Total Dissolved Solids:
Going From Tedious to TDS
Michael Bechtold, Technical Specialist
David Smith
Smith, Technical Director
Total Dissolved Solids (TDS)
Total Dissolved Solids (TDS)
• What is it and why does it matter?
Wh t i it d h d
it tt ?
• How is it currently being tested?
How is it currently being tested?
• Why is TDS so tedious?
y
• New products that alleviate these frustrations.
What is it and why does it matter?
What is it and why does it matter?
• TDS
TDS, or Total Dissolved Solids, refers to the or Total Dissolved Solids refers to the
amount of organic and inorganic dissolved substances that may be found in your water
substances that may be found in your water.
– Minerals
– Metals
– Salts
– Pesticides
Pesti ides
What is it and why does it matter?
What is it and why does it matter?
• Principal
Principal application of TDS is in the study of application of TDS is in the study of
water quality for streams, rivers, and lakes. • Not generally considered a primary pollutant.
Not generally considered a primary pollutant
• Used as an indication of aesthetic characteristic of drinking water.
h
i i f d i ki
• Aggregate indicator of the presence of a broad array of chemical contaminants.
What is it and why does it matter?
What is it and why does it matter?
• Practical implications of TDS:
Practical implications of TDS:
– Hard water
•
•
•
•
•
Magnesium, calcium, and variety of other metals
Magnesium
calcium and variety of other metals
Scale buildup in pipes, valves, and filters
p
Reduces effectiveness of soap
Dry, itchy skin
Soap scum
What is it and why does it matter?
What is it and why does it matter?
What is it and why does it matter?
What is it and why does it matter?
What is it and why does it matter?
What is it and why does it matter?
What is it and why does it matter?
What is it and why does it matter?
What is it and why does it matter?
What is it and why does it matter?
What is it and why does it matter?
What is it and why does it matter?
What is it and why does it matter?
What is it and why does it matter?
• Practical implications of TDS:
Practical implications of TDS:
– Water aesthetics
•
•
•
•
Odor
Odor Taste
Color
Turbidity What is it and why does it matter?
What is it and why does it matter?
What is it and why does it matter?
What is it and why does it matter?
What is it and why does it matter?
What is it and why does it matter?
What is it and why does it matter?
What is it and why does it matter?
• Practical implications of TDS:
Practical implications of TDS:
– Life
• Aquatic and terrestrial organisms
Aquatic and terrestrial organisms
How is it currently being tested?
How is it currently being tested?
• Three approved methods:
Three approved methods:
– SM2540C – 1997
– ASTM D5907‐03
ASTM D5907 03
– USGS I‐1750‐85
• TDS range of various water sources. TDS
f i
t
–
–
–
–
Ocean water – 30,000‐40,000 mg/L TDS
Fresh Water – 100‐500 mg/L TDS
Drinking Water – <300 mg/L TDS
Laboratory grade water – <10 mg/L TDS
How is it currently being tested?
How is it currently being tested?
• TDS meter
– Digital or analog meters that measure the electrical conductivity or water.
conductivity or water.
– Estimate what the true TDS levels might be.
– Use conversion factors to account for different quantities of dissolved
quantities of dissolved substances.
– Not approved for reporting purposes
How is it currently being tested?
How is it currently being tested?
• Sample is filtered through a 1.5m, washed and dried, glass fiber filter.
• Filtrate transferred into an evaporating dish.
• Liquid evaporated to dryness.
• Dish and residue heated to 180°C
180
C for one hour.
for one hour.
• Dish and residue cooled to room temperature and weighed on balance.
weighed on balance.
• Repeat cycle of 180°C heating, cooling, and weighing until two consecutive ± 0.0005 g results.
consecutive ±
0 0005 g results
Why is TDS so tedious?
Why is TDS so tedious?
• Weight comparison Weight comparison – sample vs. apparatus
sample vs apparatus
– Method approved sample yield 2.5‐200 mg.
– Currently approved TDS apparatuses set forth in Currently approved TDS apparatuses set forth in
SM 2540B. 2a. 1‐3.
1) Porcelain
Porcelain – most common, least expensive
most common, least expensive
2) Platinum – lightest but most expensive
3) High‐silica glass
– Porcelain weighs 80 grams on average
• 400x – 32,000x difference between sample
Why is TDS so tedious?
Why is TDS so tedious?
• Weight comparison Weight comparison – sample vs. apparatus
sample vs apparatus
– 400x
Why is TDS so tedious?
Why is TDS so tedious?
• Weight comparison Weight comparison – sample vs. apparatus
sample vs apparatus
– 32,000x
Why is TDS so tedious?
Why is TDS so tedious?
• Weight
Weight comparison comparison – weight stability vs. weight stability vs
apparatus
– Porcelain is a porous material and gains weight
Porcelain is a porous material and gains weight
– ±0.0005 g – relative to 80 g porcelain crucible
•160,000X difference
Why is TDS so tedious?
Why is TDS so tedious?
• Weight
Weight comparison comparison – weight stability vs. weight stability vs
apparatus
– 160,000x 160 000x
Why is TDS so tedious?
Why is TDS so tedious?
• Time to cool crucible to room temperature
Time to cool crucible to room temperature
– Takes at least 1 hr to cool to balance temperature
– The best way to achieve consistent results is to The best way to achieve consistent results is to
allow the same cooling/desiccating time each time the sample is weighed
time the sample is weighed
Why is TDS so tedious?
Why is TDS so tedious?
• Washing and preparing crucibles for use
Washing and preparing crucibles for use
– heat clean dish to 180 ± 2°C for 1 h in an oven. – Store in desiccator
Store in desiccator until needed. until needed
– Weigh immediately before use.
StableWeigh™ TDS Vessels
StableWeigh
TDS Vessels
• Made
Made from a patented from a patented
proprietary material that is functional up to 200°C
is functional up to 200
C
• Preconditioned and preweighed.
preweighed
• Holds about 300 mL of sample
l
StableWeigh™ TDS Vessels
StableWeigh
TDS Vessels
StableWeigh™ TDS Vessels
StableWeigh
TDS Vessels
StableWeigh™ TDS Vessels
StableWeigh
TDS Vessels
StableWeigh™ TDS Vessels
StableWeigh
TDS Vessels
StableWeigh™ TDS Vessels
StableWeigh
TDS Vessels
StableWeigh™ TDS Vessels
StableWeigh
TDS Vessels
• Vessels weigh around 3.8 grams
Vessels weigh around 3 8 grams
– About 20x less than a crucible
• Weight stable to ±0.0005 g Weight stable to ±0 0005 g
– Less reweighing
• Cools to balance temperature in 15 minutes.
• Ready to use out of box
• Disposable StableWeigh™ TDS Vessels
StableWeigh
TDS Vessels
• Internal Testing Data
Internal Testing Data
– 5 mg standard; 106.5%, 4.43 std. dev.
– 10 mg standard; 106.0%, 4.24 std. dev.
g
;
,
– 50 mg standard; 101.8%, 0.60 std. dev.
– 100 mg standard; 102.6% 0.34 std. dev.
g
;
– 200 mg standard; 101.9% 0.43 std. dev.
• External Testing Data
g
– 20 mg standard; 100.3%, 1.72 std. dev.
– 100 mg standard; 100.0%, 0.52 std. dev.
g
…what about method compliance?
StableWeigh™ TDS Vessels
StableWeigh
TDS Vessels
ASTM D5907‐03:
StableWeigh™ TDS Vessels
StableWeigh
TDS Vessels
Standard Methods 2540 B/C
Current Requirements:
2a.1)Porcelain
2)Platinum
3)High‐silica glass
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l
Update:
2a.4 Other material shown to be resistant to 2
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i l h
b
i
the sample matrix and weight stable at the required evaporation and drying temperatures.* Aluminum is not appropriate for this purpose.
appropriate for this purpose
*Environmental Express StableWeigh or other products giving demonstrably equivalent results to the proscribed crucibles.
Samples available for trials. TDS100S – 5 pack of vessels to work with. Also applicable to total solids, all the same regulatory statements apply.
Thank you for attending
y
g
Questions?
800‐745‐8218 Tech Support Line
[email protected]
[email protected]
04/26/2016