What are the limitations of UltraViolet (UV) in disinfection of water?

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Hi all,

What are the limitations of UltraViolet (UV) in disinfection of water? Apart from the limitation of using UV at point of treatment and distributing the treated water through a pipeline distribution network which might re-contaminate the water, what other limitations exist?

Thanks

Justin

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22 Answers

  1. You might want to explore Photo Catalytic Oxidation  i.e UV + Photocatalyst; With or without Hydrogen peroxide.  Advantages - can handle turbid waters.   Little or no residua disinfection. 

  2. Even the UV, like all water disinfection systems, have advantages and disadvantages that can not be easily summarized in a few lines. In addition to  no residual effect there are limits related to the power of the lamps and the flow rate of the pipes, to the turbidity of the liquid to be treated, etc ...

  3. The biggest limitations of catalysed UV as a disinfection technique are firstly that there is no residual, so the product fails the requirement for potable water to be disinfecting as well as disinfected, and the techniques require a relatively thin layer to achieve disinfection.

     

    Furthermore, it is restricted to relatively low turbidity water. 

    Answered on by

    1 Comment

    1. UV is not restricted to any lower turbidity water  than any other form of disinfection except possibly membranes. 

  5. Adjusting UV brightness to destroy the Polio virus will ensure the best treatment.

    The electrical cost of UV disinfection compared to bleach treatment is higher but UV is far safer!

    UV bulbs require lots of cleaning/ maintenance and most replacement parts are only available from the manufacturers to be approved by environmental authorities.  

    No observed loss of treatment downstream in piping or storage tanks.  

  6. one major draw back of UV treatment is that no residual effect along distribution pipes which means water can recontaminate, again the quality of water less turbidity must be less than 5NTU. using the right dose of UV. uv is best at point of use.

    1 Comment

  7. It depends on the water quality you want to have. Medical, human or animals process. In my opinion you cans do both chemical and UV. If you have more data I could help you much more

  8. HI Justin,You are right for UV.Recontamination possible,Better option is to to follow Chlorination dosing with residual chlorine level should be 1 mg/l is better.

    1 Comment

    1. As everybody already aware that Ozonation can remove all viruses good effeciant for all types of micros,Chlorination can remove 99.9 percent bacteria ,U V cannot remove Helmonth eggs and protozova efficiently  

  9. I agree with Dr. Cotruvo - US applications are typical on finished high quality water.  There are also many reviews on the limitations of UV and the most notable being its inability except at very high doses to inactivate adenovirus.  Adenovirus is often found in contaminated groundwater.  

    1. In addition to all of these answers, treatment with UV is a numbers game.  This can be total numbers such as knocking down bacteria from 100,000 to 1 or the after 100,000 passing through 1 live one will get through.  In each case, the UV causes the dead cells to leak their cell contents so the one live cell is able to grow on the cell contents unless there is chlorine or similar to control its outgrowth.  Some iron bacteria are also not reduced because of the iron content surrounding the cell.  UV does not work well on recirculating systems.

  12. UV is only applicable as for all disinfection where the turbidity is less than 1 NTU. Also although it can be done on water with a low UV transmissivity it  will require more power etc and bigger units and ultimately may be outside of the UV system verification conditions. 

    The biggest thing with UV is that not all biology is equally affected, bacteria are destroyed by low levels and the same level is great for rendering oocysts none infective but much higher doses are required to have a high reduction of certain viruses. However these are quickly destroyed by low levels of chlorine so a residual chlorine dose for distribution sorts that out.

  13.  As others have noted here, the water supply must be relatively low Hardness, Iron, Manganese, Minerals or Metals that may coat the Quartz Sleeves, and they will still require a regular cleaning schedule. Suspended Sediments, Collodials or Tannins which will block the UV transmittance through the Reaction chambers. And there is no downstream residual disinfection. For a pipeline supply, it would be recommended to have a disinfectant  injected post UV. 

      The upside is that UV with the proper sizing, dosing, and flow , WILL deactivate even the toughest Protozoans, Bacteria, and Viruses! Also amounts of residual disinfectants needed are substantially reduced.

  14. Dear Chinenye,

     

    You would not have any residual effecti.

    If you have any water leek in pipe, any contaminant can go into the pipe due to fugacity, even if the water supply is suspended, the negative pressure in pipe will suck the contaminated water around the pipe..

     

    Regards,

     

    Orlando D. Gutiérrez Coronado

     

     

  15. Hi Engr, Chinenye, Alternative to UV or other approaches to disinfection you might consider treatment using the water filter media of TAM Ceramics, coated with a small amount of silver.  This approach is natural, requiring neither chemicals nor electricity: https://tzenvirohealth.wixsite.com/filtermedia

  18. Hi Justin,

     

    Turbidity plays a role, as well as iron concentration and SS. You have plenty of applications with UV disinfection.

    Many WWTP now replaces their chlorine installation with UV disinfection systems.

    On this page, you have a form that calculates online the best UV solution for your project (in French) : https://www.1h2o3.com/outils/dimensionnement-de-reacteurs-uv/

    You can compare the price with other technologies.

    Have a good day

    Nicolas

  19. Hello Chinenye,

    Have you considered using an alternative method of disinfection?

    Have a look at this product

    http://www.ecabiotec-me.com/images/uploads/general/ANOSAN-TW-Product-Profile.pdf

    and see if it might work for you. It is for both small and large scale use, has readily available monitoring and dosing systems and, above all, is environmentally friendly and is safe for humans, animals, birds, fish etc. It is so safe that you can even drink it.

    It also removes the biofilm in the distribution network and needs no flushing other than to rid the pipeline of released dirt/slime.

    UV is good, chlorine is old hat and Ecabiotec is excellent!

  20. If they are well designed they can be a great and trouble-free process, but it is a big if.

    I agree with Jan-Peter that transmissivity can be a big issue, particularly if something happens that can change the quality of the incoming water.  It only takes a small change in water composition to have a big effect on transmissivity.

    One of the major issues we had disinfecting waste water was keeping the lamps clean and the scraper mechanism was not always reliable requiring regular removal and hand cleaning.

    Sensors can be another area of concern both in the quality and reliability of the sensor and also the location so you can be sure that the transmissivity reading and lamp intensity reading are accurate for the entire flow.  How quickly the system can react to changes in flow rate is also an important design consdieration.

    We also had reliability problems with the ballasts driving the lamps but that was an early generation so may not be a problem these days.

    What I was most uncomfortable about is that there was no simple way to ensure disinfection was right.  Generally we know how much chlorine to add to get disinfection and it handles small variations well but with UV we have to balance transmissivity, lamp intensity and flow rate so you can never be 100% sure.

    If you really put the effort in and do full due diligence and risk analysis during the design phase you should be ok.  Just remember each plant's installation is unique.

    My final comment would be to ensure you have some significant performance guarantees with your supplier that cover not only the UV equipment but the UV equipment as installed in your plant.

    Marcus

    1 Comment

    1. With modern systems they will be USEPA or DVGW verified and this will incorporate the control system to calculate the reduction efficiency dose(RED) from the flow, UV intensity and transmissivity so that the effectiveness is as much known as it is with chlorine, particularly as there is no risk of bypassing or contamination of the contact tank.

  21. Turbidity in water  is one problem , apart from this it is not recomended for high contaimimnation.Also with UV disinfection storage time is limited. It is not effective in case of recontamination. Unlike of chlorine where residuals are mantained which can counter minor contaimination post disinfection. Storage time for disinfected water should not be more then 4 - 6 hours.

  22. Hello Justin,

    The main problem, that can occur with an UV disinfection are turbidity problems in the water. The turbidity causes, that the uv light does not reach every part of the water and allowing bacteria to survive. Due to the availability of killed bacteria in the water, nutrients for a multiplication are available in the water. Turbidity can be caused by suspended solids as well as by air or gasses in the water. Further more UV resistance virus will survive an UV disinfection.

    Those are the main issues, that can occur with an UV disinfection.

    Regards,

    Jan-Peter

    1 Comment

    1. In several projects with changing water conditions we have moved from pure UV to AOP (Advanced Oxidation Process)systems. The effective free radicals of AOP will secure not only as disinfection but as a destruction of any unwanted material. We tend to call it "police guarding" the inlet.  

      I was trying to insert a direct link to the technical page of the product, but have problems pasting. If you send me an email to bjorn.dorum@enwa.com I can e mail you the link.

      Regards Björn