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Published on December 16th, 2014 | by Sponsored Content


UV Light Systems & How They Clean Water

December 16th, 2014 by  

Water certainly isn’t our primary focus, but technologies that make our water cleaner are an important part of cleantech, and we do have 531 articles published on the category. Water purification and water desalination technologies are very useful and to some perhaps even interesting, but they don’t exactly put a spring in my mental boot… for the most part. One that I really think is interesting, however, is water disinfection via UV light. It’s just fascinating how many useful things light can do, from generating electricity in a solar PV system to disinfecting water.

This method of cleaning water is also extremely useful since it is so cheap. It’s absurd how many people in poor countries don’t have access to clean water, one of the most essential things for human life. Millions and millions of people die from lack of clean water. Makes your first-world problems seem completely lame, doesn’t it?

Ultraviolet light systems are some of the best solutions to this lack of clean water. As I wrote more than two years ago, “Ultraviolet light is a very effective, easy way to clean contaminated water, preventing and reducing the occurrence of a wide variety of bacterial and viral diseases in areas without access to clean water.” The story was focused on one particular UV light system, but we’ve covered others over the years. The beautiful thing about this solution is that it’s quite simple.

If you want to learn more about the basics of UV light systems, and infographic below from Pelican Water Systems (which kindly sponsored this article), explains the process. Pelican Water Systems also makes the case for people in the developed world getting a UV light system. Before the infographic, it writes: “Water utilities must meet high quality standards, but the water supply still can be contaminated after it leaves the treatment plant. One of the best ways to ensure the purity and safety of water at home is to install a UV light system. In the infographic below, learn how UV light can keep your family and water supply safe from harmful bacteria.”

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  • Ronald Brakels

    UV lights have been a standard part of Australian household rainwater systems for a longtime now. So much so there has been concern about their energy consumption and its environmental effects that result from our dirty dirty grid. Of course, if we stopped burning so much dirty dirty coal there would be a lot less dirty dirty toxins in our rain water that can only really be filtered out with clean clean activated charcoal that almost no one bothers with. Anyway, now that LEDs have greatly improved the efficiency of producing UV light and the cost of solar PV has come down so much it should be a much more affordable method of improving water safety in not yet rich countries. Of course, using it on town water in a place like Australia with safe water supplies is a waste of resources. One would be much better off putting that money into some extra solar panels on the roof or on grandma’s roof.

    • nakedChimp

      The last I heard of this was that they still worked on it (not at market) as current UV-LEDs don’t have the right wavelength to work for incapacitating bacteria/etc. in water and their output energy wise was lacking as well..?

      • Ronald Brakels

        People are selling LED water purifiers. Hopfully they work. But current UV LEDs are sufficient to kill microorganisms, or at least that’s what Wikipedia tells me and it’s not as it that is written by a bunch of random people off the internet.

        Wait a minute…

      • Ronald Brakels

        As you mentioned the main problem may be that current LED efficiency doesn’t appear to be good at producing UV light, so it may not be much of a saving. Or any saving at all. But perhaps if their lifespan is good they still might be worthwhile.

      • Larmion

        True. We decided against LED in our microbiology lab for that reason.

        LED’s have a spectacular efficiency in the (roughly) >370nm band. That makes them ideal for UV curing (hardening resins, treating polymers and such like) and also for certain forms of microscopy, but not for sterillization.

        The ideal wavelength for killing bacteria (and humans, if you wanted to) is UVC (around 254nm). That’s presently only viable with a mercury arch lamp.

        And mind you, those have excellent efficiency. The best ones emit 35% of their light as UVC, as opposed to a few percent for LED. That more than makes up for their higher power consumption (who needs a powerful lamp if most of its output is wasted?).

        I can see why LEDs would be used for home use though. For starters, the longer bulb lifespan makes them more convenient, but more importantly: nobody cares how purified rainwater really is. A good pulse at higher wavelengths will at least kill most bacteria and that’s good enough for average joe. Home UV disinfection is mostly about feeling safe rather than about being safe.

  • Marion Meads

    Microorganisms are only one of the many problems with water purification. We still have heavy metals, pesticides, pollutants, and other toxins that cannot be rendered harmless as inexpensively as using UV treatment.

  • Larmion

    UV is an excellent way of eliminating most waterborne pathogens, but endospores are usually highly resistant and viruses are also at least partially tolerant. Unlike chemical sterilization, the water is also wide open to re-infection. And the water must have a low percentage of dissolved solids.

    Where nothing else is available (parts of the developing world) old-fashioned chemical techniques like chlorination are both cheaper and more effective. In rich countries, UV is great as part of a water treatment plant, but it’s hardly something you need at home.

    • Offgridman

      While it hasn’t affected me due to having my own water source, the local small town has had a lot of problems in just the past year and a half, three ‘do not use’ or ‘boil alerts’ from 2-10 days. Various reasons from old infrastructure (some of the piping is over a century), the town has a river running through the middle, and extreme weather events. For the one really long event a lot of people were unaware until four days in when the weekly paper carried the notification.
      Some friends are already using softeners and various filters for quality and maintenance reasons and it would seem reasonable for them to add something like this for an extra bit of security.
      It would be best if this was done at the main plant, but with how poor the community is it doesn’t seem to likely to happen soon.
      I think what you expect to be taken care of by the municipality is entirely right, but in parts of the US the social contract isn’t as well honored as you might want. This is just as much the fault of the people as the government. There was an attempt to raise property taxes this year that had to be approved by voting, in order to do improvements to the water plant and road repairs. On 100,000$ valuation the taxes would have gone from about 400$ up to 500$,so for 95% of the population less than a hundred dollar increase. But the tea party faction had their signs up and kept writing to the editor about ‘no more taxes’, so we go for another two years with minimal repairs to the water system and roads.

      • Larmion

        You say you live in a poor community. Can residents be reasonably expected to be willing and/or able to pay for personal treatment systems, even the simplest of which are expensive, if they cannot or don’t want to pay for a cheap municipal station?

        The US urgently needs to spend more on public infrastructure, that’s a fact. But by buying personal water treatment units, you’re just going to help postpone those investments: rich, concerned residents will pay for their own system and give up their activism.

        The result? Economic inefficiency (no economies of scale), greater health inequality and massive waste of resources.

        It’s not a popular statement these days, but I sincerely hope we’ll see fewer ballots, polls and referenda and more bureaucrats. Things like energy, health, water and so on are too complicated, too technical and too important to leave to voters. Voting is a great way to decide questions that have no ‘right’ answer or are purely moral in nature, but engineering should be left to engineers.

        As a side note: water softeners do nothing to improve water ‘quality’. They reduce calcium content through ion exchange, thereby actually making the water less suited to human consumption (more salt). No water treatment system anywhere in the world reduces water hardness – prolonging the lifespan of your washing machine is not part of their mission statement.

        • Offgridman

          I am well aware that it is a systemic social/political problem, and my efforts are towards making it more equitable for all.
          I was just trying to provide one small example of why while it would be better to implement this on the community scale it is going to end up being done per household.
          Also while you disagree with the use of personal water softeners and filtration, some people think that the cost is worthwhile compared to fixture and appliance maintenance and replacement. I don’t bother myself other than particulate filters to protect pumps and etc, but through the years have seen many go to much more bother and expense.

          • Larmion

            Oh, I certainly don’t say a water softener is a bad idea. All I’m saying is that the fact that your friends have to install one isn’t proof of a failing water treatment system: reducing water hardness simply isn’t a part of the job description of a municipal water system.

            Drinking water systems should produce… drinking water. Water that is safe and has good sensory characteristics. Water softening has its role and I can see why someone would want to install it in their home, but you can’t reasonably expect the water treatment plant to do it.

            As for filtration: that depends. Many people choose filtration for sensory reasons (‘it tastes better’). Water that contains chlorine, for example, is safe and healthy but might taste unpleasant. If that’s the problem, it’s again not a sign of a failing water treatment plant.

            If, on the other hand, they chose filtration after water samples showed unacceptable levels of contaminants or colony forming units, there’s something profoundly wrong.

    • Marion Meads

      At home, I’d rather have filtration against pesticides, hormones, chemicals, toxins, heavy metals, organo-phosphates, nitrates, sulfites than the UV treatment.

      • Larmion

        Nothing wrong with most of the ones you mention. Nitrate and sulphate levels do not exceed safe levels anywhere afaik, and those norms are far more stringent than needed.

        Heavy metals are very local. If you live in an area with high levels of metal pollution (generally through natural causes, sometimes due to pollution or old lead piping), go ahead. But for the vast majority of us, metal levels never exceed safe levels.

        That leaves organophosphates. That’s a very broad category; some have known health effects (parathion comes to mind), but those are banned or regulated in most developed countries. And since they biodegrade rather quickly, once they fall from common use concentrations quickly drop to safe levels. Many other phosphate esters have no health effects whatsoever.

        ‘Chemicals’ is not a realistic moniker. Water itself is a chemical. Should you leave it out of your diet?

        Same thing goes for pesticides: some I wouldn’t touch with a ten feet pole, others are safe enough to have for lunch.

        • Marion Meads

          I’ll give you a hint: most California cities get their water from wells.

          • Larmion

            The article makes no distinction between pollutants with effects on human health and those that are ‘only’ affecting aquatic life. The nitrates mentioned, for example, wreak havoc on aquatic ecosystems but have no negative effect on human health. And filtration doesn’t effectively remove them anyway, even with activated carbon. The same applies for many others.

            The pollutants you describe can only be properly removed from water through large, centralized treatment systems.

            To return to nitrates, you would ideally use OLAND – hardly something you can use at home.

            Btw, ‘toxic’ chlorine? As a gas, sure. But it’s perfectly healthy as an aqueous solution. It’s a crucial regulator of osmotic potential in every single human cell.

  • JamesWimberley

    They could have taken the trouble to get the electromagnetic spectrum correct. Radio waves should be at the right-hand end, after infrared and microwaves. Howlers like this do not inspire confidence in the rest.

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