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?