United States EPA-600/4-81-044
Environmental Protection Aoril 1982
Agency
&EPA Research and
Development
THE DETERMINATION OF THE MAXIMUM
TOTAL TRIHALOMETHANE POTENTIAL
METHOD 510.1
Prepared for
Joseph A. Cotruvo
Director
Criteria and Standards Division
Office of Drinking Water
Prepared by
Thomas A Beliar
James J. Lichtenberg
Physical and Chemical Methods Branch
Environmental Monitoring and Support Laboratory
Cincinnati, Ohio 45268
Herbert J. Brass
Technical Support Division
Cincinnati, Ohio 45268
Alan A. Stevens
Leown A. Moore
Physical and Chemical Research Branch
Drinking Water Research Division
Municipal Environmental Research Laboratory
Cincinnati, Ohio 45268
U.S. Environmental Protection Agencv
Region 5, Library (PL-12J)
77 West Jackson Boulevard, 12th Floor
Chicago. IL 60604-3590
-------
METHOD FOR THE DETERMINATION OF THE
MAXIMUM TOTAL TRIHALOMETHANE POTENTIAL
METHOD 510.1
1. Scope and Application
1.1 This method is to be used for regulatory purposes only pursuant to
section 141.30 of the trihalomethane (THM) regulation Reference 1.
It should not be used to estimate THM concentrations for any other
purpose in conjunction with the regulation.
1.2 This method is applicable to the determination of the maximum total
trihalomethane potential (MTP) of finished drinking water for those
groundwater supplies that have failed the MTP test due to the
absence of excess disinfectant after seven days of storage as
described in Reference 1.
1.3 The method is designed to yield THM concentrations higher than
those normally found in a distribution system. It is neither a
predictor of distribution system THM concentrations nor a measure
of total precursor and should not be used for these purposes.
Precursor tests are more appropriately conducted under sample
storage conditions that simulate conditions found at specific
locations. Reference 2.
1.4 Other than sample collection, the entire procedure must be
•performed by a laboratory certified for the analysis of total
trihalomethanes (TTHM).
-------
1.5 The method as described is capable of monitoring MTP values between
5 and 200 ug/'. for water supplies with a seven day chlorine demand
of less than 5 ppm using a sample storage temperature of 25°C (or
higher) and a buffered pH range of 9.0 to 9.5.
2. Summary
2.1 Duplicate field samples are collected and transported to the
testing laboratory. At the testing laboratory, the pH of the
sample is adjusted to 9.2 and the free chlorine residual is
increased at least 5 mg/L through the addition of a solution
containing a boric acid buffer and hypcchlorite. The resulting
mixture is hermetically sealed and stored at 25°C or above for
seven days. After seven days, the presence of free chlorine
residual of at least 0.2 mg/L is verified and then is chemically
reduced with a dechlorinating agent. The samples are then analyzed
for their TTHM content according to Reference 3 or 4. It is
recommended that the TTHM analysis be completed within 14 days
following incubation.
«.
3. Interferences
3.1 TTHM precursors, bromine, bromide ion, and to a lesser extent
iodine and iodide ion contained in the rsagents can add to the MTP
value. For this reason, a laboratory reagent blank (LRB) (Section
8) must be routinely monitored. If the LRB appears to add
•significantly to the MTP value, the source of interferant must be
located and eliminated. For field samples, the alternative LRB
Procedure (Section 8.3) may be used. LRB values cannot be
subtracted except as noted in Section 9.3. Blank water and the
-------
combined buffer/hypochlorite reagent are specifically treated by
exhaustive chlorination at elevated temperatures to eliminate
interferences from TTHM precursors. However, upon storage the
combined buffer/hypochlorite reagent and blank water may become
contaminated with THM. Indirect tests for halide ion interference
can be accomplished by an added precursor test (Section 9) or can
be performed by routinely analyzing an EMSL-Cincinnati MTP sample.
Excessive bromide ion interference is indicated by these tests when
the summation of the brominated trihalomethanes exceed 10 % of the
TTHM value.
3.2 Other sources of interferences are discussed in the appropriate
3 4
sections of the required analytical methods. '
4. Apparatus
4.1 Constant temperature storage container — water bath or incubator,
25°C and or above.
4.2 Reagent water system ~ Carbon filtered distilled water or carbon
filtered deionized water.
4.3 Free available chlorine test equipment — as required by the choice
of method (See Sections 7.7 and 7.7.1).
4.4 Reflux apparatus — 1 to 3 L boiling flask, Reflux condenser and
heater.
4.5 Sample Bottles and Seals
.4.5.1 240 ml amber reagent bottles with open top screw caps and
Teflon faced silicone septum liners.
4.5.2 25 ml vials with open top screw caps and Teflon faced
silicone septum liners.
-------
4.6 Narrow range pH paper —- pH range approximately 8 to 10.
4.7 TTHM analytical equipment — See Apparatus in Reference 3 or 4
Section 4.
4.8 Convection Oven - (Optional) Vented, operating temperature near
100°C.
5. Reagents
5.1 Chlorine Solution — approximately 2000 mg/L.
5.1.1 An aqueous solution of chlorine (hypochlorite) is prepared
by either of tne following two methods: (1) dilute 40 ml of
commercial solution of 5.25 percent sodium hypochlorite
(laundry bleach) to 1000 ml with reagent water, or (2)
bubble chlorine gas into reagent water until the solution
turns dark yellow, then adjust the pH to 9.2 or higher with
sodium hydroxide solution.
5.1.2 Reflux the hypochlorite solution for six hours, then remove
the condenser and boil for at least 30 minutes longer to
remove THM's that may have been produced. Cool and store in
an amber glass bottle with a Teflon lined screw cap.
5.1.3 Prior to use, analyze the refluxed chlorine solution to
determine the concentration of free chlorine. Use the
lodometric Method 409A for chlorine as described in Standard
Methods Reference 5.
NOTE: For this test, dilute the chlorine solution such that
10 to 30 ml of titrant is used.
5.2 Blank Water
5.2.1 Treat the reagent water (4.2) as follows: To each liter of
reagent water, add 1.0 ml of 1.0 N sodium hydroxide solution
-------
and 5 mg/L of free chlorine (5.1.3). Reflux the mixture for
16 hours. Cool to 90°C then bubble a contaminant free gas
such as He or N~ through the solution at 50 mL/minute for
at least one hour. Allow the solution to cool to room
temperature, then neutralize with 1.0 ml of 1.0 N sulfuric
acid. Check to make certain that a free chlorine residual
. in excess of 0.2 mg/L remains. If not, repeat the entire
procedure using a higher concentration of free chlorine.
After this treatment, the water should be free of THM's and
THM precursors. Store blank water in a screw cap
septum-sealed bottle in an area known to be free of THMs,
but be certain to check for THM contamination before using.
Blank water is used for the added precursor test (Section 9)
and laboratory reagent blank tests (Section 8).
NOTE: As an alternative to refluxing and gas purging, place
the mixture in a narrow mouth flask and heat in a convection
oven overnight at the boiling point of water. The
temperature of the oven must be adjusted so that the mixture
does not boil.
5.3 Combined Buffer/Hypochlorite Reagent
5.3.1 Boric acid ~ anhydrous, ACS reagent
5.3.2 Sodium hydroxide — ACS reagent (store in a desiccator).
5.3.3 Dissolve 3.5g of dry sodium hydroxide in 400 ml of reagent
water. Add 10.0 g of boric acid. Stir until completely
dissolved. Calculate the volume of chlorine solution
(5.1.3) that contains 60 mg of free chlorine. Add this
volume to the boric acid buffer solution. Reflux the
resulting solution using a magnetic stirrer/hot plate for 16
-------
hours. Remove the reflux condenser and gently boil until
the volume is reduced to about 250 ml. Cool. Take a small
sample and determine the free chlorine residual using one of
the methods referenced in Section 7.7.1, and read the
special note. The free chlorine concentration of this
reagent must be at least 125 mg/L Cl when finally diluted to
300 ml. If sufficient chlorine is not present, then
determine the amount of refluxed hypochlorite solution
(5.1.3) required to produce this final concentration. Add
this amount, then dilute to 300 ml with blank water (Section
5.2). Store this solution in an amber glass bottle with a
Teflon lined screw cap. If.the free chlorine residual drops
below 125 mg/L, then additional refluxed hypochlorite
solution may be added. Ten ml of the buffer/hypochlorite
solution added to 250 ml of sample should provide a buffered
pH of 9.2 (acceptable range 9.0 to 9.5) and a free residual
chlorine value of 5 or more mg/L.
NOTE: As an alternative to refluxing and boiling down to
250 mL, place the solution in a narrow mouth flask and heat
in a convection oven overnight at the boiling point of
water. The temperature of the oven must be adjusted so that
the solution does not boil.
5.4 Dechlorinating agent — sodium sulfite, A.C.S.
5.4.1 Dissolve 2.0 g sodium sulfite in 100 mL of blank water.
Discard after one week.
5.5 3,5-dihydroxybenzoic acid (DHBA) - 97% pure.
5.5.1 Stock DHBA solution: dissolve 0.154 g of DHBA in 1000 mL of
reagent water (4.2).
-------
6. Sample Collection and Handling
6.1 All samples are collected in duplicate, Field Sample 1 (FS-1) and
Field Sample 2 (FS-2), in 240 to 300 ml narrow mouth amber glass
bottles with Teflon lined screw caps.
6.2 Samples are collected from a point in the distribution system
reflecting the maximum residence time.
6.3 Samples are collected headspace free according to the sampling
procedure described in the TTHM analytical method Reference 3 or 4.
6.4 Store all samples at 4°C in the dark in a protected area known to
be free from contamination. Process all samples within 14 days of
collection.
7. Procedure
7.1 Pour about 20 ml of the FS-1 sample into a clean beaker.
7.2 Add the combined buffer/hypochlorite solution (Section 5.3) to the
FS-1 sample contained in the FS-1 sample bottle at the rate of 1.0
ml solution/25 ml sample. Check the pH of the buffered sample with
narrow range pH paper to make certain that the pH is within the
acceptable range (9.0 to 9.5).
NOTE: Do not dip the pH paper into the sample. Touch the pH paper
to a sample wetted stirring rod.
7.3 Fill the FS-1 bottle with the aliquot removed in 7.1.
7.4 Seal the bottle with a Teflon lined septum seal according to the
TTHM method used Reference 3 or 4. Shake for one minute.
7.5 'Store the modified FS-1 sample in the dark at 25°C or higher for
seven days.
7.6 After the storage period, aliquots of the FS-1 sample are
transferred (with minimum agitation) into two 25 ml screw cap
-------
septum seal vials containing 0.2 mL sodium sulfite solution
(Section 5.4'). Seal both vials according to the TTHM procedure.
Identify these containers as Field Sample 1A (FS-1A) and Field
Sample 18 (FS-1B). It is recommended that the FS-1A sample be
analyzed for TTHM within 14 days following incubation, provided the
test is valid (See Sections 7.7 and 7.8).
7.7 Analyze the remaining FS-1 sample to determine the free chlorine
residual content.
7.7.1 Use Standard Methods 409C, 409E, or 409F. 5
NOTE: The buffer required in the Standard Method (Section 7.7.1)
for free chlorine residual may not be strong enough to overcome the
boric acid buffer that is already present in the sample, and
therefore, the sample pH may need to be adjusted to the required
value with 1.0 normal sulfuric acid before proceeding with the free
chlorine residual test.
7.8 The free chlorine residual must be at least 0.2 mg/L. If it is
not, then the entire test is invalid. If the test is invalid,
discard the vials prepared in Section 7.6.
7.8.1 The procedure may be repeated using duplicate or fresh
samples for those Water Supplies that have failed 7.8.
Additional combined buffer/hypochlorite solution should be
added at 7.2 to ensure that the free chlorine residual is in
excess of 0.2 mg/L after 7 days of incubation (7.8).
7.9 If the test is valid, then determine the TTHM content of FS-1A, or
FS-1B if a duplicate is needed, according to the TTHM methods
Reference 3 or 4.
7.10 Use the FS-2 sample as a duplicate for Section 7.8.1, quality
control, or in case of shipping or laboratory accidents only if the
14 day holding time has not been exceeded.
-------
8. Procedure for Laboratory Reagent Blank (LRB) Test
8.1 Substitute blank water (Section 5.2) in the sample bottle for the
sample and analyze according to Section 7.
8.2 An LRB of less than 5 ug/L TTHM should be obtained, otherwise,
abnormally high TTHM values for the field samples will result. If
LRB values are in excess of 5 ug/L TTHM then the laboratory should
obtain a new source of reagent water and/or reagents. If the
contamination source is the reagent water, the alternate procedure
for measuring the LRB in field samples only may be used as
described in Section 8.3; this is allowed only because reagent
water is not added to the field samples.
8.3 Alternate Field Sample Blank.
8.3.1 Purge approximately 100 mL of blank water (Section 5.2) and
the combined buffer/hypochlorite reagent (Section 5.3) in
separate containers for approximately 30 minutes with
nitrogen to remove any THMs.
8.3.2 Add 1.0 mL of the purged buffer/hypochlorite reagent and 0.2
mL of the dechlorinating agent (Section 5.4) to a 25 mL
sample bottle. Fill the bottle just to overflowing with the
purged blank water and seal. Mix by shaking, then determine
the TTHM concentration according to reference 3 or 4 within
14 days. If the solutions were properly purged, the TTHM
value will be less than 1 ug/L.
8.3.3 Store an aliquot of the purged buffer/hypochlorite reagent
(Sectin 8.3.1) headspace free along with MTP samples at
25°C (or higher) for 7 days.
-------
8.3.4 At the end of 7 days prepare a second LRB according to
(8.3.2) using freshly purged blank water, dechlorinating
agent and the 7 day old buffer/hypochlorite reagent from
(8.3.3); but do not repurge the stored buffer/hypochlorite
reagent. The TTHM concentration in this LRB determines the
amount of THM produced by the reaction of free chlorine with
precursors contained in the buffer/hypochlorite reagent. If
the TTHM concentration is less than 5 yg/L, then proceed
with the TTHM measurements of field samples using the same
batch of buffer/hypochlorite reagent. If TTHM values exceed
5 ug/L, then an alternate source of reagents must be
obtained that provide less than 5 ug/L TTHM interference.
9. Procedure for Added Precursor Test
9.1 Fill and seal a tared sample bottle with blank water prepared
according to Section 5.2. Reweigh the filled bottle. Determine
the volume of water contained in the bottle to the nearest mL
assuming that the density of the blank water is 1.0 g/mL.
9.2 Process the blank water according to Section 7 except at Step 7.2
add 10.0 yL of the DHBA solution/25 mL of sample bottle volume
(Section 5.5.1) just before the addition of the buffer/hypochlorite
solution.
9.3 For 100 % recovery, this test should produce 46 yg/L of TTHM.
.These data may be corrected for reagent water blanks (Section 8.1
only). See Table 2 for single laboratory test data.
10. Quality Control
10.1 Analyze EMSL-Cincinnati maximum trihalomethane potential quality
control samples quarterly.
-------
10.1.1 If the brominated species are abnormally high, check
reagents for bromide ion interferences (Section 3.1).
10.1.2 The results must be within 20% of the true value.
10.2 Analyze 10% of all samples in duplicate.
10.2.1 Compare the FS-1A and FS-2A results. The two values must
agree within 20 % at concentrations above 50 ug/L TTHM.
10.3 Analyze laboratory reagent blanks according to Section 3.1, and 8.1
only. See Table 1 for single labortory test data.
11. Calculations
11.1 Calculate the concentration of the TTHM by the procedure described
in the THM method used, do not subtract LRB concentrations for
field samples.
12. Precision and Accuracy
12.1 Single laboratory accuracy and precision data have been collected
by the Technical Support Division (TSD), Office of Drinking Water,
and the Municipal Environmental Research Laboratory (MERL),
Cincinnati, Ohio 45268. These data appear in Tables 1 through 4.
At this time no inter laboratory data are available.
-------
References
1. Federal Register, Thursday, Nov. 29, 1979, Volume 44. No. 231 40 CFR
141.30(C)
2. Stevens, A.A., Symons, J.M. Journal .American Water Works Association,
69, 546, (1977).
3. Federal Register. Thursday, Nov. 29, 1979, Volume 44. No. 231 40 CFR,
Appendix C - Part I
4. Federal Register. Thursday, Nov. 29, 1979, Volume 44. No. 231 40 CFR
Appendix C - Part II
5. Standard Methods. 14th Edition. (1975)
-------
TABLE 1
Single Laboratory (MERL) Test Results for Laboratory Reagent Blanks1^
Sample
Number
1
2
3
4
5
6
7
CHC13
3
1
1
1
2
2
2
.0
.7
.3
.6
.3
.6
.5
Concentration ug/1
CHBrCl2 CHB^Cl
0.3
< 0.1
< 0.1
< 0.1
0.2
0.1
0.2
< 0.1
< 0.1
< 0.1
< 0.1
< 0.1
< 0.1
< 0.1
Standard
Relative Standard
CHBr3
< 0.1
< 0.1
< 0.1
< 0.1
< 0.1
< 0.1
< 0.1
Average
Deviation
Deviation
TTHM
3
1
1
1
2
2
2
.3
.7
.3
.6
.5
.7
.7
2.
0.
3
73
32%
See Section 8
-------
TABLE 2
Single Laboratory (MERL) Accuracy and Precision for
Added Precursor Test^
Sample
Number
1
2
3
4
5
6
7
CHC13
45
51
39
48
48
43
46
Concentration yg/1
CHBrCl2 CHB^Cl CHBr3
3.3
3.9
3.0
3.6
3.7
3.2
3.6
< 0.1 < 0.1
< 0.1 < 0.1
< 0.1 < 0.1
< 0.1 < 0.1
< 0.1 < 0.1
0.1 < 0.1
0.1 < 0.1
Average TTHM
Standard Deviation
Relative Standard Deviation
Average Blank for Test
Expected test Value
TTHM
48
55
42
52
52
46
50
49 yg/L
4.1
8.3%
2 yg/L
46 yg/L
Total Expected Value
Recovery 102%
See Section 9
-------
TABLE 3
Single Laboratory (TSD) Accuracy and Precision
for Addded Precursor Test°
Concentration yg/1
Sample
QC-A
QC-B
QC-B
CHC13
66
100
no
CHBrCl2
0.1
1.9
3.3
CHB^Cl
< 0.1
0.1
0.3
CHBr3
< 0.1
< 0.1
< 0.1
TTHM
66
100
no
True
Value
78
120
120
Percent
Error
-15
-17
-8
BSee Section 10.1.
-------
TABLE 4.
Single Laboratory (TSD) Maximum Total
Trihalomethane Potential For Goundwater
Sample Concentration yg/1
Number CHC13 CHBrClg CHBijCl CHBr 3 TTHM
1 61 20 8.3 1.5 91
2 67 21 9.8 1.3 99
3 71 22 10 1.4 100
4 63 17 8.1 1.1 89
5 68 22 10 1.4 100
6 64 21 10 1.5 97
7 71 22 10 1.4 104
Average 98 yg/L
Standard Deviation 5.3
Relative Standard Deviation 5%
U.S. Environmental Protection Age«c»
Region 5. library (PL-12J)
77 West Jackson Boulevard, I2tn
Chicago. »L 60604-3590
-------
MAXIMUM TRIHALOMETHANE POTENTIAL (MTP) FOR GROUNDWATERS
#
1
2
3
4
5
Sample
Sample Prep.
Flkhart, Circle R
Collected - 5/7/81
In - 5/12, Out - 5/19
Oxford, 6557 Todd Rd.
Collected - 5/15
In - 5/19, Out - 5/26
Clermont, Gulf, Vera Cruz
Collected - 5/15
In 5,19, Out 5/26
Indian Hill, Taft tap
Collected - 5/14
In - 5/19, Out 5/26
Middletown, 3455 Town Bid.
Collected - 5/15
In - 5/19, Out 5/26
Inst.
MTP-1
MTP-2
Inst.
MTP-1
MTP-2
Inst.
MTP-1
MTP-2
Inst
MTP-1
MTP-2
Inst
MTP-1
MTP-2
Free
Residual'
Cl
(ng/L)
__
NF
2.0
< 0.1
NF
4.2
< 0.1
NF
4.6
0.1+
NF
3.9
< 0.1
NF
4.8
TOC
(ng/L)
2.74
3.05
—
1.98
2.88
—
1.12
1.46
—
2.22
2.07
__
1.28
1.18
—
CHC13
22.0
23.7
222.1
5.6
5.7
56.1
4.6
4.5
49.2
5.2
5.3
66.0
2.9
5.2
36.6
THM (yg/L)
CHBrCl2 CHBgCl
4.5
5.6
27.3
4.6
4.4
17.1
7.5
7.9
18.9
6.1
6.0
17.7
7.0
8.3
14.9
1.3
1.4
4.4
3.8
3.0
7.9
12.8
12.0
15.3
6.2
6.3
10.9
12.1
11.5
13.0
CHBr3
0.1
0.2
0.3
0.4
0.3
1.1
2.5
5.1
3.8
0.8
0.9
1.2
5.5
6.2
6.9
TTHM
(lig/l.)
25.9
30.9
254.1
14.4
13.4
82.2
27.4
29.5
87.2
18.3
13.5
95.8
27.5
31.2
71.4
------- |