Embed Size (px)
Citation preview
Total Solids Environmental Express StableWeigh™ Analytical Testing Vessels Method Equivalency Report
Dr. Edward F. Askew
January 11, 2017
Page | 2
Table of Contents Abstract ........................................................................................................................................... 5
Introduction ..................................................................................................................................... 6
Historical Review of Total Solids (Residue) Methods ................................................................... 6
Table 1: Summary of Total Solids Methods in Standard Methods for the Examination of Water and Wastewater ........................................................................................................ 7
TS Method Changes in Standard Methods for the Examination of Water and Wastewater........... 8
Definitions....................................................................................................................................... 9
Environmental Express StableWeigh System: Meeting USEPA TS Testing Requirements .......... 9
Environmental Express StableWeigh Vessels and Support Supplies ........................................... 10
Comparison and Review of Traditional TS Analyses Compared to StableWeigh TS ................. 12
Precision of Analyses ................................................................................................................. 12
Standard Methods QC Requirements.................................................................................... 12
Analytical QC Results........................................................................................................... 13
Table 2: StableWeigh and Porcelain Evaporation Dish Precision .................................... 15
Table 3: StableWeigh Laboratory Reagent Blank Percent Variance ................................ 16
StableWeigh Method Equivalency ............................................................................................. 26
StableWeigh 3-D Drying vs. Evaporation Dish 2-D Drying Mechanisms ................................ 26
StableWeigh Vessel Thermal Stability ....................................................................................... 26
Time to Thermal Equilibrium ..................................................................................................... 26
Labor and Material Costs for TS Analysis ................................................................................. 27
Table 4: Porcelain Evaporation Dish Lifetime Costs for Total Solids ............................. 28
Summary and Conclusion ............................................................................................................. 29
References ..................................................................................................................................... 30
Appendixes ................................................................................................................................... 31
Appendix 1: StableWeigh and Porcelain Evaporation Dish Study Data .................................... 32
Table A1: LRB Stable Weigh Blank, Oven ...................................................................... 33
Table A2: LRB Stable Weigh Blank, Hot Block .............................................................. 34
Table A3: LFB Low Inorganic Standard TS Stable Weigh Oven .................................... 35
Table A4: LFB Low Inorganic Standard TS Stable Weigh Hot Block ............................ 36
Table A5: LFB Low Inorganic Standard TS Evaporation Dish ....................................... 37
Page | 3
Table A6: LFB High Inorganic Standard TS Stable Weigh Oven.................................... 38
Table A7: LFB High Inorganic Standard TS Stable Weigh Hot Block ............................ 39
Table A8: LFB High Inorganic Standard TS Evaporation Dish ....................................... 40
Table A9: Biosolids, Drying Oven, Stable Weigh ............................................................ 41
Table A10: Biosolids, Hot Block, Stable Weigh .............................................................. 42
Table A11: Biosolids, Drying Oven, Evaporation Dish ................................................... 43
Appendix 2: Redding Equivalent Method Check Off Table ...................................................... 44
EPA Method Equivalency Check-Off Table from Richard Redding Memo, Flexibility to Modify CWA Methods, 2007 ........................................................................................... 45
Page | 4
Table of Figures
Figure 1: StableWeigh Total Solids Disposable Vessel ............................................................... 10
Figure 2: StableWeigh Hot Block ................................................................................................. 11
Figure 3: StableWeigh Modular Rack, 5-Place ............................................................................ 11
Figure 4: StableWeigh Weighing Bracket .................................................................................... 12
Figure 5: LFB IDC Low Inorganic Standard TS Stable Weigh Oven .......................................... 17
Figure 6: LFB IDC Low Inorganic Standard TS Stable Weigh Hot Block .................................. 18
Figure 7: LFB IDC Low Inorganic Standard TS Evaporation Dish ............................................. 19
Figure 8: LFB IDC High Inorganic Standard TS Stable Weigh Oven ......................................... 20
Figure 9: LFB IDC High Inorganic Standard TS Stable Weigh Hot Block ................................. 21
Figure 10: LFB IDC Low Inorganic Standard TS Evaporation Dish ........................................... 22
Figure 11: IDC Biosolids, Drying Oven, Stable Weigh ............................................................... 23
Figure 12: IDC Biosolids, Hot Block, Stable Weigh .................................................................... 24
Figure 13: High Inorganic Standard Averages vs. Standard Value .............................................. 25
Page | 5
Abstract
This report summarizes the evaluation of the StableWeigh™ vessel and system for Total Solids determination under the Clean Water Act rules in 40 CFR part 136. Data from multiple Total Solids (TS) concentrations were collected. The results for the StableWeigh vessels Quality Control (QC) met the requirements of Standard Methods for the Examination of Water and Wastewater (SM) 2540 B TS and were more precise and accurate than the traditional porcelain evaporation dish. As the StableWeigh vessel dries in a 3D manner, crusting seen in evaporation dishes was not seen. Data collected at weights at almost four (4) times the maximum weight limit of 200 mg set in SM 2540 B showed that the StableWeigh system could meet the requirements of two consecutive weight difference of ≤ 05 mg. This was even seen with biosolids from a wastewater anaerobic digester. Evaluation of the thermal stability and cooling time results shows that the StableWeigh system reduces the overall time and labor to complete a TS test. Review of the labor costs for just maintaining the traditional porcelain evaporation dish indicates significant labor and cost recovery utilizing the StableWeigh disposable vessel.
Page | 6
Introduction
This report summarizes the evaluation of the StableWeigh™ vessel and system. It has produced results that show it reduces the amount of time spent preparing, weighing, cooling, and cleaning the laboratory Total Solids (TS) equipment. The StableWeigh vessels Quality Control (QC) results met the requirements of Standard Methods for the Examination of Water and Wastewater 2540 B TS and were more precise and accurate than the traditional porcelain evaporation dish.[1, 2]
Data collected at weights at almost four (4) times the maximum weight limit of 200 mg set in SM 2540 B showed that the StableWeigh system could meet the requirements of two consecutive weight difference of ≤ 05 mg. This was even seen with biosolids from a wastewater anaerobic digester.
Review of the labor costs for just maintaining the traditional porcelain evaporation dish shows significant labor and cost recovery of utilizing the StableWeigh disposable vessel.
Historical Review of Total Solids (Residue) Methods
Historically TS have been recognized as a water use (quality) measurement over the last 3 centuries, though the analytical chemistry that defines what is a solid is constantly changing.[3] TS is defined as the residue left after drying at a constant temperature [1, 2, 4, 5].
The TS residue method is defined by the United States Environmental Protection Agency (USEPA) as a Method Defined Analyte (MDA). The MDA relies on descriptive results, mass of residue, for the analyte measured. The TS determined by this method is only the mass of analyte that is stable after a set period of drying between 103 °C to 105°C.
The current USEPA approved method for TS can be found in Standard Methods for the Examination of Water and Wastewater (SM). [1, 2] SM has been a consensus method organization for over 3 centuries (1895-Present) and has focused on developing analytical methods that are Standard to the profession. A Standard method is defined by the SM editorial board as "the best current practice of American water analysts". As these current practices have changed over time, a summary of these changes is provided in Table 1 below.
Page | 7
Table 1: Summary of Total Solids Methods in Standard Methods for the Examination of Water and Wastewater
SM Edition Water Drying Temperature
1st 1905 103 ºC
3rd
1917 103 ºC or 180 ºC
6th 1925 180 ºC
7th 1933 103 ºC
8th 1936 103 ºC
9th 1946 103 ºC
10th 1955 103-105 ºC
11th 1960 103-105 ºC or 179-181 ºC
12th 1965 103-105 ºC or 179-181 ºC
13th 1971 103-105 ºC or 179-181 ºC
17th 1989 2540 B 103-105 ºC
18th 1992 2540 B 103-105 ºC
20th 1998 2540 B 103-105 ºC
Page | 8
TS Method Changes in Standard Methods for the Examination of Water and Wastewater
The main analytical differences that can be seen in Table 1 are:
1. 1st edition TS is dried at 103 °C.
2. 3rd edition TS temperature is either 103 °C or 180°C.
3. 6th edition is only 180°C.
4. 7th through the 9th editions drops the temperature back to 103 °C.
5. 10th edition allows a temperature bracket of 103-105 ºC.
6. The 11th through the 13th editions have two temperature brackets 103-105 ºC or 179-181 ºC.
7. From the 17th edition to the current 22nd edition, the temperature bracket is 103-105 ºC. This is the current temperature bracket in the 40 CFR part 136 promulgated Standard Methods method.
Page | 9
Definitions
1. Detection Limit (DL), also called Method Detection Limit (MDL) -: The minimum concentration of an analyte that can be identified, measured, and reported with 99% confidence that the analyte concentration is greater than zero.
2. Laboratory Fortified Blank (LFB) - An aliquot of reagent water or other blank matrix to which known quantities of the method analytes and all the preservation compounds are added. The LFB is processed and analyzed exactly like a sample, and its purpose is to determine whether the methodology is in control, and whether the laboratory is capable of making accurate and precise measurements.
3. Laboratory Matrix/Duplicate (LM/LMD) also called Matrix / Duplicate (M/D): An aliquot of an environmental sample and a duplicate which are analyzed and its purpose is to determine whether the sample matrix contributes bias to the analytical results.
4. Laboratory Reagent Blank (LRB) - A volume of reagent water or other blank matrix that is processed exactly as a sample including exposure to all glassware and equipment, that are used in the analysis batches. The LRB is used to determine if the method analytes or other interferences are present in the laboratory environment, the reagents, or the apparatus.
5. Minimum Reporting Level (MRL) - The minimum concentration that can be reported by a laboratory as a quantitated value for a method analyte in a sample following analysis. This concentration must not be any lower than the concentration of the lowest calibration standard for that instrument.
6. Water Sample: For the purpose of this method, a sample taken from one of the following sources: drinking water, surface water, storm runoff, industrial or domestic wastewater.
Environmental Express StableWeigh System: Meeting USEPA TS Testing Requirements
The traditional TS method requires that
1. A well-mixed sample of known volume transferred to a tared porcelain evaporation dish.
2. The porcelain evaporation dish is then transferred to a steam bath or oven and the water sample is evaporated to dryness at 103-105 ºC.
3. The porcelain evaporation dish is then transferred to a desiccator and allowed to cool to room temperature.
4. The porcelain evaporation dish is then weighed to the nearest 0.1 mg.
5. The porcelain evaporation dish is then returned to an oven and heated to 104 ± 1 ºC for at least 1 hour.
6. The porcelain evaporation dish is then transferred to a desiccator and allowed to cool to room temperature.
Page | 10
7. The porcelain evaporation dish is then weighed to the nearest 0.1 mg.
8. Steps 5-6 are repeated until two consecutive weight differences are less than 4% of previous weight or 0.5 mg, whichever is less.
9. Then the porcelain evaporation dish must then be
a. cleaned,
b. dried at 104 ± 1 ºC,
c. cooled in a desiccator
d. tared and stored in a desiccator
The StableWeigh system provides the following improvements/changes to the traditional TS analyses;
1. Tared fluorinated polymer disposable weighing vessels to take the place of porcelain evaporation dishes.
2. Modular racks to hold vessels in the oven, in the desiccator and at the balance.
3. Modular racks to hold vessels from Hot Block® in the desiccator and at the balance.
4. Weighing bracket to position the vessel on the balance.
Environmental Express StableWeigh Vessels and Support Supplies
Environmental Express StableWeigh TS vessels are fabricated from a thermally inert fluorinated polymer that can sustain an extended period in the drying oven at 105 °C. The StableWeigh vessel comes pre-weighed to 0.1 mg and this weight does not change during the TS test.
Figure 1: StableWeigh Total Solids Disposable Vessel
Page | 11
The StableWeigh system also includes analytical support equipment to allow the laboratory to maximize labor savings. The Hot Block system can be used in lieu of a convection or gravity oven.
Figure 2: StableWeigh Hot Block
Figure 3: StableWeigh Modular Rack, 5-Place
Once the TS sample has been transferred to the StableWeigh vessel it can then be transferred to the Modular Rack. The Modular Rack comes with 5 rows that can be assembled together to fit the depth of your oven or desiccator. The rack helps to easily transport the vessels to the oven or Hot Block, to the desiccator, and finally to the balance.
Page | 12
Figure 4: StableWeigh Weighing Bracket
At the balance, the Weighing Bracket will stabilize the StableWeigh vessel and allow the efficient weighing of the TS sample.
Comparison and Review of Traditional TS Analyses Compared to StableWeigh TS
The data obtained from the study is provided in detail in the appendixes (Appendix 1). Formulas to determine all precision and duplicate analyses can be found in the current edition of Standard Methods for the Examination of Water and Wastewater Parts 1010 and 2020. [1, 2]
Precision of Analyses Standard Methods QC Requirements
The Quality Control (QC) determinations of the Part 2540 B TS analytical results are detailed in Standard Methods for the Examination of Water and Wastewater Parts 1010 and 2020. The requirements are divided into the Initial Quality Control that must be performed to show laboratory and analysts capabilities to determine TS and Ongoing QC.
The Initial Quality Control for most Part 2000 methods in Standard Methods for the Examination of Water and Wastewater require:
1. Initial Demonstration of Capability (IDC) is performed with known Laboratory Fortified Blank (LFB) in which a known amount of analyte is dissolved in water. Sodium Chloride and Celite® was used for the TS LFB. It was dissolved/suspended in DI water and a known aliquot was transferred to a StableWeigh vessel and the TS was determined. This data was then used to set control limits for acceptable data ranges.
Page | 13
2. Method Detection Level (MDL) and Operational Range (OR) are set by the Mettler Toledo balance as 1 mg with a reproducibility of 0.1 mg. As additional aliquots of TS samples can be added to the vessel, the OR will be dependent on the total sample size evaporated.
The Quality Control Table in Part 2020 specifically lists the following Ongoing QC parameter must be determined for the Total Dissolved Solids 2540 C:
1. Method Blank (MB) or Laboratory Reagent Blank (LRB) is performed with DI water. A 100 mL aliquot was transferred to a StableWeigh vessel and the TS was determined. This data was then used compared to set OR limits for acceptable data ranges. For this study TS balance MDL of 1 mg was used.
2. Laboratory Fortified Blank (LFB) is a known amount of analyte dissolved in water. Sodium Chloride and Celite was used for the TS LFB. It was dissolved/suspended in DI water and a known aliquot after filtration was transferred to a StableWeigh vessel and the TS was determined. This data was then compared to IDC control limits for acceptable data ranges.
3. Duplicates are run per each analysis sample set or batch. For this study as the LFBs were analyzed ten (10) times, the minimum and maximum value was used to calculate the Relative Percent Difference (RPD)
4. Wastewater Matrix: Biosolids from a wastewater anaerobic digester were used to challenge the capabilities of the StableWeigh vessel with an organic high TS matrix.
5. Initial Demonstration of Capability for LFB samples is an additional requirement from 40 CFR part 136.7.
Analytical QC Results 1. Figures 5-12 chart the IDC for each batch of StableWeigh vessels at different TS weights,
convection drying oven vs. Hot Block and for porcelain evaporation dishes.
a. IDC was calculated from the data set by:
IDC = Standard Deviation x TT= TwoSidedStudent T-test Value for (n-1) Degrees of Freedom
b. All data points for the inorganic standards (NaCl & Celite) fall within the IDC limits. Theses LFBs show Initial and Ongoing QC at acceptable levels.
c. The StableWeigh values for biosolids had acceptable Initial and Ongoing QC while the porcelain evaporation dishes had a 30% failure due to crusting of the dried sample.
2. Table 2 contains the % RSD and the RPD for each analysis set.
Page | 14
Percent RelativeStandard Deviation= ×100Xs
( )1 2
1 2
1
2
D -D*100 = RPD
D +D2
D = Concentration determined for Highest Sample WeightD = Concentration determined for Lowest sample weight
a. The % RSD increases with the smaller mass sample, which is expected due to small variations in a result’s value impacts lower mass values more that higher mass numbers.
b. The porcelain evaporation dishes had a 30% failure due to crusting of the dried sample and precision was not calculated due to this high rate of sample failure..
c. All StableWeigh results produced % RSD < 4%. 15% RSD has been set as the acceptable variance limit.
d. The StableWeigh duplicate relative percent difference between the maximum and minimum values for each analyses set are well below the standard 20% maximum.
i. That this is seen for the High and Low Inorganic standards and the Organic Biosolids indicates that the StableWeigh vessel can produce valid results with difficult matrices (Biosolids) and at weights almost four times higher than the 200 mg recommended by Standard Methods.
3. Figure 13 charts the values of both the StableWeigh vessels from the convection oven and the Hot Block and porcelain evaporation dish. The average TS value for the StableWeigh vessels showed better agreement with the standard value. The greater variation of the mean compared to the known value for the porcelain evaporation dish indicates less accurate precision.
4. Table 3 contains the StableWeigh percent variance for the LRB for a sample set. The slight variations of the LRB are acceptable.
Page | 15
Table 2: StableWeigh and Porcelain Evaporation Dish Precision
TS Mass Vessel Average Standard Deviation % RSD Duplicate Relative
Percent Difference
58 mg StableWeigh, Oven 56.8 0.6 1.138% 3.866%
58 mg StableWeigh, Hot Block 57.3 0.3 0.495% 1.572%
58 mg Porcelain Evaporation Dish 56.5 1.0 1.710% 5.319%
783 mg StableWeigh, Oven 782.9 2.7 0.342% 1.097%
783 mg StableWeigh, Hot Block 783.4 3.0 0.00384% 1.174%
783 mg Porcelain Evaporation Dish 780.8 2.1 0.273% 0.922%
Biosolids StableWeigh, Oven 719.5 3.9 0.547% 1.640%
Biosolids StableWeigh, Hot Block 705.3 7.1 1.012% 3.289%
Biosolids Porcelain Evaporation Dish ** ** ** **
**: Biosolids in Evaporation Dish crusted over 30% of the samples and no stable weight difference (0.5 mg or less in two consecutive weighing) was achieved.
Page | 16
Table 3: StableWeigh Laboratory Reagent Blank Percent Variance
Sample # 1 2 3 4 5 6 7 8 9 10 Average Standard Deviation
StableWeigh, Oven LRB Weight Difference (%) 0.0154% 0.0335% 0.0050% 0.0027% 0.0162% 0.0108% 0.0108% 0.0000% -0.0054% 0.0218% 0.0111% 0.0114%
StableWeigh, Hot Block LRB Weight Difference (%) 0.0508% 0.0350% 0.0352% 0.0267% 0.0324% 0.0284% 0.0305% 0.0206% 0.0256% 0.0204% 0.0306% 0.0088%
Page | 17
Figure 5: LFB IDC Low Inorganic Standard TS Stable Weigh Oven
Page | 18
Figure 6: LFB IDC Low Inorganic Standard TS Stable Weigh Hot Block
Page | 19
Figure 7: LFB IDC Low Inorganic Standard TS Evaporation Dish
Page | 20
Figure 8: LFB IDC High Inorganic Standard TS Stable Weigh Oven
Page | 21
Figure 9: LFB IDC High Inorganic Standard TS Stable Weigh Hot Block
Page | 22
Figure 10: LFB IDC Low Inorganic Standard TS Evaporation Dish
Page | 23
Figure 11: IDC Biosolids, Drying Oven, Stable Weigh
Page | 24
Figure 12: IDC Biosolids, Hot Block, Stable Weigh
Page | 25
Figure 13: High Inorganic Standard Averages vs. Standard Value
Page | 26
StableWeigh Method Equivalency The StableWeigh system is covered under the method flexibility allowed in the EPA rules 40 CFR part 136.6 [6] The rule lays out the requirements a modified analytical method must meet to be considered equivalent to a promulgated analytical method. These requirements are explained in detail in a memo authored by Richard Redding [7]:
The March 12th Methods Update Rule promulgated 136.6 which allows the regulated community more flexibility that includes:
1. If the underlying chemistry and determinative technique in a modified method are essentially the same.
2. The modified method must be sufficiently sensitive and meet or exceed performance of the approved method.
This method equivalency report for the StableWeigh system provide in the appendixes a check off table of all equivalency requirements listed in the Redding memo. The LRB, IDC-LFB, Duplicate RPD and % RSD all show good agreement with the Quality Control parameters that is expected in 40 CFR part 136.7 [6]
StableWeigh 3-D Drying vs. Evaporation Dish 2-D Drying Mechanisms The physics of drying on TS samples is moderated by the pathways for water loss. The traditional evaporation dish follows a 2-D model. That is, the pathway for water vapor to leave the sample is limited by the impervious porcelain walls of the evaporation dish. That is why samples with TS greater than 200 mg per sample volume may crust over and prevent complete drying. This is illustrated in the organic anaerobic digester Biosolids samples (Appendix 1, Table 11A).
The StableWeigh vessel instead follows a 3-D drying model. Due to the fluorinated polymer vessel construction, the solids formed during the drying fall away from the vessel walls and the water vapor can leave the sample from all directions. This allows higher sample samples with TS greater than 200 mg per sample volume (~ 800 mg). The 3-D drying efficiency also allows the final sample to reach weight stability within two drying/weighing cycle. This is illustrated in the organic anaerobic digester Biosolids samples (Appendix 1, Table 9-10A).
StableWeigh Vessel Thermal Stability The StableWeigh vessel is thermally inert at 104 ± 1 ºC over extended periods of time (24 hrs.). This thermal stability allows the laboratory flexibility in performing the TS determination over the course of a typical laboratory work day.
Time to Thermal Equilibrium Due to the thermal mass of a porcelain evaporation dish, cool down time in a desiccator is significantly longer than the StableWeigh vessel (1 hr. or more). This cool-down time adds to the laboratory completion time for traditional TS analyses.
Page | 27
The time required to cool a heated porcelain evaporation dish TS sample in a desiccator must be monitored as storing a TS sample too long in a desiccator during cool-down can cause the difference weight to vary outside of the less than 4% of previous weight or 0.5 mg range.
The StableWeigh vessel mass is an order of magnitude lower than a traditional porcelain evaporation dish and does not hold as much heat energy and will cool to balance temperature much faster. Having the mass of the vessel closer to the mass of the weighed residue also gives greater precision and accuracy. This will help to reduce the number of drying and weighing cycles needed to obtain a constant weight
Labor and Material Costs for TS Analysis The costs associate with porcelain evaporation dishes are not only the initial purchase cost, but also the costs to clean, dry, tare and store the vessel before the next TS analysis. Tables 4 summarize just the porcelain evaporation dish cleaning costs for TS analysis.
The porcelain evaporation dish costs summarized do not include:
1. Continued drying/weighing cycles to reach the two consecutive ≤ 0.5 mg requirements.
2. Resampling or dilution of the TS sample to reach the 200 mg limit set by Standard Methods.
3. The value of extra analyst time available for performing tasks other than washing.
a. Taring the porcelain evaporation dish.
b. Checking the tared value after a set desiccator storing time.
4. The elimination of quality issues associated with detergent or sample-residue contamination in the crucibles
5. Glass/ceramic safety
The StableWeigh vessel cost savings:
1. Comes tared with the weight to the nearest 0.1 mg printed on the vessel.
2. The StableWeigh vessel is a disposable vessel and requires no labor to clean and store.
3. The StableWeigh’s 3-D drying efficiency allows samples of > 200 mg final weight to be run. Thus reducing TS reanalysis due to sample crusting.
Page | 28
Table 4: Porcelain Evaporation Dish Lifetime Costs for Total Solids
Hand Wash Cost Dishwasher Cost Crucible Amortization Crucible Amortization
Initial Porcelain Crucible Cost $13.25 Initial Porcelain Crucible Cost $13.25 Avg. # of Uses (life of crucible) 100 uses Avg. # of Uses (life of crucible) 100 uses
Labor Costs Labor Costs Hourly Labor Rate $15.00 Hourly Labor Rate $15.00 Actual Hourly Cost ( = Rate X 1.4) $21.00 Actual Hourly Cost ( = Rate X 1.4) $21.00 Wash/Handling Minutes Per Crucible 1.00 minutes Handling Minutes Per Crucible 0.50 minutes
Cleaning Reagent Costs Cleaning Reagent Costs Crucibles Cleaned Per Reagent-Batch 1,000 Crucibles Cleaned Per Reagent-Batch 1,000 Cleaning Reagent Cost-Per-Batch $35 Reagent Cost-Per-Batch $35
Water Costs Water Costs Potable H2O Cost-per-Gallon $0.0007 Potable H2O Cost-per-Gallon $0.0007 DI/Lab Water Cost-per-Liter $0.0500 DI Water Cost-per-Liter $0.0500 Sewage Cost-per-Gallon $0.0005 Sewage Cost-per-Gallon $0.0005 Wash & Rinse Water Per Crucible 0.50 liters Wash & Rinse Water Per Crucible 5.00 liters
Extra Time Costs vs. StableWeigh Extra Time Costs vs. StableWeigh Batch (24) Preconditioning 5 minutes Batch (24) Preconditioning 5 minutes Batch (24) Cooling Wait Time 60 minutes Batch (24) Cooling Wait Time 60 minutes Batch (24) Crucible Weighing Time 30 minutes Batch (24) Crucible Weighing Time 30 minutes
Totals Totals Crucible Amortization $0.13 Crucible Amortization $0.13 Labor Costs $0.25 Labor Costs $0.13 Water and Reagent Costs $0.06 Water and Reagent Costs $0.29 Time Costs - Crucibles $0.99 Time Costs - Crucibles $0.99 Total Cost-Per-Crucible to use $1.4322 * Total Cost-Per-Crucible to use $1.5337 * * Three categories that the cost-calculation form does not take into account are (1) the value of extra analyst time available for performing tasks other than washing, (2) the elimination of quality issues associated with detergent or sample-residue contamination in the crucibles, and (3) glass/ceramic safety
Page | 29
Summary and Conclusion
Summarization of the analyses of the StableWeigh tests results, the QC and the overall vessel performance in the SM 2540B TS method:
1. The StableWeigh final sample weight can be > 200 mg, even with difficult Biosolids samples.
2. The StableWeigh vessels consistently met the IDC requirements.
3. The StableWeigh vessels had more acceptable precision and duplicate recovery than the traditional porcelain evaporation dish.
4. The StableWeigh vessels had MB acceptable results.
5. The StableWeigh vessels reach thermal stability sooner than the traditional porcelain evaporation dish and allow the TS measurement to meet the TS difference requirements.
6. The StableWeigh vessels reduce or eliminate the additional time and labor needed to clean and tare traditional porcelain evaporation dishes and filter flasks.
In conclusion, the StableWeigh system is equivalent to SM 2540B and exceeds the requirements for the USEPA approved SM 2540B TS method with larger final sample weights.
Time and cost savings are also seen when compared to the traditional porcelain evaporation dishes and filter flasks.
Page | 30
References
1. Rice, E.W., R.B. Baird, and A.D. Eaton, eds. Standard Methods for the Examination of Water and Wastewater. Vol. 22nd. 2012, APHA, AWWA, WEF: Washington D.C.
2. Baird, R.B., A.D. Eaton, and E.W. Rice, Standard Methods for the Examination of Water and Wastewater, in On Line Edition. 2016, APHA, AWWA, WEF.
3. Porter, J.A., Principles of chemistry. 1865, Ney York: Barnes and Burr.
4. Doolittle, R.E., et al., eds. Official and Tentative Methods of Analysis of the Association of Official Agricultural Chemists. 1919, Association of Official Agricultural Chemists: Washington D. C.
5. Theroux, F.R., E.F. Eldridge, and W.L. Mallmann, Laboratory Manual for Chemical and Bacterial Analysis of Water and Sewage. 1943, New York: McGraw Hill.
6. EPA, Guidelines Establishing Test Procedures for the Analysis of Pollutants Under the Clean Water Act; Analysis and Sampling Procedures. 2012. p. 29758-29846.
7. Reding, R., Flexibility to Modify CWA Methods, E. Engineering & Analytical Support Branch, OST, Editor. 2007, EPA.
Page | 31
Appendixes
Page | 32
Appendix 1: StableWeigh and Porcelain Evaporation Dish Study Data
Page | 33
Table A1: LRB Stable Weigh Blank, Oven
Sample # Volume (ml)
Initial weight
(g)
Final weight 1
(g)
Final weight 2
(g)
Final weight 3
(g)
Two Consecutive
Weights Difference
(mg)
Final weight used (mg)
Percent Change
1 25 3.9073 3.9075 3.9079 0.4 3.9079 0.01536% 2 25 3.8838 3.8848 3.8851 0.3 3.8851 0.03347% 3 25 3.9673 3.9673 3.9675 0.2 3.9675 0.00504% 4 25 3.6667 3.6667 3.6668 0.1 3.6668 0.00273% 5 25 3.6966 3.6969 3.6972 0.3 3.6972 0.01623% 6 25 3.6898 3.6897 3.6902 0.5 3.6902 0.01084% 7 25 3.7101 3.7100 3.7105 0.5 3.7105 0.01078% 8 25 3.6792 3.6790 3.6792 0.2 3.6792 0.00000% 9 25 3.7136 3.7134 3.7134 0.0 3.7134 -0.00539% 10 25 3.6771 3.6775 3.6779 0.4 3.6779 0.02176%
Average 0.01108%
Standard Deviation 0.01136%
Page | 34
Table A2: LRB Stable Weigh Blank, Hot Block
Sample # Volume (ml)
Initial weight
(g)
Final weight 1
(g)
Final weight 2
(g)
Final weight 3
(g)
Two Consecutive
Weights Difference
(mg)
Final weight used (mg)
Percent Change
1 25 3.7370 3.7390 3.7389 -0.1 3.7389 0.05084% 2 25 3.7109 3.7126 3.7122 -0.4 3.7122 0.03503% 3 25 3.6983 3.7000 3.6996 -0.4 3.6996 0.03515% 4 25 3.7418 3.7432 3.7428 -0.4 3.7428 0.02673% 5 25 3.7066 3.7080 3.7078 -0.2 3.7078 0.03237% 6 25 3.8762 3.8772 3.8773 0.1 3.8773 0.02838% 7 25 3.9364 3.9380 3.9376 -0.4 3.9376 0.03048% 8 25 3.8830 3.8840 3.8838 -0.2 3.8838 0.02060% 9 25 3.9131 3.9146 3.9141 -0.5 3.9141 0.02556% 10 25 3.9127 3.9138 3.9135 -0.3 3.9135 0.02045%
Average 0.03056%
Standard Deviation 0.00883%
Page | 35
Table A3: LFB Low Inorganic Standard TS Stable Weigh Oven
Sample # Bag # Volume
(ml)
Initial weight
(g)
Final weight 1
(g)
Final weight 2
(g)
Final weight 3
(g)
Two Consecutive
Weights Difference
(mg)
Final weight used (mg)
Final Solids Recovered
Weight (mg)
Percent Recovery
1 1 25 3.9096 3.9676 3.9676 0.0 3.9676 58.0 100.00% 2 2 25 3.6663 3.7238 3.7237 -0.1 3.7237 57.4 98.97% 3 3 25 3.8910 3.9483 3.9482 -0.1 3.9482 57.2 98.62% 4 4 25 3.8949 3.9521 3.9521 0.0 3.9521 57.2 98.62% 5 5 25 3.6003 3.6570 3.6570 0.0 3.6570 56.7 97.76% 6 6 25 3.8687 3.9254 3.9251 -0.3 3.9251 56.4 97.24% 7 7 25 3.5858 3.6423 3.6420 -0.3 3.6420 56.2 96.90% 8 8 25 3.9043 3.9612 3.9608 -0.4 3.9608 56.5 97.41% 9 9 25 3.9007 3.9568 3.9565 -0.3 3.9565 55.8 96.21% 10 10 25 3.8964 3.9536 3.9534 -0.2 3.9534 57.0 98.28%
Average 56.8 98.00%
Standard Deviation 0.6 1.12%
Page | 36
Table A4: LFB Low Inorganic Standard TS Stable Weigh Hot Block
Sample # Bag # Volume
(ml)
Initial weight
(g)
Final weight 1
(g)
Final weight 2
(g)
Final weight 3
(g)
Two Consecutive
Weights Difference
(mg)
Final weight used (mg)
Final Solids Recovered
Weight (mg)
Percent Recovery
1 1 25 3.9219 3.9798 3.9794 -0.4 3.9794 57.5 99.14% 2 2 25 3.9052 3.9629 3.9626 -0.3 3.9626 57.4 98.97% 3 3 25 3.9091 3.9668 3.9664 -0.4 3.9664 57.3 98.79% 4 4 25 3.9040 3.9616 3.9612 -0.4 3.9612 57.2 98.62% 5 5 25 3.9139 3.9713 3.9713 0.0 3.9713 57.4 98.97% 6 6 25 3.8814 3.9386 3.9384 -0.2 3.9384 57.0 98.28% 7 7 25 3.9011 3.9589 3.9585 -0.4 3.9585 57.4 98.97% 8 8 25 3.9131 3.9710 3.9708 -0.2 3.9708 57.7 99.48% 9 9 25 3.8918 3.9485 3.9487 0.2 3.9487 56.9 98.10% 10 10 25 3.8914 3.9483 3.9482 -0.1 3.9482 56.8 97.93%
Average 57.3 98.72%
Standard Deviation 0.3 0.49%
Page | 37
Table A5: LFB Low Inorganic Standard TS Evaporation Dish
Sample #
Dish #
Volume (ml)
Initial weight
(g)
Final weight 1
(g)
Final weight 2
(g)
Final weight 3
(g)
Two Consecutive
Weights Difference
(mg)
Final weight used (mg)
Final Solids Recovered
Weight (mg)
Percent Recovery
1 3 25 80.7460 80.8000 80.8022 80.8017 -0.5 80.8017 55.7 96.03% 2 23 25 92.0546 92.1084 92.1108 92.1106 -0.2 92.1106 56.0 96.55% 3 16 25 70.3770 70.4318 70.4319 0.1 70.4319 54.9 94.66% 4 5 25 80.1832 80.2397 80.2401 0.4 80.2401 56.9 98.10% 5 7 25 77.3485 77.4038 77.4048 77.4045 -0.3 77.4045 56.0 96.55% 6 A 25 83.3934 83.4492 83.4490 -0.2 83.4490 55.6 95.86% 7 13 25 71.7404 71.7981 71.7975 71.7972 -0.3 71.7972 56.8 97.93% 8 18 25 69.7256 69.7826 69.7826 0.0 69.7826 57.0 98.28% 9 20 25 91.8968 91.9542 91.9547 0.5 91.9547 57.9 99.83% 10 1 25 80.0774 80.1351 80.1351 0.0 80.1351 57.7 99.48%
Average 56.5 97.33%
Standard Deviation 1.0 1.66%
Page | 38
Table A6: LFB High Inorganic Standard TS Stable Weigh Oven
Sample #
Bag #
Volume (ml)
Initial weight
(g)
Final weight 1
(g)
Final weight 2
(g)
Final weight 3
(g)
Two Consecutive
Weights Difference
(mg)
Final weight used
(mg)
Final Solids
Recovered Weight
(mg)
Percent Recovery
1 1 25 3.9114 4.6998 4.6995 -0.3 4.6995 788.1 100.65% 2 2 25 3.8915 4.6771 4.6768 -0.3 4.6768 785.3 100.29% 3 3 25 3.9142 4.6961 4.6958 -0.3 4.6958 781.6 99.82% 4 4 25 3.9286 4.7117 4.7117 0.0 4.7117 783.1 100.01% 5 5 25 3.5072 4.2915 4.2912 -0.3 4.2912 784.0 100.13% 6 6 25 3.5009 4.2860 4.2857 -0.3 4.2857 784.8 100.23% 7 7 25 3.6093 4.3913 4.3911 -0.2 4.3911 781.8 99.85% 8 8 25 3.8950 4.6748 4.6745 -0.3 4.6745 779.5 99.55% 9 9 25 3.9039 4.6843 4.6840 -0.3 4.6840 780.1 99.63% 10 10 25 3.6310 4.4122 4.4118 -0.4 4.4118 780.8 99.72%
Average 782.9 99.99%
Standard Deviation 2.7 0.34%
Page | 39
Table A7: LFB High Inorganic Standard TS Stable Weigh Hot Block
Sample #
Bag #
Volume (ml)
Initial weight
(g)
Final weight 1
(g)
Final weight 2
(g)
Final weight 3
(g)
Two Consecutive
Weights Difference
(mg)
Final weight used
(mg)
Final Solids
Recovered Weight
(mg)
Percent Recovery
1 1 25 3.9158 4.7038 4.7033 -0.5 4.7038 788.0 100.64% 2 2 25 3.8754 4.6621 4.6619 -0.2 4.6621 786.7 100.47% 3 3 25 3.5794 4.3651 4.3651 0.0 4.3651 785.7 100.34% 4 4 25 3.8957 4.6814 4.6812 -0.2 4.6814 785.7 100.34% 5 5 25 3.6152 4.3965 4.3963 -0.2 4.3965 781.3 99.78% 6 6 25 3.6449 4.4288 4.4285 -0.3 4.4288 783.9 100.11% 7 7 25 3.5953 4.3767 4.3770 0.3 4.3767 781.4 99.80% 8 8 25 3.9047 4.6853 4.6850 -0.3 4.6853 780.6 99.69% 9 9 25 3.6048 4.3836 4.3835 -0.1 4.3836 778.8 99.46% 10 10 25 3.8922 4.6745 4.6742 -0.3 4.6745 782.3 99.91%
Average 783.4 100.06%
Standard Deviation 3.0 0.38%
Page | 40
Table A8: LFB High Inorganic Standard TS Evaporation Dish
Sample #
Dish #
Volume (ml)
Initial weight
(g)
Final weight 1
(g)
Final weight 2
(g)
Final weight 3
(g)
Two Consecutive
Weights Difference
(mg)
Final weight used
(mg)
Final Solids
Recovered Weight
(mg)
Percent Recovery
1 24 25 94.5861 95.3642 95.3646 0.4 95.3646 778.5 99.43% 2 4 25 80.6523 81.4280 81.4294 81.4295 0.1 81.4295 777.2 99.26% 3 9 25 71.0454 71.8256 71.8261 0.5 71.8261 780.7 99.71% 4 12 25 71.3363 72.1176 72.1185 72.1180 -0.5 72.1180 781.7 99.83% 5 2 25 88.0683 88.8486 88.8500 88.8499 -0.1 88.8499 781.6 99.82% 6 14 25 70.1568 70.9349 70.9366 70.9365 -0.1 70.9365 779.7 99.58% 7 10 25 70.3863 71.1705 71.1707 0.2 71.1707 784.4 100.18% 8 8 25 71.2983 72.0807 72.0812 0.5 72.0812 782.9 99.99% 9 17 25 71.1083 71.8899 71.8902 0.3 71.8902 781.9 99.86% 10 6 25 71.8202 72.5993 72.5998 0.5 72.5998 779.6 99.57%
Average 780.8 99.72%
Standard Deviation 2.1 0.27%
Page | 41
Table A9: Biosolids, Drying Oven, Stable Weigh
Sample #
Bag #
Volume (ml)
Initial weight
(g)
Final weight 1
(g)
Final weight 2
(g)
Final weight 3
(g)
Two Consecutive
Weights Difference
(mg)
Final weight used (mg)
Final Solids Recovered
Weight (mg)
1 1 25 3.9184 4.6407 4.6406 -0.1 4.6406 722.2 2 2 25 3.9125 4.6331 4.6328 -0.3 4.6328 720.3 3 3 25 3.9114 4.6252 4.6252 0.0 4.6252 713.8 4 4 25 3.8827 4.5990 4.5987 -0.3 4.5987 716.0 5 5 25 3.8992 4.6250 4.6248 -0.2 4.6248 725.6 6 6 25 3.9333 4.6584 4.6582 -0.2 4.6582 724.9 7 7 25 3.8864 4.6068 4.6068 0.0 4.6068 720.4 8 8 25 3.9001 4.6197 4.6195 -0.2 4.6195 719.4 9 9 25 3.8999 4.6155 4.6159 0.4 4.6159 716.0 10 10 25 3.9105 4.6276 4.6273 -0.3 4.6273 716.8
Average 719.5
Standard Deviation 3.9
Page | 42
Table A10: Biosolids, Hot Block, Stable Weigh
Sample #
Bag #
Volume (ml)
Initial weight
(g)
Final weight 1
(g)
Final weight 2
(g)
Final weight 3
(g)
Two Consecutive
Weights Difference
(mg)
Final weight used (mg)
Final Solids Recovered
Weight (mg)
1 11 25 3.8932 4.5998 4.5980 4.5978 -0.2 4.5978 704.6 2 12 25 3.8895 4.6013 4.6008 -0.5 4.6008 711.3 3 13 25 3.8858 4.6064 4.6059 -0.5 4.6059 720.1 4 14 25 3.5462 4.2570 4.2531 4.2534 0.3 4.2534 707.2 5 15 25 3.9051 4.6063 4.6037 4.6036 -0.1 4.6036 698.5 6 16 25 3.8870 4.5899 4.5895 -0.4 4.5895 702.5 7 17 25 3.9082 4.6122 4.6117 -0.5 4.6117 703.5 8 18 25 3.9019 4.5990 4.5987 -0.3 4.5987 696.8 9 19 25 3.9025 4.6013 4.6011 -0.2 4.6011 698.6 10 20 25 3.9094 4.6202 4.6197 -0.5 4.6197 710.3
Average 705.3
Standard Deviation 7.1
Page | 43
Table A11: Biosolids, Drying Oven, Evaporation Dish
Sample #
Dish #
Volume (ml)
Initial weight
(g)
Final weight 1
(g)
Final weight 2
(g)
Final weight 3
(g)
Two Consecutive
Weights Difference
(mg)
Final weight used (mg)
Final Solids Recovered
Weight (mg)
1 20 25 91.8975 92.6090 92.6163 92.6167 0.4 92.6167 719.2 2 16 25 70.3774 71.0945 71.1032 71.1034 0.2 71.1034 726.0 3 A 25 83.3937 84.1089 84.1164 84.1169 0.5 84.1169 723.2 4 3 25 80.7467 81.4655 81.4724 81.4721 -0.3 81.4721 725.4 5 5 25 80.1838 80.9014 80.8984 * -3.0 * * 6 7 25 77.3493 78.0623 78.0624 0.1 78.0624 713.1 7 18 25 69.7260 70.4513 70.4464 * -4.9 * * 8 23 25 92.0549 92.7767 92.7743 * -2.4 * * 9 13 25 71.7408 72.4644 72.4641 -0.3 72.4641 723.3 10 1 25 80.0785 80.7966 80.7966 0.0 80.7966 718.1
Average 721.2
Standard Deviation 4.6
* Bag Weight Varies Due to Crusting on Surface
Page | 44
Appendix 2: Redding Equivalent Method Check Off Table
Page | 45
EPA Method Equivalency Check-Off Table from Richard Redding Memo, Flexibility to Modify CWA Methods, 2007
Equivalency Requirement Section in Report
Concentrations of calibration standards. Document the range of the concentrations of material used to establish the relationship between response of the measurement system and analyte concentration.
Yes, Table 2, Figures 5-13
% RSD or correlation coefficient of calibration regression. Yes, Table 2
Performance range tested with units. Yes, Yes, Table 2, Figures 5-13
Sample(s) used in initial demonstration have the recommended preservative, where applicable.
Yes, see Environmental Express StableWeigh TS Method
Sample(s) used in initial demonstration met recommended holding times, where applicable. Yes
Interferences.
None for StableWeigh, See Appendix 1 Tables. Crusting seen for traditional evaporation dish. See Appendix 1 Tables.
Document the qualitative identification criteria used.
LFB percent recovery. Table 2. LRB Table 3. % RSD from QC samples. Table 2. IDC Figures 5-13
Performance evaluation studies performed for analytes of interest, where available.
LFB percent recovery. Table 2. LRB Table 3. % RSD from QC samples. Table 2. IDC Figures 5-13
Latest study sponsor or title NA
Latest study number. NA
Analysis of external reference material NA.
Results of analyses on reference material from a source different from that used to prepare the calibration standards, if applicable.
See Appendix 1 Tables
Sources of external reference material, if applicable. NA
Page | 46
EPA Method Equivalency Check-Off Table from Richard Redding Memo, Flexibility to Modify CWA Methods, 2007
Equivalency Requirement Section in Report
Surrogates used, if applicable. Not Required
Concentrations of surrogates, if applicable. Not Required
Recoveries of surrogates appropriate to the proposed use, if applicable. Not Required
Sample preparation. As per Standard Methods 2540 (B)
Clean-up procedures. As per Standard Methods 2540 (B)
Method blank result. Table 3
Matrix (reagent water, drinking water, effluent) Wastewater Anaerobic Digester
Matrix spikes. NA
Spiking system, appropriate to the method and application. NA
Spike concentrations (with units corresponding to the final sample concentration) and recoveries.
NA
Source of spiking material. Muscatine Water Pollution Control Plant
Number of replicate spikes NA
Initial demonstration of capability. See Figures 5-13
Precision (analyte by analyte) Duplicates. See Table 2, Figures 5-13, Appendix 1 Tables
Bias (analyte by analyte). See Table 2, Figures 5-13, Appendix 1 Tables
Detection limit (with units; analyte by analyte). NA
Confirmation of detection limit, if applicable. NA
Quantitation limit (with units; analyte by analyte) Minimum level (ML), practical quantitation level (PQL) or limit of quantitation (LOQ).
NA.
Qualitative confirmation. Not Required
