Total Dissolved Solids:

Transcription

1 Total Dissolved Solids: Going From Tedious to TDS Michael Bechtold, Technical Specialist David Smith, Technical Director

2 Total Dissolved Solids (TDS) What is it and why does it matter? How is it currently being tested? Why is TDS so tedious? New products that alleviate these frustrations.

3 What is it and why does it matter? TDS, or Total Dissolved Solids, refers to the amount of organic and inorganic dissolved substances that may be found in your water. Minerals Metals Salts Pesticidesides

4 What is it and why does it matter? Principal application of TDS is in the study of water quality for streams, rivers, and lakes. Not generally considered a primary pollutant. Used as an indication of aesthetic characteristic i of drinking di water. Aggregate indicator of the presence of a broad array of chemical contaminants.

5 What is it and why does it matter? Practical implications of TDS: Hard water Magnesium, calcium, and variety of other metals Scale buildup in pipes, valves, and filters Reduces effectiveness of soap Dry, itchy skin Soap scum

6 What is it and why does it matter?

7 What is it and why does it matter?

8 What is it and why does it matter?

9 What is it and why does it matter?

10 What is it and why does it matter?

11 What is it and why does it matter?

12 What is it and why does it matter? Practical implications of TDS: Water aesthetics Odor Taste Color Turbidity

13 What is it and why does it matter?

14 What is it and why does it matter?

15 What is it and why does it matter?

16 What is it and why does it matter? Practical implications of TDS: Life Aquatic and terrestrial organisms

17 How is it currently being tested? Three approved methods: SM2540C 1997 ASTM D USGS I TDS range of various water sources. Ocean water 30,000 40,000 mg/l TDS Fresh Water mg/l TDS Drinking Water <300 mg/l TDS Laboratory grade water <10 mg/l TDS

18 How is it currently being tested? TDS meter Digital or analog meters that measure the electrical conductivity or water. Estimate what the true TDS levels might be. Use conversion factors to account for different quantities of dissolved substances. Not approved for reporting purposes

19 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 for one hour. Dish and residue cooled to room temperature and weighed onbalance. Repeat cycle of 180 C heating, cooling, and weighing until two consecutive ± g results.

20 Why is TDS so tedious? Weight comparison sample vs. apparatus Method approved sample yield mg. Currently approved TDS apparatuses set forth in SM 2540B. 2a ) Porcelain 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

21 Why is TDS so tedious? Weight comparison sample vs. apparatus 400x

22 Why is TDS so tedious? Weight comparison sample vs. apparatus 32,000x

23 Why is TDS so tedious? Weight comparison weight stability vs. apparatus Porcelain is a porous material and gains weight ± g relative to 80 g porcelain crucible 160,000X difference

24 Why is TDS so tedious? Weight comparison weight stability vs. apparatus 160,000x 000x

25 Why is TDS so tedious? 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 allow the same cooling/desiccating time each time the sample is weighed

26 Why is TDS so tedious? Washing and preparing crucibles for use heat clean dish to 180 ±2 C for 1 h in an oven. Storein desiccator until needed. Weigh immediately before use.

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29 StableWeigh TDS Vessels Made from a patented proprietary material that is functional up to 200 C Preconditioned and preweighed. Holds about 300 ml of sample

30 StableWeigh TDS Vessels

31 StableWeigh TDS Vessels

32 StableWeigh TDS Vessels

33 StableWeigh TDS Vessels

34 StableWeigh TDS Vessels StableWeigh TDS Vessels

35 StableWeigh TDS Vessels Vessels weigh around grams About 20x less than a crucible Weight stable to ± g Less reweighing Cools to balance temperature in 15 minutes. Ready to use out of box Disposable

36 StableWeigh TDS Vessels Internal Testing Data 5 mg standard; 106.5%, 4.43 std. dev. 10 mg standard; 106.0%, 4.24 std. dev. 50 mg standard; 101.8%, 0.60 std. dev. 100 mg standard; 102.6% 0.34 std. dev. 200 mg standard; 101.9% 0.43 std. dev. External Testing Data 20 mg standard; 100.3%, 1.72 std. dev. 100 mg standard; 100.0%, 0.52 std. dev.

37 what about method compliance?

38 StableWeigh TDS Vessels ASTM D :

39 StableWeigh TDS Vessels Standard Methods 2540 B/C Current Requirements: 2a.1)Porcelain 2)Platinum 3)High silica glass Update: 2a.4 Oh Other material ilshown to be resistant to the sample matrix and weight stable at the required evaporation and drying temperatures.* Aluminum is not appropriate for this purpose. *Environmental Express StableWeigh or other products giving demonstrably equivalent results to the proscribed crucibles.

40 Samples available for trials. TDS100S 5 pack of vessels to work with. Also applicable to total solids, all the same regulatory statements apply.

41 Thank you for attending Questions? Tech Support Line 04/26/2016