Hannibal Chloramine Replacement Evaluation

Transcription

1 Hannibal Chloramine Replacement Evaluation 19 DECEMBER 2017 Project Update Ben Freese Karen Marie Dietze

2 Agenda Project Timeline DBP Treatment Objectives Recap Initial Findings Report Alternative 1: Granular Activated Carbon Alternative 2: Reverse Osmosis Alternative 3: Preozone + Enhanced Coagulation + Aeration Comparison of Alternatives 2

3 Project Background & Timeline Hannibal WTP starts using chloramines GAC Engineering Report Referendum (Proposition 1) Start Chloramine Replacement Study Hannibal WTP Ordinance Compliance Deadline Initial Findings Report GAC Pilot Installed Draft Preliminary Report Final Preliminary Design Report Bench-scale & Pilot Testing Design and Construction of Selected Alternative 3

4 Maintaining Compliance with Stage 2 DBPR Treatment Objectives for Regulated DBPs: Parameter Maximum Contaminant Level Treatment Objective (80% of MCL) Total Trihalomethanes, TTHMs 80 µg/l 64 µg/l Five Haloacetic Acids, HAA5s 60 µg/l 48 µg/l Chloramines currently used to maintain compliance System will revert back to free chlorine in distribution system Water age and TOC Concentration primary factors in DBP formation Goal to reduce TOC and/or Water Age Surface water plants tend to have higher raw TOC therefore more treatment required to meet limits 4

5 Water Age Majority of system has water age of 1-2 days Water age at DBP monitoring sites up to 5-7 days Water Age in Hannibal Distribution System without Ralls County 5

6 Determination of Target TOC Target TOC 1.75 mg/l based on: TTHM formation limiting factor (not HAA5) Water age (7 days) at DBP compliance monitoring sites Based on PAC/GAC adsorption, so target TOC will vary based on treatment process selected 6

7 Finished Water TOC Goals Parameter Historical Finished Water TOC 2017 (with optimizations) New Treatment Objective Average th Percentile Additional TOC removal in the range of 35-53% based on historical values. 7

8 Alternatives Evaluated in the Initial Screening Enhanced Coagulation Increased Coagulant Dose ph Adjustment Alternative Coagulant Oxidation Ozone Chlorine Dioxide Permanganate Combination of Unit Processes Adsorption Technologies Powder Activated Carbon Granular Activated Carbon Alternative Processes Reverse Osmosis Ion-exchange Resins Aeration 8

9 Alternative 1: Granular Activated Carbon Rapid Small-Scale Column Test (RSSCT): GAC media (Calgon) tested at 15-min EBCT (July & Oct 2017) GAC media (Evoqua) tested at 7.5-min EBCT (Oct 2017) GAC Pilot Columns: Column 1: 12-inch GAC Filter Cap, 3 min EBCT Column 2: 28-inch GAC Filter Cap, 7 min EBCT Column 3: Post-filter GAC, 7.5 min EBCT Column 4: Post-filter GAC, 15 min EBCT GAC Pilot Columns at Hannibal WTP 9

10 GAC Pilot Testing 7.5 min EBCT 10

11 GAC Pilot Testing 7.5 min EBCT Conclusions: Post-filter GAC with 7.5 min EBCT is not a sustainable solution for DBP control TOC Breakthrough ~ 20 days when plant is operated at 7.5 MGD continuously 11

12 GAC Pilot Testing 15 min EBCT 12

13 GAC Pilot Testing 15 min EBCT Conclusions: Post-Filter GAC performed best with 15 minutes EBCT at 7.5 MGD TOC Breakthrough ~ 50 days when plant is operated at 7.5 MGD continuously 13

14 GAC Pilot Testing 15 min EBCT Conclusions: Post-Filter GAC performed best with 15 minutes EBCT at 7.5 MGD TOC Breakthrough ~ 50 days when plant is operated at 7.5 MGD continuously TOC removal of 43% at breakthrough 14

15 GAC Pilot Testing TTHMs GAC Pilot Testing: Issues calibrating Cl 2 dose with target residual for first 4-5 samples in SDS testing Trendline used to represent expected TTHM formation DBP formation in GAC Pilot aligns well with target effluent TOC of 1.75 mg/l 15

16 GAC Sizing Criteria Parameter 7.5 MGD Facility with 15 min EBCT 2.9 MGD Facility with 15 min EBCT Design Flow Rate, MGD Number of GAC Contactor Trains 6 3 Number of GAC vessels per train 2 2 Total Mass of GAC Installed, lb 315, ,000 Estimated Days between GAC Replacement (per train) Estimated Days between GAC Replacement (entire system) Number of complete system GAC replacements per year Annual O&M Costs, $/yr $620,000 $795, Based on GAC cost of $1.60/lb Optimal GAC configuration balances capital cost (number of GAC units) and operational costs (GAC media replacement). Sizing is based on GAC performance data from pilot. 16

17 GAC Facility New transfer pumping and equalization tank required. 17

18 Alternative 2: Reverse Osmosis Removes 95 to 99% of dissolved organic compounds and hardness RO system sized for 50% flow to meet blended effluent TOC of 1.75 mg/l RO provides a high level of confidence for meeting DBP treatment objectives Regulatory considerations RO concentrate disposal Pilot testing may be required for MDNR approval More complex to operate and maintain MF/UF Pre-treatment Cleaning System Anti-corrosion/stabilization chemical addition RO installation at San Antonio Water System Brackish Groundwater Desalination Plant 18

19 RO Facility MF/UF System RO System Electrical Mechanical MF/UF Cleaning System RO CIP System Chemical Storage RO Facility has similar footprint as GAC Facility 19

20 Alternative 3: Preozone + Enhanced Coagulation + Aeration Individual process alternatives (enhanced coagulation, ozonation or aeration) are not capable of reducing TOC and DBP formation to the required levels Incremental improvements can be achieved from each process: 17 to 20% removal DOC/reduction TTHMs from doubling coagulant dose 24 to 30% reduction in TTHMs from ozone 20 to 30% removal of TTHMs through aeration Ozone installation at Lincoln Water System 20

21 Alternative 3: Preozone + Enhanced Coagulation + Aeration 45% reduction in TTHMs through ozone and enhanced coagulation Aeration could provide an additional 20% removal of pre-formed TTHMs Additional testing is recommended: Based on few, discrete data points collected from bench-scale testing Recommend 6-12 months of additional testing to confirm process can reliably meet treatment goals under seasonal conditions Preferred Alternative 21

22 Alternative 3: Preozone + Enhanced Coagulation + Aeration Relatively simple implementation but requires close attention to performance of each treatment step 22

23 Present Worth Comparison Description ALTERNATIVE 1 ALTERNATIVE 2 ALTERNATIVE 3 Granular Activated Carbon Reverse Osmosis Ozone + Aeration + Enhanced Coagulation Project Total $13,042,000 $20,179,000 $12,004,000 Owner s Contingency (10%) $1,304,000 $2,018,000 $1,200,000 Project Total with Owner s Contingency $14,346,000 $22,197,000 $13,204,000 Annual O&M Costs $691,000 $355,000 $413,000 Present Worth Costs $27,837,000 $29,128,000 $21,267,000 23

24 Comparison of Alternatives ALTERNATIVE ADVANTAGES GAC High confidence in meeting treatment objective Relatively simple to operate High O&M Costs due to GAC media replacement Market conditions could impact long term GAC pricing Potential to lower O&M costs if regenerated material is used Reverse Osmosis Most costly to install and operate Potential roadblock if waste stream can t be discharged to River Ozone + Enhanced Coagulation Aeration Lowest initial capital costs Lowest operational costs Additional testing required to ensure feasibility Multi-treatment approach with several variable affecting performance / ability to meet target treatment goals Requires close monitoring to ensure TOC/DBP goals are met Doubling coagulant dose may impact filter operations 24

25 Next Steps Select preferred alternative Identify funding approach and how it impacts schedule Determine schedule for implementation 9 months for engineering 1-3 months for permitting 12 months for procurement & construction Alternative project delivery methods could improve schedule Design-Build Construction Manager At Risk (CMAR) 24 month project schedule w/o funding considered 25

26 Ben Freese Contact Information DECEMBER 2017

27 Comparison of Alternatives ALTERNATIVE ADVANTAGES DISADVANTAGES GAC High level of confidence for meeting DBP treatment objectives Does not require additional chemicals Relatively simple to operate Highest operational costs Additional transfer pumping Requires close monitoring to ensure correct effluent blend for target TOC removal Reverse Osmosis High level of confidence for meeting DBP treatment objectives. Advanced technology adaptable to changing regulations and future contaminants Ozone + Enhanced Coagulation Aeration Lowest initial capital cost Lowest operational costs Easiest to implement Highest capital costs Complex system with high operator oversight Approval needed for RO concentrate discharge to Mississippi River RO membranes sometimes experience more fouling in surface water plants from organics Additional testing required to ensure feasibility Multi-treatment approach with several variable affecting performance / ability to meet target treatment goals Requires close monitoring to ensure TOC/DBP goals are met Doubling coagulant dose may impact filter operations 27

28 Treatment Capacity GAC Sizing Evaluation Impacts on 2.9 MGD Facility 7.5 MGD Facility Capital Cost Reduces capital cost Increases capital cost O&M Cost Higher O&M cost for GAC Lower O&M cost for GAC Regulatory Requirements Treatment performance Reliability May need to get waiver for regulatory approval Would inhibit ability to meet target TOC/DBPs year-round Not reliable when water demand exceeds average flow MDNR guidelines require implementation for plant rated capacity Conservative approach, but may be over-sized Can reliably treat water to meet TOC/DBP treatment objectives 28

29 Cost Comparison of Previous GAC Facility Report GAC PRELIMINARY ENGINEERING REPORT CHLORAMINE REPLACEMENT Description 3.5 min 7.5 min Project Total $10,578,000 $13,042,000 Owner s Contingency (10%) $0 $1,304,000 Project Total with Owner s Contingency $10,578,000 $14,346,000 Annual O&M Costs $426,667 $691,000 Present Worth Costs $17,243,000 $27,837,000 Biggest Impacts on Costs: Facility size Transfer pumping Location of Building GAC Media life estimate 29

30 GAC Rapid-Scale Column Testing 120 Accelerated Column Testing: Good for evaluating whether GAC is a viable treatment method Good for estimating EBCT Not the best for predicting performance in surface water Provides a Snapshot which does not capture seasonal variability of TOC TOC Breakthrough refined through GAC pilot testing 30