Proficiency test SPIL-3 (2017) Organic matter, phosphorus, chloride, sulphate and suspended matter in wastewater (synthetic wastewater, effluent)

Transcription

1 Proficiency test SPIL-3 (2017) Organic matter, phosphorus, chloride, sulphate and suspended matter in wastewater (synthetic wastewater, effluent) Quality Documentation February 2018

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3 Proficiency test SPIL-3 (2017) Quality Documentation December 2017 Eurofins Miljø A/S Smedeskovvej 38 DK-8464 Galten Denmark Tlf: Fax: Web: Client Client s representative Environmental laboratories Project Project No Proficiency test SPIL-3 (2017) Authors Maj-Britt Fruekilde Date Approved by Stine Ottsen Quality Documentation Report Revision Description By Checked Approved Date Key words Analytical quality, assigned value, precision, trueness, homogenity, stability, COD, BOD5 (w. ATU), BOD7 (w. ATU), NVOC/TOC, total phosphorus, chloride, sulphate, suspended matter, wastewater. Classification Open Internal Proprietary Distribution DANAK Eurofins: Maj-Britt Fruekilde, Stine Ottsen

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5 CONTENTS 1 INTRODUCTION FEATURES OF THE PROFICIENCY TEST Sample preparation Statistical analysis of participants data Assigned and spike value Assigned and spike values Test of spike values Test of assigned values HOMOGENEITY AND STABILITY OF SAMPLES CONCLUSION REFERENCES... 6 ANNEX A LIST OF PARTICIPANTS... 9 ANNEX B SAMPLE PREPARATION ANNEX C CONTROL OF SPIKE VALUES ANNEX D CONTROL OF RECOVERY ANNEX E CONCENTRATION LEVEL ANNEX F HOMOGENEITY AND STABILITY... 30

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7 1 INTRODUCTION A proficiency test on the analysis of organic matter, phosphorus, chloride, sulphate and suspended matter in wastewater was conducted on 14 September The proficiency test was organised by Eurofins Miljø A/S. The present report contains Eurofins documentation for the quality of the proficiency test. Results of the proficiency test including data from participating laboratories and statistical analysis of these data were issued in a report to all participants /1/ on 16 October

8 2 FEATURES OF THE PROFICIENCY TEST Participants in the proficiency test were a total of 53 laboratories from Denmark and Sweden. A list of participants is shown in Appendix A. The closing date for submission of results was 29 September All participants except laboratory no. 19 had submitted their results before the dead-line. 2.1 Sample preparation The parameters covered in the proficiency test are listed in Table 2 as are the abbreviations used in this report. Eigth samples were dispatched for the proficiency test. The samples were sample pairs covering the parameters as described in Table 1. The matrix of the samples represented wastewater, in this case synthetic wastewater, effluent. Sample preparation is described in Appendix B. Table 1 Samples in the proficiency test Sample name Parameters A1/B1, COD TOC COD Cr, NVOC/TOC A1/B1, BOD BOD 5 w. ATU, BOD 7 w. ATU A2/B2 TP, Cl, SO 4 A3/B3 TSS 2.2 Statistical analysis of participants data A split-level design was used. The data analysis was performed in accordance with ISO 5725: Accuracy (trueness and precision) of measurement methods and results (1994) /2/ and as described in detail in Spliid (1992) /3/. A short introduction to the statistics and a list of symbols and abbreviations used is given in Eurofins document Schedule for a proficiency test, which is available at Eurofins home page /4/. The statistical model used is based on the assumption that the variances for the two samples in a sample pair are identical. The assumption was tested (F-test, 95% confidence level) and the result was that the two variances may be assumed to be identical for all parameters. 2.3 Assigned and spike value An overview of the concentrations in the samples (the assigned values) and the difference in concentration between the two samples of a sample pair (spike value) are shown in Table 2 compared to the range of concentrations normally encountered in synthetic wastewater, effluent. The table also gives the expanded uncertainty of the assigned values. 2

9 Table 2 Assigned and spike value Parameter Abbreviation Unit Typical Range Assigned value Uncertainty of assigned value Spike value Chemical oxygen COD Cr mg/l O demand dichromate method Five day biochemical BOD 5 w. ATU mg/l O oxygen demand Seven day biochemical BOD 7 w. ATU mg/l O oxygen demand Non-volatile organic NVOC/TOC mg/l C carbon Total phosphorus TP mg/l P Chloride Cl mg/l Sulphate SO 4 mg/l Total Suspended matter TSS mg/l Assigned and spike values The content of each parameter in each sample is given an assigned value for the sample with the lower content and a spike value, the spike value being the difference in concentration between the two samples of the sample pair. The assigned and spike values are both calculated from sample preparation except for BOD where spike values are calculated from sample preparation and assigned values are consensus values for laboratories using standardised methods (method no. 1-4), based on the median Test of spike values A comparison was made (t-test, 95% confidence level) between the spike value and the difference in concentration between the two samples in the sample pair found from the laboratories results, see Appendix C. The test revealed a significant difference between the two for NVOC and Cl. For NVOC the difference could be attributed to influence from laboratories using another method than the one prescribed by the Danish EPA (no. 1). The test was repeated after exclusion of the results for method no. 42 and now showed no significant difference. The difference for Cl has insignificant influence on the general quality of analyses estimated from the data as well as on the evaluation of accuracy of participating laboratories. The split values are kept unchanged Test of assigned values The assigned value and the average of the results obtained from all laboratories were also compared (t-test, 95% confidence level), see Appendix D. For BOD 7, TP and SO 4 the test showed no significant difference between the two. The test revealed a significant difference between the two for COD Cr, BOD 5, NVOC, Cl and TSS. Average recovery was 111% (COD Cr ), 170% (BOD 5 ), 109% (NVOC), 90,9% (Cl) and 96.5% (TSS). The difference could be attributed to influence from laboratories using methods other than those prescribed by the Danish EPA. The test was repeated after exclusion of the results for method no. 9, 71, 71B, 72, 72A, 72B, 74, 76 and 78 (COD Cr ), no. 9 and 52 (BOD 5 ), no. 42 (NVOC), no. 9, 51 and 52 (Cl) and no. A1, A9 and 99 (TSS) and now showed no significant difference. Furthermore, the results of control measurements at Eurofins confirmed the assigned values (Appendix E). The assigned values are therefore kept unchanged. 3

10 3 HOMOGENEITY AND STABILITY OF SAMPLES The homogeneity and stability of samples were tested using the following parameters as indicators: TP TSS Combined homogeneity and stability test Combined homogeneity and stability test The results of control measurements are shown in Appendix F. The appendix also gives the results of the statistical evaluation of the control data. The data are analysed by analysis of variance (ANOVA) giving: 1. the standard deviation/variance for replicates (the contribution from analytical variability), 2. the between bottle standard deviation/variance (the contribution from heterogeneity) and 3. the between days concentration difference (the contribution from instability). Homogeneity is evaluated by comparing the between bottle variance to 0.3 * the standard deviation for evaluation of participants performance ( ) specified by the Danish EPA /5/, whereas the stability is evaluated by comparing the concentration change of the samples to. This test ensures that heterogeneity and instability will not have negative influence on the evaluation of participant performance /6/. The appendix also shows the standard deviation within and between laboratories from the proficiency test to allow comparison between tests performed and average quality from participating laboratories. The tests for stability and homogeneity show that the samples are stable and homogeneous. 4

11 4 CONCLUSION The quality control performed, including test of sample stability and homogeneity as well as test of recovery of spike and assigned values, shows that the samples and their assigned values are suitable for testing the proficiency of the participating laboratories for all parameters. The results are also suitable for estimation of the general quality of analyses among all participating laboratories. For NVOC and Cl the participants could not recover the spike value. For NVOC the difference could be attributed to influence from laboratories using another method other than the one prescribed by the Danish EPA. The difference between the calculated spike value and that found by the participants for Cl has no influence on evaluation of participant performance or estimation of general quality of analyses is insignificant. For COD Cr, BOD 5, NVOC, Cl and TSS the participants did not recover the assigned value. Eurofins scrutiny of the combined evidence gave the conclusion that the assigned values are correct. The assigned values are therefore kept unchanged and it is recommended as the basis for evaluation of participating laboratories. 5

12 5 REFERENCES /1/ Eurofins A/S, Proficiency test SPIL-3 (2017), Report to participants, October /2/ ISO , Accuracy (trueness and precision) of measurement methods and results Part 2: Basic method for the determination of repeatability and reproducibility of a standard measurement method, /3/ Spliid, H., Procedure and analysis of data for proficiency tests and environmental analyses, Report to Danish Environmental Protection Agency, 1994 (in Danish). /4/ Eurofins A/S, Schedule for a proficiency test, document may be downloaded from /5/ Ministry of Environment regulation no on quality criteria for environmental measurements, 29 December 2015 (in Danish). /6/ ISO 13528, Statistical methods for use in proficiency testing by interlaboratory comparison,

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15 ANNEX A LIST OF PARTICIPANTS Laboratory Town Country ALS Denmark A/S Humlebæk Denmark Analyseenheden, Institut for Agroøkologi, Aarhus Universitet Tjele Denmark AquaDjurs A/S Grenaa Denmark Biofos A/S København K Denmark Bjergmarken R/A, Fors Spildevand Roskilde Roskilde Denmark BlueKolding A/S Kolding Denmark CP Kelco ApS, Spildevandslaboratoriet Ll. Skensved Denmark Eurofins Miljø A/S Vejen Denmark Faxe Forsyning Faxe Denmark Fors Spildevand Holbæk Holbæk Denmark Hillerød Forsyning Spildevand A/S Hillerød Denmark Holstebro renseanlæg, Vestforsyning, erhverv Holstebro Denmark Højmarklaboratoriet A/S Lem St. Denmark Højvang Laboratorier A/S, Holstebro Holstebro Denmark Kerteminde Forsyning - Spildevand A/S Kerteminde Denmark Klarforsyning, Greve Spildevand Køge Denmark Melby Renseanlæg Liseleje Denmark Nyborg Renseanlæg Nyborg Denmark Næstved Central Renseanlæg, NK-Spildevand Næstved Denmark Provas Haderslev Denmark Ringkøbing-Skjern Forsyning A/S Skjern Denmark Rønne Renseanlæg Rønne Denmark Slagelse Renseanlæg (5 participants) Slagelse Denmark Svendborg Centralrenseanlæg Skårup Fyn Denmark Vandmiljø Randers A/S Randers SØ Denmark Vejle Spildevand A/S Vejle Denmark AB Lennart Månsson International Helsingborg Sweden Fiskeby Board AB Norrköping Sweden GRYAAB AB Göteborg Sweden Gästrike Vatten AB Skutskär Sweden Hallsta Pappersbruk Hallstavik Sweden Holmen Paper AB Bravikens Pappersbruk Norrköping Sweden 9

16 Laboratory Town Country Kalmar Vatten AB, VA-lab Kalmar Sweden Kristianstad Kommun Kristianstad Sweden Laboratoriet Fillanverket, MittSverige Vatten och Avfall Sundsvall Sweden Laboratoriet vid Smedjeholms avolppsreningsverk Falkenberg Sweden Mjölby Kommun Mjölby Sweden Motala Kommun Motala Sweden NSVA/Öresundsverket Helsingborg Sweden Perstorp Oxo AB Stenungsund Sweden Preem AB Göteborg Göteborg Sweden Preemraff Lysekil Lysekil Sweden Rottneros Bruk AB Rottneros Sweden Smurfit Kappa Piteå Piteå Sweden St1 Refinery AB Göteborg Sweden Södra Cell AB, Värö Väröbacka Sweden Uddebo Laboratorium Luleå Sweden Vallviks Bruk Vallvik Sweden Västerviks Miljö & Energi AB, Vattenlaboratoriet Västervik Sweden 10

17 ANNEX B SAMPLE PREPARATION Stock solution Prepared from Concentration Concentrate A g D-glucose COD Cr : g/kg 5.70 g L-glutamic acid milli-q water up to g NVOC: g/kg BOD: g/kg Concentrate B g D-glucose 9.60 g L-glutamic acid milli-q water up to g Stock TP g Na-B.glycerophosphate milli-q water up to g Stock Cl g Sodium chloride (NaCl) milli-q water up to g Stock SO g Sodium sulphate (Na 2 SO 4 ) milli-q water up to g Stock TSS g Microcrystalline cellulose milli-q water up to g COD Cr : 1.510g/kg NVOC: g/kg BOD: g/kg TP: mg/kg Cl: 6.071g/kg SO 4 : g/kg TSS: g/kg 11

18 Sample Sample prepared from COD Cr mg/l O 2 A1- At the laboratory 1.00 ml of concentrate COD/NVOC A1 is diluted up to ml with Milli-Q water B1- COD/NVOC A1-BOD B1-BOD A2 B2 A3 B3 At the laboratory 1.00 ml of concentrate B1 is diluted up to ml with Milli-Q water At the laboratory 4.00 ml of concentrate A1 is diluted up to ml with filtered water from Vejen sewage treatment plant At the laboratory 4.00 ml of concentrate B1 is diluted up to ml with filtered water from Vejen sewage treatment plant g stock TP g stock Cl g stock SO4 Milli-Q water up to kg g stock TP g stock Cl g stock SO4 Sample A2 up to kg At the laboratory ml of Milli-Q water is added to 2.0 ml stock TSS At the laboratory ml of Milli-Q water is added to 2.5 ml stock TSS NVOC mg/l C BOD (w. ATU) mg/l O 2 c c TP mg/l P Cl mg/l SO 4 mg/l TSS mg/l

19 ANNEX C CONTROL OF SPIKE VALUES COD Cr, mg/l O 2 Control of differences within sample pairs Laboratory Difference AB UG A B UC No of labs., p 37 No of repl., n 2 d s² 4.38 s 2.09 t = p (d/s) Sign. level, p(t) No test statistics were found to be significant UC denotes a Cochran outlier UG denotes a Grubbs outlier 13

20 BOD 5, mg/l O 2 Control of differences within sample pairs Laboratory Difference AB A UC 41B No of labs., p 13 No of repl., n 2 d s² s t = p (d/s) Sign. level, p(t) No test statistics were found to be significant UC denotes a Cochran outlier 14

21 BOD 7, mg/l O 2 Control of differences within sample pairs Laboratory Difference AB A - 41B No of labs., p 8 No of repl., n 2 d s² s t = p (d/s) Sign. level, p(t) No test statistics were found to be significant 15

22 NVOC/TOC, mg/l C Control of differences within sample pairs Laboratory Difference AB UG UG A - 41B No of labs., p 22 No of repl., n 2 d s² s t = p (d/s) Sign. level, p(t) * * denotes that there is a significant difference (t-test, 5%-level) ** denotes that there is a significant difference (t-test, 1%-level) *** denotes that there is a significant difference (t-test, 0.1%-level) UG denotes a Grubbs outlier Difference for sample pair AB is significantly different from 0, and data should be corrected with the difference (in spike value), during execution of Cochran's test. 16

23 TP, mg/l P Control of differences within sample pairs Laboratory Difference AB UC UC UC UC UC 41A B UC No of labs., p 45 No of repl., n 2 d s² s t = p (d/s) Sign. level, p(t) No test statistics were found to be significant UC denotes a Cochran outlier 17

24 Cl, mg/l Control of differences within sample pairs Laboratory Difference AB UG UC 41A B No of labs., p 25 No of repl., n 2 d 3.37 s² s 4.92 t = p (d/s) Sign. level, p(t) ** * denotes that there is a significant difference (t-test, 5%-level) ** denotes that there is a significant difference (t-test, 1%-level) *** denotes that there is a significant difference (t-test, 0.1%-level) UC denotes a Cochran outlier UG denotes a Grubbs outlier Difference for sample pair AB is significantly different from 0, and data should be corrected with the difference (in spike value), during execution of Cochran's test. 18

25 SO 4, mg/l Control of differences within sample pairs Laboratory Difference AB UC UG A B UG No of labs., p 9 No of repl., n 2 d s² s t = p (d/s) Sign. level, p(t) No test statistics were found to be significant UC denotes a Cochran outlier UG denotes a Grubbs outlier 19

26 TSS, mg/l Control of differences within sample pairs Laboratory Difference AB UC UC UC A B No of labs., p 41 No of repl., n 2 d 0.03 s² 1.88 s 1.37 t = p (d/s) Sign. level, p(t) No test statistics were found to be significant UC denotes a Cochran outlie 20

27 ANNEX D CONTROL OF RECOVERY COD Cr, mg/l O 2 Control of recovery, average of results Laboratory Sample pair AB UG A B UC No of labs., p 37 No of repl., n 2 m s² 7.52 s 2.74 Assigned value, µ 11.7 Recovery, % t = p (m-µ)/s Sign. level, p(t) * * denotes that there is a significant difference (t-test, 5%-level) ** denotes that there is a significant difference (t-test, 1%-level) *** denotes that there is a significant difference (t-test, 0.1%-level) UC denotes a Cochran outlier UG denotes a Grubbs outlier 21

28 BOD 5, mg/l O 2 Control of recovery, average of results Laboratory Sample pair AB A UC 41B No of labs., p 13 No of repl., n 2 m s² s Assigned value, µ 2.1 Recovery, % t = p (m-µ)/s Sign. level, p(t) * * denotes that there is a significant difference (t-test, 5%-level) ** denotes that there is a significant difference (t-test, 1%-level) *** denotes that there is a significant difference (t-test, 0.1%-level) UC denotes a Cochran outlier 22

29 BOD 7, mg/l O 2 Control of recovery, average of results Laboratory Sample pair AB A - 41B No of labs., p 8 No of repl., n 2 m s² s Assigned value, µ 2.9 Recovery, % 95.7 t = p (m-µ)/s Sign. level, p(t) No test statistics were found to be significant 23

30 NVOC/TOC, mg/l C Control of recovery, average of results Laboratory Sample pair AB UG UG A - 41B No of labs., p 22 No of repl., n 2 m s² s Assigned value, µ 4.6 Recovery, % t = p (m-µ)/s Sign. level, p(t) ** * denotes that there is a significant difference (t-test, 5%-level) ** denotes that there is a significant difference (t-test, 1%-level) *** denotes that there is a significant difference (t-test, 0.1%-level) UG denotes a Grubbs outlier 24

31 TP, mg/l P Control of recovery, average of results Laboratory Sample pair AB UC UC UC UC UC 41A B UC No of labs., p 45 No of repl., n 2 m s² s Assigned value, µ Recovery, % t = p (m-µ)/s Sign. level, p(t) No test statistics were found to be significant UC denotes a Cochran outlier 25

32 Cl, mg/l Control of recovery, average of results Laboratory Sample pair AB UG UC 41A B No of labs., p 25 No of repl., n 2 m s² s 6.85 Assigned value, µ 81.7 Recovery, % 90.9 t = p (m-µ)/s Sign. level, p(t) *** * denotes that there is a significant difference (t-test, 5%-level) ** denotes that there is a significant difference (t-test, 1%-level) *** denotes that there is a significant difference (t-test, 0.1%-level) UC denotes a Cochran outlier UG denotes a Grubbs outlier 26

33 SO 4, mg/l Control of recovery, average of results Laboratory Sample pair AB UC UG A B UG No of labs., p 9 No of repl., n 2 m s² s Assigned value, µ 31.3 Recovery, % t = p (m-µ)/s Sign. level, p(t) No test statistics were found to be significant UC denotes a Cochran outlier UG denotes a Grubbs outlier 27

34 TSS, mg/l Control of recovery, average of results Laboratory Sample pair AB UC UC UC A B No of labs., p 41 No of repl., n 2 m s² 2.35 s 1.53 Assigned value, µ 30.0 Recovery, % 96.5 t = p (m-µ)/s Sign. level, p(t) *** * denotes that there is a significant difference (t-test, 5%-level) ** denotes that there is a significant difference (t-test, 1%-level) *** denotes that there is a significant difference (t-test, 0.1%-level) UC denotes a Cochran outlier 28

35 ANNEX E CONCENTRATION LEVEL Parameter Unit Sample Bottle no. I II Bottle Sample Assigned Spike Average Average value Measured Assigned COD mg/l O2 A1 2 12,7 12,4 12,6 12,7 11,7 2,8 3, ,3 12,5 12, ,7 13,3 13,0 B1 7 15,7 15,3 15,5 15,4 15, ,9 15,0 15, ,0 15,5 15,8 Total phosphorus mg/l P A2 10 0,460 0,463 0,46 0,462 0,468 0,108 0, ,467 0,460 0, ,461 0,463 0,46 B2 6 0,565 0,573 0,57 0,571 0, ,570 0,566 0, ,576 0,574 0,58 Chloride mg/l A ,0 80,0 80,1 81,7 14,6 17, ,0 80, ,2 80,2 B2 6 93,0 93,0 94,7 99, ,0 98, ,0 93,0 Total suspended mg/l A ,8 29,8 30,3 30,0 7,3 7,4 solids 33 30,8 30, ,4 30,4 B3 5 37,6 37,6 37,6 37, ,8 37, ,5 37,5 29

36 ANNEX F HOMOGENEITY AND STABILITY PT: Parameter: SPIL-3 TP Unit: mg/l P Sigma: 0,036 Responsible for tests: IRL/HEW Homogeneity test Date: Stability test Date: Sample x(a) x(b) average sd sd^2 Sample x(a) x(b) B2-1 0,56 0,56 0,6 0,004 0,000 B2-6 0,565 0,573 B2-11 0,56 0,56 0,6 0,001 0,00 B2-39 0,57 0,566 B2-21 0,56 0,57 0,6 0,008 0,000 B2-58 0,576 0,574 B2-26 0,58 0,57 0,6 0,001 0,000 B2-31 0,57 0,57 0,6 0,001 0,000 B2-36 0,57 0,58 0,6 0,005 0,000 For stability B2-41 0,58 0,57 0,6 0,003 0,000 General average (y): 0, B2-51 0,57 0,57 0,6 0,002 0,000 /x-y/ = 0,0005 B2-56 0,57 0,58 0,6 0,001 0,000 B2-62 0,57 0,57 0,6 0,001 0,000 B2-61 0,57 0,57 0,6 0,000 0,000 B2-71 0,57 0,58 0,6 0,004 0,000 Conclusions ss = 0,005 For homogeneity /x-y/ = 0,0005 General average (x) 0,57 Analytical Is s w < 0,15*sigma Sample average sd (s x) 0,005 quality YES Within-sample sd (s w): 0,003 Between-samples sd (ss): 0,0047 Homogeneity: Is ss < 0.3*sigma? S L in the Proficiency Test: 0,018 YES S R in the Proficiency Test: 0,018 Stability: /x-y/ < 0.3*sigma? YES 0.3*sigma = 0,01 30

37 PT: Parameter: Spil-3 TSS Unit: mg/l Sigma: 3,6 Responsible for tests: IRL/HEW Homogeneity test Date: Stability test Date: Sample x(a) x(b) average sd sd^2 Sample x(a) x(b) B3-2 38,3 38,3 B3-5 37,6 B3-9 38,0 38,0 B ,8 B ,7 38,7 B ,5 B ,7 38,7 B ,2 38,2 B ,2 38,2 For stability B ,7 38,7 General average (y): 37,63333 B ,6 38,6 /x-y/ = 0, B ,5 38,5 B ,6 38,6 B ,4 38,4 B ,5 38,5 Conclusions For homogeneity /x-y/ = General average (x) 38,5 Sample average sd (s x) 0,232 Within-sample sd (s w): ss = 0,23 0, Between-samples sd (ss): 0,232 Homogeneity: Is ss < 0.3*sigma? S L in the Proficiency Test: 1,37 YES S R in the Proficiency Test: 1,68 Stability: /x-y/ < 0.3*sigma? YES 0.3*sigma = 1,08 31