Engineering Assessment of Hydrogen Sulfide Issues

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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

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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

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Figure 1. 1999 Emissions Inventory Total 4.2
Million lb H2S/yr
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Figure 2. Revised 2002 Inventory Total 11.9
Million lb H2S/yr
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Table 1. H2S Emissions Inventories
Affected Industries 1999 Emission Inventory (lb) 1999 Emission Inventory (lb) 2002 Revised Inventory (lb) 2002 Revised Inventory (lb)
Fertilizer 3,500,000 82 6,617,304 56
Pulp Paper 672,281 16 5,226,227 44
Mineral Wool 51,562 1 51,562 0
Asphalt 7,044 0 7,044 0
Other 19,263 0 12,621 0
(a)
(a)
(a) Potential emissions, max hour repeated all
year.
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Table 2. Pulp Mill Emission Sources
Percent WWTS WWTS (lb/yr) PLANT PROPER (lb/yr)
Blue Ridge 51 110,989 107,990
Wey-Plymouth 97 3,524,823 107,152
Wey-New Bern 93 558,450 39,858
IP-Riegelwood 80 582,540 141,912
IP-Roanoke Rpd 47 210,280 236,914
TOTAL 4,987,082 633,826
Weighted Avg. 89
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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

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Figure 3. All states with H2S Standards
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Figure 4. States with 1-hr H2S Standards
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Figure 5. States with 24-hr H2S Standards
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H2S Regulatory Practice in Other States

• Contacted 4 similar states
• - South Carolina
• - Georgia
• - Minnesota
• - Wisconsin

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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

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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

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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

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Minnesota H2S Program (cond)

• 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

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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 reqts for paper mill WWTS
• Considering hog lagoon solutions

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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

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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

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Table 3. Paper Mill Modeling Results
Averaging period Average No. of Exceedances per year Impact Radius (km) Maximum impact (ug/m3)
1-hr 56 ug/m3 (40 ppb) 30 40 15,311
24-hr 33 ug/m3 (23 ppb) 22 15 2,565
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Table 4. Fertilizer Plant Modeling Results
Averaging period Average No. of Exceedances per year Impact Radius (km) Maximum impact (ug/m3)
1-hr 56 ug/m3 (40 ppb) 45 20 1,940
24-hr 33 ug/m3 (23 ppb) 17 30 54
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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

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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

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Figure 6. Aerial Photograph Weyerhaeuser-Plymouth
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Figure 7. Aerial Photograph International Paper
Roanoke Rapids
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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