying to keep my own wastewater just good ol’ clean pee and poop, at least as far as what goes down my toilet. I can’t easily help the dish soap that goes down my kitchen sink or the remnants of antibiotics in my excreta.
Oh. One last thing. My sewage plant uses a Rotating Biological Contactor in its processing. I never knew about this thing until I visited the sewer plant. Pretty cool.
This video (below) is the best one I could find on how they work. The narrator’s speech is a bit difficult to make out at points, but in short they work by allowing bacteria to break down small solids into microscopic-sized particles, and in the process also break down harmful pollutants and chemicals.
The RBC process allows the wastewater to come in contact with a biological film in order to remove pollutants in the wastewater before discharge of the treated wastewater to the environment, usually a body of water (river, lake or ocean). A rotating biological contactor is a type of secondary (biological) treatment process. It consists of a series of closely spaced, parallel discs mounted on a rotating shaft which is supported just above the surface of the wastewater. Microorganisms grow on the surface of the discs where biological degradation of the wastewater pollutants takes place.
--wikipedia
Here’s what the real things look like:
I do hope I haven’t spoiled your breakfast today.
;-)>~