Cleveland Morgan Water Treatment Plant Finished Water Reservoir

Transcription

1 Cleveland Moran Water Treatment Plant Finished Water Reservoir Joseph G. Stanley, PE September 22, 2010 The Ohio Section of the American Water Works Association 72 nd Annual Conference

2 What you won t be seein today They aren t even from New Jersey.

3 Acknowledements Cleveland Division of Water J. Christopher Nielson Commissioner Alex Marevicius Asst. Commissioner, Enineerin Hicham Ali Enineer Maie Roders Water Quality Manaer Tyrone Butler Moran Plant Manaer Hatch Mott MacDonald Norman Rhodes, Ph.D. URS Corporation Keith Mast Alan Stadler, Ph. D., PE Tim Lauth, PE

4 Presentation Outline Project constraints Process challenes Explanation of disinfection criteria Computation fluid dynamics (CFD) modelin Hydraulic refinements Construction photoraphs

5 Moran Plant Site N RWPS Filters 20 MG Reservoir (to be replaced) New Pump Station New Pump Reservoir Station Pretreatment Facilities

6 Site (Horizontal) Constraints Poor supportin soils N Unsupported Filtered Water Conduit Twin 72 Raw Water Mains Steep Slope Finished Water Pipelines New Reservoir

7 Desin Parameters Plant to remain in operation durin construction Reservoir to be split into 2 equivalent cells Provide sufficient volume for disinfection contact time for 0.5 lo inactivation of Giardia at: 1.0 m/l of free chlorine ph = 7.6 Water temperature = 0.5 C 150 MGD throuh both reservoir cells Optimize volume for plant flow equalization 7.8 MG storae required for disinfectant contact time

8 Vertical Constraints Maximum water surface constrained by ravity filter hydraulic limitations backpressure on filters Reservoir bottom determined by Lake Erie induced roundwater level Low water operatin level is constrained by the NPSH conditions of the Finished Water Pump Station Volume below the low operatin level can only be used for disinfection residence, or contact, time - CT Finished Water Pumps NPSH Req d Lake Erie induced roundwater level Operatin Rane (Equalization) CT Reservoir Gravity Filters

9 Process challenes Reservoir volume within the vertical constraints, not required for disinfection residence time, CT, can be used for flow equalization storae Optimizin the CT volume maximizes the equalization volume, which enhances operations flexibility Critical Desin Element Due to the size of the facilities, desin Rules of Thumb are not adequate increased confidence is required Good candidate for Computational Fluid Dynamics (CFD) modelin Operatin Rane (Equalization) CT Reservoir

10 What is CT? The disinfectant concentration multiplied by the time it takes for the water to flow throuh a sement Flow is not typically uniform throuh a process sement T 10 is the time that it takes for 10% of water to flow throuh a sement 90% of the flow would take loner Reulations are based upon multiplyin the T 10 time by the disinfectant concentration refinement of first bullet Microoranism inactivation based on a iven CT for a particular condition (disinfectant, temperature and ph)

11 T 10 and the theory of rubber duckies Race Time 10 duckies decide to race T 10 is when 10% of duckies pass the finish line

12 Methods to reduce short-circuitin A lare lenth to width ratios (L:W) tends to reduce shortcircuitin Abrupt chanes in direction impact the flow reime

13 CFD Modelin 3D eometry is defined by a rid of elements Boundary conditions are set Inlet water flow Wall friction Outlet conditions

14 Physical Situation Baffle Outlet Sluice Gate 30:1 L:W Flow Channel One of Two Reservoir Cells Inlet Weir Wall

15 Base Case w/o Flow Straihtenin

16 Base Case Velocity ft/s

17 Wall Foils Neliible Impact Velocity ft/s

18 With Flow Vanes

19 Flow Vanes Velocity ft/s

20 Residence Time Distribution (RTD) RTD curves are determined by simulatin tracer injection into the inlet Particles uniformly mixed at the inlet enter the calculation domain at t = 0 The particles are carried and mixed by the flow They are counted as they exit the domain Remember the duckie race?

21 Fraction of Released Particles (Tracers) Cumulated Fraction of Released Particles (Tracers) Fraction of Released Particles (Tracers) Cumulated Fraction of Released Particles (Tracers) RTD curves 17.5 and 13.1 ft depth 17.5 ft Residence Time (s) Residence Time (s) 13.1 ft Residence Time (s) Residence Time (s)

22 Baffle Factors Confiuration Flow Rate (MGD) Depth (ft) HDT (min) T 10 /HDT Base case Wall foils Vanes OEPA minimum baffle factor = 0.6 Numerical accuracy about 10%

23 Impact from optimized CT desin Condition Required CT Volume Equalization Volume Increase Over Base Case Base 7.8 MG 0.60 = 13.0 MG 2.0 MG --- CFD 7.8 MG 0.82 = 9.5 MG 5.5 MG 175% Tracer 7.8 MG 0.90 = 8.7 MG 6.3 MG 215%

24 Reservoir Construction

25 Reservoir Construction Retainin walls at slope area Constructin wall sections

26 Reservoir baffle wall channel Reservoir Construction

27 Before and After Before After

28 Finished Reservoir

29 Thank you Questions Joseph G. Stanley, PE