Standard Operating Procedure s38

SOP Turbidity

Revision No.3a

Date: 11/11/11

Page 1 of 5

STANDARD OPERATING PROCEDURE

SOP Description Turbidity By Nephelometry

Document Name Turbidity

Revision #3a

MWC_SOP_TURB_rev3a.doc

Method: SM 18-20 2130B

ELAP Code: 1165

Technology: Color

August 27, 2012

Approved By: ______

Group Supervisor

______

QA Officer

______

Technical Director

Monroe County Environmental Laboratory ID 10373

1574 Lakeshore Blvd.

Rochester, NY 14617

“ORIGINAL” Watermark Must Be Visible

1. Identification of Test Method: Turbidity by Nephelometric Method; Standard Method 19th edition, 1995, 2130B

2. Matrix: Potable and non-potable water samples.

3. Detection Level: 0.01 NTU (Instrument)

4. Scope and Application: This method covers the determination of turbidity in potable and non-potable waters including public surveillance and surface. The application range is 0 – 4000 nephelometric turbidity units (NTU).

5. Summary of Method: The method is based on a comparison of the intensity of light scattered by the sample under defined conditions with standard reference suspensions under the same conditions. A set of primary standards are used to calibrate the instrument. A secondary set of standards is used as a daily calibration check.

6. Definitions:

a. Nephelometric turbidity units (NTU) - Nepholometer consisting of a light source for illuminating the sample and one or more photoelectric detectors with a readout device to indicate intensity of light scattered at 90° to the path of incidental light.

b. Primary Calibration Standard (PCAL) - The PCAL suspensions are used to calibrate the instrument.

c. Secondary Calibration Standard (SCAL) - SCAL suspensions are used as a daily calibration check.

d. Material Safety Data Sheet (MSDS) - Written information provided by vendors concerning a chemical’s toxicity, health hazards, physical properties, fire and reactivity data including storage, spill and handling precautions.

7. Interferences: Dirty glassware, the presence of air bubbles, the presence of floating debris and coarse sediments, which settle out rapidly resulting in low readings. “True color,” that is, water color due to dissolved substances that absorb light, causes measured turbidities to be low, although this effect is generally not significant.

8. Safety: Use protective eye gear (safety glasses with eye shields) and gloves. Analysts should follow the lab’s Chemical Hygiene Plan (CHP) with lab coat and glasses as well.

9. Equipment and Supplies:

a. Turbidimeter (Model #2100N, HACH)

b. Cuvettes to fit the instrument.

c. Volumetric pipettes.

d. Silicone oil (Hach)

e. Ultrasonic bath

10. Reagents and Standards:

a. Primary Standards(PCAL) – StablCal Stabilized Formazin Standards (<0.1NTU, 20NTU, 200NTU, 1000NTU, 4000NTU

b. Secondary Standards(SCAL) – Gelex Secondary Turbidity Standarization Kit (Straylight, 0-2NTU, 0-20NTU, 0-200NTU & 200-4000NTU

11. Sample Acceptance, Preservation and Storage: Determine turbidity as soon as possible after the sample is taken.

a. Collect sample in either glass or plastic bottle.

b. Refrigerate or cool to 4°C, if storage is required.

c. Samples must be analyzed within 24 hours.

12. Quality Control:

a. The Turbidimeter should be calibrated every 3 months with Primary Standards (StablCal)

b. Laboratory Control Sample (Gelex Secondary Standards): Five LCS (Straylight, 0-2NTU, 0-20NTU, 0-200NTU & 200-4000NTU) at the beginning of the analytical run, followed by one per ten samples.

c. Precision: Replicates, analyzed 1 per 20 samples or 1 per run if less than 20 samples.

13. Calibration and Standardization:

The instrument should be calibrated under the following conditions:

a. Upon introduction of new lot of primary / secondary standards.

b. Once every 3 months for 2100N.

c. When standard values are drifting upward or downward in a consistent manner even if values are within 5%.

d. Calibration procedure: Remove box of Calibration standards from refrigerator. Bring vials to room temperature by placing in a beaker of warm water. Wipe vials with Kimwipe to dry. On turbidity meter, press the ‘CAL’ key. Put Std. 0 (<0.01NTU) into meter, close cover, press the Enter key. The display counts down from 60 to 0, stores the value, then indicates the next standard to put in. Remove Std. 0, put in Std. 1 (20NTU), press enter. Repeat with Std. 2 (200NTU), Std. 3 (1000NTU), and STD 4 (4000NTU), shaking each vial well to mix thoroughly. After Std. 4 is done, the calibration values are calculated and stored internally and calibration is complete. Press the ‘CAL’ button to bring the meter back to measurement mode.

e. Read and record Gelex standards, calculate new limits, note value in note book.

14. Procedure:

a. Read and record values for the Gelex standards. Check to make sure they are in control.

b. Invert sample gently 5 times. Pour 30 ml of sample into a cuvette. Hold and immerse cuvette in an ultrasonic bath for 1 to 2 seconds. Wipe off water and make sure there are no water spots or finger prints on cuvette. Apply silicone oil from the top to the bottom of the cell with black velvet cloth, wipe with Kimwipe.

c. Place cuvette in the sample compartment with the triangle on the vial aligned with the index mark on the instrument. Close the sample cell cover. Press Enter key. Wait 14 seconds. Read and record results.

d. Procedure for cleaning cuvettes: After use, cuvettes should be immediately rinsed three times with tap water, and 3 times with deionized water. Soap wash cuvettes monthly, without scrubbing to avoid scratches, followed by daily routine cleaning procedure. Air-dry by inverting in a rack.

15. Calculations:

Dilution Factor = 30 / #mL of sample used

Turbidity = Dilution Factor x Reading

Reporting: Round values to reportable numbers as follows:

Turbidity Reading in NTU Round and Report to the nearest NTU

<0.05 <0.05

0 – 1.0 0.05

1 – 10 0.1

10 - 40 1

40 – 100 5

100 – 400 10

400 - 1000 50

>1000 100

16. Method Performance: Gelex standards read as daily calibration check.

17. Pollution Prevention: The less is better philosophy is used.

18. Data Assessment and Acceptance Criteria for Quality Control Measures: Please see Appendix A.

19. Corrective Actions for Out of Control Data: Follow the procedure outlined in M:\LAB\QC\QUALITY\SOP\QC FLOW CHART.xls

20. Contingencies for Handling Out-of-Control Data: Follow the procedure outlined in M:\LAB\QC\QUALITY\SOP\QC FLOW CHART.xls

21. Waste Management: The laboratory is responsible in complying with all Federal, State and local regulations governing waste management, particularly the hazardous waste identification rules and land-disposal restrictions. Compliance with all sewage discharge permits and regulations is required. The “Less is Better” philosophy is encouraged. The reference for waste disposal is Prudent Practices in the Laboratory, NRC, 1995. There are no hazardous wastes associated with this method. Therefore, all waste can be discarded down the drain.

22. References:

a. 1998. Clesceri, L.S., A.E. Greenberg and A.D. Eaton (editors). Standard Methods for the Examination of Water and Wastewater, 20th edition.

b. Prudent Practices in the Laboratory

23. Validation Data: This method is validated through performance on Laboratory Control Samples.

Revision History:

Revision / Date / Author / Change
Rev 3
Rev 3a / 8/29/07
1/11/11 / KE\SAG
SAG / New SOP Format
Changed spelling and punctuation in section 6 & 7
Replaced section 13a
Added section 13e
Path change for flow chart to M:\

Distribution List:

Assigned Person/Area / Copy #
QA\QC / 1
Manual Wet Chem. / 2

The analysts identified below have read this method and have agreed to implement this method for future analysis.