HomeMy WebLinkAbout#176_2010
INSPECTION REPORT ROUTING SHEET
To be attached to all inspection reports in-house only.
Laboratory Cert. #: 176
Laboratory Name: City of Durham Water & Wastewater Laboratory
Environmental Resources
101 City Hall Plaza
Durham, NC 27701
Inspection Type: Technical Assistance and Municipal Maintenance Follow-up
Inspector Name(s): Jeff Adams, Gary Francies and Dana Satterwhite
Inspection Date: January 27, 2010
Date Report Completed: January 28, 2010
Date Forwarded to Reviewer: January 28, 2010
Reviewed by: Gary Francies
Date Review Completed: January 29, 2010
Cover Letter to use: Insp. Initial X Insp. Reg. Insp. No Finding Insp. CP
Unit Supervisor: Dana Satterwhite
Date Received: January 29, 2010
Date Forwarded to Alberta: January 29, 2010
Date Mailed: January 29, 2010
_____________________________________________________________________
On-Site Inspection Report
LABORATORY NAME: City of Durham Water & Wastewater Laboratory
Environmental Resources
NPDES PERMIT #: NC0047597
ADDRESS: 101 City Hall Plaza
Durham, NC 27701
CERTIFICATE #: 176
DATE OF INSPECTION: January 27, 2010
TYPE OF INSPECTION: Technical Assistance and
Municipal Maintenance Inspection Follow-up
AUDITOR(S): Jeff Adams, Gary Francies and Dana Satterwhite
LOCAL PERSON(S) CONTACTED: Sheila Hopkins and Henry Plachinski
I. INTRODUCTION:
This laboratory was inspected to verify its compliance with the requirements of 15A NCAC 2H .0800 for
the analysis of environmental samples.
II. GENERAL COMMENTS:
This visit to the laboratory was to provide technical assistance and follow-up to the maintenance
inspection performed on August 19, 2009. Technical assistance was provided and troubleshooting was
performed for Total Kjeldahl Nitrogen (TKN) analysis. The laboratory was instructed to disregard the
findings cited for TKN in the previous inspection report and submit written responses to this report under
separate cover.
The preparatory work that the laboratory analysts performed in advance was instrumental in effectively
troubleshooting the TKN procedure. We appreciate the cooperation and diligence of the analysts in
working to resolve the questions about the TKN procedure and derivation of the calculated results. It was
also noted that the laboratory has implemented many of the recommendations and requirements cited in
the August 19, 2009 inspection (e.g., the laboratory has developed and implemented the use of a
digestion log for TKN digestion).
III. FINDINGS, REQUIREMENTS, COMMENTS AND RECOMMENDATIONS:
Recommendation: It is recommended that the laboratory rotate the position of samples, blanks and
quality control samples in the block digester during TKN digestion. Random placement will help to identify
when optimal performance is not achieved in an individual sample well. It is also recommended that the
laboratory implement a temperature grid check of the block digester by alternating the well location of
the thermometer each time samples are digested. This will document heating uniformity and
consistency of all sample wells in the block.
Page 2
#176 City of Durham Water and Wastewater Laboratory
Recommendation: It is recommended that the laboratory analyze the digested organic nitrogen standard
at a concentration in the range of the concentration of effluent samples. Establish acceptance limits
based upon three standard deviations of the mean concentration of a minimum of 25 measurements. The
laboratory may adopt a default acceptance criterion until sufficient data points are collected to calculate
historical control limits.
Recommendation: It is recommended that the laboratory contact the block digester manufacturer (i.e.,
Lachat Instruments) to obtain a copy of the published TKN digestion method for the BD-46 block digester.
Recommendation: It is recommended that the laboratory insert the electrode into a low concentration
standard solution after measurement of high concentration samples and standards to help decrease the
stabilization time of the meter reading.
A. Finding: An inconsistency was noted between the TKN Standard Operating Procedure (SOP)
and laboratory practice as follows: Personnel were not following procedures as stated in the
Laboratory’s SOP.
Requirement: Each laboratory shall develop and maintain a document outlining the analytical
quality control practices used for the parameters included in their certification. Ref: 15A NCAC 2H
.0805 (a) (7).
Comment: The SOP stated that 20 mL sample volumes are pipetted into digestion tubes. The
laboratory analyst was pouring sample volumes to the 20 mL mark imprinted on the digestion
tubes.
Recommendation: It is recommended that sample volumes be dispensed using volumetric
pipettes. As an alternative, digestion tubes may be calibrated volumetrically or gravimetrically and
etched at the appropriate volume mark. In either case, the SOP must accurately describe the
procedure employed during analysis.
B. Finding: The laboratory is not using the catalyst cited in the referenced method.
Requirement: All of the reagents listed for the determination of Nitrogen (Ammonia) (Section
4500-NH3.B.3) and Nitrogen (Organic) macro-kjeldahl (Section 4500-Norg.B.3) are required.
Prepare all reagents and dilutions with ammonia-free water. Ref: Standard Methods, 19th Edition,
4500-Norg C. (3).
Comment: The laboratory is citing Standard Methods, 19th Edition, 4500-Norg C. This method
(which refers to 4500-Norg B for the reagents) specifies the use of copper sulfate (CuSO4) as the
digestion catalyst. The lab is using mercuric sulfate (HgSO4) as the digestion catalyst. The more
recently published methods have replaced the mercury catalysts with copper sulfate because of
mercury’s toxicity and problems associated with legal disposal of mercury residues. In addition,
the Code of Federal Regulations, Title 40, Part 136; Federal Register Vol. 72, No. 47, March 12,
2007; Table IB, footnote 5 allows the use of copper sulfate in place of mercuric sulfate where
older methods specify the mercury catalyst.
C. Finding: Total Kjeldahl Nitrogen results are not calculated according to the instrument
manufacturer’s manual or the approved method.
Requirement: Refer to the manufacturer’s instructions and proceed as in ¶s 4a and b [of
Standard Methods, 19th Edition, 4500-NH3 D.].
Page 3
#176 City of Durham Water and Wastewater Laboratory
Comment: The laboratory is equipped with a specific ion meter, which is capable of producing
direct-read measurements in mg/L based upon the slope obtained for the specified calibration
standards (undigested). Although the laboratory calibrated the instrument in a manner consistent
with manufacturer’s instructions initially, raw environmental sample results were then manually
calculated using a linear regression of digested standard readings versus the theoretical
concentration of those digested standards. This manual regression of digested standards step
must be eliminated. When the meter is properly calibrated with undigested standards and a slope
in the approximate range of 54 to 60 mV/decade is obtained, a direct reading of samples, blanks
and standards (in mg/L) may be used to calculate the final result. This is done using the
calculation in Standard Methods, 19th Edition, 4500-NH3 D. (5). Note: Both pre- and post-digestion
dilutions must be taken into account when calculating final results. In addition to calculating
sample results from an improper “secondary” manual regression, the laboratory was not including
a 10X dilution factor (derived from bringing the initial digestion volume (Vi) of 20 mL to a final
volume (Vf) of 200 mL) in the final calculated results.
Comment: It appears that, in spite of using improper means for calculating TKN results (as
described above), the data was not significantly impacted. As further support of this assessment,
the laboratory has been able to obtain acceptable results on blind TKN proficiency testing
samples obtained by an approved A2LA-accredited vendor.
D. Finding: The proper ratio of digestion solution to sample was not maintained.
Requirement: Except as set forth in paragraph (b) (3) of this section, an analyst may modify an
approved test procedure (analytical method) provided that the chemistry of the method or the
determinative technique is not changed, and provided that the requirements of paragraph (b)
(2) of this section are met. Ref: Code of Federal Regulations, Title 40, Part 136.6; Federal
Register Vol. 72, No. 47, March 12, 2007. When adjusting sample volumes, the proper ratios of
reagents must be maintained.
Comment: When using the Lachat BD-46 hot block digestion apparatus, the laboratory would
need to add 4 mL digestion solution to 20 mL sample to maintain the ratio described in the
approved method.
E. Finding: The laboratory is not recording the volume of 10N NaOH added.
Requirement: Record volume of 10N NaOH added. Ref: Standard Methods, 19th Edition, 4500-
NH3 D. (4) (e).
F. Finding: The laboratory was not documenting all information necessary to calculate the final
results (i.e., final volume after digestion).
Requirement: All analytical data pertinent to each certified analysis must be filed in an orderly
manner so as to be readily available for inspection upon request. Ref: 15A NCAC 2H .0805 (a) (7)
(A). This is considered pertinent data.
Comment: The volume of sample digested and dilution factor for pre-digestion dilutions was
recorded on the benchsheet, however, the final volume of the digested sample must be recorded
in order to reconstruct the calculated results.
Recommendation: Add an additional column to the TKN bench worksheet to record the final
volume after digestion.
Page 4
#176 City of Durham Water and Wastewater Laboratory
G. Finding: The laboratory was not compensating for any difference between the volume of sodium
hydroxide solution added to samples and standards in the results calculation.
Requirement: When the volume of 10N NaOH used for the samples is different than that used
for the calibration standards this must be compensated for in the calculation. Ref: North
Carolina Wastewater/Groundwater Laboratory Certification Policy based upon SM 19th, 20th,
21st 4500-NH3 D. (5).
Comment: The following formula must be used in the calculation:
mg NH3 – N/L = A x B x (100 + D)
(100 + C)
A= Dilution Factor
B= Concentration of NH3-N/L, mg/L, from calibration curve
C= Volume of 10N NaOH added to the calibration standards, mL
D= Volume of 10N NaOH added to sample, mL
H. Finding: The laboratory is not documenting the pH adjustment (i.e., to >11 pH units) of samples,
blanks and quality control samples after 10N NaOH addition.
Requirement: All analytical data pertinent to each certified analysis must be filed in an orderly
manner so as to be readily available for inspection upon request. All analytical records must be
available for a period of five years. Ref: 15A NCAC 2H .0805 (a) (7) (A) and (G).
Comment: This pH adjustment may be performed using pH test strips, a meter or color-
indicating Ionic Strength Adjuster (ISA).
Recommendation: It is recommended that the laboratory consider using the color-indicating
ISA.
I. Finding: The volume of spike solution used in matrix spike preparation exceeds 1% (but is
<10%) of the total matrix spike volume, and this volume adjustment is not factored into the
calculated results.
Requirement: The volume of spike solution used in matrix spike preparation must in all cases
be ≤ 10% of the total matrix spike volume. It is preferable that the spike solution constitutes ≤
1% of the total matrix spike volume so that the matrix spike can be considered a whole volume
sample with no adjustment by calculation necessary. If the spike solution volume constitutes
>1% of the total sample volume, the sample concentration or spike concentration must be
adjusted by calculation. Ref: North Carolina Wastewater/Groundwater Laboratory Certification
Policy.
Comment: The laboratory had corrected the issue of using >10% spike volume, but was not
factoring the volume adjustment in the calculated results.
IV. PAPER TRAIL INVESTIGATION:
No paper trail performed.
Page 5
#176 City of Durham Water and Wastewater Laboratory
V. CONCLUSIONS:
Correcting the above-cited findings and implementing the recommendations will help this lab to produce
quality data and meet certification requirements. The inspectors would like to thank the staff for their
assistance during the inspection and troubleshooting process. Please respond to all findings.
Report prepared by: Dana Satterwhite Date: January 27, 2010
Report reviewed by: Gary Francies Date: January 29, 2010