Transcript Testing Field Parameters

William G. Maddox
Environmental Specialist II, Valley Regional Office
Department of Environmental Quality
4411 Early Road, Harrisonburg, Virginia
Office: 540-574-7831, FAX: 540-574-7878
[email protected]
Web: www.deq.virginia.gov
Mail: P.O. Box 3000, Harrisonburg, Virginia 22801
List of Field Parameters
 Dissolved Oxygen
 pH
 Total and Free Residual Chlorine
 Temperature
 (Turbidity – not a common effluent limitation.)
 Note: Flow rate is a measurement, though not
obtained using a water sample analysis. It is an effluent
discharge characteristic or parameter.
Regulation
 DEQ Mission Statement:
 DEQ protects and enhances Virginia's
environment, and promotes the health and wellbeing of the citizens of the Commonwealth.
 Over 5,000 people die worldwide everyday from
drinking or bathing in water containing the same
contaminants that are removed at wastewater
treatment plants.
Regulation
 Clean water regulations accounted for benefits of up to
$8 billion at a cost of $2.4 to $2.9 billion. Clean air
regulations provided up to $163 billion in benefits,
while costing taxpayers only about $21 billion.
 http://usgovinfo.about.com/library/weekly/aacost-benefit.htm
Regulation
 Bureaucratic red tape, the difficulty of
finding information, lengthy training in
regulatory requirements, having to
constantly revisit changing regulatory
policy, and haphazard enforcement of the
rules may be an immediate concern but…
 http://www.berr.gov.uk/files/file53236.pdf
Regulation
 You have a stronger, fuller, more aware understanding
of regulation than average and can see that…
 Your efforts support living in a clean and healthy
Virginia environment, benefitting your family and
avoiding health risks for you and others around you.
 You can help others understand this.
Regulation
 Testing is intended to be “reliable, uniform, and
accurate.” (SM, Preface)
 We are considering “field testing and measurement” of
water at the site where the sample was taken or nearby,
not testing and measurement performed in an
environmental laboratory. Analysis is immediately or
within 15 minutes holding time maximum.
 “Field testing” term originated in testing military
equipment under field conditions.
Field Testing
 Characteristics of the parameter dictate the equipment
design and sampling (grab or in situ).
 The ideal design could obtain the same result from any
such instrument of a test of a sample anywhere, every
time. No ideal instrument exists.
 We do our best (hence method regulation, choices,
and lots of care, and the dynamics of improvements).
Field Test – Be Aware of Individual
Variables
 Example - a simple contact sensor like a thermistor
for temperature (or liquid in glass or thermocouples
and such):
 Measures its own temperature, so must be in
equilibrium with the media it is contacting (water –
no heat flow between them)
 Electrical properties are important (resistance, current
– THERMal resISTOR)
 Water is dynamic with lots of possible variations in
temperature (surface, depth, aeration, movement)
Field Testing – Four Basics
 Measure or sample for a representative result of the
discharge characteristics
 Follow approved method
 Follow instrument manufacturer’s recommendations
 Keep good records
Field Testing – You Know….
 VPDES Permit Part II A 2:
 Monitoring shall be conducted according to procedures
approved under Title 40 Code of Federal Regulations Part
136 or alternative methods approved by the U.S.
Environmental Protection Agency, unless other procedures
have been specified in this permit.
 40 CFR Part 136…
 EPA Federal Register - Guidelines Establishing Test
Procedures for the Analysis of Pollutants Under the Clean
Water Act; Analysis and Sampling Procedures
Field Testing
 Need initial demonstration of capability (IDC)
available for each analyst/operator performing
analysis. SM 1020 B.1
 For once per month analysis frequency or less,
establish a set time each monitoring period for
sampling and analysis. If that will not provide a sample
representative of the monitoring period, collect more
samples/perform more analyses.
Dissolved Oxygen
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Winkler (Azide modification)
SM 4500–O B–2001, C–2001, D–2001, E–2001, F–2001.
ASTM D888–09 (A)
USGS/AOAC/Other 973.45B3, I–1575–78.8
Electrode
SM 4500–O G–2001
ASTM D888–09 (B)
USGS/AOAC/Other I–1576–78.8
Luminescence Based Sensor
ASTM D888–09 (C)
USGS/AOAC/Other Footnote 63 Hach Method 10360, Luminescence Measurement of
Dissolved Oxygen in Water and Wastewater and for Use in the Determination of BOD5
and cBOD5. Revision 1.2, October 2011. Hach Company. This method may be used to
measure dissolved oxygen when performing the methods approved in Table IB for
measurement of biochemical oxygen demand (BOD) and carbonaceous biochemical
oxygen demand (CBOD). Footnote 64 In-Situ Method 1002–8–2009, Dissolved Oxygen
(DO) Measurement by Optical Probe. 2009. In-Situ Incorporated.
Dissolved Oxygen
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Oxygen, Dissolved Probe
Container - G, Bottle and top
Preservation - None required
Maximum holding time - Analyze within 15 minutes.
Winkler
Container - G, Bottle and top
Preservation - Fix on site and store in dark.
Maximum holding time - 8 hours.
 Use APHA-type sampler (American Public Health Association
specifications - Displaces three times bottle volume without aeration)
 …or analyze in-situ (Latin – literally “in place”)
Dissolved Oxygen
 Guides:
 Verify the accuracy of the temperature monitoring device
on the meter at least annually over the operating range of
the meter.
 Show calculations of correction factors applied for each
recorded temperature measurement.
 Be careful not to represent the temperature recorded as
effluent temperature if the sample was not collected in
accordance with effluent temperature monitoring
procedures.
Dissolved Oxygen
 Guides:
 Reactive compounds and gases (like hydrogen sulfide and
other sulfur compounds) can interfere with the reading by
reducing probe sensitivity for membrane probes (optical
probes not affected by gases like hydrogen sulfide).
 Measure D.O. after all treatment, including post aeration.
 Keep sensor in moist environment.
 For the optical D.O. method, do not use organic solvents to
clean the sensor but just wipe off any fouling gently with
lens cleaning tissue.
Dissolved Oxygen
 Guides:
 The instrument, both electrochemical and optical, senses
the partial pressure of oxygen at the surface of the
membrane, rather than the actual concentration of oxygen
(weight/volume). The relationship between partial
pressure and concentration is dependent upon
atmospheric pressure and temperature when a reading is
made in the air (i.e., during the air calibration procedure),
whereas, the equilibrium solubility of oxygen in water is
influenced by temperature, salinity, and pressure (of the
gaseous phase).
Dissolved oxygen
 Guides:
 For digital instruments (YSI), the software
compensates for the temperature-related factors after
instrument calibration and during readings
(temperature measured by a thermistor).
Importance of D.O.
 Low dissolved oxygen can impact a stream or lake from
microscopic consumption of organics in wastewater
treatment plant discharges by reducing oxygen sensitive
animal populations.
 Warm water discharges can lower the oxygen content in
streams and lakes as well because warm water holds less
dissolved oxygen than can cooler waters.
 Low dissolved oxygen in streams and lakes can result in
anaerobic activity byproducts that are objectionable,
odorous.
 Oxygen levels high and low are important for treatment
processes.
pH
 Electrometric measurement.
 SM 4500–H+ B–2000
 ASTM D1293–99 (A or B)
 USGS/AOAC/Other 973.41,3 I–1586–85.2
 Automated electrode
 EPA 150.2 (Dec. 1982)1
 USGS/AOAC/Other - See footnote,21 I–2587–85.2
pH
 Container – P (polyethylene), FP (fluoropolymer –
PTFE, Teflon), G
 Preservation - None required
 Maximum holding time - Analyze within 15 minutes.
pH
 Guides:
 Verify the accuracy of the temperature monitoring
device on the meter at least annually over the
operating range of the meter.
 Show calculations of correction factors applied for
each recorded temperature measurement.
 Be careful not to represent the temperature recorded
as effluent temperature if the sample was not collected
in accordance with effluent temperature monitoring
procedures.
pH
 Guides:
 The change in the dissociation constant of water with
temperature means that a temperature recording will need
to go with each pH measurement.
 A true pH neutral point at 7 with no acid or base, pure
water, only applies at 25  C. For the same pure water, at 0
C the measured pH would be 7.47 and at 60 C would be
6.51.
 Most pH measurement issues are due to fouled or poisoned
electrolytes and a clogged reference junction. So,
manufactures of pH electrodes spend a lot of effort to
create and design electrodes that deal with those issues.
pH
 Guides:
 Know that pH is measuring the hydrogen ion
concentration altered by a combination of known and
unknown effects of the meter and electrode.
Calibration is the means to allow for these.
 The outer surface condition of the glass bulb is critical.
The voltage measurement is between the two surfaces
of the glass (sample solution side and conductor of
electrode side).
pH
 Guides:
 The electrode glass surface must come into
equilibrium with the solution being measured.
 Each glass membrane has an imperfection in its
potential-generating nature (asymmetry potential).
Calibration takes care of all if electrode is cared for.
 One error of electrodes can be caused by light below
470 nm(is why they often have light-shielding – dark
color and such). Silver metal exhibits photoelectric
effect.
pH
 Guides:
 Reference electrode portion has a junction or double
junction that can clog, particularly in protein solutions
(double junctions help prevent this).
 Small currents can be induced from fluorescent
lighting and AC motors and such.
 Do not let glass electrodes go dry. Several layers of
water molecules form a hydration layer on the glass
membrane before potentials stabilize.
pH
 Guides:
 Sealed electrodes should not be stored in DI water—
Reason: the sample will accelerate the leaching of reference
solution, which cannot be replaced.
 Alkaline buffers will dissolved the glass and shorten
electrode life (store according to manufacturer).
 Static charges can be transferred to glass electrodes.
 The pH buffers contain high concentrations of phosphate.
Care must be taken during calibration to avoid leaving
traces of buffer on equipment or at the workplace that
could contaminate water samples.
Importance of pH
 pH affects solubility and biological availability of
chemicals in water, including nutrients.
 pH affects life processes that require conditions within
a certain range of pH.
 Certain compounds are more toxic at lower pHs
(metals more soluble).
Total Residual Chlorine (TRC)
 Field TRC measurements have a number of EPA-
approved methods. Most common are DPD and
amperometric methods discussed here.
TRC
 Amperometric direct
 SM 4500–Cl D–2000
 ASTM D1253
 DPD–FAS
 SM 4500–Cl F–2000.
 Spectrophotometric, DPD
 SM 4500–Cl G–2000.
TRC
 Container - P, G
 Preservation - None required
 Maximum holding time - Analyze within 15 minutes.
TRC
 Guides:
 DPD method most widely used.
 Protect DPD powder reagents from temperature extremes
(keep between 50 – 70 F).
 Avoid excess agitation and exposure to sunlight when
sampling.
 Rinse sampler container with several volumes of sample
before collection to help eliminate any possible chlorine
demand on the sample container.
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Source Chlorine Analysis Technical Information Series, Daniel L. Harp, – Booklet No. 17, HACH
TRC
 Guides:
 Testing can have oxidizing agent interferences –
chlorite, chlorate, bromine, oxidized manganese and
such (most methods subject to interferences from
turbidity, color, inorganic and organic compounds and
sample buffer capacity.
 Photometer zeroing compensates for some color and
turbidity.
 Check DPD reagent buffering capacity annually.
Temperature
 Thermometric
 SM 2550 B–2000
 USGS/AOAC/Other - See footnote.32
 (Footnote 32 ‘‘Water Temperature–Influential Factors,
Field Measurement and Data Presentation,’’
Techniques of Water-Resources Investigations of the
U.S. Geological Survey, Book 1, Chapter D1. 1975.
USGS.)
Temperature
 Container - P, FP, G
 Preservation - None required
 Maximum holding time - Analyze.
Temperature
 Guides:
 Many technologies exist to measure temperature. DEQ normally
will see the liquid in glass thermometer, the thermistor, and the
dial-type thermometers (bimetallic).
 DEQ supports not using mercury thermometers for field testing.
 Annual verifications or units purchased and being used within
the expiration dates are needed. Verification is against an NISTtraceable thermometer over the operating range of the unit
(multiple check temperatures), with records on site indicating
the information with the reference thermometer certification
and that that certification is up to date as well.
Temperature
 Guides:
 Do not report held samples’ temperature as “effluent”
temperature (common error). Analyze effluent
temperature immediately and/or in situ.
 Common means of measurement is by an instrument
that measures the temperature of itself, so no heat
exchange should be occurring between the unit and
the sample (needs to be stable).
Record Keeping – From the Permit Records
 Records of monitoring information shall include:
 The date, exact place, and time of sampling or
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measurements
The individual(s) who performed the sampling or
measurements
The date(s) and time(s) analyses were performed
The individual(s) who performed the analyses
The analytical techniques or methods used; and
The results of such analyses.
Record Keeping
 Guides:
 The test method references on site should be up to
date for all records (often see up-to-date references
mixed with older ones – very commonly seen).
 E-documents are to be as accessible on site as
would be hard-copy paper documents.
Record Keeping
 Guides:
 Use no faulty field test equipment for permit-required
monitoring records (temptation is to use it if can and
then get it fixed later). Critical equipment should have
spares available. If pH electrode reading too slow – do
not use it to record a pH. If DPD reagent expired, do
not use it (same with buffers). May be good past dates,
but cannot know.
 For recording errors – line through once and initial.
 Use indelible ink for writing.
Record Keeping
 Guides:
 Exact sample location is to be exact (correct in all
details) - often see inexact location records.
 Keep separate sample times and analysis times
(common problem) unless in situ.
 Thermistor verification check tags are often missing
from meters and should not be (verification by name,
the date, and any correction factors for tags).
Record Keeping
 Guides:
 Detailed field equipment maintenance records are
important for a number of reasons – help preserve
assets - in an enforcement action they may become
critical.
 The wastewater field involves discharging toward
neighboring properties. YOU ARE NOT ALONE.
Record Keeping
 Guide (IMPORTANT):
 Keep accurate records. Plant conditions can change
rapidly.
 Do not try to write a book in a 1 mm X 1 mm form
space, or a book all on one page.
Record Keeping
 Guides:
 When a letter of explanation is required for an
exceedance, and the cause of a problem is not known,
often the permittee states the result must have been a
sampling or analysis error.
 Another cause or two might be – using this reasoning –
an unknown substance discharged, temporarily
affecting the result, or an unknown interferent with
the test may have discharged temporarily.
Record Keeping
 Guides
 Keep an up-to-date O & M Manual on site for field
testing information.
 What records the manual states are suggested to be
kept and what actually are kept can be world’s apart.
Test methods often out of date, and equipment used
out of date.
Record Keeping
 Guide:
 If a problem occurs and a helpful record keeping was
found insufficient for any reason, start keeping it.
 Case-specific record keeping can be GREAT for you
(e.g., spare meter operations check).