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most common. Here, too, convenient packaging and simplicity are the key to
portability and accuracy. This method is preferred in determining corrosion
to water supplies, and offers the operator an easy, inexpensive approach to
meeting lead/copper requirements.
Turbidimetric Method
Some test procedures do not use color as a way to determine results. In-
stead, a sample is taken and a reagent is added which produces turbidity or
cloudiness in the sample. The greater the turbidity, the greater the concentra-
tion. As with the colorimetric method, turbidimetric results can be “read” us-
ing a visual comparator, or by the use of a colourimeter. Results are ex-
pressed in ppms or mg/L. Typical tests using this method are those for potas-
sium and sulfates. Again, the mechanism employing this method can be to-
tally portable and conveniently packaged as a kit.
Electrometric Method
One of the most commonly used: an electrode is inserted into a sample.
A small current or voltage is produced and electronically amplified and read
on a meter scale. Typical tests of this sort are for pH and conductivity, but a
variety of substances can be measured using ion specific electrodes (ISE), in-
cluding calcium,
nitrates, chlorine.
Generally, electrometric methods are initially quite costly and they re-
quire a high degree of care and maintenance because of the electrode sys-
tems.
Nephlometric Method
This method is specifically for measuring water turbidity. Suspended
matter within a sample is measured via a specially designed meter which
sends a focused light beam through the water sample. Suspended solids, dirt,
and silt scatter the light. The scattering is measured by a photodiode at a 90°
angle incident to the light source. Results are expressed as Nephlometric
Turbidity Units (NTU’s), and are more qualitative than quantitative.
Portable battery-powered units are available for field use. Private and
municipal water treatment systems using surface water supplies such as
lakes, streams, etc. are required to measure turbidity routinely as a guide to
monitoring various water treatment systems like settling basins and sand fil-
ter performance. Continuous monitoring turbidity meters and recorders are
becoming the rule rather than the exception.
Gravimetric Test Methods
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