Some work recently out of my former institute, Eawag, has been optimizing a novel method, flow cytometry, to measure microbes swimming/floating in water. A couple of fluorescent DNA dyes are added to the water, then as a very narrow capillary stream flows by a laser, the cell numbers are counted. Initial results have shown that there are a lot more microbial cells in water supplies than we might like to think. Ambient water in the environment (e.g., a lake) generally has maybe 10^7 cells per milliliter (i.e., 10,000,000 cells per drop of water). A soil or sediment has 1-2 orders of magnitude more cells per milliliter in general. The flow cytometry results show that treated drinking water has roughly 10^5 cells per milliliter (i.e., 100,000 cells per drop of water). That’s a lot of microbes in your water! Time to freak out, set your hair on fire, and switch to bottled water! The government is trying to kill you!!
Ok, it’s not that bad. When water leaves a drinking water treatment plant, it is usually given a healthy dose of chlorine (“chlorine residual”) to keep microbial growth low in the piping network to your house. Furthermore, there are tests for potentially dangerous bacteria, with standards to be met before the water is allowed to be delivered to you. A common problem with standard tests is that they require the cells to grow on agar plates, even though many cells don’t grow under those conditions, and the results take up to 3 days. Flow cytometry is available just minutes after sample collection. The Eawag method has revealed that the standard test is a little misleading — no “bad” microbes doesn’t mean no microbes at all, and that’s ok.
What’s interesting is that the Swiss authorities have added this method to the list of acceptable tests for drinking water quality. Who knows, maybe you’ll soon see this method coming to a water treatment plant near you!
Oh, and if you were going to switch to bottled water, just remember, it might have more microbes in it than tap water. It will be ok.
You know how fracking is so controversial, because applying high pressure to deep formations might cause hydrocarbons to migrate upwards and contaminate shallow drinking water aquifers? Texas has got the next best thing. This article calls it “fracking for uranium” which is just plain wrong. Fracking relies on high pressure to break apart rocks holding oil and gas. Uranium harvesting relies upon geochemistry to leach uranium out of rocks – no high pressure needed – and it has relatively low water requirements. Unfortunately, it does have one other difference that makes it way more controversial: uranium harvesting is occurring within drinking water aquifers.
Here’s how it works. Uranium is naturally present at trace levels in certain rock formations. A company in Texas is injecting oxygenated water into underground aquifers that are normally anoxic. This exposes the rock formations to different geochemistry and induces the uranium to dissolve into solution. Extraction wells recover the uranium-laced groundwater and precipitate out the uranium.
I’m sure the process works, but at what cost? Injection typically acts like a “bubble” that expands outward, with some mixing at the fringes. In other settings, like aquifer storage and recovery, it has already been shown that it’s virtually impossible to completely recover the injected “bubble” due to the mixing at the fringes. If you’re just talking about water storage, as in aquifer storage and recovery, that’s one thing. But we’re talking about intentionally mobilizing a contaminant in a drinking water aquifer. The mixing at the fringes means that uranium is going to stay in the groundwater, and potentially be pulled into someone else’s well eventually.
Maybe it doesn’t seem like a big deal now, especially if the aquifer in question isn’t heavily used. But Texas is really running out of water. The drought hit Texas hard this year, and their response has largely been to push for further conservation, rather than to expand long-term plans for water recycling or desalination (the only two realistic long-term options). So even if energy is at stake, I’d be awfully hesitant to sign away aquifers for uranium leaching, given that there are many sources of energy, but Texas is running short of water sources.
Dear readers –
A friendly reminder to go get a flu shot, if you haven’t gotten one already. I’d been only about a week over my cold/strep throat bonanza this winter when I picked up the flu. What a pain. I highly recommend avoiding the flu in any way possible. Then, if you do get the flu, follow the CDC’s advice and don’t go out at all (not for shopping, not for the doctor, not for work) at least 24 hours after your fever is past. The CDC’s advice is not for the sick person, but rather for the healthy people that the sick person could easily infect on short errands.
That said, I’m home today, recovering from yesterday’s fever, and writing about another group learning from past issues. Remember the “Restore Hetch Hetchy” ballot measure in San Francisco? It basically enabled the City of San Francisco to vote on whether the water supply of the City, the peninsula, and much of the South Bay would be dismantled. The measure was voted down (77% said no!), but the water utilities around the Bay, who are tasked with maintaining supply, have decided not to wait for the Restore Hetch Hetchy folks to rally the City for Round 2. Instead, they passed an amendment to their contract (that is, the San Francisco Public Utility Commission, SFPUC, and the Bay Area Water Supply and Conservation Agency, which is made up of the 26 water agencies that purchase Hetch Hetchy water) that requires any modifications to the Hetch Hetchy reservoir to be approved by all 26 agencies.
Now I don’t think that SFPUC and the Bay Area Water Supply and Conservation Agency are necessarily against modifying the Hetch Hetchy, but consider that the ballot measure would have allowed the City of San Francisco to dismantle a water supply in which 2/3rds of the customers (who pay for operations and maintenance) had no voice. That seems pretty unfair. The Restore Hetch Hetchy folks of course call this an “end-run around democracy”, but what was the ballot measure in that case?
Welcome to the new year! I unfortunately started the new year with a bout of strep throat that ran rampant through our office over the holidays, but I’m nearly 100% again, and ready to get back to writing! I’ll start off the year with a quick follow-up to my last post of 2012, on the geochemistry of carbon capture and sequestration.
My favorite journal, Environmental Science and Technology, has started off 2013 with a special issue entitled, “Environmental and Geochemical Aspects of Geologic Carbon Sequestration.” ES&T has a running policy to open each year with a special issue, freely available to the public. So take a look at the Table of Contents and read what the top environmental scientists and engineers have to say about long-term carbon storage in geological formations! (Props to my undergrad advisor, Dan Giammar at Washington University in St. Louis, for co-editing this special issue.)
Of note, the opening letter from the co-editors has an overview of the technical geochemical issues of carbon storage. They identify gaps such as “the rates and mechanisms of key geochemical reactions and their impacts on carbon storage performance, the multiphase reactive transport of CO2, and the management of environmental risks.” I agree completely, and this issue is a great step in the right direction.