VAPOR PHASE ODOR CONTROL FOR COLLECTIONS SYSTEMS AND LIFT STATIONS KHALED ROUEIHEB, IMS 2017 SCAP Collection Systems Committee Meeting January 24, 2017 13135 Danielson Street, Suite 204 1 Poway, CA 92064
Outline What is Odor Control? Types of Odors Sources of Odors Conditions for Odors Treatment Options Gas Phase Odor Control Systems Design Considerations/Applications Technology Selection 2 COMPANY CONFIDENTIAL
What is Odor? The term “odor” refers to the perception experienced when one or more chemical substances in the air come in contact with human sensory system. Therefore “odor” is a human response. “Odor Control” treats chemical compounds in the air that are perceived as offensive odors. Different reagent chemicals, bacteria, adsorbents are needed to target different odorous chemical compounds. It is necessary to know what chemical compounds are causing the odor, and then determine the best chemical, physical or biological means to eliminate those chemicals or render them “odorless”. 3 COMPANY CONFIDENTIAL
Odor Control is Necessary Mitigate Health Hazards, Neighbor Complaints and Prevent Corrosion Damage ppm H 2 S Odor Profile .001 -0.1 Rotten Egg Odor Threshold Odor Alarm 3 Offensive Odor OSHA 10 Headache, Nausea Serious Eye PEL (8‐hr Injury Throat and Eye Irritation avg.) 50 Eye Injury Loss of 100 Sense IDLH Conjunctivitis, Respiratory Tract of Smell Irritation, Olfactory Paralysis 300 Pulmonary Edema Imminent Life 500 Strong Nervous System Stimulation Threat Apnea 1,000 Immediate Death Collapse 2,000 4 COMPANY CONFIDENTIAL
How Are Odors Produced? 5 COMPANY CONFIDENTIAL
Conditions Promoting Hydrogen Sulfide Release High Temperature • Solubility of H 2 S is temperature dependent • Increased biological activity Low pH • Three species of sulfides exist: H 2 S, HS ‐ , S = (Only H 2 S is volatile) • Low pH favors H 2 S High Turbulence • High velocities induce turbulence, which in turn increase the liquid/vapor mass transfer area Long Force Mains/Long Detention Times • More time, more sulfate uptake, more sulfide 6 COMPANY CONFIDENTIAL
Treatment Options Liquid Phase Gas Phase or Vapor Phase – – Prevent Atmospheric Sulfide Provide Point‐Source Solution – – Effective Corrosion Control for Treat Wider Range of Compounds pipes and structures – Provide Area Ventilation – Treat Multiple Downstream Locations 7 COMPANY CONFIDENTIAL
Liquid Phase Options Chemical Reaction – Nitrates – Iron salts – Oxidizers – Peroxide, Hypochlorite, Permanganate pH Adjustment – Sodium or potassium hydroxide Oxygen injection Others – ozone, etc. 8 COMPANY CONFIDENTIAL
Vapor Phase Options Vapor Phase Treatment is technology to control odors in the air or gas stream: Absorption (Chemical Reaction) • Wet Chemical Scrubbers Adsorption (Physical Process) • Carbon Adsorbers Biological Systems (Biological Process) • Biotrickling filters (inorganic media) • Biofilters (organic media) 9 COMPANY CONFIDENTIAL
Collection Systems Characterized by: • 99% H 2 S odors, 1% organic sulfides, low ammonia & amines • H 2 S can range from < 1ppm to > 500 ppm, with wide daily and seasonal variations • Smaller air flow requirements: 100 to 3000 cfm typical. Unoccupied with 3‐6 ACPH typical • Residential locations, aesthetics and noise are equally important • Remote, un‐manned locations – Low maintenance – Reliable operation – Simple process – Safety/vandal resistant 10 COMPANY CONFIDENTIAL
Vapor Phase Odor Control Systems 13135 Danielson Street, Suite 204 11 Poway, CA 92064
Carbon Odor Control Systems 12 COMPANY CONFIDENTIAL
How Does It Work? 13 COMPANY CONFIDENTIAL
Activated Carbon is Most Commonly Made from Bituminous/Anthracite Coal or Coconut Shells • COCONUT SHELL CARBON • ANTHRACITE COAL Increasing • BITUMINOUS COAL Microporosity • ORGANIC POLYMERS • SUB‐BITUMINOUS COAL (20 - 40 Angstrom • in diameter) LIGNITE • PEAT • WOOD 1 Angstrom = 1 x 10 -10 meters 14 COMPANY CONFIDENTIAL
Carbon Capacity Comparison 0.65 0.06 0.12 0.25 0.18 0.04 Virgin Caustic Water High Capacity Activated Treated Regenerated 15 COMPANY CONFIDENTIAL
How Odor Control Carbons Differ With Respect to H 2 S Reaction Products? Products From H 2 S pH of Spent Carbon Reaction Coconut Shell & Both Sulfur and Sulfuric Acidic Coal Carbons Acid pH <2 Impregnated (Caustic Both Sulfur and Sulfuric Acidic Treated) Carbons Acid pH <2 Water Regenerable >95% Sulfuric Acid Acidic Catalytic Carbon pH <1 High H 2 S Capacity >95% Elemental Sulfur Neutral or Slightly Acidic Carbon pH >5 16 COMPANY CONFIDENTIAL
Where Does Carbon Odor Control Fit? Advantages: • Simplest odor control technology • Reliable and effective until breakthrough • Low operator attention/Low maintenance • Lower capital cost • Treat H 2 S and many organic odors • Moderate air flow capacity (~60‐70 cfm/ft 2 ) • Good response to odor spikes Disadvantages: Best Application: • Limited H 2 S/odor capacity and life • Low odor levels (< ~1‐10 ppm) • Can be high operating cost because media • Polishing stage behind chemical or replacement/regeneration can be biological systems expensive • Limited capacity for some organics odors • Some carbons are hazardous/flammable 17 COMPANY CONFIDENTIAL
Biological Odor Control Systems 18 COMPANY CONFIDENTIAL
Biological odor control systems are designed to promote the growth of sulfur‐oxidizing bacteria which under proper conditions will biologically oxidize H 2 S and other sulfur compounds to soluble sulfates Biofiltration – Technology Advantages • No hazardous chemicals Three (3) Steps are involved in • No regular media change‐out‐ Long Biological Odor Control media life • • Media promote bacteria growth Absorption [H 2 S and other compounds are dissolved into the water film on • “Green” surface of media] • Low Maintenance / Operating cost • Oxidation [Bacteria that reside in the water film biologically degrade the dissolved compounds] Requirements • Removal of sulfates (byproduct) • Need regular load of H 2 S • Acclimation • No intermittent use 19 COMPANY CONFIDENTIAL
Requirements of Sulfur‐Oxidizing Bacteria • Energy source: – H 2 S and other sulfur compounds • Carbon source: – Organic matter (heterotrophic bacteria) – Carbon dioxide (autotrophic bacteria) • Nutrients: nitrate, phosphate, potassium • Water • Oxygen (H 2 S + O 2 → H 2 SO 4 ) • Temperature (10 to 50 o C) • Time (for absorption and reaction) 20 COMPANY CONFIDENTIAL
Biofilters (Organic Media) • Organic media – typically dirt, compost, wood chips • In‐ground most common • Very large footprint, low flow rate (30 to 60 second contact times) • Good removal of organic sulfides and VOC’s • Good removal of low H 2 S concentrations • Limited media life • Sensitive to compaction and drying out 21 COMPANY CONFIDENTIAL
Biotrickling Filters (Inorganic Media) • Inorganic media – typically plastic or mineral • Smaller footprint, higher flow rate (8 to 20 second contact times) • Some proprietary media • Very good removal of H 2 S, not as good for organic sulfides • Long media life 22 COMPANY CONFIDENTIAL
Process Flow (Example) 23 COMPANY CONFIDENTIAL
Biological Odor Control Systems Packaged Systems 24 COMPANY CONFIDENTIAL
Chemical Scrubber Systems 25 COMPANY CONFIDENTIAL
Chemical Odor Control Systems Wet chemical scrubbers are defined as devices which utilize a liquid to separate gaseous or particulate contaminants from a gas stream – utilizing mass transfer and chemical reactions 26 COMPANY CONFIDENTIAL
Chemical Reactions Chemical reagents selected based on odorous compounds: – Ammonia/Amines ‐ removed by Sulfuric Acid (H 2 SO 4 ) • 2NH 3 + H 2 SO4 (NH 4 ) 2 SO 4 – Hydrogen Sulfide ‐ solubilization with Sodium Hydroxide (NaOH) or oxidation with Sodium Hydroxide and Sodium Hypochlorite (NaOCl) • H 2 S + 2NaOH Na 2 S + 2H 2 O • H 2 S + 2NaOH + 4NaOCl Na 2 SO4 + 4NaCl + 2H 2 O 27 COMPANY CONFIDENTIAL
Chemical Scrubber System 28 COMPANY CONFIDENTIAL
Chemical Odor Control Scrubbers Packaged Multistage Systems 29 COMPANY CONFIDENTIAL
Where do Chemical Scrubbers Fit? Benefits: Most reliable and flexible vapor phase treatment technology High removal efficiency (99.5%+) Can respond instantly to changing H 2 S loads Small footprint required ( up to 500 ft/min velocity) Can remove any water soluble compound Can run intermittently Drawbacks : Chemical requirements Higher operating cost Maintenance requirements 30 COMPANY CONFIDENTIAL
Applications Information needed to select appropriate technology • Air Flow Rate or Ventilation Rate (cfm) • H 2 S Concentration (average and peak) • Required level of odor removal (H 2 S removal efficiency, others?) • Concentration of other odorous compounds present • Site location • Temperatures (ambient air and odor stream) • Need freeze protection? • Indoor or Outdoor location? • Hazardous area classification? 31 COMPANY CONFIDENTIAL
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