Which is the best technology for water & wastewater disinfection?

Published on by in Technology

Dear All,

Please share your experience regarding the disinfection method/methods used in your plants and in your experience.

Which one would you most recommend and why?

CAPEX, OPEX and being ecologically friendly is important.   

Awaiting replies to begin a knowledge-sharing experience.

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6 Answers

  3. UV is the most effective one, it required radiant energy.

    1 Comment

    1. @ Phetla Mangena thank you for sharing. UV  is indeed very effective however the effectiveness of UV disinfection is very much dependent on the pretreatment given to the water. 

  4. Mr. Skaria,

    You make some very valid points. I should have mentioned the DBPs in my previous writing on this issue. I agree this is another factor why chlorine is being phased out. With so many different technologies, when they 1st come on the market, often issues arise that were not seen during testing periods by manufacturers. Through time, often the technologies improve. The same is true with UV. It seems like bulb life has really increased compared to when UV 1st came out.

    Your comment that chlorine requires other needs like transportation, storage, etc. is very pertinent and I agree UV does not need as much of this attention by an operator.

    Thank you for sharing your thoughts.

     

  5. Dear Mr.Kenneth Keil,

    Thank you for sharing your experience. 

    It is the DBP's that chlorine causes rather than the dangers associated with the handelling of chlorine which I see as the main reason for it being phased out now.  

    UV has indeed gained in popularity because it is easy to use and needs limited to very limited human maintenance or monitoring. I have 15+ years experience with UV systems and have worked with many WTP and WWTP plant operators. The white film that deposits on the quartz sleeve covering the UV bulb is most probably the salts in the water that scales/fouls the quartz sleeve reducing the UV systems effectiveness. Nowadays low pressure UV lamps/bulbs have a rated lamp life of 16,000 burning hours which works out to almost 2 years and generaly the replacement costs of these UV lamps is around 10-15% of the UV systems Capex which is not so high. Running costs are very low. 

    Chlorine gas on the other hand requires transportation, material handeling equipment, trained personell, safety precuations for usage, hazardous materials storage and usage licences, dosage monitoring etc, not to speak of the DBP's and enviro issues.

    I have limited experience with O3 systems and have found it to be a very effective disinfectant. The Capex and Opex is much higher than UV per m3/hour of water flow. 

    Awaiting more comments from fellow members.

  6. It seems to me the best people to answer this question are operators of water and wastewater facilities, especially those who have experienced more than one disinfection method. I've been involved with disinfection as a plant engineer, start-up engineer, and design engineer. Personally, I like chlorine and I believe it maybe the cheapest disinfection method though I have not seen costs for disinfection methods in recent years. There is a lot of hoopla about the dangers of chlorine and we know it can be dangerous. However, how many chlorine leaks have occurred at water and wastewater facilities in the last few decades. I as a young start-up engineer many years ago had to switch from an empty chlorine tank to a full one and found the disconnecting and reconnecting simple. Sodium hypochlorite has often been used in recent years to replace chlorine gas systems. One problem with NaOCl is that it weakens over time. With warm temperatures, it weakens faster. So if NaOCl has a long detention time in a storage tank, it could be significantly weaker by time the tank is nearly empty. UV has grown in popularity which I have heard operators praise and cuss at. The bulbs can be expensive to replace. I had a client who wanted UV put in on the back end of an AWT process and they eventually hated it and replaced it with NaOCL. A white film kept depositing on the bulbs causing the bulbs to prematurely burn out. I suspect the heat of the bulbs was causing a carbonate or possibly some type of metals deposition on the bulb. I designed another UV system for a secondary treatment plant and the client loved it. Said they'd never go back to chlorine. I have not worked with ozone, hydrogen peroxide or other disinfection methods to comment on. However, I'd really like to hear operators comment on this question.