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Engineering Assessment of Hydrogen Sulfide Issues Confirmed industry cost estimates Relative costs & performance of WWTS controls Emerging activated sludge.

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Presentation on theme: "Engineering Assessment of Hydrogen Sulfide Issues Confirmed industry cost estimates Relative costs & performance of WWTS controls Emerging activated sludge."— Presentation transcript:

1 Engineering Assessment of Hydrogen Sulfide Issues Confirmed industry cost estimates Relative costs & performance of WWTS controls Emerging activated sludge trend Cost impact of activated sludge in other states Phasing-in new activated sludge units Reporting and controlling H 2 S from WWTS in other states Methyl mercaptan issues from WWTS?

2 Confirmed Paper Industry Cost Estimates Published cost data for activated sludge in close agreement with industry aggregate capital cost estimate; based on M. Fels Optimized design of WWTS, 1997; referenced in Feb. 6 DAQ package Also confirmed by WWTS consultant No clear cost differences for 3 AALs

3 Paper Industry Cost Estimates for Activated Sludge Paper industry estimate $ MillionProposed AALs Capital cost increment 340All 3 Operating cost increment All 3

4 Fertilizer Facility Cost Estimates for 3 Proposed AALS Relative costProposed AALSources controlled 1.0 X 1.8 X 2.1 X 120 ug/m 3 24-hr 33 ug/m 3 24-hr 56 ug/m 3 1-hr

5 Relative Cost & Performance: Aerated basin vs Activated sludge Aerated stabilization basin - More cost effective - Comparable but slightly less performance - 2 of 3 US mills installed aerated basins - 4 of 5 NC mills installed aerated basins, typical of southern mills - Most installed years ago

6 Relative Cost & Performance: Activated sludge vs Aerated basin Activated sludge Better wastewater treatment performance Less space, more effective in colder climates Irony that the following not air quality driven - 2 of 3 Canadian mills with AS due to improved water quality discharge, especially during winter - 1 of 3 US mills with AS due to space constraints, - Trend of US & Canadian mills switching to AS

7 Relative cost & performance: Activated sludge vs Aerated basin ParameterActivated Sludge Aerated Basin Relative annualized cost BOD treatment performance - Warm weather - Cold weather 90% 75% 50% Relative cost / performance - Warm weather - Cold weather $/BOD 2.1 $/BOD

8 Cost Impact in Other States Paper mills able to bear costs for installing / switching to activated sludge in 6 states: Florida, Michigan, Minnesota, North Carolina, Washington, Wisconsin, Canada

9 Phasing-in New Activated Sludge Few mills in south have limited success combining AS with AB In contrast, 3 mills in Washington successfully combined AS with AB - Most concentrated wastewaters to AS - Less concentrated wastewaters to AB

10 Reporting & Controlling Air Emissions from Paper Mills WWTS Based on states contacted, common practice for most mills not to report air emissions from WWTS Measured air emission data limited from WWTS - So limited any generalizations are indefensible Paper industry uses computerized model to predict/estimate emissions No incentive to report, yet alone control emissions Limited experience in cost effective controls

11 Methyl Mercaptan from WWTS One NC mill indicates MM emissions 10% of H 2 S - Suggests 1,500 ug/m 3 at property line - 30 times AAL - Methyl Mercaptan current AAL = 50 mg/m 3 NCASI data shows MM emissions 100% of H 2 S - Suggests 15,000 ug/m 3 at property line times AAL Another NC mill shows MM emissions non issue

12 Summary ( page 1 of 2 ) Industry capital cost estimates confirmed - Paper industry -- $340 million across range of 3 AALs if WWTS not exempt - Paper industry -- $5-10 million across AAL range if WWTS exempt - Fertilizer plant $ range 2-fold across AAL range Aerated basins more common / cost-effective Activated sludge cost more / perform better Emerging trend for activated sludge for sensitive waters in at least 6 states and Canada

13 Summary (page 2 of 2) Phasing-in - Mixed results, good and bad NC paper mills reporting consistent w/industry Methyl mercaptan may be air quality issue with paper mill WWTS DAQ recommends exempting paper mill WWTS: - Incomplete understanding of extent & control of emissions as well as factors affecting emissions - Need time to further study complex issues - Economic hardship argument


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