In general, the important properties are:
1. Conductivity: A measure of water’s
ability to conduct electricity in cooling water. It indicates the amount of
dissolved minerals in water. Conductivity is measured in micro-mhos and can
vary from a few for distilled water to over 10000 for saline water.
2. pH: A measure of acidity or basicity of water. The
pH scale runs from 0 to 14 with 0 representing the maximum acidity and 14, the
maximum basicity.
§ How pH does
affect the system?
Control of pH is critical for the majority of cooling water treatment
programs.
In general, when pH is below recommended ranges, the chances for
corrosion increase and when pH is above recommended ranges, the chances for
scale formation increase. The effectiveness of many biocides also depends on
pH; therefore high or low pHs may alleviate the growth of microbiological
problems.
3) Alkalinity: In cooling water two forms of alkalinity play
a key role. These are carbonate (CO3) alkalinity and bicarbonate
(HCO3) alkalinity. Bicarbonate alkalinity is by far the most common.
Alkalinity and pH are related because increase in pH indicates increases in
alkalinity and vice versa.
§
How does
Alkalinity affect the system?
When water with carbonate or bicarbonate alkalinity is heated, the
alkalinity is broken down to carbon dioxide. The carbon dioxide released,
combines with the water to give carbonic acid, which can cause corrosion of
iron or steel equipment. The corrosion products react further with alkalinity
and the deposits can build up in the same manner as calcium carbonate scale.
4)
Hardness: The hardness in water is the amount of
alkaline-earth cations, calcium and magnesium minerals. The sum of these two is the total hardness.
The hardness of natural waters can vary from a few parts per million (ppm) to
over 800 ppm.
The total hardness is then broken down into two
categories
a)
The carbonate or temporary hardness
b)
The non-carbonate or permanent hardness
§
How does
Hardness affect the system?
Hardness particularly the temporary hardness is the most common and is
responsible for the deposition of calcium carbonate scale in pipes and
equipment.
ü The
other important parameters are:
§ Total Suspended Solids: The measure of
particulate matter suspended in a sample of water or wastewater. After
filtering a sample of a known volume, the filter is dried and weighed to
determine the residue retained. The
amount of suspended solids measured in mg/l
§
Total
Dissolved Solids: This represents all the dissolved constituents for e.g. Ca,
Cl, and Na etc. It is measured in mg/l
§ Total Cations: Represents positive ions, Na+,
Ca++ etc
§ Total Anions: Represents negative ions, SO-4,
Cl-, etc
§ BOD: Signify Biological Oxygen
Demand and is measured in mg/l
§ COD: Chemical Oxygen Demand and
is measured in mg/l
§ TOC: Total Organic Carbon and is
measured in mg/l
§ Total Silica that is measured in
mg/l of SiO2
§ Turbidity: signify suspended matter in water or
wastewater that scatters or otherwise interferes with the passage of light
through the water.
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