In-Situ TROLL 9500 Operators Manual - Manual (Page 115)

110
Multi-Parameter
Water Quality TROLL ®
TROLL 9500 Operator’s Manual 0095110 rev. 007 01/09
16 CHLORIDE
WHAT IS CHLORIDE?
Chloride (Cl – ) is a highly soluble ion in water and can potentially be
present in high concentrations. Chloride enters the water supply when
runoff from rain or irrigation dissolves a variety of chloride-containing
salts in rock and soil. Freshwater sources, streams, lakes, and un-
derground aquifers typically have less than 10 ppm Cl
– . Some waters
with as little as 250 ppm Cl – will taste salty to sensitive individuals,
especially if the sodium cation (Na + ) is also present. Wastewater from
sewage or industrial facilities will normally contain higher amounts of
chloride. Chloride is naturally present in higher concentrations near
coastal areas where it can infiltrate canals and sewers.
WHY MEASURE CHLORIDE?
Chloride ions are not toxic to humans. However, a high chloride
content may harm some structures, especially those made of metal.
Chloride can increase the rate of corrosion on metals in the presence
of water. Vegetation is also sensitive to the amount of chloride in the
soil. Agriculturally productive soils can be turned into unproductive
wastelands over a period of time by irrigating with water containing
high amounts of chloride. The WHO (World Health Organization) has
established 100 ppm Cl
– as a maximum for water used for irrigation,
while 250 ppm Cl – is the maximum for drinking water.
THE CHLORIDE SENSOR
The In-Situ sensor is an ion-selective electrode (ISE) that is selective
for the chloride ion (Cl
– ). It is a double-junction combination ISE with a
silver/silver-chloride reference half-cell, solid-state sensing electrode,
and reference electrolyte gel. It measures the concentration in parts
per million of chloride ion in solution (ppm Cl
– ).
SENSOR PREPARATION
To insure the chloride sensor is thoroughly hydrated, soak it in distilled
water for about 15 minutes before installation. The sensor kit includes
an empty bottle for this purpose. Unlike the ammonium and nitrate
sensors, the solid-state chloride sensor does not require soaking in a
solution of specific concentration.
SENSOR INSTALLATION
Unpack the chloride sensor, hydrate it as described above, and install
in port 1, 2, or 3 in the sensor block at the front end of the MP TROLL
9500 as follows.
TIP: Remember that a polarographic D.O. sensor (if present)
will operate properly only in port 2, and a turbidity wiper
accessory only in port 3 .
1. Remove the restrictor from the front end of the MP TROLL 9500.
This allows access to the sensor block depicted in the drawing
below.
Fresh water < 10 ppm Cl –
Sea water 20,000 ppm Cl –
Irrigation water standard (WHO) 100 ppm Cl –
Drinking water standard (WHO) 250 ppm Cl –
Typical Chloride values
Pressure/turbidity
(or plug)
Temperature
Chloride sensor may be installed
in port 1, 2, or 3
alignment mark