Akvo - chlorine dioxide

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Chlorine dioxide was discovered in 1811 by Sir Humphrey Davy
No progressed as no means of compressing or controlling such a volatile and potentially explosive material.

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Akvo - chlorine dioxide

  1. 1. CHLORINE DIOXIDE Jonathan Beresford BSc (Hons) MSc AKVO Ltd www.akvo.co.uk
  2. 2. History of Chlorine Dioxide Discovered in 1811 by Sir Humphrey Davy No progressed as no means of compressing or controlling such a volatile and potentially explosive material. First commercial user was the City of Niagra Falls Public Water Authority in 1944. High levels of natural phenols in the water made the use of chlorine unacceptable. By 1977 over 100 US utility companies were using the material along with several thousand utilities in Europe.
  3. 3. Physical properties Pure ClO2 is a dark brown oily liquid. Explosive in air at concentrations above 10%. Highly soluble gas that does not react with water Eg chlorine produces hypochlorous acid in water. Very stable when dissolved in water at <3g/l In aqueous state it is a non polar free radical oxidising agent. Solutions are yellow/greenish yellow and smell of chlorine.
  4. 4. Benefits of ClO2 Effective against all micro organisms at very low concentrations  DWi limit in drinking water 0.5mg/l total oxidant  Total oxidant = chlorite + chlorate + chlorine dioxide Rapid Killing action Effective against Legionella Excellent Biofilm control. Excellent Biofilm Disruption / Removal  But not at DWI limits  Diffuses into biofilm to kill from within, Cl2/Br2 burn the surface.
  5. 5. Benefits of ClO2 Does not react with organics to form ecotoxic and bioaccumulative byproducts Maintains biocidal activity to pH 10 Not corrosive to pipes and metals at normal use concentrations No reaction with amines or phenolics  No taint potential compared to Cl2 or Br2 Better tolerance to organics than Cl2 or Br2
  6. 6. Chlorine Dioxide - Options  Acid Chlorite generators  AKVO preferred option, safest & most efficient dosing method  Electrolytic generators, feedstock chlorite solution  Nalco Halox  Clearwater also have similar system,   CLOX CAT R self regenerating units, uses sulphuric acid CLOX CAT X non regenerating units, cartridge sent back for regen.  Both these show poor conversion rate of chlorite to Chlorine dioxide, approx 50%.  Dilute Chlorine Dioxide solution  3% chlorite solution requires activation with weak acid.  “Stabilised” Chlorine Dioxide  Solutions of approx. 2g/l - short shelf life, chlorite often is active biocide, not chlorine dioxide  Chlorine Dioxide Tablets  Available from AKVO
  7. 7. Acid/Chlorite Generators Prominent & LMI the most common. Can use hydrochloric acid/sodium chlorite in a range of concentrations. 5NaClO2 + 4HCl = 4ClO2 + 5NaCl + 2H2O In practice this typically means 7.5 % solution of chlorite reacted with a weak 10% solution of HCl
  8. 8. The various Parts Control Panel Receives water meter pulses and doses set amounts of the precursor chemicals to match the water flow.
  9. 9. The dosing pumps These draw the two precursor chemicals from their tanks, across flow sensors to the mixing chamber.  Click to edit the outline text format  Second Outline Level − Third Outline Level  Fourth Outline Level − Fifth Outline Level
  10. 10. Chemical mixing chamber The precursor chemical mixing chamber is contained inside an air tight housing that it is evacuated using water and air every 5 mins.  Click to edit the outline text format  Second Outline Level − Third Outline Level  Fourth Outline Level − Fifth Outline Level
  11. 11. Water flow A magnet on the back of the flow gauge will shut down the generator if the water flow ever drops to low level The generator will automatically recommence dosing once flow is detected again.  Click to edit the outline text format  Second Outline Level − Third Outline Level  Fourth Outline Level − Fifth Outline Level
  12. 12. Chlorine Dioxide Monitor This samples water and constantly monitors the chlorine dioxide level. Below the probe is a sample tap.  Click to edit the outline text format  Second Outline Level − Third Outline Level  Fourth Outline Level − Fifth Outline Level
  13. 13. Checks that are required Use a digital tester to check the chlorine dioxide level in the water (random sample point at a use location). Check the digital readout from the continuous sampler Check the main control panel display for fault messages Check the water flow gauge shows a flow Check the chemical levels in the tanks
  14. 14. Chlorine dioxide summary  ClO2 is an effective means of controlling the growth of Legionella and other contaminating micro-organisms in engineered water systems.  Used extensively in the food and beverage industries – safe for direct food contact.  Used for potable water supplies  DWi approved  Prime recommendation via HTM04 for NHS sites
  15. 15. FOR FURTHER INFORMATION on our bespoke chlorine dioxide products Contact AKVO Ltd Tel 0844 244 8726 Or visit www.akvo.co.uk

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