Hydrogen Sulfide Control in BioSolids Processing with Hydrogen
Hydrogen Sulfide Control in Bio-Solids Processing with Hydrogen Peroxide The Cedar Rapids Experience
City of Cedar Rapids Water Pollution Control Facility 39 MGD Flow 300 k lb. BOD per day Interceptor Sulfides of 2. 0 mg/l
Primary & Secondary Sludge l l Primary Sludge thickened in DAF units dewatered in BFP Biosolids from the RF are passed on to CAS Carry a large inventory of solids in activated sludge CAS & NAS sludge is dewatered in Gravity Belt Thickeners
Secondary Sludge in GBTs l l l Original design was to capture odors above GBT Resulting levels of gas in GBT room was +100 ppm Capture of odors was ~20%, New system ~90% Goal of 0 -2 ppm H 2 S in habitable space Goal of 10 ppm directly above the GBTs
Corrosion
Safety
City of Cedar Rapids Water Pollution Control Facility
Implementation & results H 2 O 2 & H 2 S chemistry l Laboratory evaluation l Field demonstration & results l
50% Hydrogen Peroxide Physical/Chemical Properties l l l l Chemical Formula: H 2 O 2 Clear, colorless liquid Infinitely soluble in water Oxidizer Non-flammable Boiling/Freezing Points: 237 F, -62 F Density: 10 lbs/gallon Decomposition products: Oxygen and Water
Hydrogen Peroxide Reactions in Bio-Solids l H 2 S + H 2 O 2 ----- S + 2 H 20 l Product of reaction: Colloidal Sulfur Will not reform H 2 S downstream Oxidation complete in 5 min. in bio-solids l l 2 H 2 O 2 ------- O 2 + 2 H 2 O Adds dissolved oxygen
Lab Test Set-up and Procedure l l l 1 L bio-solids/2 L jug Gently stir in H 2 O 2, let react with top off Sparge headspace above bio-solids Cap and shake vigorously 10 sec. Place Odalog over cap and squeeze jug
H 2 S Monitoring Method l l l Odalog. TM H 2 S datalogger Continuous H 2 S measurements Analytical tool – not specifically designed for personal safety device
Bio-Solids Lab Tests with H 2 O 2 Headspace H 2 S
Field Demonstration – H 2 O 2 Dosing System @ Final Lift
GBT H 2 S Levels without H 2 O 2
GBT H 2 S Levels without H 2 O 2
GBT H 2 S Levels Start of H 2 O 2 Dosing
GBT H 2 S Levels with H 2 O 2
GBT H 2 S Levels with H 2 O 2
GBT H 2 S Levels with H 2 O 2
GBT H 2 S Levels with H 2 O 2
GBT H 2 S Levels with H 2 O 2
GBT Building H 2 S Levels
GBT H 2 S Control Project Results l l l Improved Operator Safety – Average GBT H 2 S levels reduced by 90% Cedar Rapids WPCF H 2 S exposure limit of 10 ppm routinely maintained Reduced GBT Downtime Reduced Corrosion Potential Reduced Odors
Future Process Optimization l Evaluation of automated H 2 O 2 dose rate control via gaseous H 2 S sensor in GBT building
Acknowledgments l l Co-Authors: John Haase, Sam Kamhawy Cedar Rapids WPCF And Chester Szczucki – US Peroxide Chris Hatch, Larry Kaeding, Pat Ball – Cedar Rapids WPCF
- Slides: 26