LaMotte LTC3000wi Turbidity & Chlorine Lab Meter - Manual (Page 12)

lose all capacity; they just have less capacity after hundreds of charge
cycles. This unit uses a custom battery assembly that is only available
from LaMotte Company. Battery replacement must be performed at a
LaMotte authorized repair facility. Contact LaMotte Company by phone
(1-800-344-3100) or email ([email protected]) for a return authorization
number.
INTRODUCTION
 TURBIDITY
WHAT IS TURBIDITY?
Turbidity is an aggregate property of the solution, which is water in most
cases. Turbidity is not specifi c to the types of particles in the water.
The particles could be suspended or colloidal matter, and they can
be inorganic, organic, or biological. At high concentrations, turbidity
is perceived as cloudiness, haze, or an absence of clarity in the water.
Turbidity is an optical property that results when light passing through
a liquid sample is scattered. The scattering of light results in a change
in the direction of the light passing through the liquid. This is most
often caused when the light strikes particles in solution and is scattered
backward, sideways and forward. If the turbidity is low, much of the light
will continue in the original direction. Light scattered by the particles
allows the particle to be ”seen” or detected in solution, just as sunlight
allows dust particles in the air to be seen.
In the past 10 years, turbidity has become more than just a measure
of water clarity. Because of the emergence of pathogens such as
Cryptosporidium and Giardia, turbidity now holds the key to assuring
proper water fi ltration. In 1998, the EPA published the IESWTR (interim
enhanced surface water treatment rule) mandating turbidities in
combined fi lter effl uent to read at or below 0.3 NTU. By doing so, the
EPA hoped to achieve a 2 log (99%) removal of Cryptosporidium. There
is presently consideration to lower this to 0.1 NTU. The trend has been
to check the calibration of on-line turbidimeters with hand-held fi eld
units. The optical design and low detection limit of the LTC3000we/wi
allows very accurate readings for such calibrations.
The meter also allows the user to choose the units of measure for
expressing turbidity. While nephelometric turbidity unit (NTU) has
been the standard for years, FNU (formazin nephelometric unit) and
FAU (formazin attenuation unit) are now being used in ISO 7027 units.
American Society of Brewing Chemists (ASBC) units and European
Brewery Convention (EBC) units allow the brewing industry to check
process waters.
HOW IS TURBIDITY MEASURED?
Turbidity is measured by detecting and quantifying the scattering of light
in water (solution). Turbidity can be measured in many ways. There are
visual methods and instrumental methods. Visual methods are more
suitable for samples with high turbidity. Instrumental methods can be
used on samples with both high and low levels of turbidity.
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