Hi Mike,
You will be receiving hard copies of the attached OER today. | also wanted to respond to the written comments you
provided on the last OER submitted, The following correspond to your numbered comments which | have also attached:
1. Alltables in the report have been revised to correlate the TTHM results to the sample site numbers matching
MDEQ records. References to the number of exceedences have also been revised accordingly.
2. The average ozone dosage for April 2015 was 2.4 mg/l. The system is capable of much more than that, but
higher dosages are not necessary and bromate formation is a concern.
3. The current model is adequate to evaluate the transmission main size along Dupont and Bishop from a
conservative standpoint. Although all model domestic demands have not been revised yet, the fire flow demand
is much larger and dictates the main size. Additionally, domestic demands will be decreasing.
4. Veolia provided recommendations in a Technical Memo dated 3/30/15. In that memo Veolia recommended a
permanganate dosage of about 1.0 mg/I and referred to 10% TOC removal improvement. Pages 4 and 17 of the
report have been revised accordingly.
Comment noted — no changes to report needed.
City staff are investigating the existence of valves shown on the system map for the pressure zone.
Comment noted — no changes to report needed.
Agree. Options in the report to reduce storage used have been revised so as not to limit the volume of Reservoir
#3.
9. Comment noted — no changes to report needed.
ANA
Jeffrey R. Hansen
Senior Project Manager
Lockwood, Andrews
& &Newnam, Inc. Inc.
KACO WN DALY COMPANY
1311 South Linden Road, Suite B « Flint, MI 48532
T 810.820.2682 C 810.333.3201
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xxxEND_PAGE:deq04_b578_6377_6764_117
Operational Evaluation Report
city of Flint .
: : Trihalomethane
_ Formation Concern
_ May.29, 2015
_ In Response to February 2015 Sample Results
4 Lockwood, Andrews
& Newnam, Inc.
: A“LEOJA DALY COMPANY.
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CITY OF FLINT
Operational Evaluation Report
May 29, 2015
TABLE OF CONTENTS
“l. Background
_Water Supply Trai
1
Recent Improvements an‘
1. Phase | WTP Improvements
_..2. Past Pilot Study & Testing
Improvements for Full Time Oper:
g by Oth
6. Conclusions _
‘ Lockwood, Andrews
Page i [an & Newnam, Inc.
ALEG A DALY COMPANY
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CITY OF FLINT
Operational Evaluation Report
May 29, 2015
TABLE OF CONTENTS
perational Recommendations
frastructure Change Recomm
C._ Distribution System _
<i Lockwood, Andrews
Page ii [on & Newnam, Inc.
A LEG A DALY COMPANY
|
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CITY OF FLINT
Operational Evaluation Report
May 29, 2015
EXECUTIVE SUMMARY
Environmental Protection Agency (EPA) and Michigan Department of Environmental Quality
(MDEQ) regulations require that public water suppliers test drinking water quarterly
throughout the distribution system for disinfectant by-products (DBP’s). Two categories of
DBP’s, tri-halomethanes (THM) and halo-acetic acids (HAA5), are regulated and must be
tested for. The City of Flint began operation of their water treatment plant (WTP) full time
with the Flint River as the source on April 25, 2014. Since that time, five quarters of samples
taken have resulted in annual average violations for total THM. Prior to the first violation
(Nov. 2014), the City hired Lockwood, Andrews & Newnam, Inc. (LAN) to complete this
Operational Evaluation Report (OER) in conformance with EPA guidelines with the goal to
determine the cause(s) of high levels of THM and evaluate possible solutions.
The EPA promulgated the Stage 2 Disinfectants and Disinfection By-Products Rule (DBPR) in
January 2006 which set maximum contaminant levels (MCLs) for total trihalomethanes
(TTHM) and HAAS based on an annual running average, tested quarterly, for a given
sampling location. The City of Flint reports levels from 8 sampling test locations. Of the five
quarterly sampling cycles since Flint began operating the WTP full time, HAA5 levels have
been acceptable but TTHM levels have exceeded the MCL. Four sampling sites were in
violation following the third sampling cycle and those sites in violation have been reduced to
a single site for the most recent cycle.
A number of issues were identified as possibly contributing to the high THM levels measured.
1. Inefficient ozone system functionality which led to in increased chlorine feed.
2.. Upstream source influences in terms of increased chlorine demand.
3. Bypass stream around softening contributed to chlorine demand and increased total
organic carbon (TOC) levels in the effluent.
4, Unlined cast iron pipes in the distribution system contributing to chlorine demand.
5. High water age in the distribution system due to:
a. Broken valves causing less than ideal flow patterns
b. Inefficient pump station pressure zones
c. Water storage volumes in excess of that needed for today’s demands
d. Oversized water mains
e. Low water demands
6. High chlorine demand in filters.
7, High THM formation potential (THMFP) in source water.
8. Less than optimal removal of THM precursors.
A graphical representation of how the factors above relate to the timing of THM compliance
sampling is shown as Table 1. Compliance sampling dates are hatched. Each row in Table 1
describes a factor than can lead to increased THM levels and the table defines when each of
those factors applied. Note the convergence of nearly all factors around the second sampling
period on August 21, 2014 to create what appears to be a worst case scenario. The table also
shows that the factors listed as those that the City can control have been addressed prior to
cl sampling periods. Monthly operating report data up to May 1, 2015 is depicted on the
Table,
Page 1 of 22 Lockwood, Andrews
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ZZ 40 Z aBeq
Uo!
ANVdWOD AIVO V 033 ¥
“OU} UBUMON PF
SMOIPUY "POOMyd07]
TABLE 7 ~ SUMMARY OF NEGATI
Softening bypass stiéam over’ 20% of plant flow |
lOzone system not teeding optimally eee
Using tull water storage capacity of WSR & CSR
IChiarine teed at WTP 7.0 mg/ or'more
Dates of occurrence
Dates of occurrence and expected to repeat in future years
Comptiance sampling date
Factors under Flint stall control
fint River characteristics
system factors
INFLUENCES ON THM COMPLIANCE SAMPLING.
S10z ‘6c ACW
Henjeaq jeuoHessdO
INIT 40 ALD
Hoday uo:
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CITY OF FLINT
Operational Evaluation Report
May 29, 2015
ACTION PLAN
The City of Flint has signed an agreement with the Karegnondi Water Authority (KWA) to
purchase raw water drawn from Lake Huron. The KWA system is currently under
construction and expected to be operational by late 2016. The water supply from Lake Huron
will have entirely different water quality characteristics from the Flint River and those
characteristics are expected to yield drastically reduced DPB formation. With that, non-
structural options to help reduce THM levels are much preferred over solutions requiring new
construction. Therefore, two categories of actions have been devised: Stage 1 being actions
that can be completed relatively quickly without major construction and Stage 2 consisting of
either long term actions or solutions requiring major construction. The City is actively
working to complete Stage 1 actions as soon as possible. Stage 2 actions are to be
implemented only if Stage 1 actions are ineffective in adequately reducing TTHM levels and
therefore Stage 2 is contingent upon the outcome of Stage 1. As of the date of this report,
status updates for action items are shown in red.
Stage 1 — Immediate Actions
¢ Hire third party water quality expert to complete independent ‘water audit’
o The City hired Veolia Water to review all water quality related operations,
procedures, actions taken and planned responses. Recommendations from
Veolia were provided in a report and technical memo dated 3/12/15 and
3/30/15 respectively.
¢ Obtain an in house THM analyzer to allow regular operational monitoring of THM
levels
o THM analyzer was installed 2/17/15.
* Hire ozone system manufacturer to troubleshoot ozone system
o Manufacturer and controls programmers performed on site evaluations
followed by corrective modifications in January 2015.
« Bench scale jar testing
© Match existing process and assess possible areas of improvement
= Existing process was simulated and an evaluation of existing chemical
feed dosages has been completed by LAN.
= Existing process TOC profile was developed by Veolia.
o Simulate potential modifications to treatment process
= Soda ash softening evaluation completed and PAC feed testing
completed by LAN.
o Evaluate coagulation and flocculation polymer aid feeds to assist with TOC
removal
* Evaluations of polymer aids completed by LAN and PVS Technologies.
© WTP operational changes
o Discontinue softening bypass stream to reduce chlorine demand
= Operational directive has been set to soften no less than 80% of flow.
o Disinfection of filter beds to reduce chlorine demand
= Utility Service Group contracted by City and condition assessment
completed. Controls improvements have been completed.
o Begin coagulation and flocculation polymer aid feeds to assist with TOC
removal if bench scale test results are positive
= Jar testing completed to date has not indicated a meaningful benefit to
feeding coagulation/flocculation polymer aids. Increased ferric doses
have been implemented at the WTP based on positive jar test results.
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A ® LEG A DALY COMPANY A DALY COMPANY
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CITY OF FLINT
Operational Evaluation Report
May 29, 2015
e Increase water main flushing efforts to minimize stagnant water
o Flushing efforts are ongoing as needed based on chlorine residual levels
measured in the system.
« Water system modeling to identify areas with high water age and potential solutions |
o The water model has been improved and preliminary results, including
system wide water age, have been produced. Water demand updates and |
reconciliation with operator’s data are underway with expected completion in |
mid June, 2015. |
o Cedar Street Pump Station potential recirculation
= Water model analysis to be completed in June 2015,
o West Side Pump Station potential recirculation
= Water model analysis to be completed in June 2015.
o Storage tank volume use
= Operating levels of West Side and Cedar Street reservoirs have been
lowered to reduce water age
eo Possible broken closed vaive locations
= Model has been updated with known broken valve locations. Model
results are being evaluated for indications of other possible broken |
valves. City has also initiated valve assessment program. |
o Locations in need of flushing |
|
|
= High water age areas have been identified in the water model, Further
evaluation is expected to be done by July 1, 2015 to determine most
effective flushing points.
Stage 2 — Contingent Actions
e Fix ozone system
o Repairs have been made to gauges and programming and the system is
producing proper ozone and functioning under manual operation. Further
minor repairs are planned for the 1* quarter 2015 to allow automatic
operation,
« Start feeding coagulation and flocculation polymer aids to lower TOC, if not
completed in Stage 1
o Polymers evaluated by LAN did not demonstrate notable benefit.
o PVS Technologies evaluated a proprietary polymer that showed little benefit.
© Convert to lime and soda ash softening
© Cost effective analysis to be developed, if necessary, based on effectiveness of
new GAC filter media.
¢ Change disinfectant to chloramine or chlorine dioxide until KWA
o Cost effective analysis to be developed, if necessary, based on effectiveness of
new GAC filter media.
¢ Install pre-oxidant feed at intake to optimize ozone disinfection
o Permanganate feed at intake was evaluated! and recommended by Veolia to
help with TOC removal.
¢ Replace filter media with granular activated carbon (GAC) media
o Design of filter anthracite media replacement with GAC media is in progress.
GAC medlia is expected to be installed by mid July 2015.
« Implement advanced treatment for THM precursor removal
o Cost effective analysis to be developed, if necessary, based on effectiveness of
new GAC filter media.
,
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CITY OF. FLINT
Operational Evaluation Report
May 29, 2015
® Increased main flushing based on water modeling results
o Water model analysis to be completed in June 2015.
e Continue valve replacements with water model assistance
o Water model analysis to be completed in June 2015.
e Emphasize cast iron pipes on water main replacement priority list
o Flint has bid replacement of over 2 miles of 24” steel pipe along Dupont and
Bishop Streets to be completed this coming construction season if the City
can allocate funds. The water main section is considered a critical
transmission main, and is expected to contribute to decreases in water age
when complete.
THM samples have been taken and tested 5 times for regulatory reporting since the City
began using the Flint River for supply. Numerous additional sets of samples have been
taken by the City for internal operational monitoring. Compliance samples were taken in
May 2014, August 2014, November 2014, January 2015, February 2015, and May 2015.
The average of all eight sample sites in May 2014 was 100.2 ug/l and the most recent
average of samples taken in May 2015 was 56.7 ug/l. The MCL defined by the EPA is 80
ug/l.
Page 5 of 22 Lockwood, Andrews
&Newnam, Inc.
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CITY OF FLINT nse
Operational Evaluation Report %
May 29, 2015 .
1 BACKGROUND
The City of Detroit Water and Sewer Department (DWSD) has historically provided drinking
water for the City of Flint and Genesee County. In the late 1990's growing concern regarding
the reliability of the DWSD supply prompted the City of Flint to upgrade their existing water
treatment plant (WTP). Those improvements, defined as Phase I, were completed in 2005
and were intended to allow the Flint WTP to operate, using the Flint River as the source, for
an extended period of time in the event that supply from the DWSD was temporarily
interrupted. Additionally, the Phase | improvements set the stage for Flint to break free from
dependence on the DWSD supply and water charges over which they had no control,
A. WATER SUPPLY TRANSITION
1. Detroit Water and Sewer Department (DWSD)
Until recently the Genesee County and Flint region had been provided drinking water
by the DWSD. However, due to excessive cost increases and reliability issues with
the DWSD system other options had to be explored.
2. Karegnondi Water Authority (KWA)
In 2010 the Karegnondi Water Authority (KWA) was formed for the purpose of
developing a new water supply from Lake Huron to serve the region in lieu of the
DWSD supply and the City of Flint elected to join. The KWA expects the new system
which is currently being constructed to become operational by the fall of 2016.
3. Flint River — Interim Period
With a renewing water supply agreement between Flint and the DWSD being
terminated by the DWSD (effective April 30, 2014) and the KWA system not
expected to be operational until late 2016, the City of Flint decided. to initiate
operation of the existing WTP full time utilizing the Flint River as the interim water
source. A variety of WTP improvements were necessary for the Flint plant to become
a full time plant. For purposes of this report, Phase Il improvements to the Flint WTP
are improvements intended to allow the plant to operate full time with either the Flint
River as the source or the KWA supply as the source.
B. TTHM VIOLATIONS
The EPA and MDEQ method of determining if TTHM sample results exceed the MCL uses
a locational running annual average (LRAA). Flint’s first TTHM violation was cited by the
MDEQ following the third cycle of sampling completed in November 2014, Of the 8
sampling sites, 4 were in violation. At that time the MDEQ used the following calculation
for determining if the MCL had been violated:
(2 x current quarter value + previous 2 quarter values) / 4 = Operational Evaluation Value
Flint has now completed tests for 5 quarters and a straight annual running average
applies. Based on samples taken on May 18, 2015 the number of sites in violation of the
THM MCL limit has decreased to one. The May 2014 average across all test sites was
100.2 ug/l and the May 2015 average is 56.7 ug/l with the highest individual site result of
72.4 ug/l. Test results are tabulated in Table 2. HAA5 sample results are shown in Table
3, of which Flint has had no violations.
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CITY OF FLINT.
Operational Evaluation Report
May 29, 2015
TABLE z= TTHM TEST RESULTS CO)
WIP Tap
1) 3719 Davison
McDonalds
2) 822 S, Dort Hwy
BP Gas Sta.
3) 3302 S. Dort Hwy
Liquor Palace
4) 3606 Corunna
46.1 60.8 53.6
111.6 127.2 63.5 72.2 60.2
Taco Bell 79.2 | 181.3 54.7 78.1 72.0
Papo) mening 106.4 | 196.2 50.8 | 1052 | 935
Saliern Housing. 82.2 | 112.4 72.7 | 68.3 | 65.9
als} Cli 88.2 | 144.4 60.5 | 76.4 | 69.4 |
eee 1 Sacinaw 96.5 118.3 45.2 67.7 54.9
TTHM MCL = 80 ug/l
WIP Tap a 36 (taken June 14, 2014) wa | a
Davis Baan 64 43 16 9.0 16 33.0 21.0
oe 38 40 21 9.0 16 27.0 | 21.5
Cee teisce Hwy) 59 31 15 9.0 17 26.8 | 18.0
a 50 24 15 9.0 16 24.5 16.0
peaee ening 55 17 24 9.0 15 | 26.3 16.3
Se Hotere 41 25 5 2.0 10 18.3 | 10.5
oe 49 30 17 9.0 22 26.3 19.5
N. lint im | 48 37 18 9.0 17 | 28.0 | 20.3
HAAS MCL = 60 ug/l
C. WATER TREATMENT PLANT RECENT IMPROVEMENTS & STATUS
1. Phase | WTP Improvements
Since 1965, the Flint WTP has remained a secondary or backup supply system to the
DWSD primary supply. Typically the secondary supply for a public water system is
expected to be needed only during emergency situations and normally is designed for
short term operation such as providing the average daily demand for a few days.
Conversely, Phase | improvements were designed with the intent to upgrade the Flint
WTP in order to allow for an extended short term period (6 weeks) because of the
perceived high risk that the DWSD supply would fail and remain out of service for an
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CITY OF. FLINT.
Operational Evaluation Report
May 29, 2015
extended duration. Regardless, the Flint WTP was still intended to serve as a standby
‘plant and as such the Phase | improvements lacked redundancies that would be
required for a primary supply WTP.
2. Past Pilot Study & Testing
During design of the Phase | improvements a treatability study was completed by
Alvord, Burdick & Howson, LLC (AB&H) in 2002. The Treatability Study evaluated
the current treatment processes that are in place at the Flint WTP today with the Flint
River as the source. The report recommended the following:
TABLE ame — 2002 WTP TREATMENT RECOMMENDATIONS
se Point of
E = Purpose Application _
Sodium permanganate Zebra mussel control Troe
Taste & odor removal, disinfection | Diffusor basin
Coagulation Rapid mix
Turbidity & TOC removal Rapid mix
Turbidity & TOC removal Floc basin
Ozone
Ferric chloride
Coag aid polymer
Floc aid polymer
Lime Softening Softening basin
Soda ash Softening Softening basin
Carbon dioxide pH adjustment Recarb basin
Media filters Filtration N/A
Chlorine Disinfection Filter effluent
Of the recommended items, zebra mussel control, coagulant and flocculation
polymer aids, and soda ash feed have not been incorporated into the treatment
process.
3. Phase Il WTP Improvements for Full Time Operation
Phase i] WTP improvements are those needed to convert the Flint WTP from a back-
up supply to a primary supply plant. A number of improvements have already been
constructed as they were necessary to operate full time when treating water from the
Flint River. The improvements under the title of Phase II that have been completed or
are nearly complete include installation of the future raw water feed connection point
and valving for the KWA supply, upgrades to the lime sludge lagoon, the lime sludge
lagoon decant and disposal system, decant pump station and force main, installation
of mid-point chlorination before filtration, and upgrade of the electric feed sub-
station.
Additional improvements to the Flint WTP that are to be completed to become part of
the normal treatment process using water supplied by the KWA are:
« New oxygen and nitrogen storage facilities for the ozone system (under
construction)
e New coagulant feed system
Electrical
© Pump Station #4 upgrades (under construction)
© SCADA and controls upgrades
o Filter transfer pump station feeders |
¢ Pump replacements and VFD installation in the low and high service pump |
station (under construction) '
* Filter transfer pump station to Dort Reservoir
e Facility security improvements
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CITY OF FLINT
Operational Evaluation Report 4
May 29, 2015 5 :
ee ao
Il, SOURCE WATER EVALUATION
A, DATA ANALYSIS
Based on past data collected and the 2002 Treatability Study by AB&H, the Flint River
water quality varies seasonally with higher hardness and alkalinity experienced in the
winter. Higher magnesium concentrations are also experienced in the winter, adding
difficulty to the settling process due to neutrally buoyant floc. General water quality
average characteristics recorded for the 2002 Treatability Study as compared with average
characteristics recorded in 2014 are shown in Table 5 below.
TABLE 5
FLINT RIVER WATER QUALITY CHARACTERISTICS
‘Hardness - a
870-1230
2001
Apr—Oct (7300 max)
2014 10.3 1900-9000
May—Oct 522ii4 | 207 (48,300 max) ney
The Flint River characteristics do not appear to have changed significantly over the past
10+ years. Note that near the time Flint initiated withdrawal from the Flint River
investigation by City staff revealed a sewer leak upstream of the plant that may have
contributed to the total Coliform count. The leak was subsequently repaired.
B. CONCLUSIONS
Considering the minor changes in Flint River water quality, much of the information
contained in the 2002 Treatability Study by AB&H remains relevant today. Data from that
report assumed to be consistent today include the following:
e Flint River is influenced by groundwater from a dolomitic aquifer
¢ Hardness varies seasonally with higher hardness and alkalinity in the winter
¢ Hardness, alkalinity, magnesium concentrations tend to be reduced by run-off
In development of the 2002 Treatability Study, processes were simulated which resulted
in low THM levels. Therefore, information contained in that report was used to assist
with establishing a baseline jar testing procedure as discussed further in Section Ill.
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CITY OF FLINT
Operational Evaluation Report Ei! :
May 29, 2015 ay i
aa
IH. TREATMENT PROCESS EVALUATION
A, EXISTING PROCESS DESCRIPTION
The existing WTP consists of an intake with screening from the Flint River, low lift
pumping, ozonation, rapid mix, flocculation, settling, softening, recarbonation, filtration,
storage and high service pumping. A process diagram is shown as Figure 1.
1. Intake
A 72” diameter pipe draws water from the Flint River through 2 traveling screens to
the low lift pump structure. No chemicals are currently fed for Zebra mussel control
or pre-oxidation as recommended by the 2002 Treatability Study. Manual removal of
zebra mussels is more economical than installation of chemical feed equipment
considering the short term need,
2. Ozone
There are 2 ozone generators designed to provide adequate ozone for a WTP flow of
up to 36 mgd. There are 3 ozone contact basins. The ozone generators were
designed to produce 900 Ibs/day at 10% concentration and up to 1300 Ibs/day at 6%
concentration each. Prior to recent repairs, readings indicated a production rate of
approximately 700 Ibs/day at 4% concentration. It is possible that before the recent
improvements the ozone feed might not have been optimized. In fact, it is known
that less than optimal ozonation previously led to increased chlorine feed which
would have contributed to THM formation.
3. Rapid Mix
East and West rapid mix chambers allow chemical feed prior to the flocculation
basins. Each rapid mix chamber is equipped with a 5 hp mixer.
4. Coagulation / Flocculation
The WTP contains two equally sized flocculation basins, east and west, and each
basin provides tapered or gradually slowed mixing from inlet to outlet. There are
fifteen 2 hp mixers for each basin with VFDs to control mixing speed. The 2002
Treatability Study recommended feeding both coagulation and flocculation polymer
aids. Neither polymer aid is being used today because turbidity and TOC removals
have been sufficient to meet regulatory requirements.
5. Settling
Primary clarification takes place within 3 basins containing plate settlers. The settlers
are operating as designed but are due for cleaning.
6. Softening
Again, there are two basins for softening: east and west. Each basin is 120’ in
diameter and contains a solids contact softening unit. Each softening basin/unit has a
design capacity of 18 mgd. The east clarifier has an effluent weir imbalance that the
City intends to fix when low demands allow for construction. Low lift pumping
limitations, flow control to the basins, malfunctioning polymer feed pumps, control
restrictions on residuals removal, and fluctuating demands have made it difficult for
WTP staff to stabilize the softening process. Softening is accomplished by feeding
lime. The decision was made by the City not to feed soda ash in order to remove
non-carbonate hardness because acceptable hardness levels could be achieved with
lime feed only and softening is short term until Lake Huron water becomes available.
Lime and soda ash softening is a possible consideration to assist with TOC removal
and thus reduce THM formation.
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CITY OF FLINT
Operational Evaluation Report
May 29, 2015
7. Recarbonation
Recarbonation for pH adjustment is accomplished in east and west recarbonation
basins between and to the north of the softening basins. Carbon dioxide storage and
feed equipment is located west of the recarbonation basins.
8. Filtration
Filtration is accomplished with 12 dual media filters, equally sized and designed to
filter 3.0 mgd each. Media consists of 12” of sand and 18” of anthracite. The filters
have been operated intermittently over the years due to the standby nature of the
WTP and until recently, chlorine injection took place downstream of the filters. It is
possible some microbial growth had developed in the filters leading to increased
chlorine demand. Late 2014, the City recently hired a contractor to upgrade the
electrical controls for the filters and that work has been completed.
9. Disinfection
Disinfection is provided by ozonation and by feeding chlorine. Ozonation occurs at
the front end of the WTP. Chlorine is fed prior to filtration and prior to finish water
storage / high service pumping. The intermediate chlorine injection location was
recently constructed under the Phase II, Segment 1 contract.
10. Clear Well & Pumping
The pump building sits adjacent to a 3 MG clear well and contains both low and
high service pumps.
B. JAR TESTS / EXPERIMENTS
1. Approach
There are several well practiced methods by which DBPs can be reduced. First, the
disinfectant can be changed to an alternate that has a lower tendency to form DBPs.
Second, additional treatment systems such as activated carbon or air stripping
(depending on the nature of the precursors) can be added to remove DBP precursors.
Lastly, the existing treatment processes can be optimized to remove as much DBP
precursor as possible. Of these options, optimizing existing treatment processes is the
only strategy that does not require the construction of new and expensive facilities. It
is anticipated that Flint will be receiving Lake Huron water by late 2016 and this
water will have a completely different chemistry from the Flint River. Major process
changes instituted to address THM levels using Flint River water are likely to be
unnecessary for Lake Huron water and may even be inappropriate. Therefore, those
options which require addition of new treatment processes are undesirable at this
time. In recognition of this upcoming change in water source, efforts for this study
have concentrated on improving the existing processes, rather than adding new ones.
New treatment processes will only be recommended if operational changes to the
existing treatment train prove ineffective. |
|
Recent sample test results suggest that most of the DBPs are formed in the distribution
system rather than within the treatment plant. Therefore, the most logical approach is
to reduce the DBP formation potential (DBPFP) rather than simply lowering the levels
of DBPs leaving the plant. During bench scale testing, formation potential (FP) levels |
were the primary indicator of success or failure of proposed process modifications. |
2. Protocol
Bench scale pilot testing is intended to reflect actual plant operating and hydraulic
conditions so the bench scale treatment units were sized based on various
Lockwood, Andrews.
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Operational Evaluation Report
May 29, 2015
dimensionless factors to ensure the pilot treatment matched the actual system. Bench
scale ozonation was not practical due to time and cost limitations. Therefore, water
samples were withdrawn from the plant ozone basin effluent. These samples were
transported to the laboratory and dispensed into square testing jars. The jars were
used to simulate rapid mix, three-stage flocculation, and settling. Rapid mix and
flocculation conditions were matched to the plant based on “Gt” values, The “G”
value is a measure of the mixing intensity and is a function of mix time, viscosity of
the liquid, and mixing power applied to the water. “Gt” then, is a size scaling factor
where time has been accounted for. Settling time was scaled to match the shorter
settling depth of the testing jars. After settling, samples were decanted from the test
jars. The decanted samples were then lime softened; softening conditions were
similarly matched on the basis of “Gt’. Carbon dioxide was sparged into the samples
to reduce the pH. The water was then vacuum filtered through filter paper, sized to
simulate the plant’s dual media filters. The samples were dosed with excess chlorine
and allowed to react for seven days at 25° C before testing for DBPs to determine the
formation potential.
The following conditions were applied during testing to properly match small scale
testing to actual plant processes.
TABLE 6 — BENCH SCALE TEST MIXING INTENSITIES
‘zonation:
Rapid Mix 160
Flocculation, Stage 1 55
Flocculation, Stage 1 30
Flocculation, Stage 1 19
Settling :
Softening =
Recarbonation
The primary variables during testing were chemical additions and chemical dosages.
Specific chemicals and dosages used for initial testing conditions were selected to
reflect current plant usage and the recommendations of the 2002 Treatability Study:
TABLE 7 — BENCH SCALE TEST CHEMICAL FEED RATES
Chemical | Current Usage | 2002 Study | — Test Values _
Ozonation 4.66 mg/l 1.5 mg/l
Ferric Chloride 7.7 mg/l Fe3+ 40 mg/l Fe3+ 7.7 — 80 mg/l Fe3+
Coagulant Aid Polymer Not used 2.0 mg/l 1—2 mg/l
Flocculation Aid Polymer Not used 0.05 mg/l 0 — 0.05 mg/l
Powdered Activated Carbon Not used N/A 20 — 100 mg/l
Lime 120 -— 175 mg/l
Soda Ash 0 —~ 52 mg/l
Cationic Softening Polymer
Anionic Softening Polymer 0.88 mei 0.88 mg/
Fluoride 0.45 mg/l Not used
Fed to reach pH of
7.5 +- 0.3
T mei 10 mg/l | /
Carbon Dioxide
Chlorine
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CITY OF FLINT
Operational Evaluation Report :
May 29, 2015 4
3. Considerations
The 2002 Treatability Study did not note significant formation of DBPs. This may be a
function of different Flint River water chemistry at that time. However, recognizing
the considerable differences in chemical usage and dosages between that study and
current operations, those differences in chemical use and dosage are an obvious
starting point for optimizing treatment to prevent DBP limit exceedance.
Although it is believed that optimization of current treatment can correct the DBP
issue, should optimization of present treatment prove insufficient, alternate residual
disinfectants (chloramines and chlorine dioxide) will be investigated as additional
treatment measures.
4. LAN Test Results
Two rounds of jar testing were completed by LAN during the weeks of December 15,
2014 and January 26, 2015. Detailed test data is included in Appendix A. Testing
results can be summarized as follows:
« Increased dosages of ferric chloride resulted in higher reduction of THMFP.
e The currently utilized feed rate of lime at 120 mg/l is appropriate
* Softening with soda ash in addition to lime resulted in minor additional THMFP
reduction — in the range of 0% - 10%.
¢ The benefits of using a cationic polymer during softening at a dosage range of
0.31 - 3.13 mg/l to help reduce THM’s are unclear
¢ The benefits of using an anionic polymer during softening at a dosage range of
0.09 — 0.88 mg/l to help reduce THM’s are unclear
e Feeding PAC was ineffective in reducing THMFP within the dosage range of 20
— 100 mg/l.
5. Testing by Others
In addition to jar testing completed by LAN, the chemical supplier who provides |
ferric chloride for the City, PVS Technologies, ran tests using their recommended |
flocculant polymer aid. Plus, Veolia Water completed jars testing of their own the
week of February 16" to analyze other process details and current WTP parameters.
Experiments completed by PVS Technologies showed very little TOC removal beyond |
that obtained with straight ferric chloride feed.
6. Conclusions
Increasing the dose rate of ferric chloride is an operational change that can easily be
implemented without the need for any additional equipment. Test results show that
over 40% THMFP removal can be obtained with a dosage of 60 mg/l Fe3+ or higher.
Increased dosing of ferric chloride would be most ideal coupled with regular raw
water TOC monitoring so that TOC levels would dictate the appropriate ferric
chloride feed rate.
\
|
|
Softening with soda ash in addition to lime is another option the City should consider
if increased ferric chloride doses are not adequate to maintain THM levels under the
MCL, particularly during warmer months. Again, monitoring of TOC in the raw water /
could provide useful information of when lime/soda ash softening is necessary.
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CITY OF FLINT
Operational Evaluation Report
May 29, 2015
IV. DISTRIBUTION SYSTEM EVALUATION
EPA guidance for the distribution evaluation portion of an OER is focused on identification
and isolation of a specific portion of the distribution system that led to the exceedance. The
circumstances of Flint’s apparent pending TTHM exeedances are unusual in that a new
supply has been implemented which clearly corresponds to the high TTHM sample results.
Although the new source is one element in increased TTHM levels, value remains in
evaluating the distribution system since water age is also a critical factor. Additionally, there
may be distribution improvements that can be made to help alleviate the problem.
A. INFRASTRUCTURE
1. Piping
According to the most recent MDEQ Sanitary Survey, the distribution system is
estimated to contain 70% cast iron, 20% ductile iron, 2% concrete and 8% steel
water mains. Based on discussions with City staff, the percentage of cast iron pipe
may be higher than that stated in the MDEQ Sanitary Survey. Unlined cast iron pipe
can become pitted, allowing colonization sites for microorganisms leading to
chlorine demand. Additionally, much of the piping in the system is aged and in poor
condition. Increased chlorine demand could be resulting from biofilm in older pipes
and from main breaks/repairs. The extent of contribution is not known but any water
main replacement project will decrease chlorine demand somewhat if constructed
properly. Unfortunately, water main breaks may also assist with decreasing water age
by providing unintentional flushing. All things considered, it is impossible to quantify
the impact existing piping has on THM formation.
The City utilizes City Point software and GPS equipment to document main breaks
and prioritize replacements. However, main break information is more pertinent to
rusty water complaints and has little relevance to THM levels. Areas that have been
targeted for main replacements include the transmission main from the WTP west to
Dupont and south to the West Side reservoir, Fenton Road, Atherton Road, Dort
Highway, Averil Street, and Boulevard Drive.
2. Storage
There are 4 finish water storage tanks and 1 raw water tank as tabulated below:
TABLE 8 - STORAGE TANKS
; : Operatin: ‘
Type LW [HWE ‘Bottom | OF |
| Dort Reservoir Ground : 730 | 750 i
WTP Tank Elevated | Finished ; j 863.0 | 898.0 |
WIP Clear Well — PS #4 | Ground | Finished 11’ 15’ | 708.5 | 726.0 | |
Cedar Street Reservoir Ground [| Finished - 11’ 737.2 | 757.2 |
Westside Reservoir Finished
The MDEQ typically recommends providing a minimum finish water storage volume
of 1/3 the maximum daily demand (MDD). According to the 2013 MDEQ Sanitary
Survey, the 5 and 10 year MDDs are 21.57 mgd and 30.05 mgd respectively, A ;
common rule of thumb for clear well storage volume at a WTP is 10% of the design |
flow rate. Another general guideline for reliability is to provide total storage to allow /
for 2 X the average daily demand plus fire flow demand. For this analysis, fire flow is
assumed to be 2,500 gpm for either one industrial fire (2,500 gpm) or a combination
of one residential (1,000 gpm) and one commercial (1,500 gpm) fire at a 4 hour
duration which results in a total volume of 600,000 gallons. These go-by
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Operational Evaluation Report
May 29, 2015
approximations are summarized below with the applicable flow rates and are
compared to the existing storage volumes currently being utilized.
Recommended Volume In
Common Practice Flow Rate Volume by ROT Use
Clear well 10% of Design Flow 18 MGD 1.8 MG 3.0 MG
Finish Storage = 1/3 MDD 30.05 MGD 10.0 MG 37 MG
Total Storage = 2 * ADD + FFD 13.87 MGD 28.3 MG 57 MG
Based on the values above, it appears the storage volume used in the Flint system
could be decreased without negatively effecting reliability. The appropriate volumes
of individual tanks will be further evaluated using the water system model and
discussed in Section V (C),
All reservoirs have baffling to minimize stagnant water. Also, all tanks have been
maintained and are in reasonable condition. The Westside reservoir has an exposed
roof that is in need of rehabilitation, but its current condition has no influence on
THM formation.
3. Pump Stations
All pump stations are in good condition but pumps are generally oversized. As an
independent consideration, oversized pumps are not a contributing factor to high
THM levels. Control of pumps and pressure zones are discussed in detail below.
B. OPERATIONS AND MAINTENANCE
1. Pump Station & Storage Operations
Pump stations and storage tank levels are controlled as shown in Table 9.
TABLE 9 — FUME STATION CONTROES
PS No. 4 Raw
Cpa
PS No, 4 Finish Match plant flow - -
Westside |_ System pressure (elevated tank) | 22.57 33’
Cedar Street [System pressure (elevated tank) 22.5" 33’
Torrey Road | Distr. — Brown/Bradley < 45 psi > 45 psi
Cedar Street and Westside pump stations are operated as needed and they are
alternated. Typically, Cedar Street is run in the morning and Westside is run in the
evening and reservoirs for each are filled during low demand periods at night.
Westside, Cedar Street and Torrey Road pump stations are used to boost system
pressure when high demands warrant it, but there are not well defined pressure zones
within the system. Therefore, the possibility exists that water is being recirculated
allowing for increased water age.
2. Booster Disinfection Practices
Booster disinfection is provided at the Cedar Street and Westside pump stations.
When sustained residuals are not provided by chlorine feed at the WTP, sodium
hypochlorite is applied at the reservoirs while being filled.
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a AA weenie”
3. Changes in System Demands ‘
Water demands in the City have been declining since the 1960's as the population
has dropped. As a result, many of the water system components are oversized
including storage tanks and water mains which both increase the time for water to
reach the user.