Integrating Ozone and Ion Exchange into a 40 Year Old Lime Softening Plant

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1 Integrating Ozone and Ion Exchange into a 40 Year Old Lime Softening Plant City of Columbus Division of Water: Matt Steele CH2M HILL: Enoch Nicholson

2 DRWP Source Water and Treatment

3 DRWP Overview Current plant built in mid 70 s Surface water plant Two stage lime softening plant Free chlorine is disinfectant Approved capacity 65 MGD Average day 49 MGD Being upgraded to 80 MGD Serve over 400,000 people No major upgrades

4 DRWP Source Water Scioto River Small reservoirs (6.2 BG) Griggs and O Shaughnessy Fast flowing (12.7 day detention time) Large watershed (1044 sq miles) 80% agricultural Supplemental water supply is the newly constructed upground reservoir

5 DRWP Raw Water Quality Variable alkalinity, hardness, and turbidity TOC range 4 to 13 mg/l Atrazine spikes up to 30 ug/l Nitrates (can spike above 10 mg/l) Seasonal algal blooms (taste and odor issues)

6 Nitrates MCL is 10 mg/l acute immediate health impacts to infants Have violated MCL 12 times Nitrates have peaked at 15 mg/l Events can last days to weeks (longest 21 days) When this project started we averaged a nitrate violation every other year Continue to experience elevated nitrates, the past three years we have peaked mg/l.

7 Disinfection byproducts MCL is 80 ppb for THM and 60 for HAA DOW goal 80% of the MCL (64 ppb THM and 48 HAA) THM LRAA range ppb HAA LRAA ppb We have not violated MCL nor OEL, but several of our master metered communities have Interim compliance strategy feed 20 mg/l PAC from mid May through mid October expensive short term solution

8 DRWP Upgrades Currently undergoing $200 million upgrade 5 separate contracts Contracts 1 3 and 5 are under construction Contract 4 is out for bid now Contract 3 is ozone with biologically active carbon filtration to address DBP and atrazine issues Contract 4 is ion exchange to address nitrate issues

9 System wide coordination All 3 water plants under major construction Each plant has multiple shutdowns during construction Need to coordinate work at each plant with: Plant staff DOW engineers Design professionals Professional construction managers Contractors Plus Coordinate between plants Administration Distribution Control Center And perform routine maintenance activities (basin washouts) All while meeting system demands and water quality goals

10 Process Overview

11 Dublin Road Water Plant Conventional Lime Softening Plant 65 MGD Capacity Rapid Mix Flocculator Turbidity Settling Rapid Mix Flocculator Softening Settling Re-carbonation Filters Clearwell POTASSIUM PERMANGANATE PAC R3 ALUM Turbidity Basins 1 & 2 SODIUM HYDROXIDE SODA ASH LIME Softening Basins 2 & 3 Recarbonation Basin 4 CO2 SODIUM HYPOCHLORITE FLUORIDE Dual Media Filters West East ZN ORTHO-PHOSPHATE Scioto River Residual R7 Residual R1 Residual R2 Residual R3 Residual R2

12 DRWP Revised Process Flow Diagram Scioto River Intake Low Service Pumps Rapid Mix Flocculator Turbidity Settling Rapid Mix Flocculator Softening Settling Re-carbonation Ozonation Filtration Ion Exchange Clearwells High Service Pumps POTASSIUM PERMANGANATE PAC R4 ALUM Turbidity Basins 1 & 2 Residual R1 SODIUM HYDROXIDE SODA ASH LIME Softening Basins 3 & 4 CO2 H2O2 OZONE QUENCH FILTER AID GAC Filters Rehab Existing ZN ORTHO-PHOSPHATE SODIUM HYPOCHLORITE FLUORIDE Scioto River Residual R7 Residual R1 Residual R2 New Recarbonation O3 New Ozone Residual R3 West East Residual R2 Refit Basin 4 for Softening Residual R5 Residual R6 New Ion Exchange Backwash Handling Facility Quarry Sludge Pump Station R1 R2 R6 Residual R4 New Facilities R3 R5 New Facilities NORMAL CHEMICAL ADDITION POINT 5/15/2013

13 Integration into Existing Plant Ozone and Recarbonation

14 Existing DRWP

15 Existing Basin Flow Path

16 Existing Basin Flow Path Turbidity Settling

17 Existing Basin Flow Path Lime Softening

18 Existing Basin Flow Path Recarbonation

19 New Recarbonation and Ozonation Basin Location

20 Ozone and Recarbonation Facilities

21 Existing Settled Water Flume

22 Plant Shutdown Planning Ozone and Recarb

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24 CO2 Injection Pressurized Solution Feed As compared to Gas CO2 Feed PSF: Increases ph Stability Reduces CO2 Loss and CO2 Effeciency Reduces necessary contact time for stabilization Eliminates need for deep basins Carrier Water From Process Stream Booster Pump(s) Pressurized Solution Feed Panel Carbonic Acid To Process Stream CO2 Storage Tank

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26 Integration into Existing Plant Anion Exchange

27 Ion Exchange Treatment System

28 Ion Exchange Supply Connection Existing Backwash Pumps To Backwash Supply Discharge Piping Plan From Filter Effluent To IX Influent Inlet Piping Plan

29 Ion Exchange Effluent Connection From Filter Effluent New Chemical/IX Effluent Mixers From IX Effluent

30 1975 Clearwell Mixing Chamber

31 Take Home Messages Involve the whole team early (Operators, Engineers, Constructability Reviewers, etc). Determine if contractor sequencing is acceptable? No tie in to an existing plant is simple. Supply, demand and regulatory restrictions may impact flexibility. Careful consideration is essential to maintain plant operations.

32 Acknowledgements CDM Smith Erin Stachler, PE Process Engineer CH2M HILL Dean Ramsey, PE Project Manager City of Columbus Division of Water Rick Reinhold, PE Project Manager Mark Eppich, PE Project Engineer Matt Steele Water Supply and Treatment Coordinator Tony Kohler DRWP Superintendent Scott Lockhart DRWP Operations Manager Dan Davis DRWP Maintenance Manager Dave Opferman, PE (CDM Smith Project Manager for Design)

33 Questions? Matt Steele Enoch Nicholson