That's probably the most attention-grabbing headline I've had the opportunity to write. For those of you trying to figure out what-in-god's-name-he's talking about, it's actually the environmental problem of pharmaceutical residues in wastewater.
A Green Diary Rescue the other day highlighted a new facet of this problem; that there is now evidence that estrogen residue (typically from birth-control pills) increases the susceptibility of fish to disease. Another well-known problem is that these increased estrogen levels can have gender-bending effects on fish and amphibians - hence the title.
I've got a chemical engineering degree (even if I haven't seen a McCabe-Thiele diagram for years), and so I'm generally optimistic about finding technological solutions to problems, including ones caused by technology. After all, it's not likely pharmaceuticals are going to go away. So the question is, what options exist to do something about it?
Well, I recently read an article in the Swedish tech magazine Ny Teknik about a pilot project currently being conducted in Stockholm to evaluate methods of removing pharmaceutical residues. So I thought I'd share an overview (in my own words of course, no plagiarism here) with some - educated, I'd hope - commentary.
The problem
You take pills with some 'active' substance in them, usually an organic (as in carbon-compound) molecule of some sort. Eventually it gets metabolized or filtered out, in the kidney or livers, and passes into your waste. Here the problem begins, because many pharmaceuticals pass through your body unscathed to a high degree. Wastewater treatment doesn't do much better; the study from the Stockholm municipal water company (Horror! Socialism!) showed that out of 60 pharmaceutical compounds detected in sewage, 48 of them remained after treatment.
This shouldn't be entirely surprising; drugs aren't typically easily biodegraded. If they were, they'd be metabolized in our body - possibly before having a chance to do their job, and so not be a very good drug. The main difference between wastewater treatment and our livers is the difference between human metabolism and bacterial. We're just a lot more similar to bacteria than we'd like to think. (Horror! Darwinism!)
To get more specific, one of nature's big 'cleaning agents' is an enzyme (actually, a whole family of similar enzymes) known as cytochrome P450. It's an pretty strong oxidizer and can break down more molecules than I can list. Many bacteria use it as well. When drugs are metabolized in your body, it's more often the case than not that P450 did part of the job. So when drugs are developed these days, they usually test to see what P450 does to it. If P450 chops it up like a razor-blade through butter, then it'll probably not be a very effective drug. If the drug is relatively resistant (reacts slowly) to P450, then it'll be effective and probably require lower doses. But it also means it won't be metabolized well by all those bacteria who also use P450. Some drugs are even given 'protection'; they're combined with substances that inhibit P450, allowing the drug to do its job. (something which can cause overdoses if the patient is taking another drug - where the dosage was intended for a patient with fully-active P450).
But I disgress. What can we do about it?
Filter it out
To the layperson (and I intend no offense) that's the obvious solution. It's not a bad idea in itself, but probably a bit more difficult than might be first imagined. A water molecule is about a tenth-of-a-billionth meter large, and a pharmaceutical molecule, which can be pretty 'big', relatively speaking, is only about ten times larger.
Nevertheless, the swedes tried out two variants of filtration. Reverse osmosis and 'nanofiltration'. Essentially both are the same thing; the difference essentially being really, really small holes versus really, really, really small holes. Small enough to let water, and possibly some other very small molecules through, but not pharmaceuticals. This isn't entirely new technology and obviously filters out a lot more nasty stuff than just drugs. So if it was efficient, you'd have to ask why we're not using it already.
The answer to that (corroborated in the study) is that it's very costly in terms of energy. The reason for which shouldn't be too hard to imagine - if you have incredibly tiny holes, it takes a lot of pressure to force the water through them. And you'll be left with solid waste that'll need taking care of.
Microbiological methods
Wastewater treatment has always been at the forefront of doing stuff with bacteria. Bioreactors are used, mainly to remove nitrogen from wastewater, which would otherwise cause eutrophication (over-fertilization) in the ecosystems where the water is released. (The #1 environmental problem sewage creates). So using bacteria to get rid of drugs is an excellent idea; it can be integrated easily into existing processes, is cheap, and uses little energy.
The method the swedes tried out was to simply let the sewage process longer in their bio-reactors, and hopefully the bacteria would 'learn' to break down drugs more efficiently (more evolutionary heresy!). Unfortunately, they found that this method didn't eliminate drug residues as efficiently as the other methods they tested. In my opinion though, there's a lot of unrealized potential here. Modern biotechnology gives us the ability to 'help evolution out' here - we may be able to genetically engineer bacteria that clean up drugs efficiently.
(should someone voice concern, I should say that it's unlikely that such an organism would do well in the wild, or cause trouble if it ended up there. But in any case, wastewater is typically disinfected before release)
Chemical oxidation
The big guns. No drugs can withstand being broken down by the more powerful chemical oxidants. While there are a lot of them, the two studied are really the only ones worth studying - ozone (O3) and hydrogen peroxide (H2O2). These are 'nice' oxidants because they ultimately form water or carbon dioxide, harmless end products. You don't have to worry about any left-over oxidant; they're so reactive they don't stick around. What you do have to worry about, though, is not having enough. Partial oxidation, like a smoldering flame, typically results in a huge array of difficult-to-predict byproducts. So it needs to be monitored and done with care.
Ozone is typically produced from oxygen using UV light or an electrical discharge. (for which reason you can often smell ozone around a photocopier or lightning strike) So the downside here is that it requires a lot of energy - enough to double the cost of water treatment, according to the study.
Hydrogen peroxide is a less powerful oxidant, but can be made more powerful by subjecting it to UV light, which is what they did. This splits the H2O2 into HO*, hydroxyl radicals, which are very powerful oxidants that'll pretty much oxidize any unfortunate organic molecule they run in to. The downside is the cost of the UV lights, which require even more energy than in the case of ozone.
The upside of both these methods is that they're devastatingly efficient, and more-or-less guaranteed to destroy not only every drug, past, present and future, but almost any organic substance still left in the water. It also integrates somewhat into existing processes, where UV light or ozone is sometimes used for disinfection, as a greener alternative to chlorine.
Activated carbon
A good old standard from high-school chemistry is activated carbon (or activated charcoal). Campers or survivalists may also know that it's often used for portable water purification. It's simply charcoal that's been processed to give it huge surface area. It will adsorb (adsorption is chemistry lingo for 'sticking to a surface') large quantities of many molecules, including drugs and organic molecules. You simply filter the water through a bed of it.
The upside is that it's been now shown to be very efficient. It's also relatively cheap. The downside is that it doesn't integrate into the existing processes; it'd have to be a new step. You'd also have to continuously replace the carbon as it becomes saturated. While it can be 're-activated', it may be more economical to dispose of it (e.g. it could be cleanly and efficiently incinerated for power)
And the winner is..
According to the article, the study is still ongoing, but even at this stage, the last two techniques, UV/Peroxide and activated carbon, show the greatest promise. I still personally suspect that biological methods may well hold the greatest promise in the long term - provided that someone pays for the research.
The ultimate question is naturally not technological but political. What price are we prepared to pay, literally, to avoid transgender frogs and other ecological effects of our drug consumption. But given the already low cost of tap water, I'd wager it won't be too high.
In the meantime, folks, remember: Never flush your left-over drugs down the toilet or drain. Dispose of them properly. Many pharmacies will do that for you.