Diesel Fuel Contaminated Water Treatment by Sonication: a Potential 20-Minute Sump and Stormwater Remedy Presented by: Roxanne Bessette, E.I. Co-author: Dr. Robert W. Peters, P.E. UAB Department of Civil, Construction, and Environmental Engineering Presented at the 2007 Alabama Water Resources Conference, Orange Beach, AL, September 5-7, 2007.
Situation: Diesel Usage = Diesel Spills = Receiving Waters Impacted
Current Treatment: Gravity Phase Separation and Mechanical Recovery
Limitations of Current Treatment • Cannot handle large spills rapidly; • Cannot handle peak storm flows of the Southeastern U.S.; • Minimal removal at <100mg/L, NPDES O&G discharge limit is usually 15 mg/L; and • Overflow must be sent to local POTW at a per gallon service charge ($$$$!).
Sonochemical Treatment: Unique Aspects • Organic compounds rapidly oxidized (seconds to minutes) • Rapid emulsification of immiscible liquids (seconds) • Extreme conditions on the micro-scale with ambient bulk solution conditions
Cavitation:Quick Overview • Microbubble is spherical at first and then shrinks rapidly • Microbubble formed near solid surface yielding an asymmetric implosion expelling a ~400 kph liquid jet • The jet develops opposite the solid surface and moves towards it • Implosion heats gases to ~5,500ºC • Pressure ~500-1000 atm at collapsing interface • Microbubble shown is ~150 μm …can be much larger depending on kHz Source: Suslick, Scientific American Feb 1989
Acoustical Cavitation = Micro High Energy Rapidly Quenched • In less than a μs, implosion energy causes: • Ionization • N2 NOx NO2- • Radical Creation • O2 and H2O OH • Luminescence • Visible and UV • Pressures of ~500 atm • Temperatures of • ~5,500oC for gases • ~2,100oC for immediately surrounding liquid
Bench-Scale Treatment Method Experimental Conditions • Initial Off Road No. 2 Diesel Fuel Concentration: • 195 mg/L • Volume Treated: • 100 mL • Sonicator Frequency: • 20 kHz • Sonicator Max Power Output: • 950 W Sonication Equipment: Branson 910 BC Power Supply and 902 J Converter
Bench-Scale Treatment Method Experimental Matrix CV= Calibration Verification;DUP= Duplicate Sample; MS=Matrix Spike; IB=Instrument Blank; Meth Blk=Method Blank
Bench-Scale Analytical Method Sample Preparation by SW846 3510C Separatory Funnel Liquid to Liquid Extraction
Bench-Scale Analytical Method Sample Analysis by SW846 8015B Nonhalogenated Organics Using GC/FID
EE/M= (106) P t (60) V (Ci-Cf) Electrical Energy per Mass of Contaminate Removed (kWh/kg) where: P = Power, (kW) t = treatment time, (min) V = Volume of Treated Solution, (L) Ci = Initial Contaminate Concentration, (mg/L) Cf = Final Contaminate Concentration, (mg/L) 93% removal of No. 2 Diesel Fuel requires 8,203.8 kWh/kg (0.0082 kWh/mg) This number is approximately 3-4 fold greater than the TCE and CCl4 sonication energy requirements found by Peters, et al. (2005); Paper presented at the 15th Annual AEHS Meeting and West Coast Conference on Soils, Sediments, and Water, San Diego, CA.
Published Sonochemical Degradation Rates of Various Organic Compounds(Reality Check)
Belt Strippers(common current technology) Removal Efficiencies Comparison *DRO is a subgroup of O&G **Removal time frame commonly on the order of hours to days Sonication(proposed technology) 198 mg/L No.2 Off-road Diesel 95% removed 10 mg/L in 20 min
Bench-Scale Diesel Sump Water Treatment Conclusions • Sonochemical Treatment Potential • Rapid treatment to handle storm event runoff (minutes vs. days) • Exceeds gravity separation treatment efficiency by 45% • 0.002 kWh/mg removal energy requirement for ~200mg/L initial concentration • Tested conditions achieves NPDES discharge standard of 15 mg/L
Acknowledgements • Dr. Robert W. Peters, P.E. • for opportunities and encouragement • UAB Department of Civil, Construction, • and Environmental Engineering • -for research facilities support • Sound Environmental Practice LLC • -for funding