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Philip Roberts Presentation
Desalinate Concentrate Disposal Philip J. W. Roberts School of Civil and Environmental Engineering Georgia Institute of Technology Georgia Tech Fluid Mechanics Seawater Desalination – Capacity by Sea Area Georgia Tech Fluid Mechanics Mediterranean Sea Georgia Tech Fluid Mechanics RO Plant Ashkelon (Israel) Source: Safrai & Zask (2007) Georgia Tech Fluid Mechanics Gulf of Arabia Georgia Tech Fluid Mechanics Discharge in Kuwait Mixing devices desalination plant discharge in Kuwait http://www.icaen.uiowa.edu/fluidslab/gallery/images/flo20.jpg Georgia Tech Fluid Mechanics Red Sea Mozilla Firefox.lnk Georgia Tech Fluid Mechanics Are We Filling the Seas With Salt? The Red Sea Evaporates 2 m/yr! Area 248,000 km 2 Flow 2 248,000 106 / (365 days/yr 86400 sec/day) 16,000 m3 /s Desal flow 100 m3 /s (2 billion gals/day) < 1% Georgia Tech Fluid Mechanics Australia Source: IDA (2006), GWI (2007), www.DesalData.com Georgia Tech Fluid Mechanics Typical RO Seawater Scheme Fresh water Brine concentrate 2x salinity Seawater intake Salinity 34 ppt Density 1025 kg/m3 25 t Outfall and diffuser Salinity 68 ppt Density 1050 kg/m3 +25 kg/m3 (t) Georgia Tech Fluid Mechanics Discharge Modes Flow augmentation After Bleninger & Jirka (2009) Georgia Tech Fluid Mechanics Carlsbad California Desalination Plant Intake Lagoon Discharge pond Outfall Intake area Proposed SWRO plant Power plant Source: City of Carlsbad and Poseidon Resources 2005 Georgia Tech Fluid Mechanics California Ocean Plan Georgia Tech Fluid Mechanics Expert Panel: Scientific Basis for Brine Discharge Guidelines Philip Roberts, Georgia Tech, Chairman Scott Jenkins, Scripps Institution of Oceanography Civil Engineering Physical Oceanography Jeff Paduan, Naval Postgraduate School Daniel Schlenk, UC Riverside Judith Weis, Rutgers University Biochemistry/Toxicology Other SWRCB Desalination Activities: Expert panel review of Intakes: design and mitigation approaches Laboratory studies on brine toxicity (UC Davis) Georgia Tech Fluid Mechanics Review of International Regulations Region/Authority Salinity Limit Compliance Point Source US EPA Increment ≤ 4 ppt Carlsbad, CA Absolute ≤ 40 ppt 1,000 ft San Diego Regional Water Quality Control Board 2006 Huntington Beach, CA Absolute ≤ 40 ppt salinity (expressed as discharge dilution ratio of 7.5:1) 1,000 ft Santa Ana Regional Water Quality Control Board 2012 Western Australia guidelines Increment < 5% The Waters of Victoria State Environment Protection Policy Oakajee Port, Western Australia Increment ≤ 1 ppt Perth, Australia/Western Australia EPA Increment ≤ 1.2 ppt at 50 m and ≤ 0.8 ppt at 1,000m 50 m and 1,000 m Sydney, Australia Increment ≤ 1 ppt 50-75 m Gold Coast, Australia Increment ≤ 2 ppt 120 m GCD Alliance (2006). Okinawa, Japan Increment ≤ 1 ppt Mixing zone boundary Okinawa Bureau for Enterprises Abu Dhabi Increment ≤ 5% Mixing zone boundary Kastner (2008) Oman Increment ≤ 2 ppt 300 m Sultanate of Oman (2005) Wec, 2002 ANZECC (2000); Sydney Water et al. (2005). Georgia Tech Fluid Mechanics Literature Georgia Tech Fluid Mechanics Georgia Tech Fluid Mechanics Executive Summary Georgia Tech Fluid Mechanics Main Environmental Recommendations • Concentrate can be disposed of with minimal environmental effects if properly executed; • Regulate by a mixing zone approach wherein the water quality regulations are met at the mixing zone boundary; • Mixing zone should encompass the near field processes: influenced hydrodynamically by the discharge itself; • 100 m from the discharge structure in all directions and over the whole water column; • Incremental salinity limit at the mixing zone boundary of less than 5% (about 1.7 ppt, dilution of about 20:1); • Dilution can be any combination of in-pipe dilution and near field mixing; • Should also meet toxicity and other requirements in the Ocean Plan at the edge of the mixing zone; • For positively buoyant discharges, the regulatory framework of the Ocean Plan should be sufficient (e.g. OCSD). Georgia Tech Fluid Mechanics Main Recommendations of Expert Panel on Discharges • Preferred methods of discharge: • Diffuser that results in significant near field mixing; • Co-disposal if significant in-pipe dilution with: • power plant cooling water - Discharge can be shoreline surface discharge (if positively buoyant) or through an existing multiport diffuser • domestic wastewater • Shoreline discharge of raw effluent is discouraged. Georgia Tech Fluid Mechanics Suggested Reading! Georgia Tech Fluid Mechanics Amendment Discussions Options and recommendations for: • Disposal methods • Regulation Georgia Tech Fluid Mechanics Discharge Modes After Bleninger & Jirka (2009) Georgia Tech Fluid Mechanics Definitions Near field Far field u Near field: Self-induced turbulence Far field: Ambient turbulence Mixing zones: Regulatory Georgia Tech Fluid Mechanics Clean Water Act 301(h) ZID 10 percentile current Georgia Tech Fluid Mechanics Single Inclined Dense Jet Discharge as high velocity jet to achieve high dilution and reduce salinity to safe levels yt xi Kinematic fluxes: Volume: Q = 4 d 2 u Momentum: M = uQ Buoyancy: B = goQ where: Length scale: go g Sn xn Near field a M 3/ 4 l M 1/ 2 B Dimensional analysis: yL Si dF F yt f M , B ... yt , dF u g od yL , dF Densimetric Froude number Sn Constants F Georgia Tech Fluid Mechanics Laser-Induced Fluorescence (LIF) Argon-Ion Laser Cylindrical lenses CCD Camera Density-stratified tank Image Processing System Georgia Tech Fluid Mechanics LIF Images of Horizontal Buoyant Jet Georgia Tech Fluid Mechanics 3D Laser-Induced Fluorescence Experiments Towing carriage Inflow Plano-convex lens Scanning mirrors Uniform density towing tank Tow Laser sheets Argon Ion laser Mirror signals Jet Nozzle Density current Camera signal Timing signal High speed CCD camera Images Scanning mirror and timing control computer Image acquisition computer Georgia Tech Fluid Mechanics Vertical Dense Jet Georgia Tech Fluid Mechanics 60 Inclined Jet Georgia Tech Fluid Mechanics Long-Term Flushing: Box Model Treatment plant Outfall, Q Y Flushing current, U Decay, k Mass exchange, ve X Long-term dilution: Sp = khXY Q Decay For example, U 5 cm/s Y 1 km h5m Q 2 m3/s + ve hX Q Cross-shore exchange Sp + UhY Q Flushing 0.05 x 5 x 1000 2 125 Georgia Tech Fluid Mechanics What Does 2 ppt Increment Mean? Return point, Sr Impact point, Si Near field, Sn Georgia Tech Fluid Mechanics Effect of Currents on Dense Jets Flow characteristics for various urF ua urF = 0 Falls back Perth: urF 0.2 Slight deflection, upstream wedge 3 cm/s urF 0.5 No upstream wedge, maximum rise height 9 cm/s urF 1 Significantly bent 17 cm/s urF 2 Almost horizontal 34 cm/s Georgia Tech Fluid Mechanics Results Fast current: urF = 0.9 DJV03 Report9 Georgia Tech Fluid Mechanics Dense Jet in Counter Current Georgia Tech Fluid Mechanics Turbulence and Shear Effects on Organisms Perth Diffuser Georgia Tech Fluid Mechanics Turbulence and Shear Effects? Neitzel et al. 2004 Georgia Tech Fluid Mechanics Perth Desalination Plant Georgia Tech Fluid Mechanics LIF Video Georgia Tech Fluid Mechanics Jet Diffusion Velocity, u Diameter, d Rehmann, C. R., et al. (2003). "Effect of turbulence on the mortality of zebra mussel veligers." Canadian Journal Zoology 81: 1063-1069. Kolmogorov scale on centerline: c x 0.24 Re 3/4 Re ud Georgia Tech Fluid Mechanics Diffuser Jet Effects on Living Organisms? For the Perth brine diffuser, we have: u = 4.1 m/s, d = 0.13 m, so assuming = 10-6 m2/s, Re = 5.3x105 Conclusions: Kolmogorov scales 0.01 to 0.1 mm Mean shear rates range from about 21 sec-1 near the nozzle to 0.2 sec-1 at the terminal rise height Exposure times 10 - 50 sec Only 23-38% of entrained water is exposed to potentially damaging turbulence Potentially damaging turbulence Significant?? Entrained water CONCLUSION: ENTRAINMENT IMPACTS FROM DIFFUSERS ARE LIKELY TO BE LOW, and likely lower than impacts from yet to be demonstrated in-plant dilution where impacts can occur from passing through pipes and pumps, during inplant mixing with brine water, and from possible discharge into unfavorable environments. Need field measurements. Georgia Tech Fluid Mechanics Multiport Diffusers Conventional Two-sided One-sided s Optimum design? USBR Effects of currents? Georgia Tech Fluid Mechanics Multiport Diffuser Unsteady Animation F 29 s 0.93 dF Georgia Tech Fluid Mechanics Multiport Diffuser Unsteady Animation - Side View F 29 s 0.93 dF Abessi, O., and Roberts, P. J. W. (2014). "Multiport Diffusers for Dense Discharges." J. Hydraul. Eng., ASCE, Published online April 1, 2014 Georgia Tech Fluid Mechanics One-Sided Multiport Diffuser Counter flow current Georgia Tech Fluid Mechanics Rosette Diffusers e.g. Sydney, Australia Georgia Tech Fluid Mechanics Sydney SWRO Plant Source: Sydney Water and Fichtner 2005 Georgia Tech Fluid Mechanics Aldbrough, England Georgia Tech Fluid Mechanics Single Rosette No Current F 33 s 9.9 dF Georgia Tech Fluid Mechanics San Francisco NPDES Field Studies Georgia Tech Fluid Mechanics Field Studies Georgia Tech Fluid Mechanics Ocean Plan Revisions Georgia Tech Fluid Mechanics Ocean Plan Revisions Georgia Tech Fluid Mechanics Ocean Plan Revisions Georgia Tech Fluid Mechanics Coastal Outfall Dispersion Processes Treatment plant Wind Far field mixing: Oceanic turbulence Current Near field mixing: Self-induced turbulence Shear effect mortality estimates must be included Alternative mixing zone of 200 m may be considered if plant 80% completed Georgia Tech Fluid Mechanics Final Comments • Design and siting are important! • Wouldn't normally expect widespread effects • Mostly near field effects • Use caution with entrainment models • Often simple empirical formulae ok • Physical modeling may be needed • Emerging issue: Turbulence and/or shear mortality of fish and organisms Georgia Tech Fluid Mechanics