The secret life of sewage
Most of us give no thought to what happens after we flush, says Texas Monthly
They say that excrement runs downhill. This is commonly understood to mean that the world is an unfair place, except among those few people who actually work with the substance, for whom it is considered something of an article of faith. This is because municipal sewerage systems are powered almost entirely by gravity, which means that when working properly, they move millions of gallons of sewage a day across considerable distances with only a minimum expenditure of energy, a feat of efficiency virtually unparalleled in the annals of engineering. When sewage stops running downhill, as it inevitably does from time to time, very bad things indeed can happen, as they did on Pecan Springs Road in Austin one morning last September.
I was spending the day with an emergency-response crew when dispatch got a call from a woman reporting that two rooms of her house were flooded with sewage. Our crew consisted of a TV truck, piloted by line-maintenance worker David Eller, and a flusher truck, driven by his colleague Dale Crocker. At the house, Eller unspooled a thick red cable from the back of his truck. On the end of the cable was a camera about the size of a roll of quarters, which Crocker shoved down into a PVC clean-out pipe near the curb in the front yard. The woman leaned on a walker in her driveway, looking worried.
The pipe came into view on a screen mounted near the truck’s rear doors. The walls of the pipe were colored a pleasing aquamarine, and the inside looked remarkably clean as the camera moved slowly forward, scudding along through the trickle of water on the bottom of the pipe. After only a few feet, however, something white and fibrous appeared at the top of the screen. “Tree roots at three feet,” Eller announced.
Trees are the bane of all underground infrastructure, but they are particularly hard on wastewater systems. Tree roots end in tiny tendrils, which act as notoriously efficient water diviners, constantly probing for moisture under the earth. If a pipe has even a pinhole leak, which often occurs at joints, the tree will find it and begin slowly working its way into the opening. Root tendrils no more rigid than a stalk of celery can penetrate concrete or iron. There is no way to stop this, though many ideas have come and gone, including pipelines that exude their own herbicide. Once inside a pipe, roots flourish in the moisture-rich environment, eventually forming dense root-balls through which solids cannot pass.
In this case, the culprit was almost certainly a 50-foot cottonwood in the middle of the front yard. Eller assured me that the woman had gotten off easy. Clogs in sewer mains—the larger lines that run under the street collecting sewage from the smaller service laterals that connect to homes—can be much worse. If you happen to live just upstream of the spot where the main in your street is clogged, what backs up in your toilet is not just your own sewage but your neighbors’ too. Like all flooding victims, the lower you are in the topography of your neighborhood, the worse you get it. Eller recalled one emergency he went out on last year in East Austin. “This guy indicated to me that s--- water was shooting out of his toilet with 500 roaches coming out of it,” he said, outlining with his arms an imaginary column of brown water.
Sewerage is the sine qua non of urban life. London, the first megacity, might not have survived the 19th century had a medical researcher named John Snow not correctly theorized that recurring cholera epidemics were caused not, as was commonly believed, by the inescapable smell of raw sewage that plagued every corner of the city but by the bacteria leaking from countless overflowing cesspools into wells used for drinking water. London eventually replaced its army of shovel-toting cesspool muckers with a citywide sewer system, which became known throughout the Western world as one of the marvels of the Industrial Age—though it was in reality not much more advanced than the system devised by the Romans more than 2,000 years earlier.
Designed to collect both wastewater and rainwater, the original sewers of Europe tended to have enormous tunnels, big enough to house an entire caste of unfortunates who made their livelihood off things they found in the sewers: bits of copper, lumps of coal, even bone fragments, anything that could conceivably be resold.
“A sewer is a cynic,” wrote Victor Hugo in Les Misérables, much of which takes place in the sewers of Paris. “It tells all.”
If there is one area of human behavior that baffles contemporary wastewater engineers and operators, it is the seemingly endless variety of things people will flush down a toilet or, for the more determined utility customer, shove into a manhole. Bedsheets from a mental hospital. Rags soaked in every kind of substance you can imagine. Dead parakeets, dead pit bulls. Fish, alive or dead. Engagement rings (by accident—usually). Broken glass, cocaine, battery acid. Even shopping carts and wheelbarrows. These things are not gone forever. If they don’t get stuck in a pipe, most of them wash up on a screen in the headworks of a wastewater treatment plant, like the one at the Walnut Creek plant, in East Austin, where I stood one day last May and watched the screens being cleared by a pair of long robotic arms. Every few minutes, the arms crept up out of churning pools of murky water, hauling up loads of trash. I had to fight a powerful urge to step away from the open pools and back into the sunlight. Yet there was something weirdly fascinating about the machine’s methodical dredging, and I found myself lingering to see what would come out of the water next. It could have been anything. As it happened, the majority of the detritus consisted of two pretty mundane items: condoms and tampon applicators.
According to my guide at the plant, Raj Bhattarai, the manager of Austin Water Utility’s environmental and regulatory services division, an aversion to foul-smelling water is a product of human evolution: Over the millennia, our ancestors who learned to avoid bacteria-laden water were more likely to survive. This means that sewer workers have to learn to ignore their innate survival instincts, though most of the veterans I talked to insisted that the smell was not that bad—much more tolerable than, say, the odor of a landfill.
Much of my tour of the plant was spent in dank-smelling underground chambers filled with the sound of roaring water, where I struggled to hear Bhattarai explain the automated operation of machines with names like “scum beach” and “sludge pig.” Then he led me back outdoors, to the aeration basins, where the true genius of a modern wastewater treatment plant is found. The basins are huge concrete tanks where the partially treated sewage is roiled by thousands of air diffusers. Bacteria are the primary problem wastewater engineering was created to solve, but in the tanks they are actually encouraged to grow. In a natural setting, like a pond, bacteria from raw sewage will consume the dissolved oxygen in the water molecule by molecule until there is none left. Fish start to die. Eventually the water turns black and starts to smell like rotten eggs.
If, on the other hand, the bacteria have a steady flow of oxygen, as they get in the aeration basins, something else happens. By way of explanation, Bhattarai hooked a plastic beaker onto the end of a pole and dipped it into the frothing liquid. After a few minutes, the mixture in the beaker had separated into a top layer of clear liquid and a bottom layer of what looked like a loose pile of watery brown snowflakes. These were bundles of microscopic bacteria, known as flocs, gathered together in such huge numbers that they could actually be seen with the naked eye. “They are providing the treatment,” Bhattarai said. The flocs form around soluble and colloidal (grease-like) particles in the sewage, which have little weight and don’t tend to separate from the water on their own. Over time, the flocs
drag these particles to the bottom of the basins and form a layer of sludge, which can be sucked out and piped away.
Today, there is a strange kind of anthropology available to students of sewage. One thing our sewers are telling us, for example, is that we are a self-medicating society. Last August, researchers at Oregon State University announced that they had studied the raw sewage of 10 U.S. cities and ranked them according to the recreational drug of choice in each town: cocaine, methamphetamine, Ecstasy, and so forth. The researchers would not give the names of the towns, but the Drug Enforcement Administration is reportedly interested in the technology, which essentially amounts to urine testing an entire city.
Many of the compounds found in recreational drugs and medicines actually survive the chlorination and filtering process in a wastewater treatment plant and make it into nearby rivers and streams, where they flow into the water systems of other cities downstream. In this way, a dose of acetaminophen consumed in a mountain town in the Sierra Nevada eventually turns up in the digestive tracts of people living hundreds of miles away in Southern California. Some of the most popular barbiturates of the ’50s and ’60s are also among the longest-lived pharmaceutical compounds. In all likelihood, some of the downers Elvis swallowed are still out there, somewhere, floating around in the ocean.
What we put into our bodies also has a direct effect on how well our sewers run. For instance, there is a sense in the pipeline world that concrete wastewater pipe is not lasting as long as it used to, though nobody is sure exactly why. The consensus is that there is nothing necessarily wrong with the pipe, but that something we are doing differently aboveground is causing the waste stream to become, as the engineers say, more “aggressive.” Garbage disposals are at least partly to blame. They increase the amount of grease in the system, which slows the rate of flow in the pipes, which in turn allows more time for corrosive sewer gas to form. Other engineers point to the increase in protein consumption after World War II, when Americans began eating a lot more meat.
A few years ago, during the Atkins diet craze, millions of Americans switched to a heavy-protein diet, so much so that it affected the futures market for commodities like cattle feed. If increased protein consumption really does make wastewater more aggressive, then our eating habits during the Atkins era must have put quite a stress on the nation’s sewers as well, something like putting 50,000 miles a year on your car instead of the usual 10,000.
Meanwhile, decades of neglect have left an estimated $500 billion in needed repairs and upgrades to wastewater pipes and treatment plants nationwide. Illnesses related to overflows are becoming increasingly common. If sewerage is the cornerstone of civilization, then ours is a civilization in decline.
From a longer story that appears in the December issue of Texas Monthly. Used with permission.