Utilizing Duckbill Valve Manifold Systems to Improve

The Science of Mixing and Improving Water
Quality in Water Storage Tanks
Ohio AWWA Southeast District Fall Meeting
November 21, 2013
Presented by:
Michael Duer, P.E., Chief Engineer
Red Valve Co., Tideflex Technologies Division
2013 Red Valve Co. / Tideflex Technologies. All rights reserved.
Presentation Outline




Types of Storage Tanks
2 Keys to Maintaining Water Quality
WaterRF 11 Design Recommendations for
Water Storage Tanks
The Science of Mixing Storage Tanks
CFD and Scale Modeling
Water Quality Sampling and Monitoring
Passive Mixing Systems
Active Mixing Systems
Case Studies





Common Types of Water Storage Tanks




Ground Level Tanks (Rectangular)
Ground Level Tanks (Circular)
Elevated Tanks
Standpipes
All Have Unique Challenges with Short-Circuiting and Mixing Solely
based on Volume, Geometry, Inlet/Outlet Pipe Configuration, Turnover
How to Improve Water Quality in Water
Storage Tanks



Correct Structural, Sanitary, Security Defects
Periodic Cleaning
(not the focus of today’
today’s seminar)
1) Maximize
Volume Turnover to Minimize Water
Age (Operation of Distribution System)
2) Achieve Complete Mixing (eliminate ShortCircuiting (Design of tank, inlet/outlet, mixing
system)
 Have to do Both
AWWARF Manuals Related to Reservoirs
Maintaining Water
Quality in Finished
Water Storage
Facilities
1999
Water Quality
Modeling of
Distribution System
Storage Facilities
2000
AWWARF Design Recommendations
For Distribution System Reservoirs
1. Achieve Good Mixing
6. Avoid Certain Inlet Config’
Config’s
(Tangential Inlets, Deflectors)
2. Baffling Should be Avoided
7. Standpipe Likely to Stratify
3. Mixing by Turbulent Jet
8. Minimize Detention Time
4. Avoid Stratification
5. Mixing Time < Fill Time
9. Include Sampling Ports
10. Monitor Temperature
11. CFD or Scale Models
Tideflex Technologies’ Tideflex® Mixing System
Water Age Assumes
Tank is Mixed
Methods to Reduce Water Age
Existing Tanks
 Increase Drawdown in Each Fill/Draw Cycle
 Increase Number of Daily Fill/Draw Cycles
 Take Tanks out of Service During Low Demand
 Operate at Lower High Water Level During Low
Demand
 Overflow Tanks
 Flush
New Tanks
 Build Two Smaller Tanks Rather Than One Larger Tank.
Or, Build a Tank within Tank (Smaller Footprint)
 Consider Site Location with Respect to Water Source
and Demands
AWWARF Design Recommendations
For Distribution System Reservoirs
1. Achieve Good Mixing
6. Avoid Certain Inlet Config’
Config’s
(Tangential Inlets, Deflectors)
2. Baffling Should be Avoided
3. Mixing by Turbulent Jet
4. Avoid Stratification
7. Standpipe Likely to Stratify
8. Minimize Detention Time
9. Include Sampling Ports
5. Mixing Time < Fill Time
10. Monitor Temperature
11. CFD or Scale Models
Computational Fluid Dynamics (CFD) Modeling
Mesh
Tracer
Animation
Velocity Contour/Vector
AwwaRF Research Projects on Distribution Storage Tanks
Georgia Institute of Technology
and Red Valve Company
2006 AwwaRF Project
2006 AwwaRF ProjectProject- Red Valve & Georgia Tech
“Physical Modeling Of Mixing in Water Storage Tanks”
Tanks”
Studied the Effects of the Following on Mixing:
• Tank Style
• Single and Multiple Ports
• Low and High Flow Momentum
• Temperature Differences between Inlet and Tank Water
Short Circuiting

First In, Last Out (Last in, First Out)
Water in Close Proximity to Inlet/Outlet is
Continually Turned Over. Water away from
Inlet/Outlet stagnates.

Some States Now Mandate Separate Inlet/Outlet
Pipes

Common Inlet / Outlet
Separate Inlet / Outlet
DAY AFTER DAY, WEEK
AFTER WEEK OPERATION
OF TANK WITH
INCOMPLETE MIXING AND
SHORT-CIRCUITING IS
WHAT LEADS TO WATER
QUALITY DEGRADATION
CAUTION When Separating Inlet and Outlet
•
•
•
Must Understand the Circulation Patterns in Order to Know Where Mixing
Happens Last. Outlet(s) Would Go in Those Locations
Getting Inlet and Outlet “As Far Apart As Possible” is Often the Wrong
Assumption
Circulation Patterns Change with Temperature Differences Between Inlet and
Tank Water
AWWARF Design Recommendations
For Distribution System Reservoirs
1. Achieve Good Mixing
2. Baffling Should be Avoided
3. Mixing by Turbulent Jet
4. Avoid Stratification
5. Mixing Time < Fill Time
6. Avoid Certain Inlet Config’
Config’s
(Tangential Inlets, Deflectors)
7. Standpipe Likely to Stratify
8. Minimize Detention Time
9. Include Sampling Ports
10. Monitor Temperature
11. CFD or Scale Models
AWWARF Design Recommendations
For Distribution System Reservoirs
1. Achieve Good Mixing
2. Baffling Should be Avoided
6. Avoid Certain Inlet Config’
Config’s
(Tangential Inlets, Deflectors)
7. Standpipe Likely to Stratify
3. Mixing by Turbulent
Jet
8. Minimize Detention Time
4. Avoid Stratification
9. Include Sampling Ports
5. Mixing Time < Fill Time
10. Monitor Temperature
11. CFD or Scale Models
Hydrodynamic Mixing
■ Turbulent Inlet Jet (Only source of
Energy) into Large Waterbody
■ Velocity Discontinuity between Inlet and
Ambient yields Entrainment
■ Circulation Patterns form due to
Conservation of Momentum
■ Can be Strongly Dampened by
Temperature Differentials (+ and
- Buoyancy)
Tideflex Technologies’ Tideflex® Mixing System
AWWARF Design Recommendations
For Distribution System Reservoirs
1. Achieve Good Mixing
6. Avoid Certain Inlet Config’
Config’s
(Tangential Inlets, Deflectors)
2. Baffling Should be
Avoided
7. Standpipe Likely to Stratify
3. Mixing by Turbulent Jet
8. Minimize Detention Time
4. Avoid Stratification
9. Include Sampling Ports
5. Mixing Time < Fill Time
10. Monitor Temperature
11. CFD or Scale Models
Baffles (Plug Flow)
AWWARF Research Testing Results
0.50
0.50
mg/l
mg/l
Mixed Flow
Plug Flow
AWWARF Design Recommendations
For Distribution System Reservoirs
1. Achieve Good Mixing
2. Baffling Should be Avoided
3. Mixing by Turbulent Jet
4. Avoid Stratification
5. Mixing Time < Fill Time
6. Avoid Certain Inlet Config’
Config’s
(Tangential Inlets, Deflectors)
7. Standpipe Likely to Stratify
8. Minimize Detention Time
9. Include Sampling Ports
10. Monitor Temperature
11. CFD or Scale Models
Inlet Configurations
to Avoid
INLET IN A SUMP
Does not allow jet to develop completely
DISCHARGE ABOVE WATER SURFACE
Does not allow jet to develop completely
AWWARF Design Recommendations
For Distribution System Reservoirs
1. Achieve Good Mixing
2. Baffling Should be Avoided
3. Mixing by Turbulent Jet
4. Avoid Stratification
5. Mixing Time < Fill Time
6. Avoid Certain Inlet Config’
Config’s
(Tangential Inlets, Deflectors)
7. Standpipe Likely to Stratify
8. Minimize Detention Time
9. Include Sampling Ports
10. Monitor Temperature
11. CFD or Scale Models
Empirical Mixing Time Equation
How Long doYou Need to Fill Tank to Mix it?
Mixing time (hours) =
K (V2/3 / M1/2)
K = Coefficient (based on Mixing Efficiency of
Pipe/Manifold)
V = Volume of water in tank at start of fill, feet3
M = Momentum = flow rate x velocity (Q * U)
Q = Inflow rate, cfs
U = Inflow velocity, feet per second
Caution: No Variables in Equations or Limitations of
Equation for Considering Temperature Differences
Between Inlet Water and Tank Water
Mixing Time Comparison ( 48” and 12” Inlet )
Increasing Velocity Easier To Do Thank Increasing Flow Rates,
but Requires Careful Considerations With Headloss
AWWARF Design Recommendations
For Distribution System Reservoirs
1. Achieve Good Mixing
6. Avoid Certain Inlet Config’
Config’s
(Tangential Inlets, Deflectors)
2. Baffling Should be Avoided
7. Standpipe Likely to Stratify
3. Mixing by Turbulent Jet
8. Minimize Detention Time
9. Include Sampling Ports
4. Avoid Stratification
5. Mixing Time < Fill Time
10. Monitor Temperature
11. CFD or Scale Models
Tideflex Technologies’ Tideflex® Mixing System
Effect of Colder Inlet Water (Summer Conditions) on Mixing
2oF Colder Inlet Water
■ Mixing Time Equation May Grossly Underestimate Fill Time
Required to Mix
■ Jet Must Reach Water Surface to Mix Tank
■ Mixing Will Only Occur to Terminal Rise Height (TRH) of Jet
■ Below TRH - Adequate Mixing, Temperature, and Residual
■ Above TRH – No Mixing, Water Age Continually Increases
With Each Fill & Draw Cycle, Lose Residual
■ Have No Idea of Potential Problem Even if Sampling Outside
of Tank
Water Quality Problems Associated with ShortCircuiting and Incomplete Mixing In Storage Tanks
A Localized Increase in Water Age and Hotter Water
Responsible for:
• LOSS OF DISINFECTANT RESIDUAL
• DBP SPIKES (THM AND HAA5)
• BACTERIA FORMATION
• NITRIFICATION (CHLORAMINES)
• VARIANCE IN pH and DISSOLVED
OXYGEN
• HPC SPIKES
• TASTE & ODOR
Unmixed
Older, Hotter
Water
(Localized Increase
in Water Age)
Mixed
• BIOFILM GROWTH
TTHM, HAA5,Temperature and Cl2 Residual Data
1.5MG Standpipe – Champlain W.D., VT
Dangerously close to
Stage II MCL of 80 ppb
Increasing Depth
Effect Of Colder Inlet Water on Mixing in Reservoir
CFD Model – 2.5MG Reservoir (120’ Dia. X 30’ SWD)
ISOTHERMAL
 Will Not ShortShort-Circuit with Separate Outlet Pipe
 Will Mix Tank IF Fill Long Enough
INLET 4°
4° F COLDER  Will ShortShort-Circuit Even with Separate Outlet Pipe
 Will Not Mix Tank Regardless How Long it is Filled
Temperature and Cl2 Residual Data
4MG Steel Reservoir – Northern California
Water Quality Problem
Thermocline
Temperature Variation Thru Depth (Thermocline
(Thermocline)) Indicates Incomplete
Mixing and Warns of Potential Water Quality Problems
Warning: Samples Taken Just Outside of Tank Would Never Show the W.Q. Problem
Problem
Example of Water Quality Decay
Continuous Monitoring of I/O Pipe –
0.5MG Hydropillar
Courtesy
Paul Handke,
PA DEP
Example of Water Quality Decay
Continuous Monitoring of I/O Pipe – 1.0MG Multileg
Courtesy
Paul Handke,
PA DEP
Effect Of Warmer Inlet Water
on Mixing in Reservoir (Winter)
• Inlet Water Positively Buoyant
• Mixing from Top Down
• Cannot Short-Circuit
AWWARF Design Recommendations
For Distribution System Reservoirs
1. Achieve Good Mixing
6. Avoid Certain Inlet Config’
Config’s
(Tangential Inlets, Deflectors)
2. Baffling Should be
Avoided
7. Standpipe Likely to Stratify
3. Mixing by Turbulent Jet
8. Minimize Detention Time
4. Avoid Stratification
9. Include Sampling Ports
5. Mixing Time < Fill Time
10. Monitor Temperature
11. CFD or Scale Models
Sampling Lines
Sampling Lines
On Wall
Manual Sampling
Water Quality Monitoring Panel
(courtesy Spiess Construction)
(courtesy Lakewood Water District)
Sampling Lines To Different
Locations and Depths
Crude But Effective Top-Bottom Sampling
• Only a 1-time snapshot
• Don’t have to climb
Take Sample at
Inlet/Outlet Pipe
Overflow Tank
and Sample
Overflow Water
Sampling for Temperature Stratification


Digital Thermometers (Instantaneous Measurement)
Temperature Data Loggers (Continuous Measurement at
User-Specified Intervals)
Tideflex Technologies’ Tideflex® Mixing System
Temperature Data Logger String
Float
Data Logger
Temperature
Data
Loggers
• Long-Term Monitoring
• Most Applicable in Summer
Inlet / Outlet
Tideflex Technologies’ Tideflex® Mixing System
ROV and Diving Inspections
Can Identify Thermal Stratification
Tideflex Technologies’ Tideflex® Mixing System
Grab Sampling – Chemical and Microbiological
pH Kit
Pocket Colorimeter
Depth
Sampler
It is possible for tanks to not
be temperature-stratified, but
can be chemically or
microbiologically stratified.
“Methods” and Mixing System Alternatives


Baffles (not recommended)
Simple Inlet/Outlet Separation
–

Passive Mixing Systems (Mix During Fill Cycle)
–
–
–

May Not be Effective
Passive Tideflex Mixing Systems (PTMS)
Draft Tube
Complex Piping Systems
Active Mixing Systems (24/7 Mixing)
–
–
–
–
Active Tideflex Mixing System (ATMS)
Electric Submersible Mechanic Mixers
Solar Powered Mechanical Mixers
Air Bubblers
Effect of Colder Inlet Water (Summer Conditions) on Mixing
Inlet Riser Still Results in
Incomplete Mixing and Stratification
Dedicated Inlet
Pipe Riser
Dedicated Outlet Pipe on
Opposite Side of Tank
Unmixed Older,
Hotter Water
Mixed
Draft Tube Mixing System
Pros
 Simple and Passive
 No Maintenance
Cons
 Caution: Review the Research
 Proprietary to a Tank
Manufacturer (Determine if
Causes Bidding Issues)
Draft Tube
Elaborate Piping Systems
Pros
 Passive
 Low Maintenance
 Effective if Properly Designed
Cons
 Design is Often Overkill
 Costly
 Longer to Install
Tideflex Mixing System (TMS)
Tideflex Inlet
Nozzles
Outlet Check
Valves
Circular Reservoirs
Rectangular Reservoirs
Standpipes
Tideflex Inlet Nozzles
optimize jet velocity
at all flow rates
Dry Riser Elevated
Wet Riser Elevated
Waterflex Outlet
Check Valves
Properly Designed Multiple Port Manifolds Result in Up to
50% Faster Mixing Compared to a Single Inlet Pipe
Multiple Inlet Ports Distribute Inlet Flow
Momentum Thru Tank Similar to Large Public
Swimming Pools. Results in Faster Mixing
Scale Modeling of 1.0MG Reservoir
Single
Inlet Pipe
5-Port
Tideflex
Mixing
System
Properly
Designed
Multiport
System Result
in 50% Faster
Mixing
Images courtesy of: Los Angeles Department of Water & Power and Northwest Hydraulic Consultants
CIRCULAR and RECTANGULAR RESERVOIRS
Multiple Inlet Ports Achieve Mixing in Summer with Colder Inlet
Water (AwwaRF Research)
A Single Inlet Pipe - Often Results in Incomplete Mixing and Stratification
Properly Designed Tideflex Mixing System - Completely Mix in Summer
Optimized Jet Velocity of Tideflex Inlet Nozzles
Fixed-Diameter pipes cannot
optimize jet velocity
Tideflex Inlet Nozzles optimize jet
velocity at all flow rates
Tideflex Inlet Nozzles Maximize Jet
Velocity at ALL Flow Rates
Compared to Fixed-Diameter Pipe
Tideflex Mixing System (TMS)
Pros








Green. Uses Energy Already in Distribution System - Pressure
Separates Inlet and Outlet on a Single Manifold Pipe
Achieves Complete Mixing Using Existing Energy Source
CFD Modeled, Scale Modeled, Field Validated in Every Tank Style
(3,500+ Installations)
No Maintenance - No Mechanical Parts
30 Year Life
NSF61 Certified Valves
Rubber Tested for Chlorine and Chloramine Exposure – No
Degradation
Cons
 Fitting Components thru Roof and Shell Hatches
(Retrofits)
 May Not Be Able to install “in the wet” Without Taking
Tank Out of Service
TMS for Circular Reservoirs
DISTRIBUTION SYSTEM OPTIMIZATION
Poor Mixing and Short-Circuiting
Localized Increase in
Temperature and Water Age
Treatment Plant
With Complete Mixing
Cl2
With Poor Mixing and Short-Circuiting
THM
With Complete Mixing
Town of Hillsborough, CA
Sampling of (2) 0.5MG Reservoirs (60.5’
(60.5’ Dia. x 23’
23’ SWD)
Quarterly Samples taken in 3 quadrants and 3 depths (low, mid, high)
HIGH
MID
LOW
Town of Hillsborough, CA
Sampling of (2) 0.5MG Reservoirs (60.5’
(60.5’ Dia. x 23’
23’ SWD)
Opportunity for Distribution System Optimization (lowering disinfectant
dosage to reduce THMs) since residuals are 2 mg/L
Preventing Water Stagnation in Storage Tanks
Reservoir Case Study
Eugene Water & Electric Board
Brown & Caldwell Engineering
Tideflex Technologies’ Tideflex® Mixing System
1MG Reservoir
Eugene Water and Electric Board
Chlorine Residuals are Consistent Throughout Tank
Slide Courtesy of Brown & Caldwell
Chlorine Residuals Have Increased Throughout
System
Active (Mechanical) Mixing (If Required)
Air Bubblers
Passive TMS + Recirculation Pump
(Mechanical Components Outside of
Tank, Passive TMS Inside of Tank)
Submersible Mixers
PAX Mechanical Mixer
Solarbee Mechanical Mixer
Severn Trent Clortec and Tank Shark
Water Sample
Chlorite Supply
Ammonia Supply
Hatch
Controls
FRP Shelf
Water Circulation
Submersible Pump
Water Suction
Active (Mechanical) Mixing
What They Do
Mechanical Mixers Add Another Energy Source (Solar, Electric, Battery) into tank
to mix.
But Consider
Distribution Systems Already Have an Energy Source. Pumped Systems and
Gravity-Driven Systems are Designed to Refill Tanks to High Water Level After
Drawdown.
• Tanks Designed to Fluctuate/Turnover
• Tanks NEED to Fluctuate/Turnover to Minimize Water Age
• (Existing Energy Source) + (Properly Designed Passive Mixing System) = Mixed Tanks
Determine if Active Mixing is Needed
Run a Mixing Analysis to Confirm Passive Mixing System can Mix Tank Based
on Tank Turnover. Tideflex Technologies provides a Design Report for every
tank that includes a Mixing Analysis and Water Age Analysis.
Active (Mechanical) Mixing
Pros
 Effective if Properly Sized, Designed and Validated
 Some Can be Used for Disinfectant Injection
(Consider Whether to Inject on Way in or on Way Out)
Cons
Maintenance/Replacement Costs Every 33-5 Years
 Energy Cost
 Take 22-3 Days to Mix
 May Need Multiple Mixers for Tanks with Higher Flow
Rates and Turnover
 Some Mixers Fairly New to Market
 Removal/Inspection Difficulty
 Additional Tank Penetration, Roof Mounts, etc.
 Battery Disposal not Green (Solar Option)

Active Tideflex Mixing System (ATMS)
Passive TMS
installed in tank
IF active mixing is required:






A Passive TMS can be turned into an Active TMS with a
recirculation pump
– Passive TMS installed INSIDE of Tank (No mechanical
components inside tank so tank access not required for
inspection or maintenance)
– All Mechanical Components in Vault OUTSIDE of tank (easily
accessed in vault/structure for inspection and maintenance)
Recirculation pump is low flow, low head, low energy
Can perform continuous mixing
Can perform forced-draw down to minimize water age
Can perform chemical injection for rechlorination, forming
chloramines, or performing breakpoint chlorination
Can turn recirculation pump off when not needed
Recirculation
and let passive TMS mix tank
Pipe
Tank Inlet
Pipe to
Passive TMS
Recirculation
Pump
Chemical Injection Alternatives
Into Tideflex
Jet In Tank
Into Inlet or Outlet Pipe
TMS for Rectangular Reservoirs
Tideflex Mixing System (TMS) for Pedesphere,
Hydropillar and Composite Elevated Tanks
Tideflex Inlet
Nozzles
2.0MG Elevated
Tank
Waterflex Outlet
Valves
Sampling 1.5MG and 2MG Elevated Tanks
with and without TMS - McKinney, TX
(3) Dedicated sampling lines (low, mid, high) run to continuous chlorine
analyzer. Data for entire month of August 2007
2MG Composite
Elevated with TMS
1.5MG Composite
Elevated without TMS
Chlorine Residual (mg/L)
2MG Composite
Elevated with TMS
AUGUST 2007
TMS for Elevated Tank with Wet Riser
Wet Riser Typically 36”-96” Diameter
KNOCKS MOMENTUM OUT OF INFLOW!!
INLET
NOZZLES
OUTLETS
TMS for Standpipes
TIDEFLEX INLET
NOZZLES
WATERFLEX
OUTLET VALVES
2011 Red Valve Company/Tideflex Technologies. All rights reserved
Clark Public Utilities, WA Temperature Profiling
Adjacent Standpipes, 0.5 MG and 1.5MG (125’ Deep)
Temp. Data Loggers
Installed Every 20’
20’ Thru
Depth. Logged Temp’
Temp’s
Every 30 minutes for
Over 1 Year
Common
Inlet/Outlet
With TMS
Temperature vs. Depth Data
 Stratification Gets Worse in Smaller Tank from July to August
 Stratification Eliminated in Larger Tank with Mixing System
7/12/03
8/1/03
76
76
74
74
Without
Mixing System
70
68
66
64
With Mixing
System
72
Temperature (F)
Temperature (F)
72
Without
Mixing System
70
68
66
With Mixing
System
64
62
62
Depth (ft)
60
Depth (ft)
60
10
30
50
0.5 MG
70
1.5 MG
90
10
30
50
0.5 MG
70
1.5 MG
ICING Case Study (Before Mixing System)
Region of Peel 0.55MG Standpipe (30’ Dia. X 110.5’)
Discovered 30’ Dia. x 10’ Deep Slug
of Ice in May of 2005
Ice removal took 2 weeks and $27,000
90
ICING Case Study (with TMS Installed)
Region of Peel 0.55MG Standpipe (30’ Dia. X 110.5’)
Ice Mitigation




Bulk Mixing Improved
Higher Jet Velocity with Tideflex Nozzles
Inlet Jets are Higher in Tank so there is
more Turbulence on Water Surface
Injecting Warmer Water on Water
Surface
Slush/Thin Ice, Never
formed Ice Cap
QUESTIONS ?
Mike Duer, P.E., Chief Engineer
Tideflex Technologies
Division of Red Valve Company, Inc.
(412) 279-0044 phone
[email protected]
Authorized Representative
Dan Caskey
Hydro Controls, Inc.
513-474-7400
[email protected]