Cliff Denholm, Stream Restoration Incorporated, "Passive Treatment of Acidic High-Metal Discharges Part 1"
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Because of the extent of AMD impacts in Pennsylvania, the Commonwealth has become, by necessity, a leader in the development of passive treatment technology. People from around the world travel to Pennsylvania to learn about the successes we have collectively achieved, including the installation of over 300 passive treatment systems. In recent years, the capabilities of passive systems to treat highly acidic mine discharges with high concentrations of dissolved metals has been questioned. It is important to remember that with any treatment system, whether passive or active, proper design, suitable land characteristics, quality construction, proper maintenance and sufficient funding, are needed to provide a long-term, cost-effective approach for watershed restoration. This presentation will provide mini case studies that demonstrate, by example, that passive systems can and are effectively treating acidic, high-metal, discharges in Pennsylvania.
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Cliff Denholm, Stream Restoration Incorporated, "Passive Treatment of Acidic High-Metal Discharges Part 1"
- 1. Co-Conspirators: S. Busler, T. Danehy, M. Dunn, D. Guy, R.Mahony, C. Neely Presenter: Cliff Denholm
- 2. <300 publicly funded PTS in PA1 >77 billion gal/yr of AMD treated in PA alone1 >16 Million Pounds of Iron removed/year >3 Million Pounds of Aluminum removed/year 1www.datashed.org
- 4. We all know that Passive Systems Don’t Work Passive Systems require too much maintenance Vertical Flow Ponds Don’t Work You can’t passively treat High Aluminum AMD You can’t passively treat High Iron AMD Active Treatment is the only answer Watershed Groups are failing Watershed Groups are not maintaining systems
- 7. Treatment Technology ~30 years old ◦ Developed over time ◦ Still developing Mistakes had to be made to learn Early excitement & funding availability allowed for experimentation ◦ Sometimes it worked, Sometimes it didn’t Do something or do nothing Yes and No
- 10. Point Flow (GPM) pH Alk mg/L Acid mg/L T. Fe mg/L T. Al mg/L T. Mn mg/L SO4 mg/L In 34 2.9 0 258 22 19 6 516 Out NA 3.3 0 154 15 14 6 519
- 11. Point Flow (GPM) pH Alk mg/L Acid mg/L T. Fe mg/L T. Al mg/L T. Mn mg/L SO4 mg/L In NA 3.3 0 NA 81 21 9 691 Out 24 6.3 177 NA 62 <1 9 680
- 12. Point Flow (GPM) pH Alk mg/L Acid mg/L T. Fe mg/L T. Al mg/L T. Mn mg/L SO4 mg/L Raw 20 3.0 NA 261 34 14 14 693 WL4 33 6.5 48 -2 <1 <1 6 642
- 14. VFPs Chemical Plants Refuse Removal & CFB Plants Land Reclamation Aquafix Coal Ash ALDs Wetlands Lime dosers TIFs HFLBs
- 15. Why Do Passive Systems “Fail”? •Design - undersized, wrong application/developing technology, etc. •Construction - sloppiness, short-cuts, accidental errors •Site conditions - not enough room, something vs. nothing •Unanticipated issues - water quality or quantity changes •Design life met and/or treatment media spent •Lack of O&M
- 16. Passive Treatment Systems Are LOW Maintenance Not NO Maintenance
- 18. Flow pH Acid Alk Fe Mn Al Raw 36 4.1 319 NA 82 55 12
- 20. Constructed 1999 (16 Years Old) Cost $391,000 Upgrades Cost ~$10,000 O&M Costs ~$8,000 Volunteer = $? O&M Annualized ~$500 Flow pH Acid Alk Fe Mn Al Raw 36 4.1 319 NA 82 55 12 Treated 44 6.6 -2 81 1 31 <1
- 21. Flow pH Acid Alk Fe Mn Al Raw 36 4.1 319 NA 82 55 12 Forbay N 10 3.3 201 NA 20 40 11 Forbay S 21 3.4 228 NA 48 42 10
- 23. Upgrades ◦ Installed Forebay ◦ Replaced VFP Outlet Pipes to adjustable peri-pipes ◦ Inlet & Outlet pools in HFLB O&M Flushing/Backflushing Cleaning out low pH iron from pipes Removed low pH iron from top of VFPs Stirred top layer of VFP treatment media Stir HFLB Remaining O&M Needs ◦ Stir HFLB
- 26. 162- 2162-8 162- 3 CC 1 162-6 & 162- 10 OPC Moa t VFP 1 SB1 AL D CC 1 CC 1 CC 1 162-6 & 162- 10 CC 1 SB1 162-6 & 162- 10 CC 1 Moa t SB1 162-6 & 162- 10 CC 1 VFP 1 Moa t SB1 162-6 & 162- 10 CC 1 VFP 1 Moa t SB1 162-6 & 162- 10 CC 1 OPC VFP 1 Moa t SB1 162-6 & 162- 10 CC 1 AL D OPC VFP 1 Moa t SB1 162-6 & 162- 10 CC 1 AL D OPC VFP 1 Moa t SB1 162-6 & 162- 10 CC 1 162-8 AL D OPC VFP 1 Moa t SB1 162-6 & 162- 10 CC 1 162- 2162-8 AL D OPC Moa t SB1 162-6 & 162- 10 CC 1 162- 3 162- 2162-8 AL D OPC Moa t SB1 162-6 & 162- 10 CC 1 Forebay 162-3162-2 162-8 ALD OPC VFP1 Moat SB1 162-6 & 162-10 CC1 Aka TIFs
- 28. Flow GPM pH Alk mg/L Acid mg/L T. Fe mg/L T. Al mg/L T. Mn mg/L SO4 mg/L 5-10 2.67 0 1385 304 142 20 2620
- 30. Flow GPM pH Alk mg/L Acid mg/L T. Fe mg/L T. Al mg/L T. Mn mg/L SO4 mg/L 3.12 0 512 28 83 26 2130 Avg 80% Fe Loading Removed In ~600 Feet!!!
- 38. Flow GPM pH Alk mg/L Acid mg/L T. Fe mg/L T. Al mg/L T. Mn mg/L SO4 mg/L 46 7.51 214 -180 0.1 0.2 5.3 1097
- 39. Vegetation in Channels and Spillways
- 40. Box outlet clogged Vegetation removed, outlet depth increased
- 43. 2008-Site constructed Hydraulic issues noted
- 45. Flow pH Acid Alk Fe Mn Al Raw 135 3.2 257 NA 26 55 10 Treated 135 6.3 0 74 <1 25 <1 Source: www.datashed.org
- 47. 2000-Site constructed 2012- decreased treatment performance noted VFP East Stir Forebay inlet and outlet cleaned
- 48. WL outlet cleared of vegetation HFLB stone re-leveled VFP outlet spillway cleared of vegetation buildup
- 49. Multiple issues noted during site visit by SRWC Forebay pipe inlet clogged VFP performance decreased
- 53. Pre- and Post- O&M Effluent Field Water Quality Data Parameter Pre- O&M Post- O&M pH 6.0 6.9 alkalinity 20 ~70 Fe (mg/l) 4-8 0.5 - 1 Total metals mg/L, acidity and alkalinity as CaCO3 mg/L
- 54. Flow pH Acid Alk Fe Mn Al Forebay 12 3.1 509 NA 107 107 29 Treated 13 6.9 30 64 <1 53 <1 Source: www.datashed.org
- 59. Replace baffle curtains Removed Fe off of VFP & stirred VFP Backflushed & Stirred HFLB Fixed access road entry
- 60. Assist PA watershed groups, non-profits, conservation districts, etc. 2011-Current (multiple grants) Technical assistance & water sampling Funding Sources ◦ PA DEP Growing Greener Program ◦ Foundation for PA Watersheds ◦ In-kind/match watershed groups
- 61. Construction Cost = $200,000 Annual O&M = 1% Need = ~$40,000 to invest Replacement Cost every 20 Years Need = ~$60,000 to invest If provide an extra $100,000 at time of grant to the watershed group, they could maintain treatment for “perpetuity”
- 62. High Risk (High Metal) AMD can be passively treated IF ◦ Good Design ◦ Sufficient Site Conditions Area Elevation Change ◦ Proper Construction ◦ Maintained
- 63. Require Sufficient Funding At All Stages: ◦ Design ◦ Construction ◦ Monitoring ◦ Maintenance
- 64. Watershed Groups Can and Should be part of the long-term plan to maintain treatment systems as they can do it cheaper but they need: ◦ Support ◦ Funding Lab Samples Field Equipment Travel Expenses ◦ Maintenance ◦ Technical Assistance like SRI’s O&M TAG
- 65. Passive treatment is not maintenance free; Like a car, regular inspections and occasional maintenance are needed for a treatment system to reach it’s design life;
- 66. Poor water quality does not always mean the system is a failure or has reached its design life; Treatment performance can often be restored through maintenance activities that rejuvenate the system instead of replacing the treatment media or rebuilding the system and thus saving money;
- 70. Most sites require maintenance over time Regular site visits and observations allow many problems to be addressed quickly and efficiently PA PTS Snapshot
- 71. Passive is the only answer All of our systems work 100%, 100% of the time Passive systems don’t require maintenance All watershed groups are fine
- 72. Slippery Rock Watershed Coalition 1994 Stream Restoration Incorporated 1996 BioMost, Inc 1998 Designed over 60 Passive Treatment Systems Designed/modified a handful of Active Systems Maintained/repaired numerous systems Inspected & evaluated >100 systems Managed Statewide AMD Treatment Snapshots in 2009, 2010, 2012, 2015 Created & Manage Datashed (www.datashed.org)
- 73. BEFORE Flow GPM pH Alk mg/L Acid mg/L T. Fe mg/L T. Al mg/L T. Mn mg/L SO4 mg/L 69 3.0 0 498 51 26 21 1340 AFTER Flow GPM pH Alk mg/L Acid mg/L T. Fe mg/L T. Al mg/L T. Mn mg/L SO4 mg/L 319 6.0 22 12 4 4 13 830
- 74. Don’t let the perfect get in the way of the good
- 75. Need to fund maintenance not just the design & construction to ensure long-term treatment