What happens to hospital wastewater?

Illustration by Slug Signorino

Cecil replies:

Boy, do they ever. And is such sewage, like Chicago recycling, commingled? You bet it is. In developed countries that don’t regularly enjoy epidemics of intestinal diseases, the World Health Organization figures it’s generally OK for hospitals to dump their wastewater right into the municipal system with all the other crap.

It’s worth spending some time on what it is we’re flushing, though. If you’re picturing hospital discharge brimming with Ebola-laden blood and other infectious effluvia, my friend, you’re not quite thinking big enough: there’s viruses and bacteria, of course, but the stuff we use to treat various maladies also has the potential to cause real headaches — despite significant concentrations of pain relievers in the wastewater mix. Here’s a grab bag:

Chemicals. Estrogens, for instance, which can at certain concentrations lead to birth defects, reduced fertility, and breast and testicular cancer in humans, and in male fish can essentially induce a sex change — an effect that’s been observed at the discharge sites of wastewater treatment plants (WWTPs, in the lingo). Interacting with the chlorine used by WWTPs, estrogens can also form chlorinated byproducts whose effects are unclear. (In general, as I explained a few years back, the fact that we don’t know how the various medical residues in the sewage system interact with one another is a matter of slight concern.) Painkillers like acetaminophen, meanwhile, are found in relatively high concentrations in hospital wastewater. And don’t forget about inorganic chemicals, such as those found in X-ray and MRI contrast media, and disinfectants.

Radioactive waste. Hospitals aren’t dumping it directly down the drain — er, one hopes— but still, patients who ingest radioactive isotopes, say, as part of an imaging procedure, will pass some into the toilet. Studies have found radioactive medical residues in sewage, surface water, and food chains, including high levels of technetium and radioactive iodine in algae, seaweed, fish, and freshwater mussels that had the misfortune of living downstream from plants that treat hospital wastewater. (And that humans might subsequently be dining on.) The workers in such plants were found to have received measurable doses, too, but nothing sufficient to cause alarm.

Antibiotics. If you’re concerned about picking up Ebola while splashing around in the municipal sewer, Scott, you’ll be heartened to learn that some studies have found that the concentration of bacteria and viruses can actually be lower in hospital wastewater than it is in your given municipal effluent, largely due to the antibiotics that are also in the system. Unsurprising, really: we use a lot of antibiotics overall (more than 50 million pounds are produced annually in the U.S.), and 25 to 75 percent of what’s administered passes through the recipients’ bodies unmetabolized. Antibiotics running wild in the water system encourage the development of antibiotic-resistant bacteria, such as the famously unpleasant methicillin-resistant Staphylococcus aureus, or MRSA; hospital wastewater has been found to have antibiotic-resistant bacteria at two to ten times the level of regular domestic wastewater.

So we know there’s a bunch of questionable stuff in hospital wastewater, though our understanding of what it’s doing to the environment (and, in turn, us), is limited and varies depending on the substance. Currently, as I mentioned, hospitals direct their effluent to the nearest municipal treatment plant by way of the sewer. OK, but: Are those plants actually equipped to filter all this stuff out? With what’s going on in Flint, Michigan, I can’t say the American way of water filtration’s looking all that robust right now. And what happens when, for instance, heavy rains cause the system to overflow? Better to dump the affluent into the sewers, I say. Other options exist, but are rarer: some hospitals treat their wastewater in situ and then release it into the nearest stream — which technique requires strict public oversight, for obvious reasons — and some use a combination of the foregoing, treating their output on-site and then pouring it into the municipal system for a second round of treatment.

Where does that leave us? At the reality that, as a 2010 study in the Journal of Hydrology put it, there remains “no specific treatment to remove, at high percentage, all the kinds of micropollutants typically found” in hospital wastewater; another paper bemoaned the “remarkable paucity” of information regarding the downstream impacts of such untreated waste, and suggested that what’s needed are separate systems for treating hospital wastewater — a “matrix of treatment scenarios.” Reverse osmosis, for instance, could remove endocrine-disrupting compounds such as estrogen. Nanofiltration takes out certain pharmaceuticals. Patients whose treatment involves taking in radioactive materials could relieve themselves into a separate system, their waste set aside for special processing. Given the expense of such technologies, though — and an absence thus far of any clear medical-wastewater horror stories — you couldn’t call this a number-one priority.

Cecil Adams

Send questions to Cecil via cecil@straightdope.com.