Application of UV And Ozone in Recirculation Systems

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By Didier Leclercq, ACUI-T.

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Application of UV And Ozone in Recirculation Systems

  1. 1. Application of U.V. and ozone in recirculation systems Workshop CEFAS UK June 18th 2009 18/06/2009 ACUI-T- PRESENTATION
  2. 2. What do we want to disinfect? New water intake:  According to where it is sourced, it may contain live organisms that we are not interested to find in the system.  Different sources may be available:  River water  Pond water  Bore hole water  Public supply System water:  Beside of the fish, the system houses a high load of bacteria and animals grazing on these bacteria. We may need to control their developments  At a given time we may see pathogens organisms in the system and wish to get rid of them. 18/06/2009 ACUI-T- PRESENTATION
  3. 3. Disinfection of the intake water What is the flow rate we have to disinfect?  From 1 to 100m3/h What are the risks?  Bacteria  Parasites, Protozoa Which technique to use?  Filtration: yes/no  Micro-filtration: yes/no  Disinfection:  UV,  O3,  Heat,  chemical, …?  Do we have retention time before we supply the system with the water? A closed tank? An open tank? 18/06/2009 ACUI-T- PRESENTATION
  4. 4. Disinfection of the system water What is the flow rate we have to disinfect?  From 100 to 10000m3/hr What are the risks?  Bacteria  Parasites, Protozoa Which technique to use?  Filtration: yes  Micro-filtration: no  Disinfection:  UV,  O3,  Heat,  chemical, …?  Where to operate inside the system? Is the mean of disinfection inducing risks? 18/06/2009 ACUI-T- PRESENTATION
  5. 5. UV light, how it works? What is the disinfecting light wave length ? The 254 nm wave has an effect on the DNA of the organisms 18/06/2009 ACUI-T- PRESENTATION
  6. 6. 18/06/2009 ACUI-T- PRESENTATION
  7. 7. Which dose is to be used? Micro-organism Dose (mJ/cm2) Bacillus subtilis (spore) 12.0 Clostridium tetani 4.9 Pseudonomas aeruginosa 5.5 Streptococcus feacalis 4.5 Hepatitis A virus 11.0 Hepatitis Poliovirus 12.0 Saccharomyces cervisiae 6.0 Infectious pancreatic necrosis 60.0 To disinfect, a commonly accepted dose is 25miliJoule/cm², but risks remain!! Protozoos and micro algaes might be sensitive as well, but their transparancy to UV light can be poor and therefore protect them 18/06/2009 ACUI-T- PRESENTATION
  8. 8. Effect of the water transparency The water organic load modifies the capacity of the UV light to reach their goal: an intense color, and/or a high load of organic matter in the water reduces the penetration of the UV light. To obtain a given dose, the “transmittance” of UV light in the water is to be considered 18/06/2009 ACUI-T- PRESENTATION
  9. 9. Dose reduction with loss of transmitance 100 87,5 75 62,5 50 37,5 25 12,5 0 18/06/2009 ACUI-T- PRESENTATION
  10. 10. What type of equipments? 18/06/2009 ACUI-T- PRESENTATION
  11. 11. Floating UVs 18/06/2009 ACUI-T- PRESENTATION
  12. 12. OZONE: 03 18/06/2009 ACUI-T- PRESENTATION
  13. 13. What does Ozone in the water?  Ozone is a strong and powerful oxidizing product  It delivers one atom of oxygen to oxidize and one molecule of oxygen which can further oxygenate the treated water  It will oxidize indifferently organic material, bacteria, viruses and any molecule susceptible to oxidation  It goes preferably to the easiest which might not be bacteria or protozoan.  Only the dissolved part of the injected ozone will be useful  Its direct residues are harmless (oxygen!), but oxidization by- products might be harmful 18/06/2009 ACUI-T- PRESENTATION
  14. 14. What are the expected results?  Water transparency is improved greatly: the humic acids resulting from fish/feed metabolism giving their “tea like” colour to the recirc waters are easily broken by ozone.  Protein skimming is easier: large molecules are broken into smaller  Disinfection can be obtained, but it requires high dosages : the process has to be carefully engineered  All depends of the dosage!! 18/06/2009 ACUI-T- PRESENTATION
  15. 15. Are there risks?  YES !!  Fish are sensitive at a proximate level of )0,1ppm  Human lungs are as well sensitive to very low levels of residual ozone  Equipments are needed to measure and control (feed- back) the oxidizing power in the water and as well the potential leakages of ozone in the air around the ozone producing equipments  Safe levels can be insured thru correct sizing of the equipment in relation to the flow rate 18/06/2009 ACUI-T- PRESENTATION
  16. 16. What type of cost?  Equipments are obviously to be sized and costed according to flow rate  Consumables will be KWh and potentially pure oxygen  Main application is made producing ozone from pure oxygen at an enrichment rate of 6-8%, so overall dissolution process of both gases is a clue in calculating the cost  Doses from 0,1ppm to 3 ppm could be applied and therefore relative cost depends a lot of the application and expected results 18/06/2009 ACUI-T- PRESENTATION
  17. 17. 18/06/2009 ACUI-T- PRESENTATION
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