Akvo - miscellaneous water systems


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There are a variety of types of systems inculding: Vehicle wash, Chilled water systems, Heating, low, medium or high temperature, Closed loops in general and more.

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Akvo - miscellaneous water systems

  1. 1. MISCELLANEOUS WATER SYSTEMS Jonathan Beresford AKVO Ltd June 2013
  2. 2. TYPES OF SYSTEMS         Vehicle wash Chilled water systems Heating, low, medium or high temperature Closed loops in general Air handling units Fume scrubbers Cutting machines Spa pools
  3. 3. LEGIONELLA/BACTERIA CONSIDERATIONS  If it creates an aerosol you have to consider the legionella possibilities. Temp, nutrients, environment, spray, people  Bacterial/fungal growth can be an issue with process systems.  Fungal slime growth can block and reduce cooling. Similar to what scale and iron deposits can do. Bacteria can corrode metals too. Even stainless steel.
  4. 4. SCALE/CORROSION  Any system that is supplied with hard water and cools process systems can deposit scale at the hotter areas – heat exchangers.  The heat exchangers themselves can be made of brass, aluminium, copper, iron. – Different metals in a system can also add to the corrosion potential by adding to the electrolytic effect.
  5. 5. SYSTEM DESIGNS  Fume scrubbers, AHU’s, Vehicle washers spray water that is typically dirty. They can thus lead to legionella growth.  Metal cutting machinery if often a source of bacterial infection, including legionella.  Closed systems have slime, scale and corrosion issues.  Heating systems can be either low, medium or high pressure systems, the higher the pressure the higher the temperature  Chilled water systems cool water that is pumped around jacketed vessels or heat exchangers and frequently involve a holding tank(s).
  6. 6. DOSING AND CONTROL  Dosing pots provide a means to add chemical and also allow for sampling the water.  Inhibitor considerations need to take into account what could be the bigger issues. Could be lack of cooling from scale or corrosion may be a greater issue.  Bacterial control is invariably by non-oxidising biocides  Dosing can be manual, water meter pulsed, or timer controlled pumps.
  7. 7. CORROSION CONTROL  Nitrite is the most common inhibitor for closed systems, coats metals protecting against corrosion, nitrite is an anodic inhibitor.  Has the potential to foam if overdosed.  Typically dosed to systems with little water losses like chilled and heating systems.  Has to be dosed at >1200 ppm if Chlorides >100. >600ppm otherwise.  Makes pH of system water high at roughly 10-11 – aluminium corrosion pH level  If not enough is dosed it adds to the problem by localising the corrosion attack to the remaining areas not protected.
  8. 8. CORROSION POTENTIAL GALVANIC SERIES                                      Most cathodic or resistant to corrosion Platinum Gold Graphite Titanium Silver  Chlorimet 3  Hastelloy C  18-8 Mo stainless steel (passive)  18-8 stainless steel (passive)  Chromium steel >11 % Cr (passive)  Inconel (passive)  Nickel (passive)  Silver solder  Monel  Bronzes  Copper  Brasses  Chlorimet 2  Hastelloy B  Inconel (active)  Nickel (active) Tin Lead Lead-tin solders  18-8 Mo stainless steel (active)  18-8 stainless steel (active) Ni-resist Chromium steel >11 % Cr (active)  Cast iron  Steel or iron 2024 aluminum Cadmium Commercially pure aluminium Zinc Magnesium and its alloys Most anodic or easy to corrode
  9. 9. BACTERIAL CORROSION  Gallionella bacterium corrode stainless steel  There are organisms that accumulate iron or manganese. The accumulation of manganese in biofilms is blamed for several cases of corrosion of stainless steels and other ferrous alloys in water systems treated with chlorine or chlorine/bromine compounds.  Certain fungi are also capable of producing organic acids and have been blamed for corrosion of steel and aluminium. i.e. Aircraft fuel tanks, sulphate reducing bacteria will produce sulphuric acid and nitrite reducers will product nitric acid.  Aerobic slime formers can inadvertently produce enzymes that are capable of intercepting and breaking down toxic substances (such as biocides) and converting them to nutrients for the cells  Various anaerobic bacteria such as Clostridium are capable of producing organic acids. Could be a problem in closed water systems that become anaerobic. In addition anaerobic bacteria produce foul smells.
  10. 10. COPPER AND BRASS     Brass is an alloy of copper with zinc present (10-15%). The zinc component is susceptible to corrosion resulting in a weakened metal that can fracture under stress. Pitting corrosion occurred only in low dissolved inorganic carbon (DIC) (5 and 10 mg C/L) and high-pH (9) water in the presence of chloride (20 mg/L) and was not observed at pH 7 or 8. Sulphate was not necessary to develop pitting corrosion; however, it did affect the composition of the corrosion by-products associated with pitting corrosion. Increasing the DIC from 10 to 50 mg C/L or adding 3 mg PO4/L prevented pitting corrosion at pH 9. A conceptual model was established that attributed pit initiation to the deposition of copper chloride or sulphate compounds on the pipe at the anode. In other words if the pH is less than 7 raise it to between 7 & 9, ensure enough phosphate is present and the conductivity is high enough. Keep an eye on chloride levels as they seem to pit just about anything when high enough. (>200 stainless steel etc) If the water is soft, the corrosion potential is much greater. TTA is a good copper inhibitor, but protecting the zinc present in brass is difficult – filming amine is an option.
  11. 11. ALUMINIUM  Aluminium readily forms a protective layer of aluminium oxide assuming oxygen is present.  Aluminium readily corrodes usually as a result of the breakdown in the oxide layer from mechanically being removed. Also corrosion occurs greatly when iron/copper deposits on the metal. (electrolytic/battery effect)  At a high pH aluminium is corroded  Protection is via pH control, blended hardness levels and chemical protection should be at high levels to ensure sufficient coating / removal of any electrolytic effects.  In soft/softened water systems molybdate treatment, is the only option at high concentrations, at least 800ppm product.
  12. 12. Vehicle wash systems
  13. 13. VEHICLE WASH SYSTEMS  Produce substantial aerosol.  Can be contaminated with all manner of road soiling.  Can be contaminated with surface run off.  Can be contaminated with drift from cooling towers  Have lots of organic matter for food sources.  Should be treated with biocides if a recirculating system.  Have been implicated in legionellosis outbreaks.  Biocide treatment is usually with Oxycare
  15. 15. METAL CUTTING SYSTEMS  Often have central solution storage tanks.  Sometimes applied by spray, ie aerosol.  Prone to biological contamination – Including legionella  Have been implicated in legionellosis.  Treat with nonoxidising biocide
  16. 16. Legionnaires’ bug hit 115 people at spa club Jul 13 2007 by Graeme Whitfield  The Journal. ONE hundred and fifteen people are believed to have been affected by the Legionnaires’ disease bug in an outbreak at a Sunderland leisure club, a report said yesterday.  The Health Protection Agency traced the outbreak last year to faults in the water treatment system at the Springs health club, which led to the legionella pneumophila bug colonising the spa pool system.  It is now known that the 115 people became ill after visiting the leisure club from August 11 to 25 last year. Of these, two have been confirmed as having Legionnaires’ disease and five of having Pontiac Fever, a milder version caused by the same legionella organism. Three people needed hospital treatment after the outbreak, which led Springs to shut the health club earlier this year.
  17. 17. Typical Spa Pool System
  18. 18. Dosing and control  Normally two stages – Filtration – Disinfection  Control system will maintain control over pH  Control system will maintain control over chlorine/bromine via redox
  19. 19. Complex pipe work  Makes full draining difficult.  Potential dead legs  Areas for bacteria to “hide”.  Corrugated pipes should be avoided.
  20. 20. Bacterial infections  Legionella species can give rise to both Legionnaires Disease and/or Pontiac Fever.  Pseudomonas aeruginosa can give rise to folliculitis which is an infection of the hair follicles, children and young adults are most at risk.  Mycobacterium avium has been associated with respiratory infections.  Amoeba such as Naegleria fowleri is a rare cause of fatal meningitis which has been associated with natural spas. Acanthamoeba species are common in water systems and can cause eye infections especially in wearers of contact lenses. This amoeba can also cause encephalitis of the brain.
  21. 21. FOR FURTHER INFORMATION Contact AKVO Ltd Tel 0844 244 8726 Or visit www.akvo.co.uk