Engineering a Solution to Remediate FOG, Prevent Concrete Corrosion and Treat Odors in Pump Stations and Wastewater Plants Using Hydroxyl Radical Technology Suzanne Dill What We’re Going to Talk About A trifecta of applications! ✓ODOR CONTROL ✓FOG MITIGATION ✓CORROSION Wastewater Odor It smells, it corrodes and it’s downright deadly! • Hydrogen sulfide • Characteristic rotten egg smell • Corrodes infrastructure • Toxic to humans • Generated in wastewater by • Bacteria converting sulfates to sulfide ions • Sulfide ions join with hydrogen 4 Fats, Oils & Grease What’s that floating on top of the wastewater? • Fats are normally solid at room temperature • Oils are normally liquid at room temperature • Grease, a general term used to describe a soft or melted animal fat or a lubricant 5 Fats, Oils & Grease What are they? • Fats, oils & grease come in two forms: • Polar • Non-polar • Polar are associated with animal Triglyceride Molecule fat • Non-polar are associated with petrochemical hydrocarbons 6 Fats, Oils & Grease What happens? • Poor solubility • Separates from the liquid • Lower specific gravity than water • Congeals on the surface • Solid mass • Physically removed 7 Fats, Oils & Grease How does it affect us? • Sewer backups and overflows • Health hazards • Legal and criminal liabilities • Increased energy and maintenance costs • Decreased plant operating efficiency • Odors and infrastructure corrosion • Decreased infrastructure life • Estimated $25 billion annual costs Corrosion How does it happen, what does it do? • Microbial induced corrosion (MIC) • Hydrogen sulfide is slightly corrosive • Sulfur reducing bacteria (SRB) grows in moist environment where hydrogen sulfide is present • SRB metabolize hydrogen sulfide and secrete sulfuric acid - converts H2S to H2SO4 • Acid attacks infrastructure • PH below 4 - severe corrosion range for concrete 9 Oxidation & Reduction LEO says GER! • What are oxidation & reduction? • Loss of an electron is oxidation (LEO) • Gain of an electron is reduction (GER) • FOG, hydrogen sulfide and other odorous compounds are the reducing agents • Common oxidizers • Fire (spark, friction, flame) • Bleach (sodium hypochlorite) • Hydrogen peroxide • Oxygen • Free radicals 10 Advanced Oxidation Process (AOP) Radicals attack and steal to satisfy themselves! • Radicals are often called free radicals • Highly reactive having a single unpaired electron in their outermost orbit (or shell) • Unstable but accepting or donating an electron makes them stable • Free radicals reacting with each other neutralize one another • With some exceptions, the unpaired electrons cause radicals to be highly chemically reactive 11 Hydroxyl Radicals Nature’s Cleanser! • Hydroxyl radical (●OH) • Neutral diatomic molecule • A free radical • Key reactant in oxidation and removal of • Natural Compounds • Anthropogenic Compounds • Photochemically produced in natural water • Peroxides • Superoxide anions • Other names • Mother nature’s cleanser • Nature’s scrubbing bubbles 12 Hydroxyl Radicals Does that have a negative charge? • What is a hydroxyl radical? • How is it different from a hydroxyl ion? • Oxygen & hydrogen bonded together • Gains that extra electron • Oxygen has 6 electrons in outer shell • Has an negative charge • Leaves one electron unpaired • Not as reactive as a hydroxyl radical • Is neutral • Unpaired electrons are highly reactive • Very high oxidation potential •• •• •• •• O • H O • H • •• Hydroxyl Radical (•OH) Hydroxyl Ion (OH―) 13 Other Oxidants #2 but it tries harder! Oxidant Oxidation Relative Oxidation (oxidant potential voltage) (potential power) Fluorine 3.06 2.25 Hydroxyl radical (●OH) 2.80 2.05 Atomic oxygen (O) 2.42 1.78 Ozone (O3) 2.07 1.52 Hydrogen peroxide (H2O2) 1.77 1.30 Permanganate 1.67 1.23 Chlorine dioxide 1.50 1.10 Chlorine gas 1.36 1.00 Oxygen (O2) 1.23 0.90 Hypochlorite 0.94 0.96 14 Hydroxyl Radicals It does all that? • Advantages • Effective odor removal • Efficient algae control • Kills algae and algae food source • Mitigates MIC • Powerful disinfectant • Bacteria • Viruses • Prevents fats, oils & grease buildup • Breaks the double carbon bonds forming the fatty acid chain • Safe byproducts • H2O, O2, & H • Oxidation of organics to • H2O & CO2 Radical Odor Control • Treats odors where they are generated • Requires no chemicals • Designed for enclosed spaces • Lift/pump stations • Wet wells • Holding tanks • Grit chambers • Scum pits • Rotary screens • Primary clarifiers • Influent channels • Patented nozzles • Key to technology The Process Unit Oxygen Plasma Filtered Air Concentrator Generator Ozone Nozzle Hydroxyl Potable Water Radical Fog Filtered Air 3-Fluid Air Atomizing Nozzles • Hydroxyl radicals are dispersed throughout the air space • Odorous compounds oxidized • Fats, oils & grease broken down • Sulfur reducing bacteria exterminated How Does it Really Work on Odors? • HYDROXYL RADICAL! ●OH (VERY UNSTABLE) • The hydroxyl radical sees H2S… really wants to combine because of it’s instability. Radical. • The first ●OH grabs an H from the H2S – creating water and leaving HS¯ (hydrosulfide ion) ¯ • A second ●OH then combines with the HS leaving one atom of sulfur which falls into the wet well. • What’s left? Water and a harmless sulfur atom. • What’s gone? THE ODOR! − ∙ 푂퐻 + 퐻2푆 → 퐻2푂 + 퐻푆 − ∙ 푂퐻 + 퐻푆 → 퐻2푂 + S 19 How Does it Really Work on FOG? • Hydroxyl radicals break down fatty acid chains • Alcohols • Acids • Mechanism: removal of a hydrogen from an adjacent carbon • Hydroxyl radical becomes H2O • Fatty acid converts to peroxides • Peroxides form free radicals that keep breaking down the fatty acid chain • Fatty acid chain becomes alcohols & acids How Does it Really Work on Corrosion? • Hydroxyl radical technology achieves reduction in the rate of corrosion by: • Constantly washing the walls of the infrastructure with water - dilution • Oxidizing/mitigating hydrogen sulfide – removing the food source • Killing the SRB/bacteria • PH in the treated areas will be above 6 – increases the longevity of the infrastructure 21 Why Use Hydroxyl Radicals for Treatment? • High H2S loads – up to 1,500ppm • Corrosion control desired • FOG remediation desired • Vapor phase treatment – treats the air in-situ (rather than moving air through ducts with blowers) • Small footprint • Low installation, operation and maintenance costs • Proven technology 22 Design Considerations • Dimensions of tank (LWH) • Cover and hardware materials • Power and hydraulic cables in headspace • FOG accumulation rates; nozzle selection and placement • H2S ppm, peak and average • Other odorous compound concentrations • Potable water available • Single phase power available Real World Applications – Harrison, OH SUMMARY The influent well located prior to the headworks experiences high fats, oils and grease load. This led to monthly surface accumulation of 1 foot in the 31’L × 8’W × 30’D influent well. The Vapex PLC-3500 reduced FOG accumulation without the addition of chemicals. The tests also showed that the fats, oils and grease did not reform downstream and did not affect the downstream processes. PROBLEMS • Fats, oils and grease APPLICATION • Wet well SOLUTION • (1) Vapex™ PLC-3500 with 5 nozzles INSTALL DATE • December 2012 CONTACT • Jim Leslie, Public Works Director • (513) 367-2111 [email protected] Real World Applications – Ak-Chin, AZ SUMMARY Plant replaced corroding rotary screens, which had started to corrode within a few months of initial installation. The H2S levels were extremely high in the rotary screens, due to off-gassing, with an average concentration over 500 ppm. Peak H2S levels were over 1,000 ppm. PROBLEMS • Odor & corrosion APPLICATION • Two (2) rotary drum screens – 500 cubic feet treatment volume SOLUTION • (1) Vapex 2500 with 4 nozzles INSTALL DATE • May 2011 CONTACT • Ray Pulver, Water Operations Manager • (520) 568-1140 • [email protected] MANUFACTURER’S REPRESENTATIVE • Goble Sampson • (480) 969-3667 THANK YOU NC AWWA- WEA & PARTICIPANTS! SUZANNE DILL 347.924.5229 WWW.VAPEX.COM.