Reclaimed Water Aquifer Storage Recovery: Optimization of Our Freshwater Resources

Transcription

1 Reclaimed Water Aquifer Storage Recovery: Optimization of Our Freshwater Resources Presented by: Mark B. McNeal, P.G. CH2M HILL, Tampa FL Co-Authors: Mike Cannon, P.E. - Hillsborough County, FL Ed Fox - Hillsborough County, FL Kart Vaith,, P.E. - CH2M HILL, Tampa FL Presented at the Florida Section/American Water Works Association Maitland, Florida November 14, 1996

2 Presentation Overview Aquifer Storage Recovery Technology Reclaimed Water ASR Benefits Reclaimed Water ASR Feasibility Criteria Regulatory Considerations Case Study - Hillsborough County, Florida

3 ASR Technology What is ASR? Aquifer Storage Recovery,, or ASR, is the seasonal storage of large volumes of potable or non- potable water in a suitable aquifer during periods of low demand, for subsequent recovery during periods of high demand Reclaimed Water ASR is the seasonal storage of highly treated reclaimed water

4 Conceptual RW ASR Well WRF or AWTP Public Access High Quality Reclaimed Class V Injection Well Typical Recharge Operation (Excess Supply) Low Permeability Moderate to High 3, 000 mg/l TDS 10, 000 mg/l TDS Low Permeability WRF or AWTP Public Access High Quality Reclaimed Class V Injection Well Typical Recovery Operation (Excess Demand) Low Permeability Moderate to High 3, 000 mg/l TDS 10, 000 mg/l TDS Low Permeability

5 ASR Technology Large Volumes Can be Stored Typically much less Expensive than Conventional Storage Methods Environmentally Sensitive Water Supply Limited Land Requirements are Necessary A Component to Zero-Discharge to SWs Optimizes Use of Freshwater Resources

6 ASR Feasibility - A Phased Approach Phase I: Feasibility Study Demonstrate need and evaluate criteria Site selection for Phase II Construction Phase II: Site-Specific Specific Feasibility Confirmation Test well and monitoring well installation Phase III: ASR Expansion and Wellfield Development

7 RW ASR Possible Benefits Large Volumes of Wet Weather Storage Seasonal Storage at Strategic Locations to Augment Q and/or P Diurnal Supply and Demand Increase Reuse Supply through Mixing

8 RW ASR Possible Benefits (Cont.) Eliminate SW or other Less-Desirable Discharge Practices WQ Improvements Through Aquifer Treatment or Mixing with Native GW Long-term Freshening for Future Indirect Potable Reuse Saltwater Intrusion Barriers

9 RW ASR Feasibility Criteria Reasonable Scale of Reuse Facility Daily/Seasonal Variations in Supply/Demand Suitable Storage Zone Native Groundwater Quality, RW Quality, and Geochemical Compatibility Limited Competing Groundwater Users System Permittability Compatibility w/ Reuse Applications Proximity to Infrastructure

10 RW ASR Recovery Efficiency Considerations REff Generally Based on 1 or 2 Constituents Typically Brackish Storage Zones Confinement/Aquifer Characteristics Reuse Water Quality Standards Additional Blending Options

11 ASR Permitting ASR Wells are Class V Injection Wells regulated by the Florida Department of Environmental Protection s UIC Program (62-528, FAC) Reclaimed Water ASR Wells are Permitted as Class V, Group 3 Wells ( (1)(e), FAC) FDEP Treatment Facility Permit Modifications are also Required Water Management Districts Regulate Withdrawals, Typically as Zero Consumptive Use Local Permits may also be Required

12 ASR Permitting Reclaimed Water Quality Key in Permitting Approach Reclaimed Water reliably meets all State DWSs Reclaimed Water reliably meets all Federal DWSs, but certain State Standards are Exceeded (State Relief Req d) Reclaimed Water does not Reliably Meet all federal DWSs (Federal Relief Req d) Federal and state programs under review to facilitate non- potable ASR permitting Poorer RW Quality Generally Results in more Brackish Storage Zone Selection

13 Hillsborough Co. Case Study Important Component of County Reuse Program Feasibility Studies Completed at the So. County WWTP& River Oaks AWTP Sites Selected Based on Feasibility Criteria Brackish Storage Zones Identified (2000 to 3000 TDS) Initial Permitting Efforts Underway

14 Hillsborough County Northwest ASR Project Location To Northwest Regional WRF 36 Reuse 36 Reuse Connect to Existing Pump Station Pump Station Linebaugh Above Ground Storage Tank at Maintenance Facility ASR ASR Wells RIVER OAKS AWTP Waters

15 Legend Optimum Ground- water Quality Available in NWH area Chloride Concentrations in mg/l (dashed where approximate) 105D, 765 >10,000 Double Branch Creek Site 9D, D, D, NWRWRF Railroad/TECO Easement Dechlorination Facility 16D, 330 2,500 65, River Oaks AWTP PZ, D, Approximate location of the saltwater interface Potential ASR Site 15D, PZ, Well name, and depth in feet Chloride Concentration in mg/l 3,

16 Projected 2010 Dry Season Diurnal Flow at River Oaks Flow (mgd) :00 2:00 4:00 6:00 8:00 10:00 12:00 14:00 16:00 18:00 20:00 22:00 0:00 Time 2/2010 (SAT) 2/2010 (SUN) 2/2010 (MON) 2/2010 (TUE)

17 Northwest Reuse Diurnal Flow Northwest Reuse Diurnal Flow 0:00 2:00 4:00 6:00 8:00 10:00 12:00 14:00 16:00 18:00 20:00 22:00 0:00 Time Peaking Factor (X*ADF)

18 2010 Typical Dry Season WW Flow and Reclaimed Water Demand, with 3 ASR Wells Cumulative Volume(MG) Approx. 4 MG storage required 0:00 2:00 4:00 6:00 8:00 10:00 12:00 14:00 16:00 18:00 20:00 22:00 0:00 Time (WW flow+3 Well ASR Flow,MG) 2/ Reuse Demand (MG)

19 Summary of Northwest Hills. County Storage Requirements One 5 MG storage tank sufficient Approximately 3 ASR wells required to meet 2010 dry season reuse demand More ASR wells would allow reclaimed water banking and increase firm capacity

20 Proposed ASR Storage Zone Successfully Utilized Regionally

21 Suwannee Limestone ASR Test 0 Well Recommended Inch Dia. Surface Casing Feet Below Land Surface Vertical Scale Greatly Exaggerated Inch Dia. Casing to ±300 Feet Cement TD = ±400 Feet 450 Typical ASR Test Production Well

22 Hillsborough County s s Vision Will Ensure Maximization of Regional Freshwater Resources Innovative concepts will pave way for others to follow Creative ideas to reuse water will ensure freshwater resources are available for potable use Program maximizes non-potable use from non-potable resources Saltwater intrusion barrier could increase life of inland regional wellfields

23 Reclaimed Water ASR Summary New use of a proven technology to maximize reuse Favorably received by regulatory agencies May allow utility to transition into a zero-discharge - to-surface water facility Economical Approach to Large Volumes of Seasonal Storage May generate additional volumes of usable water through mixing with less desirable native waters Future saltwater intrusion barriers or indirect potable reuse applications may develop