HomeMy WebLinkAbout#107 2010-final
INSPECTION REPORT ROUTING SHEET
To be attached to all inspection reports in-house only.
Laboratory Cert. #: 107
Laboratory Name: North Cary Water Reclamation Facility
Inspection Type: Municipal Maintenance
Inspector Name(s): Jeffrey R. Adams
Inspection Date: June 22, 2010
Date Report Completed: July 1, 2010
Date Forwarded to Reviewer: July 1, 2010
Reviewed by: Todd Crawford
Date Review Completed: July 9, 2010
Cover Letter to use: Insp. Initial X Insp. Reg. Insp. No Finding Insp. CP
Unit Supervisor: Dana Satterwhite
Date Received: July 9, 2010
Date Forwarded to Alberta: September 2, 2010
Date Mailed: September 3, 2010
_____________________________________________________________________
On-Site Inspection Report
LABORATORY NAME: North Cary Water Reclamation Facility
NPDES PERMIT # NC0048879
ADDRESS: 1900 Old Reedy Creek Road
Cary, NC 27513
CERTIFICATE #: 107
DATE OF INSPECTION: June 22, 2010
TYPE OF INSPECTION: Municipal Maintenance
AUDITOR(S): Jeffrey R. Adams
LOCAL PERSON(S) CONTACTED: Jonathan Bulla and Chris Parisher
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:
The laboratory was clean and well organized. The facility has all the equipment necessary to perform the
analyses. Performance testing samples have been analyzed for all certified parameters for the 2009
proficiency testing calendar year and the graded results were 100% acceptable. Records were maintained
and well organized; however, some quality control procedures need to be implemented.
Due to normal attrition, the laboratory has undergone personnel changes recently and has a new
laboratory supervisor. The efforts taken by the new supervisor in training laboratory personnel and
implementing ICP/MS instrumentation and methodology are commendable.
The laboratory was presented a packet containing the quality control and policy changes and requirements
during the inspection and these policies were reviewed with the laboratory supervisor.
The requirements associated with Findings A, G, J and K are new policies that have been implemented
by our program since the last inspection.
III. FINDINGS, REQUIREMENTS, COMMENTS AND RECOMMENDATIONS:
Ammonia – Standard Methods, 18th Edition, 4500 NH3 F
COD – Standard Methods, 18th Edition, 5220 D
Total Kjeldahl Nitrogen – Standard Methods, 18th Edition, 4500 Norg C (NH3 F)
Nitrate – Nitrite Nitrogen – Standard Methods, 18th Edition, 4500 NO3 E
Total Phosphorous – Standard Methods, 18th Edition, 4500 P E
Metals - EPA Method 200.8
A. Finding: The laboratory is not analyzing matrix spikes.
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Requirement: Unless the referenced method states a greater frequency, spike 5% of samples
on a monthly basis. Laboratories analyzing less than 20 samples per month must analyze at
least one matrix spike each month samples are analyzed. Prepare the matrix spike from a
reference source different from that used for calibration unless otherwise stated in the method.
If matrix spike results are out of control, the results must be qualified or the laboratory must
take corrective action to rectify the effect, use another method, or employ the method of
standard additions. When the method of choice specifies matrix spike performance acceptance
criteria for accuracy, and the laboratory chooses to develop statistically valid, laboratory-specific
limits, the laboratory-generated limits cannot be less stringent than the criteria stated in the
approved method. Ref: North Carolina Wastewater/Groundwater Laboratory Certification Policy.
(See Attachment titled Matrix Spiking Policy and Technical Assistance)
Total Kjeldahl Nitrogen – Standard Methods, 18th Edition, 4500 Norg C (NH3 F)
Ammonia – Standard Methods, 18th Edition, 4500 NH3 F
B. Finding: The laboratory is not recording the volume of 10N NaOH added. This is considered
pertinent data.
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).
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 Standard
Methods, 19th, 20th, and 21st Editions, 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
Ammonia – Standard Methods, 18th Edition, 4500 NH3 F
Nitrate – Nitrite Nitrogen – Standard Methods 18th Edition, 4500 NO3 E
C. Finding: The laboratory is not analyzing a calibration blank and a calibration verification
standard (mid-range) after every ten samples analyzed and at the end of the run.
Requirement: The calibration blank and calibration verification standard (mid-range) must be
analyzed initially (i.e., prior to sample analysis), after every tenth sample and at the end of each
sample group to check for carry over and calibration drift. If either fall outside established
quality control acceptance criteria, corrective action must be taken (e.g., repeating sample
determinations since the last acceptable calibration verification, repeating the initial calibration,
etc.). Ref: North Carolina Wastewater/Groundwater Laboratory Certification Policy based upon
Standard Methods, 20th Edition, 1020 B. (10) (c), 3020 B. (2) (b), and 4020 B. (2).
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Comment: The calibration verification standard is prepared from the calibration stock standard
solution.
Turbidity – Standard Methods, 18th Edition, 2130 B
D. Finding: Turbidity samples are not analyzed in duplicate.
Requirement: Except for Oil and Grease (EPA Method 413.1), settleable solids or where
otherwise specified in an analytical method, analyze five percent of all samples in duplicate to
document precision. Laboratories analyzing less than 20 samples per month must analyze at
least one duplicate each month samples are analyzed. Ref: 15A NCAC 2H .0805 (a) (7) (C).
Fecal Coliform – Standard Methods, 19th Edition, 9222 D, (MF)
E. Finding: The mercury was separated in the maximum holding thermometer in the autoclave
yielding erroneous temperature measurements.
Requirement: Record items sterilized temperature, pressure and time for each run. Optimally
use a recording thermometer. Check operating temperature weekly with a minimum/maximum
thermometer. Ref: Standard Methods, 18th Edition, 9020 B. (2) (i).
Requirement: Each laboratory requesting certification must contain or be equipped with the
glassware, chemicals, supplies and equipment required to perform all analytical procedures
included in their certification. Ref: 15A NCAC 02H .0805 (a) (6) (H).
Comment: If the separation in mercury cannot be rejoined, the thermometer must be replaced
with a new maximum holding thermometer in order to meet these requirements.
Desiccators
F. Finding: The color-indicating desiccant in the desiccator had turned pink signaling that it was
no longer effective.
Requirement: Each laboratory requesting certification must contain or be equipped with
glassware, chemicals, supplies, and equipment required to perform all analytical procedures
included in their certification. Ref: 15A NCAC 2H .0805 (6) (H).
Comment: The desiccant must be replaced or recharged regularly. The color-indicating
desiccant turns pink when exhausted. Regenerate to the original blue color by heating in an
oven at 218°C (425°F) for 1 hour or by following the manufacturer's instructions. When the
color-indicating material no longer returns to the original blue color, the desiccating capacity of
the material also becomes questionable. Desiccant must be replaced when this occurs.
Chemicals and Reagents
G. Finding: The laboratory needs to increase the documentation of purchased materials and
reagents, as well as, documentation of standards and reagents prepared in the laboratory.
Requirement: All chemicals, reagents, standards and consumables used by the laboratory
must have the following information documented: Date received, Date Opened (in use), Vendor,
Lot Number, and Expiration Date (where specified). A system (e.g., traceable identifiers) must
be in place that links standard/reagent preparation information to analytical batches in which the
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solutions are used. Documentation of solution preparation must include the analyst’s initials,
date of preparation, the volume or weight of standard(s) used, the solvent and final volume of
the solution. This information as well as the vendor and/or manufacturer, lot number, and
expiration date must be retained for primary standards, chemicals, reagents, and materials
used for a period of five years. Consumable materials such as pH buffers, lots of pre-made
standards and/or media, solids and bacteria filters, etc. are included in this requirement. Ref:
North Carolina Wastewater/Groundwater Laboratory Certification Policy.
BOD - Standard Methods, 18th Edition, 5210 B
CBOD - Standard Methods, 18th Edition, 5210 B
Recommendation: The seed control values were erratic and the glucose-glutamic acid (GGA)
standard often failed the quality control acceptance criterion requiring qualification of the data. The
laboratory has been sampling the plant influent on a daily basis and using the influent collected as the
seed control. In an effort to achieve more consistent results for the seed controls, samples and GGAs,
it is recommended that the influent be frozen in batches. (See attached guidance on Freezing
Biological Seed.) Another option that may provide more consistency is for the laboratory to use a
commercially-prepared seeding material.
Dissolved Oxygen – Standard Methods, 18th Edition, 4500 O G
H. Finding: Reported values for Dissolved Oxygen exceed analysis hold time.
Requirement: Samples must be analyzed within 15 minutes. Ref: Code of Federal
Regulations, Title 40, Part 136; Federal Register Vol. 72, No. 47, March 12, 2007; Table II.
Comment: The laboratory is measuring Dissolved Oxygen (DO) at the effluent stream within
the 15 minute hold time, but reanalyzing samples in the laboratory and posting the laboratory
values on the Discharge Monitoring Report (DMR) rather than the measurements taken at the
effluent stream.
Conductivity – Standard Methods, 18th Edition, 2510 B
Dissolved Oxygen – Standard Methods, 18th Edition, 4500 O G
pH – Standard Methods, 18th Edition, 4500 H+ B
I. Finding: The laboratory is not posting temperature sensor corrections on the Conductivity, DO
and pH meters.
Requirement: All thermometers and temperature measuring devices must be checked every 12
months (or sooner if the thermometer has been exposed to temperature extremes or other
stresses) against a National Institute of Standards and Technology (NIST) certified or NIST
traceable thermometer and the process documented. To check a thermometer or the
temperature sensor of a meter, read the temperature of the thermometer/meter against a NIST
certified or NIST traceable thermometer and record the two temperatures. The verification must
be performed (at a minimum) at a temperature that corresponds to the temperature used by the
incubator, refrigerator, freezer, etc. In the case of temperature measuring devices used to
perform variable temperature readings, the verification must be performed at a temperature
range that approximates the range of the temperature readings. The thermometer/meter
readings must be less than or equal to 1ºC from the NIST certified or NIST traceable
thermometer reading. The laboratory shall maintain records of established correction factors to
correct all measurements. The documentation must include the serial number of the NIST
certified thermometer or NIST traceable thermometer that was used in the comparison.
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Document any correction that applies (even if zero) on both the thermometer/meter and on a
separate sheet to be filed. (NOTE: Other certified laboratories may provide assistance in
meeting this requirement.) Ref: North Carolina Wastewater/ Groundwater Laboratory
Certification Policy.
pH – Standard Methods, 18th Edition, 4500 H+ B
Comment: The laboratory is certified to analyze sludge waste for pH, but was unaware it needed to
be certified for its effluent analysis. The North Carolina Administrative Code, 15A NCAC 2H .0805 (c)
(7) states: A certified laboratory must submit a written amendment to certification each time that
changes occur in methodology, reporting limits, and major equipment. The amendment must be
received within 30 days of such changes. An Amendment to Certification Application was completed
during the inspection and the certificate attachment has been updated to include the method listed
above. No further response is necessary for this finding.
COD – Hach Method 8000
Metals – EPA Method 200.8
Recommendation: The laboratory should implement a temperature grid check of the block digester by
alternating the well location of the thermometer each time samples are digested and documenting the
location of the thermometer (as well as all samples, blanks and standards) on a grid template. This will
document heating uniformity and consistency of all sample wells in the block.
Total Solids – Standard Methods, 18th Edition, 2540 B
J. Finding: A minimum dried residue weight gain of 1 mg is used to determine the reporting limit.
Requirement: Choose sample volume to yield between 2.5 and 200 mg dried residue. To
obtain the required residue yield, successive aliquots of samples may be added to the same
dish after evaporation or adjust reporting level based upon the weight gain and sample volume
used. The minimum reporting value is established at 2.5 mg/L based upon a sample volume
used of 1000 mL. Ref: North Carolina Wastewater/Groundwater Laboratory Certification Policy
based upon Standard Methods, 20th and 21st Editions, 2540 C. (3) (d) and 2540 B. (3) (b).
Comment: For example, if 100 mL sample is analyzed, and less than 2.5 mg of dried residue is
obtained, the value reported would be <25 mg/L.
Total Suspended Solids – Standard Methods, 18th Edition, 2540 D
K. Finding: A minimum dried residue weight gain of 1 mg is used to determine the reporting limit.
Requirement: Choose sample volume to yield between 2.5 and 200 mg dried residue. If
volume filtered fails to meet minimum yield, increase sample volume up to 1 L. If complete
filtration takes more than 10 minutes increase filter diameter or decrease sample volume. Ref:
North Carolina Wastewater/Groundwater Laboratory Certification Policy based upon Standard
Methods, 20th and 21st Editions - Method 2540 D. (3) (b).
Comment: Since the publication of the Code of Federal Regulations, Title 40, Part 136; Federal
Register Vol. 72, No. 47, March 12, 2007, there is no longer an approved method that allows for
a 1 mg weight gain. Currently, the minimum weight gain allowed is 2.5 mg. In instances where
the weight gain is less than the required 2.5 mg, the value must be reported as less than the
appropriate value based upon the volume used. For example, if 500 mL of sample is analyzed
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and < 2.5 mg of dried residue is obtained, the value reported would be < 5 mg/L. The minimum
reporting value is now established at 2.5 mg/L based upon a sample volume used of 1000 mL.
Total Kjeldahl Nitrogen – Standard Methods, 18th Edition, 4500 Norg C (NH3 F)
Comment: The laboratory’s certificate attachment listed the incorrect method for Total Kjeldahl
Nitrogen (TKN). The attachment listed Standard Methods, 18th Edition, 4500 NH3 C, but the method
employed is Standard Methods, 18th Edition, 4500 Norg C (NH3 F). The North Carolina Administrative
Code, 15A NCAC 2H .0805 (c) (7) states: A certified laboratory must submit a written amendment to
certification each time that changes occur in methodology, reporting limits, and major equipment. The
amendment must be received within 30 days of such changes. An Amendment to Certification
Application was completed during the inspection and the laboratory’s certificate attachment has been
updated to reflect this change. No further response is necessary for this finding.
Metals – EPA Method 200.8
Recommendation: It is recommended that the upper limit of the linear calibration range be
established for each analyte by determining the signal responses from a minimum of three different
concentration standards, one of which is close to the upper limit of the linear range. Care should be
taken to avoid potential damage to the detector during this process. The linear calibration range which
may be used for the analysis of samples should be judged by the analyst from the resulting data. The
upper LDR limit should be an observed signal no more than 10% below the level extrapolated from
lower standards. Determined sample analyte concentrations that are greater than 90% of the
determined upper LDR limit must be diluted and reanalyzed. The LDRs should be verified whenever, in
the judgement of the analyst, a change in analytical performance caused by either a change in
instrument hardware or operating conditions would dictate they be redetermined. Ref: EPA Method
200.8, Section 9.2.2.
IV. PAPER TRAIL INVESTIGATION:
The paper trail consisted of comparing benchsheets and contract lab reports to Discharge Monitoring
Reports (DMRs) submitted to the North Carolina Division of Water Quality. Data were reviewed
for North Cary Water Reclamation Facility (NPDES permit #NC0048879) for February, March and April,
2010. The following error was noted.
Date Parameter Location Value on Benchsheet Value on DMR
2/01/10 NO3 + NO2 Effluent 3.34 mg/L 2.71 mg/L
In order to avoid questions of legality, it is recommended that you contact the appropriate Regional
Office for guidance as to whether an amended Discharge Monitoring Report will be required. A copy of
this report will be forwarded to the Regional Office.
V. CONCLUSIONS:
Correcting the above-cited findings and implementing the recommendations will help this lab to
produce quality data and meet certification requirements. The inspector would like to thank the staff for
its assistance during the inspection and data review process. Please respond to all findings.
Report prepared by: Jeffrey R. Adams Date: July 1, 2010
Report reviewed by: Todd Crawford Date: July 9, 2010
North Carolina Wastewater/Groundwater Laboratory Certification
Matrix Spiking Policy and Technical Assistance (4/6/2010)
Policy Statement
Unless the referenced method states a greater frequency, spike 5% of samples on a monthly basis. Laboratories
analyzing less than 20 samples per month must analyze at least one matrix spike (MS) each month samples are
analyzed. Prepare the MS from a reference source different from that used for calibration unless otherwise stated
in the method. If MS results are out of control, the results must be qualified or the laboratory must take corrective
action to rectify the effect, use another method, or employ the method of standard additions. When the method of
choice specifies MS performance acceptance criteria for accuracy, and the laboratory chooses to develop
statistically valid, laboratory-specific limits, the laboratory-generated limits cannot be less stringent than the criteria
stated in the approved method.
When spiking with multi-component standards, if the method does not specify the spiking components, the
Laboratory Control Spike (LCS) and MS must contain all analytes that are reported.
If the unspiked sample result is in the top 40% of the calibration range, the sample should be diluted and the MS
prepared using the diluted sample. The recovery of the MS samples must be bracketed by the calibration range.
The volume of spike solution used in MS preparation must in all cases be ≤ 10% of the total MS volume. It is
preferable that the spike solution constitutes ≤ 1% of the total MS volume so that the MS 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.
Technical Assistance
Spike Preparation
The spike concentration may be set at either 5 to 50 times the Method Detection Limit (as determined by the
Method Detection Limit or MDL study) for the analyte, or at 1 to 10 times the ambient level (average concentration)
of the analyte in samples. There are 3 options for preparing spikes:
Option 1 (Recommended - easiest) - If the spike solution volume is equal to 1% or less of the total
sample volume, direct subtraction of the unspiked sample is allowed. When the volume of the standard
solution spiked into a sample or a sample extract is less than 1% of the total volume then the final
concentration need not be adjusted (e.g., 10 µL of spike solution added to a 1 mL final extract results in
only a negligible 1% change in the final extract volume).
Option 2 - Adjust spike solution to a known volume with sample. In this case the sample concentration
must be adjusted. When the volume of spike solution exceeds 1% of the total MS volume the sample
concentration must be adjusted prior to determining spike recovery.
Option 3 (Not recommended – most difficult) - Add spike solution to a full volume sample. In this case,
the spike concentration must be adjusted. When the volume of spike solution exceeds 1% of the total MS
volume the spike concentration must be adjusted prior to determining spike recovery.
Spike Preparation Examples
Option 1 - If the spike solution volume is equal to 1% or less of the total sample volume, direct subtraction of the
unspiked sample is allowed.
Option 1 Example:
0.5 mls of a 1000 mg/L standard spike added to 100 mls of sample has a theoretical value of 5 mg/L.
(A) The spiked sample recovery is 5.1 mg/L
(B) If the unspiked sample result is 0.5 mg/L
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(C) Theoretical value is 5.0 mg/L
The Percent Recovery = spiked sample recovery (A) – unspiked sample result (B) divided by theoretical
value (C) X 100 or
5.1 – 0.5 X 100 = 92% recovery A – B X 100 = Percent recovery
5.0 C
Option 2 - Adjust spike solution to a known volume with sample. In this case the sample concentration must be
adjusted.
Option 2 Example 1:
10 mls of spike (concentration 50 mg/L) brought to 100 mls with sample the theoretical MS value is 5 mg/L.
(A) The spiked sample recovery is 5.1
(B) If the unspiked sample result is 0.5 mg/L
(C) % sample is 0.90 (sample volume used (90) divided by final volume (100))
(D) Theoretical value is 5.0 mg/L
The Percent Recovery = spiked sample recovery (A) – (unspiked sample result (B) x % sample (C))
divided by theoretical value (D) X 100 or
5.1 – (0.5 x 0.9) X 100 = 93% recovery A – (B x C) X 100 = Percent recovery
5.0 D
Option 2 Example 2: Larger spike volume
25 mls of spike (concentration 50 mg/L) brought to 250 mls with sample the theoretical MS value is 5
mg/L.
(A) The spiked sample recovery is 5.6
(B) If the unspiked sample result is 0.5 mg/L
(C) % sample is 0.90 (sample volume used (225) divided by final volume (250))
(D) Theoretical value is 5.0 mg/L
The Percent Recovery = spiked sample recovery (A) – (unspiked sample result (B) x % sample (C))
divided by theoretical value (D) X 100 or
5.6 – (0.5 x 0.9) X 100 = 103% recovery A – (B x C) X 100 = Percent recovery
5.0 D
Option 3 - Add spike solution to a full volume sample. In this case the spike concentration must be adjusted.
Option 3 Example:
5 mls of a spike (concentration 100 mg/L) is added to 100 mls of a sample (105 mls final volume).
(A) The spiked sample recovery is 5.1
(B) If unspiked sample result is 0.5 mg/L
(C) Spike conc. adjustment is 0.9524 (sample volume (100) divided by sample + spike volume (105))
(D) Actual spike value is 4.7619 (Theoretical value (5 mg/L based on 100 ml sample) x C)
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The Percent Recovery = spiked sample recovery (A) x (sample volume divided by sample volume + spike
volume (C)) – unspiked sample result (B) divided by Actual spike value (D) X 100 or
(5.1 x 100 ) – 0.5 (A x C) – B X 100 = 91.5%
100+5 X 100 = 91.5% recovery D
4.7619
Corrective Action/Qualifications for MS
Spike accuracy is usually based on a range of percent recovery (e.g., 80-120%). Refer to the method of choice for
specific acceptance criteria for the matrix spikes until the laboratory develops or adopts statistically valid,
laboratory-specific performance criteria for accuracy. If a MS fails, and the LCS is acceptable, qualify the data for
the MS sample. Repeated failures for a specific matrix may require use of an alternate method or method of
standard addition. Base the sample batch acceptance on the results of the LCS analyses (and other quality control
results) rather than the MS alone, because the matrix of the spiked sample may interfere with the method
performance. If a MS and the associated LCS fail, re-prepare and reanalyze affected samples.
Post Digestion Spikes (PDS)
Post Digestion Spikes (PDS) are used for some analyses (e.g., metals) to assess the ability of a method to
successfully recover target analytes from an actual sample matrix after the digestion process has been performed.
The PDS results are used with MS results to evaluate matrix interferences. The MS and PDS should be prepared
from the same environmental sample. A PDS is not to be analyzed in place of a MS. Post Digestion Spikes must
be reported as post-digested and must not be misrepresented as pre-digested spikes. (Exception: TCLP and
SPLP samples are always spiked post digestion.)
Corrective Action/Qualifications for Post Digestion Spikes
In general, if the MS recovery for an analyte does not fall within the quality control acceptance range but the PDS
recovery is acceptable, then a matrix affect (associated with the preparatory process) should be suspected and
the unspiked sample results must be qualified on the basis of the matrix spike recovery. However, when historical
data for the effect does not exist, the laboratory would normally be expected to perform a second digestion and
reanalysis of the MS to confirm the result. The result would be confirmed if the MS recoveries and PDS recoveries
for both sets of analyses were similar in magnitude and bias. When both the MS recovery and PDS recovery for a
particular analyte falls outside of quality control acceptance range in the same manner (i.e., the PDS and MS
failures are of similar magnitude and the direction of bias is the same), confirmatory analyses are unnecessary but
the data must be qualified.
Parameters Excluded from MS Requirements
Acidity Alkalinity
BOD/CBOD Aquatic Humic Substances
Chlorophyll All Bacteriological Parameters
Color – ADMI Color - PtCo
Conductivity Dissolved Oxygen
Ignitability All Residues
Paint Filter Test Turbidity
pH Temperature
Salinity Sulfite
Total Residual Chlorine Vector Attraction Reduction (All Options)
(Field Laboratories and Field Setting analyses are exempt.)
Freezing Biological Seed
In order to maintain a more consistent seed source, the laboratory may collect a sufficient quantity of
influent (or other viable source such as settled domestic wastewater supernatant, mixed liquor from an
activated-sludge treatment facility, etc.) and incubate overnight at 20ºC. Screen to remove large solid
particles. This may be accomplished by filtering through glass wool. Pour quantities (i.e., a sufficient
amount to be used daily) with constant stirring into smaller containers leaving some headspace to allow
for freezing. Constant stirring while filling the containers ensures homogeneity. Freeze in batch lots.
Test the lot of seed after freezing to determine the amount needed, for seed controls, GGA standards
and samples, to insure method requirements are met.