-7-
For more than 5 units of turbidity, when the water is mildly turbid (<30 units of turbidity),
a double dose of sodium hypochlorite can be used, and when the water is even more turbid
(>30 units of turbidity), it must be filtered and/or decanted and then disinfected with a
double dose of sodium hypochlorite.
However, it is absolutely necessary to verify that
residual chlorine remains in the water 30 minutes after disinfection (see chapter 10)
.
If it is not possible to use a turbidity meter, we suggest an alternative, though imprecise,
method to measure turbidity.
To determine whether the water can be used to
produce sodium hypochlorite or to chlorinate
drinking water, fill a water bottle to the height
of this manual when it is open and in a vertical
position
1
. Then place the bottle over the
WATA
®
logo and look at it from above through
the bottle
2
. If you can read the WATA
®
logo through the water, this means the water
measures less than 5 units of turbidity.
W
There should be ample illumination but the light should not be blinding. The bottle
should be transparent, colourless, clear and without scratches or dirt. A flat-
bottomed bottle is preferable. Since it is not always possible to meet all of these
conditions, catching a slight glimpse of the WATA
®
logo is acceptable.
W
Regularly check production
Production should be checked at least every hour or more frequently. Watch for bubbles in
the solution; this is proof that electrolysis is working properly. Make sure that the power
supply does not overheat. Check the temperature of the solution. A high temperature
causes a loss of efficiency during the production of active chlorine. If there is a possibility
that dust or other substances could fall into the solution, cover it with a mosquito net
type lid. This will allow the gas to escape and, if the area is well ventilated, to dissipate.
W
Precautions
Do not bend the power cables.
W
Maintenance and repair
Do not attempt to perform electrical repairs if you are not competent to do so. Contact
Antenna or a specialist who will help you or refer you to appropriate services. If the
power supply or device is defective, we recommend to dispose them in proper treatment
plants, for appropriate recycling.
W
Failure to comply with the operating instructions described in this manual will void
the warranty.
4. WATER QUALITY
The initial quality of the water used affects the efficiency of the sodium hypochlorite
production and the efficacy of the water disinfection. The main parameters characterizing
the initial quality required for the water are pH and turbidity.
PH
The pH is a measure of a solution’s acidity or alkalinity on a scale from 0 to 14, with a
pH of 7 indicating a neutral solution (such as pure water), <7 indicating an acid solution
(such as lemon juice) and >7 indicating an alkaline solution (such as soap). The pH affects
chlorine’s ability to destroy microbes and viruses. Based on World Health Organization
recommendations
*
, to effectively disinfect water with sodium hypochlorite, the water used
should have a pH between 6.5 and 8.5. It is therefore recommended to measure pH.
TURBIDITY
Turbidity measures the opacity of a liquid. Turbidity of water is caused by the presence of solid
particles in suspension (clay, sand, bacteria, chemical or metallic residues, etc.) that make
the water cloudy. Water with an elevated turbidity could lead to the formation of undesirable
products during the production of sodium hypochlorite. During the chlorination process,
elevated turbidity could diminish the treatment’s efficacy. Following recommendations in
the Sphère Handbook
**
, to guarantee optimal efficiency in producing sodium hypochlorite
and chlorinating drinking water,
the water used should measure less than 5 units of
turbidity (NTU)
.
1
2
*
WHO, 2011, Guidelines for Drinking-water Quality - Fourth edition, p227
**
Sphère Handbook, 2011, p100
