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Engineering Assessment of Hydrogen Sulfide Issues

Engineering Assessment of Hydrogen Sulfide Issues. Emission Inventory State Survey of Ambient Air Standards Regulatory Practice in Other States H 2 S from Hog Farms Dispersion Modeling Study H 2 S Stability Proposed Control Technologies. Emission Inventory.

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Engineering Assessment of Hydrogen Sulfide Issues

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  1. Engineering Assessment of Hydrogen Sulfide Issues • Emission Inventory • State Survey of Ambient Air Standards • Regulatory Practice in Other States • H2S from Hog Farms • Dispersion Modeling Study • H2S Stability • Proposed Control Technologies

  2. Emission Inventory • Initial records based on 1999 NC-DAQ Inventory • Revised in 2002 to include paper mill wastewater treatment, 89% of paper industry emissions • Soft WWT estimates; high variability data base • Fertilizer and paper are most emissive industries • Hog farms excluded due to poor data quality - Data overstates NC hog emissions by more than 10-fold

  3. Figure 1. 1999 Emissions Inventory Total = 4.2 Million lb H2S/yr

  4. Figure 2. Revised 2002 Inventory Total = 11.9 Million lb H2S/yr

  5. Table 1. H2S Emissions Inventories (a) (a) (a) = Potential emissions, max hour repeated all year.

  6. Table 2. Pulp Mill Emission Sources

  7. State Survey of Ambient Air Standards • No federal ambient air standards • 35 states set their own standards - 13 with 1-hr from 14-280 ug/m3 (10 – 200 ppb) - 13 with 24-hr from 8.4-280 ug/m3 (0.6 – 200 ppb) - 26 other standards - Several states have more than 1 standard

  8. Figure 3. All states with H2S Standards

  9. Figure 4. States with 1-hr H2S Standards

  10. Figure 5. States with 24-hr H2S Standards

  11. H2S Regulatory Practice in Other States • Contacted 4 similar states - South Carolina - Georgia - Minnesota - Wisconsin

  12. South Carolina H2S Program • Effective in 1991; 100 ppb 24-hr standard • Compliance by modeling or monitoring • Existing facilities 2 yrs to demonstrate • Modeled parameters included in permit • MACT compliant facilities are exempt • 3 of 7 paper mills modeled for H2S - Only 1 included WWTS: 1.6 Million lb/yr

  13. Georgia H2S Program • Guidelines for assessment • Facility derives acceptable ambient level • Use EPA, OSHA, ACGIH or NIOSH limits • Model with 5 yrs met data to determine maximum ground level concentration • If max concentration more than AAL, then reduce max concentration responsibly • All subject to agency review & approval

  14. Minnesota H2S Program • Effective in 1969; - 30 ppb 30-min standard - 50 ppb 30-min std w/2 exceedances/yr • In ~1988 paper mills exceeded H2S standard - Installed activated sludge units initially - Then added covers and oxygenation • Mills meet 30 and 50 ppb standards

  15. Minnesota H2S Program (con’d) • Recently found hog farm H2S problem • Trend of fewer, but larger farms • State colleges do much research • State agency responds to odor complaints - Uses ambient monitors to measure - Encourages voluntary compliance - Serves as source of helpful information

  16. Wisconsin H2S Program • Effective in 1988; 240 ppb 24-hr std • Structured similar to NC toxics - Conservative screening emission rates - Model if more than screening emission rates • No req’ts for paper mill WWTS • Considering hog lagoon solutions

  17. H2S from NC Hog Farms • NC focused on ammonia and nitrogen issues - No official NC hog farm H2S emission data • Draft EPA emission data based only on midwest farms from unpublished test - National Academy of Science criticizes EPA data as incomplete and too general - Midwest farms have dissimilar design, operations, climate and bacteria from NC farms that directly affect emissions and odors - Likely overstate NC hog H2S by more than 10-fold

  18. DAQ Dispersion Modeling Study • Modeled phosphate fertilizer and paper mill plants • Assess impact area & health benefits relative to 33 ug/m3 24-hr & 56 ug/m3 24-hr proposed AALs • Determined impact radius, i.e., distance from plant where levels more than proposed AALs • Determined avg number of exceedances, i.e., typical locations within impact radius with levels more than proposed AALs

  19. Table 3. Paper Mill Modeling Results

  20. Table 4. Fertilizer Plant Modeling Results

  21. H2S Stability in Ambient Air • Generally stable 18 hrs – 3 days • Extreme conditions 2 hrs – 42 days • H2S not photochemically reactive • Changes to sulfur dioxide or sulfuric acid

  22. Proposed Control Technologies- Paper industry • Activated sludge – biological process without chemicals to reduce H2S • Add covers, collect and incinerate off gas • Decommission settling and aeration ponds • Blue Ridge Paper has activated sludge • Few activated sludge units at mills

  23. Figure 6. Aerial Photograph Weyerhaeuser-Plymouth

  24. Figure 7. Aerial Photograph International Paper Roanoke Rapids

  25. Proposed Control Technologies- Fertilizer industry • Currently no controls • Install packed bed scrubber on phosphoric acid plant point sources • Use special solution to absorb H2S • 99 + % required to marginally meet 33 ug/m3 and 56 ug/m3 AALs • New technology for this industry

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