Westerville Water DepartmentWesterville, Ohio

Granular Activated Carbon and Plant Upgrade Project

Dick Lorenz, Bob Gardner, Erik Fulton

SE-SW District MeetingApril 24, 2017

City of Westerville

• City of Westerville • 12 Square Miles• 3 High Schools• Otterbein University• St Ann’s Hospital• Pop 38,000• Independent Water

& Electric systems

Westerville Water

• Primarily Surface Water with Well Water• 7. 5 MGD capacity• Constructed 1969 with upgrades in 1980, 1992, 1999, 2016• Conventional Lime Softening Plant• 3 Elevated Storage Tanks, One Booster Station, 2 Pressure Zones• 3.1 MGD average treatment rate

Westerville WaterTreatment Schematic

Alum Creek/wells

Flash Mix

Floc Settling Recarb

Rapid Sand Filters

GAC Filters

Clearwell

Ferric chloride

Lime & caustic soda

CO2

Chlorine ChlorineFluoride

Phosphate

sludge

Westerville WaterWater Plant Upgrade

• Challenges Faced

– Two new SDWA regulations

• DBP stage 2 RAA LRAA (3rd Qt. 2014)

• LT2 ESWTR Bin 2 +1 log (Oct. 2013)

– Aging Plant Infrastructure

• Safety

– Water Quality

• Herbicides & Emerging Contaminates

– Aesthetics

• TDS and T & O

0

20

40

60

80

100

120

140

160

180

2009 2010 2011 2012 2013 2014 2015 2016

Qt. THM Data at Four Sites

ug/L

0

10

20

30

40

50

60

70

80

90

2010 2011 2012 2013 2014 2015 2016

Previous MCL for DBP’s RAA's

TTHM HAA TTHM MCL HAA MCL

ug/L

0

20

40

60

80

100

120

2010 2011 2012 2013 2014 2015 2016

THM RAA vs LRAA

RAA 4 site avg. MCl LRAA Max site

ug/L

LRAA

Westerville WaterInitial DBP Control Measures

• Elevated tank cycling

• Tank mixer

• Manage clearwell levels

• Blending of well water

• Moved initial chlorination point

• Coagulant dose

Westerville WaterProject Phases

• Assessment of Existing Conditions - 2009 Engineer- Malcolm Pirnie

– Engineering Audits of:• Water Quality• Treatment• Capacity• Facilities

• Established Water Quality Goals– Reduce DBP’s – stage 2– LT2 – bin 2, additional log – Emerging Contaminants– TDS

• Identify & Evaluate Options• Detailed Engineering Design• Funding – OEPA Water Supply Revolving Loan Account• Construction - 2013-16 Shook Construction, CM-Smoot Construction

Westerville WaterOptions Investigated

• Chloramination

• Ozonation

• High Pressure Membranes

• Low Pressure Membranes

• Raw Water pipeline

• MIEX

• Granular Activated Carbon

• 2 stage Lime softening

• Ground water blending

• UV disinfection

Westerville WaterGAC Treatment Selected

• Disposal of membrane reject water

• Source water limitations

• Utilized existing treatment facilities

• Constructability

• Capital and O & M costs

• Streamlined OEPA approval

• Operational familiarity and ease

• Scalable

Westerville WaterDesign Summary

• Post filtration GAC pressure filters (14)

– with intermediate pumping

• New chemical delivery, storage & feed facility

– Sodium Hypochlorite to replace gas

• Modifications to admin area

• Electrical system upgrades

Westerville WaterConstruction Photos

Westerville WaterCompletion Photos

Westerville WaterCompletion Photos

Westerville Water

Westerville Water

Westerville Water

Westerville Water

Westerville Water

Westerville WaterGAC Design

• 14 tanks, 10’x20’ with 20,000 lbs carbon ea

• 3 variable speed vertical turbine pumps

• Calgon Carbon F 300 0.8-1.0 mm bituminous coal

• EBCT 13 min (4.8 gpm/SF) @ 7.5 MGD, 27 min (2.5 gpm/SF) @ 4 MGD

• Secondary filtration provides 0.5 log LT2 credit

• Backwash pump

• GAC Reactivated, exchanged using water/air

Westerville WaterFirst Year Results

March 2016 – March 2017

0

20

40

60

80

100

120

140

160

2015 2016 2017

Qt. THM Data at Four SitesPre and Post GAC

Ug/L

GAC

0

20

40

60

80

100

120

2010 2011 2012 2013 2014 2015 2016 2017

THM LRAA at each sitePre and Post GAC

Site 1 Site 2 Site 3 Site 4 MCL

Ug/L

GAC

LRAA

0

1

2

3

4

5

6

7Ja

n-1

4

Mar

-14

May

-14

Jul-

14

Sep

-14

No

v-1

4

Jan

-15

Mar

-15

May

-15

Jul-

15

Sep

-15

No

v-1

5

Jan

-16

Mar

-16

May

-16

Jul-

16

Sep

-16

No

v-1

6

Jan

-17

Mar

-17

TOC Reduction

Raw TOC Filtered TOC

mg/L

GAC

Westerville WaterAdditional GAC Benefits

• Cryptosporidium – LT2 ESWTR Bin 2– 0.5 log removal credit

• Herbicides– Went from Detects to Non Detects

• Algal Toxin barrier (if present)

• T & O event barrier• Emerging Contaminates

– Unregulated DBP’s– PPCP

• Spills and Runoff• Reduced chlorine dose and system residuals• Scalable & seasonal if in Bin 1

Westerville WaterSummary

• GAC meets current regulatory requirements

– DBP’s and LT2

• GAC provides additional barrier to multi-barrier treatment approach

– unregulated and undetected organic contaminates

• GAC fit into existing treatment facility

• Operator ease & acceptance

Westerville Water

Westerville WaterPoint of Initial Chlorination

• Post GAC– Biological RSF

• <5% TOC reduction

• Decreased Filter Run Times

• Appearance & Odor

– Lower chlorine dose

• Pre RSF– Historic operation

– Minimal feed – total residual 0.2 mg/L

– May lengthen GAC time to exhaustion for TOC removal

– Feedback if chlorine demand event