Total Dissolved Solids - Environmental Express · Total Dissolved Solids: ... • TDS, or Total...

Total Dissolved Solids:Going From Tedious to TDS

Michael Bechtold, Technical SpecialistDavid Smith Technical DirectorDavid Smith, Technical Director

Total Dissolved Solids (TDS)Total Dissolved Solids (TDS)

Wh t i it d h d it tt ?• What is it and why does it matter?

• 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 or Total Dissolved Solids refers to theTDS, or Total Dissolved Solids, refers to the amount of organic and inorganic dissolved substances that may be found in your watersubstances that may be found in your water.– MineralsMetals– Metals

– SaltsPesti ides– Pesticides


• Principal application of TDS is in the study ofPrincipal 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

h i i f d i kicharacteristic of drinking water.• Aggregate indicator of the presence of a broad array of chemical contaminants.


• Practical implications of TDS:Practical implications of TDS:– Hard water

• Magnesium calcium and variety of other metalsMagnesium, calcium, and variety of other metals• Scale buildup in pipes, valves, and filters• Reduces effectiveness of soapp• Dry, itchy skin• Soap scum


• Practical implications of TDS:Practical implications of TDS:– Water aesthetics

• OdorOdor • Taste• Color• Turbidity


• Practical implications of TDS:Practical implications of TDS:– Life

• Aquatic and terrestrial organismsAquatic and terrestrial organisms

How is it currently being tested?How is it currently being tested?

• Three approved methods:Three approved methods:– SM2540C – 1997ASTM D5907 03– ASTM D5907‐03

– USGS I‐1750‐85

TDS f i t• TDS range of various water sources. – 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 dissolvedquantities 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

1.5m, washed and dried, glass fiber filter.

• Filtrate transferred into an evaporating dish.

• Liquid evaporated to dryness.• Dish and residue heated to

180°C for one hour.180 C 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 resultsconsecutive ± 0.0005 g results.

Why is TDS so tedious?Why is TDS so tedious?

• Weight comparison – sample vs apparatusWeight comparison 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 – most common, least expensive1) Porcelain most common, least expensive2) Platinum – lightest but most expensive3) High‐silica glass

– Porcelain weighs 80 grams on average• 400x – 32,000x difference between sample


• Weight comparison – sample vs apparatusWeight comparison sample vs. apparatus– 400x


• Weight comparison – sample vs apparatusWeight comparison sample vs. apparatus– 32,000x


• Weight comparison – weight stability vsWeight comparison 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


• Weight comparison – weight stability vsWeight comparison weight stability vs. apparatus– 160 000x– 160,000x


• Time to cool crucible to room temperatureTime to cool crucible to room temperature– Takes at least 1 hr to cool to balance temperatureThe 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 weighedtime the sample is weighed


• Washing and preparing crucibles for useWashing and preparing crucibles for use– heat clean dish to 180 ± 2°C for 1 h in an oven. Store in desiccator until needed– Store in desiccator until needed.

– Weigh immediately before use.

StableWeigh™ TDS VesselsStableWeigh TDS Vessels

• Made from a patentedMade from a patented proprietary material that is functional up to 200°Cis functional up to 200 C

• Preconditioned and preweighedpreweighed.

• Holds about 300 mL of lsample


• Vessels weigh around 3 8 gramsVessels 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


• Internal Testing DataInternal 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 Datag– 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 VesselsStableWeigh TDS VesselsASTM D5907‐03:

StableWeigh™ TDS VesselsStableWeigh TDS VesselsStandard Methods 2540 B/CCurrent Requirements:2a.1)Porcelain2)Platinum) h l l3)High‐silica glass

Update:2 O h i l h b i2a.4 Other material shown to be resistant to the sample matrix and weight stable at the required evaporation and drying temperatures.* Aluminum is not appropriate for this purposenot 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 attendingy gQuestions?

800‐745‐8218 Tech Support [email protected]

[email protected]

04/26/2016

Total Dissolved Solids - Environmental Express · Total Dissolved Solids: ... • TDS, or Total...

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