A new use for those old AOL discs we have accumulated – cleaning sewage water

aol_cds[1]From The Optical Society and the “so crazy it just might work” department comes this curiosity:

Spinning CDs to Clean Sewage Water

Scientists find a potential new use for old music CDs: coating disks in photocatalytic compounds and spinning them to clean water

WASHINGTON, Sept. 23, 2013 – Audio CDs, all the rage in the ‘90s, seem increasingly obsolete in a world of MP3 files and iPods, leaving many music lovers with the question of what to do with their extensive compact disk collections. While you could turn your old disks into a work of avant-garde art, researchers in Taiwan have come up with a more practical application: breaking down sewage. The team will present its new wastewater treatment device at the Optical Society’s (OSA) Annual Meeting, Frontiers in Optics (FiO) 2013, being held Oct. 6-10 in Orlando, Fla.

“Optical disks are cheap, readily available, and very commonly used,” says Din Ping Tsai, a physicist at National Taiwan University. Close to 20 billion disks are already manufactured annually, the researchers note, so using old disks for water treatment might even be a way to cut down on waste.

Figure 1: This image shows an optical disk entirely coated with zinc oxide nanorods.

Figure 1: This image shows an optical disk entirely coated with zinc oxide nanorods. (Photo credit: Din Ping Tsai, National Taiwan University)

Click for larger image

Tsai and his colleagues from National Taiwan University, National Applied Research Laboratories in Taiwan, and the Research Center for Applied Sciences in Taiwan used the large surface area of optical disks as a platform to grow tiny, upright zinc oxide nanorods about a thousandth the width of a human hair. Zinc oxide is an inexpensive semiconductor that can function as a photocatalyst, breaking apart organic molecules like the pollutants in sewage when illuminated with UV light.

While other researchers have experimented with using zinc oxide to degrade organic pollutants, Tsai’s team is the first to grow the photocatalyst on an optical disk. Because the disks are durable and able to spin quickly, contaminated water that drips onto the device spreads out in a thin film that light can easily pass through, speeding up the degradation process.

Figure 2: This scanning electron microscope image shows tiny nanorods growing on the disk.

This scanning electron microscope image shows tiny nanorods growing on the disk. (Photo credit: Din Ping Tsai, National Taiwan University)

Click for larger image

The Taiwanese team’s complete wastewater treatment device is approximately one cubic foot in volume. In addition to the zinc oxide-coated optical disk, the device consists of a UV light source and a system that recirculates the water to further break down the pollutants.

The research team tested the reactor with a solution of methyl orange dye, a model organic compound often used to evaluate the speed of photocatalytic reactions. After treating a half-liter solution of dye for 60 minutes, they found that over 95 percent of the contaminants had been broken down. The device can treat 150 mL of waste water per minute, the researchers say.

The spinning disk reactor is small, consumes little power, and processes contaminated water more efficiently than other photocatalytic wastewater treatment methods, Tsai says. The device could be used on a small scale to clean water contaminated with domestic sewage, urban run-off, industrial effluents, and farm waste. Going forward, the team is also working on ways to increase the efficiency of the reactor, and Tsai estimates that the system could soon be improved to work even faster, perhaps by creating layers of stacked disks.

Presentation FW1A, “Zinc Oxide Nanorod Optical Disk Photocatalytic Reactor for Photodegradation,” takes place Wednesday, Oct. 9 at 8:15 a.m. EDT at the Bonnet Creek Ballroom, Salon IV at the Hilton Bonnet Creek in Orlando, Fla.

Advertisements

36 thoughts on “A new use for those old AOL discs we have accumulated – cleaning sewage water

  1. Hmmm. . . methyl orange is a polar molecule and completely soluble in water. It won’t coat the zinc oxide surface the way an oily compound would do. That makes it an easy test model.
    Sewage contains lots of oily material, not to mention solids in suspension, along with bacteria. These would coat and/or clog the zinc oxide surface probably rendering the system inoperable.
    Methyl orange indicates its own breakdown by loss of color. The paper is not available, but I’d guess that loss of color is what they monitored. Loss of color in a dye is how similar papers report their results testing zinc oxide in experimental photocatalytic pollution removal systems.
    Loss of color doesn’t really mean total breakdown of the organic. It just means the chromophore (the color-producing aspect of the molecule) as been disrupted. Probably the methyl orange molecule is split into two pieces (trying to avoid chemical arcana) by the photoprocess. The residual pieces are colorless, less susceptible to degradation, and may well remain in the water.
    I’m not saying the work is worthless. Science always starts out small and proceeds stepwise. They do have a nice result, and using spinning optical disks is a great idea. The high surface area makes the photolysis much more efficient.
    But the result has been overblown. It’s just the usual business of science reportage by press release, in which the press officers make things seem much more than they actually are. We see this all the time in climate science, and now the hyperbolic press claim has spread everywhere. It’s dishonest.

  2. I just got a bit of deja vu.. felt like I was 13 and reading a copy of Popular Science in the principal’s office.

  3. This idea using slowly spinning disks and bacterial digestion has been around for decades and shown mixed results in actual implementation with sewage. Don’t put too much hope or money into this one until they do a lot of testing with real contaminants.

  4. I’m waiting for the T.V. infomercials for this gizmo. You buy it at 2:30 in the morning ’cause it sounds like a great idea, but when you get it, it just doesn’t work like it did on T.V. Then it becomes a convenient place to pile the laundry or hang that sweater your Aunt Tillie gave you for your birthday.
    I could be wrong but that’s how it strikes me; doesn’t pass the smell test.

  5. This probably doesn’t have much potential as primary sewage treatment, but might be useful for polishing effluent for reuse. What reuse plants desperately need is something that can guarantee the last of the biohazards are gone. 6 sigma isn’t good enough QC when people are going to be drinking the stuff.

  6. I bet that actually collecting all those old discs would be FAR more expensive than actually making new ones. !

  7. During my usual one-week summer vacations, I’ve been using those old discs and worthless VHS tapes to start and maintain my campfires, particularly when the available firewood is soggy.
    I am banished to the hot place for all eternity by Al Gore, no need to tell me that.

  8. Besides. Hasn’t everybody microwaved all their old CDs?
    After doing that for about a second, even the NSA isn’t going to find out what was on there.

  9. Interesting, but what’s wrong with dumping the sewage in the nearby river, letting its bivalve inhabitants eat the stuff. Each of them can do 150 ml per minute or more.

  10. Most effluent standards limit zinc. Daphnia magna go belly up with the right concentration of Zn in the water. How do they handle this?
    Besides, the bugs do an outstanding job of chewing up the nasties in wastewater.

  11. Randall_G says:
    September 23, 2013 at 4:41 pm
    Perhaps a Creedence Clearwater Revival?

    ===========================================================
    😎
    (not a reference to Creedence Clearwater Revival but)
    Lots of CD’s were full of …. why make more of them?

  12. Gee, and here I was wondering how to cut a parabolic mold on the lathe that I could heat and use to reshape those old CD’s. If the reflective layer stays intact, they’d make great concentrators for individual solar cells.
    Group some together with the original logo printing visible, a few electronics, you can make a killing selling solar iPhone and iPad chargers made from recycled materials to the gullible.

  13. I used to save the endless deliveries of AOL CD’s, unopened, thinking they would be a nostalgia craze/collector’s item in a couple of decades, like old Coke signs.
    But when we moved my wife threw them all out, so that’s that. ☹

  14. Here’s another thought.
    Assuming this all works as advertised, what would it take to pluck all the discarded CDs out of the trash?
    Maybe it would be worth it but what would it take?
    An electromagnet wouldn’t work. A disco magnet?

  15. Using Tesla theory, that size can generate about 100 hp. remember for max efficiency discs need to be rough not smooth. So can use a similar micro coating of ceramic.
    Seed the coating with suitable bacteria and employ an air inductor, that will improve efficiency.
    Add permanent magnets to the disc rims, and wind a coil on the outside of the containing tube.. Arrange so sewage flow enters at right angles to discs. This will induce spin and generate electricity.
    A single device, generates power from sewage flow and cleans the sewage. Magnetic bearings can be used as well

  16. “After treating a half-liter solution of dye for 60 minutes, they found that over 95 percent of the contaminants had been broken down.” Incredible! I’m trying to wrap my mind around how many disks there are out there and how much potential there is in this technology. I mean, I started listening to music at the tail end of the “physical” stuff, and even I had 15-20 CDs of my own (that’s without considering all my software and DVDs). Maybe, in a few years, there will me CD collection stations in malls like they do for cellphones now? It’s a very exciting thought.

  17. From dbstealey on September 23, 2013 at 8:02 pm:

    But when we moved my wife threw them all out, so that’s that. ☹

    Even the ones in the tins? My mother always saved all the tins, from anything. My dad used them for small nails, screws. But once when I was cleaning up, I figured we had enough Sucrets tins and threw them out.
    Then Sucrets switched to plastic. I wonder what the eBay value of those tins is up to.
    In the back of the one kitchen cabinet I found a few old McCormick tins, small sheet metal wonders with sliding and twisting lids, spices still dry. One has the remains of an ink stamped price, 17 cents for 1 1/4 oz of “Double Superfine Mustard”, it nests with more-recent plastic-topped tins.
    An older tin of 1 1/2oz of ground turmeric has a penciled-on price, looks like “2/17” (two for seventeen cents?), is less flat and doesn’t nest.
    I think we got them almost four decades ago, when cleaning out the great-aunts house, from the dusty far reaches of of the kitchen cabinets. On the turmeric, label says “Bee Brand” and copyright 1942. Mustard tin has recipes for mustard plaster and mustard poultice.
    For price comparisons, my mother’s widowed mother said bread was too expensive so she’d have to make her own, around 1945 when the price jumped from 6 cents a loaf to 8 cents.
    I’m not throwing those tins out.
    And about half the people reading this are wondering if mustard poultice is made with chicken, and if it can be boneless skinless breast meat.

  18. Meanwhile I find the discs make good solar reflectors, Arrange to focus sunlight on a suspended can of water. Soon boils. 🙂

  19. I’m sure old CDs will get lost of wacky uses. I’ve been usefully stringing a bunch of them together with monofilament and hanging them a short distance under a small float in the ocean. Pelagic fish are attracted to the sun sparking off the CD surfaces and that makes it a tad easier for us Spearos to catch dinner.

  20. “GeoLurking says:
    But will it clean the fecal laced sewage spewing from Big Al’s gaping maw?”
    That will require scaling up to the LP sized Laser Discs!!!

  21. Rotating Biological Contactors have been around for a while, this is nothing new, it is a different way to produce zoogleal mass. It’s an upgrade on the trickling filter.

  22. kadaka (KD Knoebel) says:
    September 23, 2013 at 9:40 pm
    From dbstealey on September 23, 2013 at 8:02 pm:
    But when we moved my wife threw them all out, so that’s that. ☹
    Even the ones in the tins? My mother always saved all the tins, from anything. My dad used them for small nails, screws. But once when I was cleaning up, I figured we had enough Sucrets tins and threw them out.

    =======================================================================
    I remember coming across one of those little hinged tins that only held 6 tablets. It was for something called “Aspir-Lax”. I always wondered what their sales pitch was.
    “Got a pain in the butt? Try ASPIR-LAX!!

  23. I use unwanted discs to protect fruit and vegs from the birds. Having said that I don’t have too many for that job as I still like my CD collection and have a good player. Also, I spend most of my spare time reading WUWT and Jo Nova so don’t have the time for faffing around transfering my collection to iPod. I have put a few of my absolute favourites onto iPod for air travel (relaxing stuff like Tallis and Bird). I prefer the sound of my old LPs when I’m at home….much better than anything else.
    If this water-cleansing use comes to much I hope that a domestic version comes out so that we can clean grubby dam water before stock or plants get it!

  24. Clever, but a little late. Ten years ago I converted all my old AOL disks into “AOL-ian sculpture’. With pipe cleaners, ribbon, and strategically concealed duct tape, I created hanging mobiles shaped as tetrahedra, ocatahedra, and other shapes, with a Buckyball (a 60-sided semiregular polyhedron) as my magnum opus. Hanging in a window they would catch the sunlaight and scatter rainbows throughout the room!

Comments are closed.