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TRANSCRIPT
Disinfection By-Products
Reduction and SCADA Evaluation
and
WTP Sludge Removal System and
Dewatering Facility
Presentation to the SGWASA Board
October 10, 2017S
OU
TH
GR
AN
VIL
LE
WATE
R &
SE
WE
R
AUTHORITY
Locational Running Annual Average (LRAA)
for TTHM
0.00
0.01
0.02
0.03
0.04
0.05
0.06
0.07
0.08
0.09
0.10
3/2/2014 12/27/2014 10/23/2015 8/18/2016 6/14/2017 4/10/2018
TTH
M (
mg
/L)
B01 B02 B03 B04
MCL for TTHM
Locational Running Annual Average (LRAA)
for HAA5
0.00
0.01
0.02
0.03
0.04
0.05
0.06
0.07
0.08
0.09
3/2/2014 9/18/2014 4/6/2015 10/23/2015 5/10/2016 11/26/2016 6/14/2017 12/31/2017
HA
A5
(m
g/L
)
B01 B02 B03 B04
MCL for
HAA5
Project Approach
Bench-Scale Testing
• Develop bench-scale testing protocol that simulates WTP
performance “plant match”
• Evaluate alternate coagulant types, doses, and pH
• Evaluate need for, type, and required dosage of coagulant
aid polymers, pre-oxidants, and PAC
• Goal is to assess optimal strategies for DBP precursor
removal
• Holistic approach – need to ensure that any strategy does
not compromise other treatment goals
Jar Testing Calibration
Parameter Full-Scale Jar 1-4
KMnO4 (mg/L) 2.5+0.4 2.5+0.4
PAC (mg/L) 8 8
Ferric Sulfate (mg/L) 65 80
pH (Units) 4.76 4.88
UV-254 (1/cm) 0.022 0.024
Turbidity (NTU) 0.64 0.56
Alkalinity (mg/L) 2 2
Temperature (°C) 23 23
Both ferric sulfate and ferric chloride can
provide good UV reductionsNo Polymer, pH Adjusted to 5.5 - 5.7
0.074
0.033 0.033 0.033
0.0330.029
0.096
0.068
0.038
0.0410.037 0.033
0
0.02
0.04
0.06
0.08
0.1
0.12
30 40 50 60 70 80 90 100
UV
Ab
sorb
ance
(1
/cm
)
Coagulant Dose (mg/L)
Ferric Sulfate Ferric Chloride
Ashland 851 TR can provide better results
than the currently used Clarifloc N6310
0.033 0.039 0.041 0.043 0.042 0.036
1.01
1.50
7.22
7.70
0.92
2.92
0.0
1.0
2.0
3.0
4.0
5.0
6.0
7.0
8.0
9.0
851 TR LT22s N300 LT20 650 TR N6310
Sett
led
Wat
er T
urb
idit
y (N
TU)
and
UV
A
bso
rban
ce (
1/c
m)
UV Absorbance Settled Water Turbidity
Simulated Distribution Samples - DBPs
3.9 3.3 4.1 3.2
12.4 11.6 11.6
67.4
16 17 18
51
0
10
20
30
40
50
60
70
80
60 FeCl No Oxidant 60 FeCl 0.5 ClO2 60 FeS w/851TR Full Scale Tap
TOC
(m
g/L
), T
THM
(µ
g/L
), T
HA
A (
µg
/L)
TOC TTHM THAA
Lake TOC: 10.2 mg/L, Reservoir TOC: 9.2 mg/LFeCl=Ferric chlorideFeS=Ferric sulfate
Good TTHM correlation with TOC
0.0
2.0
4.0
6.0
8.0
10.0
12.0
14.0
16.0
18.0
0.00
0.02
0.04
0.06
0.08
0.10
0.12
0.14
1/31/2016 6/29/2016 11/26/2016 4/25/2017 9/22/2017
TOC
(m
g/L
)
TTH
M (
mg
/L)
B01 B02 B03 B04 Reservoir TOC CFE TOC
Ferric SulfateAlum
HAA5 vs TOC
0.0
2.0
4.0
6.0
8.0
10.0
12.0
14.0
16.0
18.0
0.00
0.02
0.04
0.06
0.08
0.10
0.12
1/31/2016 6/29/2016 11/26/2016 4/25/2017 9/22/2017
TOC
(m
g/L
)
HA
A5
(m
g/L
)
B01 B02 B03 B04 Reservoir TOC CFE TOC
Alum Ferric Sulfate
TOC removal over time
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
3/21/2016 6/29/2016 10/7/2016 1/15/2017 4/25/2017 8/3/2017 11/11/2017
TOC
Rem
ova
l
Alum Ferric Sulfate
Process Schematic
Flash Mix
Effluent
Influent Sed.
Basin 1
Filter
Effluent
Pre and Post NH3Plant Tap
DBP Sample
Taken
Chemical
Addition
TTHM profile thru WTP
0.00
0.02
0.04
0.06
0.08
0.10
0.12
0.14
6/29/2016 10/7/2016 1/15/2017 4/25/2017 8/3/2017 11/11/2017
TTH
M (
mg
/L)
FILTER EFF. PRE NH3 POST NH3 PLANT TAP
Ferric SulfateAlum
HAA5 profile thru WTP
0.00
0.01
0.02
0.03
0.04
0.05
0.06
0.07
0.08
0.09
0.10
6/29/2016 10/7/2016 1/15/2017 4/25/2017 8/3/2017 11/11/2017
HA
A5
(m
g/L
)
FILTER EFF. PRE NH3 POST NH3 PLANT TAP
Ferric SulfateAlum
Project Approach
Chemical Feed Evaluation
• Site visit to assess existing facilities.
• Determine required storage and feed
equipment capacities.
• Confirm compatibility of proposed changes.
SCADA and Automation Evaluation
• Determine automation and SCADA system
needs.
• Review SCADA system architecture at
WWTP
• Coordinate with any recommended process
changes Example HMI Workstation
In progress
In progress
Preliminary Findings
• Conversion to ferric sulfate has enhanced TOC
removal to 77% (66% prior to conversion)
• Conversion to ferric sulfate has reduced DBP
formation (based on special samples)
• THMs are ~54% lower than 1 year ago (August 2016)
• HAAs are ~40% lower than 1 year ago (August 2016)
• Continue to investigate possible impacts of full-
scale operations on DBP formation such as
sludge collection system issues, process control,
and chemical mixing
Schedule
Aug 8 Notice to proceed
Aug 21 Begin bench-scale testing
Oct 10 Present bench-scale testing preliminary results
Nov 28 Submit draft report
Dec 12Present draft DBP and SCADA evaluation
recommendations
Questions and Discussion
WTP Sludge Removal
System and
Dewatering Facility
Project Approach
Residuals Collection
System Assessment
• Evaluate existing equipment and
coordinate with manufacturers
• Recommend improvements to
enhance reliability
• Concept-level capital costs
Residuals Production
Estimates
• Critical to coordinate with DBP
project
A switch to an iron-based
coagulant and additional PAC
and potassium permanganate
results in greater solids
production.
In progress
In progress
Project Approach
Dewatering Alternatives
• New Dewatering Facility
• Thickening + Dewatering
• Relocate existing rotary
drum thickener +
dewatering
• Residuals lagoon2-M Belt Filter Press
Pending completion of prior tasks
Schedule
Aug 8 Notice to proceed
Nov 1Preliminary DBP strategy informs possible
range of residuals production
Jan 15 Submit draft report
Questions and Discussion
UV Disinfection
• UV Disinfection is a physical
process used for:
• Primary disinfection (i.e. CT
requirements at the WTP)
• Advanced oxidation (UV AOP)
• UV does not produce a
residual so a chemical
disinfectant (free chlorine or
chloramines) is also needed
to provide a residual in the
distribution system
UV Disinfection
• UV disinfection is effective for inactivation of
bacteria, Giardia, and Crypto.
• UV disinfection is less effective for virus
inactivation
Log Inactivation
0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0
Cryptosporidium 1.6 2.5 3.9 5.8 8.5 12 -- --
Giardia 1.5 2.1 3.0 5.2 7.7 11 -- --
Virus 39 58 79 100 121 143 163 186
Disinfection Mechanism
Dimerization of DNA (thymine bases)
Inability to Reproduce Bug is Non-infective
UV does not “kill” pathogens
26
Dimer
Dimer
UV Disinfection Applications
• NC Public Water Supply has approved the use
of UV disinfection for primary disinfection
• The City of Raleigh was first to obtain approval in 2013
• UV can be part of a DBP control strategy
• Meet primary disinfection (CT) requirements at the WTP
• Reduces needed free chlorine contact time in WTP
• Monochloramine as secondary disinfectant
• However, free chlorine still has a place
UV Disinfection Applications
• Feed free chlorine prior to filters for:
• Oxidation of iron and manganese
• Prevent filters from becoming biological
• Meet regulatory CT requirements for virus inactivation
Ozone NH3NaOCl
Alt. NH3
P
RawWater
ToDistr.
SuperPulsator GAC
BioFilters
Dual-Media FiltersOzone Contactor
UV Disinfection
5-MG Storage Tank
If UV Disinfection Applied at SGWASA WTP
• Recommend continue feeding free chlorine in
filter influent
• Move point of ammonia addition prior to chlorine
contact tank to reduce free chlorine contact time
• Maintain ability for free chlorine disinfection as a
backup
UV Disinfection
If UV Disinfection Applied at SGWASA WTP
• Conceptual Capital Costs: $4.5-5.5 million
• An updated SCADA system would be required
• UV Facility would be a deep structure to keep
UV reactors full of water
• Impacts on WTP electrical system and standby
power?