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.

1. MISCELLANEOUS WATER
SYSTEMS
Jonathan Beresford
AKVO Ltd
June 2013

2. TYPES OF SYSTEMS
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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. 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. 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. 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. 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. 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. CORROSION POTENTIAL
GALVANIC SERIES
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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. 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. COPPER AND BRASS
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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. 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. Vehicle wash systems

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. METAL CUTTING SYSTEMS
CNC lathe

16. 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

18. 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.

20. Typical Spa
Pool System

21. 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

22. Complex pipe work
 Makes full draining
difficult.
 Potential dead legs
 Areas for bacteria to
“hide”.
 Corrugated pipes
should be avoided.

23. 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.

24. FOR FURTHER INFORMATION
Contact AKVO Ltd
Tel 0844 244 8726
Or visit www.akvo.co.uk