Assessing Technical, Operational and Financial Feasibility September

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1 The Ohio Section of The American Water Works Association Onsite Hypochlorite Generation: Assessing Technical, Operational and Financial Feasibility September Kelly Comstock, PE

2 Outline Disinfection System Options OSHG Basics Equipment Selection and Layout Considerations Assessing Feasibility of Implementation Case Study 1: Greensboro, NC Case Study 2: DeKalb County, GA 2

3 Disinfection System Options Primary Disinfection Distribution Step 1 Step 2 Chlorine Chloramines Chlorine Dioxide Ozone UV Chlorine Chloramines 3

4 Chlorine Continues to be Necessary Chlorine Gas Bulk Hypochlorite Delivery High Strength OSHG/OSCG Low Strength OSHG 4

5 Chlorine Gas Advantages Lower operating cost Long track record with many utilities Disadvantages Significant safety concerns Risk Management Plan requirements Uncertain future exemption from chemical safety legislation Could see costs rise as use decreases 5

6 Bulk Hypochlorite Delivery Advantages Lowest capital cost hypochlorite option Simplicity / similarity to other feed systems Disadvantages Corrosion / tank replacement Variable cost Potential future perchlorate concern Safety Product Quality Product degradation 6

7 Bulk Hypochlorite Delivery 7

8 High Strength OSHG/Chlorine Gas Generation Advantages Generates chlorine gas or 10-12% NaOCL Produces NaOH High stability of salt pricing Disadvantages Higher level of complexity Higher capital cost than Low Strength OSHG ETC Brine Klorigen waste/hydrogen TM generation Limited number of installations Same disadvantages as bulk delivery/storage 8

8% NaOCl High stability of salt pricing Disadvantages

9 Low Strength OSHG Advantages Lower operating cost compared to bulk hypochlorite Stable 0.8% NaOCl High stability of salt pricing Disadvantages Higher capital cost than bulk delivery Hydrogen generation Space requirements 9

10 Onsite Sodium Hypochlorite Generation Basics 3 lb NaCl + 15 Gal H KW = 15 Gal NaOCL (0.8%) + 1/35 lb H 2 Salt Water Electricity Sodium Hypochlorite Hydrogen Gas 10

11 Low Strength OSHG System Configuration Dilution Blower Feed Pump Storage Tank Generation System Brine Tanks Water Softener Courtesy of PSI MicrOclor 11

12 OSHG Design Criteria Hypochlorite generators sized for maximum day chlorine demand. Storage: Hypochlorite storage sized for 3 days at maximum day chlorine demand Salt storage sized for 30 days at average chlorine demand. System Operations: 20 hour/day operating cycle Consider power load management for existing facilities. System Backup: Provisions for delivery and storage of bulk hypochlorite or backup power supply for OSHG system. 12

13 Low Strength OSHG System Suppliers MIOX Recently acquired by Parkson Sevren Trent s Clortec Siemen s OSEC PSI MicrOclor 13

14 Safety Considerations 0.8% NaOCl is not classified as a hazardous material Highest Hazard associated with Hydrogen Gas Generation Hydrogen Gas Safety Enhancements Level switch to shut down unit Flowmeter on inlet stream Minimization of valves / proximity switches where necessary Rupture Disks to prevent over pressurization of Cells Ambient hydrogen detectors Intrinsic safety barriers on instruments 14

15 Maintenance Requirements Acid wash of electrode assembly required quarterly Acid cleaning cart provided by suppliers Cleaning of Water / Brine Filters - quarterly Annual removal and inspection of electrode Annual service of brine pumps O&M for brine maker and dosing pumps General annual inspection (PLC Cabinet, check valves, level switches, rotameters, etc.) Annual Service Agreements Available 15

16 Case Study #1: The City of Greensboro Serve approximately 270,000 customers Two water treatment plants 30 mgd Townsend WTP 24 mgd NL Mitchell WTP Interconnections with several systems Switched to chloramines in 2011 Currently utilize bulk sodium hypochlorite storage and feed at both plants 16

17 Purpose of the Study The City has seen variations in the cost of bulk 15% sodium hypochlorite over the years Wanted to evaluate onsite generation Identify the system sizing for each plant Perform initial system location / layout Determine the capital and operating cost Wanted to answer the question Is OSHG cost effective? And if not now, when will it be? City shoots for a 6 year or better ROI for efficiency improvement projects 17

18 Cl 2 Usage Rate (lbs/day) Historic Data Analysis 3,500 3,000 2,500 Townsend Avg Cl2 lbs/day Townsend Peak Cl2 lbs/day NL Mitchell Avg Cl2 lbs/day NL Mitchell Peak Cl2 lbs/day 2,000 1,500 1, Forecast Years 18

19 Layout Considerations Townsend WTP Reuse tanks Locate generator in an existing room NL Mitchell WTP Procure new tanks Add an enclosure for generation equipment 19

20 Proposed Generator Sizing Townsend Filter Plant Year Average Chlorine Demand (lbs/day) Peak Chlorine Demand (lbs/day) Number of Generator Systems Generator Capacity (lbs/day) Cl 2 Capacity 10 hr/day (lbs/day) Cl 2 Capacity 20 hr/day (lbs/day) n-1 Cl 2 Capacity 18 hrs/day (lbs/day) ,035 2, ,600 each 1,333 2,666 1, ,325 2, ,000 each 1,666 3,333 1, ,506 3, ,000 each 1,666 3,333 1,500 Year Average Chlorine Demand (lbs/day) Peak Chlorine Demand (lbs/day) Number of Generator Systems NL Mitchell Filter Plant Generator Capacity (lbs/day) Cl 2 Capacity 10 hr/day (lbs/day) Cl 2 Capacity 20-hr/day (lbs/day) n-1 Cl 2 Capacity 18-hrs/day (lbs/day) , ,000 each 833 1, , ,200 each 1,000 2, , ,200 each 1,000 2,

21 Present-Worth Cost Analysis: Capital Costs Capital Cost Requirements for Onsite Sodium Hypochlorite Generation Cost Item Townsend Filter Plant NL Mitchell Filter Plant Onsite Hypochlorite Generation System $ 640,000 $ 517,000 Equipment Installation (30% of System) $ 192,000 $ 155,100 Building Modifications $ 75,000 $ - New Building $ - $ 245,000 Electrical Improvements $ 200,000 $ 200,000 SCADA Integration and Programming $ 75,000 $ 75,000 Mechanical Piping and Valves $ 100,000 $ 100,000 Subtotal $ 1,282,000 $ 1,292,100 Contractor OH&P (15%) $ 192,300 $ 193,800 Engineering and Contingency (25%) $ 320,500 $ 323,000 Total Capital Cost $ 1,794,800 $ 1,808,900 21

22 Present-Worth Cost Analysis: Annual Operations Annual Cost Factor Bulk Hypochlorite Cost Salt Consumption Rate Salt Cost Power Consumption Rate Power Cost Townsend Power Cost NL Mitchell Capital Recovery Term Basis of Analysis $0.73 per gallon 3.0 lb brine/lb NaOCl $0.07 per lb 2 kwh/lb NaOCl $0.0545/kWh $0.0579/kWh 20 years Capital Recovery Interest Rate 4.0% Electrolytic Cell Replacement (Mitchell/Townsend) $18,000 each/$16,000 each 22

23 Conclusions Present Worth Analysis Facility Current Bulk Delivery Cost ($/gal) Present Worth Cost of Bulk Delivery Present Worth Cost of Onsite Generation Return on investment (ROI) Period Status Greensboro Townsend Filter Plant Greensboro NL Mitchell Filter Plant $.73 $4,420,000 $4,100, Years $.73 $2,060,000 $2,960,000 Never Project on Hold Will become cost effective if bulk cost goes above $0.80 Project will never move forward Bulk would have to be over $1.00 a gallon to get a reasonable ROI 23

24 Case Study #2 DeKalb County, GA Serve approximately 700,000 people One water treatment plant 150 mgd Scott Candler WTP Switched from chlorine gas in 2006 Currently utilize bulk sodium hypochlorite storage and feed 24

25 Projected Chlorine Usage (lb/day) Equipment Sizing Near Term 3,000 lb/day of firm capacity Long Term 4,000 lb/day of firm capacity 4,000 3,500 3,000 2,500 2,000 1,500 1, Average Daily Usage Peak Daily Usage Year 25

26 System Layout Spare chemical room available Reuse existing Bulk Storage Tanks (90,000 gal) Spare capacity in electrical MCCs and PLCs Able to reuse several feed pumps / pipelines Designed vent stacks to remove hydrogen gas in generation room 26

27 Equipment Selection Evaluated high strength and low strength OSHG Eliminated high strength system based on complexity Open competitive bid of Psi Microclor and Severin Trent Weighted Criteria Evaluation Criteria Weighting Factor Siemens OSEC Psi Process Inc. MicrOchlor Sevren Trent ChlorTec Initial Capital Cost Present Worth Cost Installations Hydrogen Management Redundancy Ease of Operations Service Space Requirement Weighted Result

28 Capital Cost Capital Cost Requirements for Onsite Sodium Hypochlorite Generation Cost Item Scott Candler WTP Onsite Hypochlorite Generation System $ 1,475,000 Equipment Installation (30% of System) $ 382,500 Building Modifications $ 15,000 New Building $ - Electrical Improvements $ 300,000 SCADA Integration and Programming $ 80,000 Mechanical Piping and Valves $ 40,000 Subtotal $ 2,592,500 Contractor OH&P (15%) $ 313,900 Engineering and Contingency (25%) $ 523,100 Total Capital Cost $ 3,429,500 28

29 Present Worth Analysis and Payback Present Worth Analysis Facility Current Bulk Delivery Cost ($/gal) Present Worth Cost of Bulk Delivery Present Worth Cost of Onsite Generation Return on investment (ROI) Period Status DeKalb Co. Scott Candler WTP $.82 $11,169,000 $8,103,000 5 Years Moving Forward 29

30 Conclusions OSHG will have a higher capital cost but a lower operating cost than bulk delivery Incorporate safety enhancements to mitigate hydrogen generation risk OSHG costs are very site specific Sizing / level of redundancy Reuse of existing tankage Availability of space indoors Vendors are aggressive and don t always provide complete information do your homework to make sure that OSHG is the right fit for you 30

Problems with Hypo: Best Design Practices for Smooth and Efficient Sodium Hypochlorite Feed Systems Chad Hantelman, City of Bremerton Jeff Zahller,

Problems with Hypo: Best Design Practices for Smooth and Efficient Sodium Hypochlorite Feed Systems Chad Hantelman, City of Bremerton Jeff Zahller, PE, HDR Engineering Outline Common Options Available