Conductivity
Total Dissolved Solids
WQT 134
Aquatic Chemistry II
Standard Methods 20th ed
#2510 Conductivity
Week Objectives
Reading assignment:
American Public Health Association (APHA), American Water Works Association
(AWWA) & Water Environment Federation (WEF). 1999. Standard Methods for
the Examination of Water and Wastewater, 20th edition
1. Understand the role and function of conductivity in
water treatment.
2. Understand how to measure conductivity (SM
#2510)
•
Relate conductivity to total dissolved solids
The conductivity of the source
water indicates the quantity of
dissolved material present.
Fa
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0%
Tr
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1. True
2. False
100%
Conductivity #2510
What is conductivity?
•This test is designed to determine if the sample can carry an
electrical current via the movement of ions. This ability
depends on the presence of ions; on their total
concentration, mobility, and valence; and on the temperature
of measurement. Conductivity
is an indication of
the quantity of ions contained in a solution
Why do we care?
•Dissolved ions/substances/electrolytes in water
•Determine the presence of salt water intrusion
•Used for WQ in pipelines, channels, flowing
streams, and lakes
Conductivity #2510
What are the units and conversions?
•Conductivity is customarily reported in micromhos per
centimeter (μmho/cm). The electrical measurement of
conductivity is the inverse (reciprocal) of ohms (1/ohms) or
mhos.
•In the International System of Units (SI) the reciprocal of the
ohm is the siemens (S) and conductivity is reported as
millisiemens per meter (mS/m)
•1/ohm = 1 mho = 1 Siemen
•1000 micromhos/cm = 1000microSiemens/cm(μS/cm)
Conductivity #2510
What are disadvantages of the procedure?
Conductivities greater than 10,000 to 50,000 μmho/cm or
less than about 10 μmho/cm may be difficult to measure with
usual measurement electronics and cell capacitance.
Conductivity #2510
What are typical values in nature?
Range
 Pure Water
0.05 μS/cm
 Demineralized Water
0.1 to 1.0 μS/cm
 Distilled water
1 to 10 μS/cm
 Tap Water
100 to 1000 μS/cm
 Potable water
50 to 1500 μmhos/cm.
 Industrial wastes
1000 to 10,000 μS/cm
• Seawater
30,000 to 50,000 μS/cm
• 5% Sodium Chloride Solution 70,000 μS/cm
• 10% Sulfuric Acid Solution 140,000μS/cm
Conductivity and Total
Dissolved Solids #2510
TDS (Total Dissolved Solids): is the amount of
solids dissolved in a water sample.
SS (Suspended Solids): is the amount of solids
that have not dissolved into a water sample,
or solids that are insoluble in water.
TS (Total Solids) = TDS + SS.
What does TDS stand for?
1. Total dissolved solids
2. Temporarily dissolved
solids
3. Total disaggregated
solids
4. Total dissolved salts
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Total solids can be divided into
suspended solids and ________
solids.
83%
Colloidal
Dissolved
Settleable
Filterable
17%
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The total solids in water would
be a combination of:
1. Fixed solids and
settleable solids
2. Dissolved solids and
volatile solids
3. Dissolved solids and
suspended solids
4. Suspended solids and
fixed solids
5. Fixed solids and
dissolved solids
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Conductivity and Total
Dissolved Solids #2510
•Estimate total dissolved solids (mg/L) in a
sample by multiplying conductivity (in
micromhos per centimeter) by an empirical factor
(Conversion done on Hach Probe).
•This factor may vary from 0.55 to 0.9, depending
on the soluble components of the water and on
the temperature of measurement.
•Linear in dilute systems
Suspended solids, also referred
to as filterable residue, represent
the weight of solids remaining
on a glass fiber filter following
filtration and drying at ___
degrees C.
83%
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1.
2.
3.
4.
___________ solids remain in
liquid solution and are defined
as the solids that will pass
through a 0.45um membrane
filter.
Suspended
Colloidal
Dissolved
Settleable
67%
17% 17%
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__________ solids, extremely
fine particles, will not settle from
the liquid portion, but can
usually be filtered from the liquid
with a 0.45-um membrane filter.
83%
Dissolved
Colloidal
Suspended
Settleable
17%
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If the residue remaining on a
filter paper is the suspended
solids, these are the solids that
pass through the filter.
100%
Dissolved (TDS)
Volatile
Non-volatile
Settleable
0%
0%
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Conductivity #2510
Summary?
 Conductivity not impacted by pH
 Conductivity impacted by dissolved solids/sulfate
 Conductivity/Resistance increases with increasing
temperature.