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AMERICAN WATER WORKS ASSOCIATION
NEW JERSEY SECTION
2015 Annual Conference
Keep the Water Moving –
Rehabilitation of a 1-million
Gallon Water Storage Tank
Jonathan T. Reed
CDM Smith, Inc.
Bill Mitchell, P.E.
Trenton Water Works
March 19, 2015
Presentation Outline
• Water quality in potable water storage tanks
• Methods for optimizing water quality
in potable water storage tanks
• Trenton Water Works and the
Whitehorse Tank
• Alternatives for improving water
quality in the Whitehorse Tank
• Evaluation of alternatives and
recommendation
• Overview of tank improvements
and operation
Keep the Water Moving - Rehabilitation of a 1-million Gallon Water Storage Tank
WATER QUALITY
IN POTABLE WATER STORAGE TANKS
DBP Formation in Water Distribution Systems
and Water Storage Facilities
Keep the Water Moving - Rehabilitation of a 1-million Gallon Water Storage Tank
DBP Formation in Water Distribution Systems
and Water Storage Facilities
Given a chlorine residual and a high chemical
contact times, DBPs can form in storage facilities
Keep the Water Moving - Rehabilitation of a 1-million Gallon Water Storage Tank
METHODS FOR OPTIMIZING WATER QUALITY
IN POTABLE WATER STORAGE TANKS
Method No. 1 – Maintain Adequate Turnover
Rates to Decrease Water Age
Turnover
GOAL
3-5 days
20%-35%
Turnover Per Day
Change in Water Age with Increased Cycling
Keep the Water Moving - Rehabilitation of a 1-million Gallon Water Storage Tank
Method No. 2 – Ensure Complete Mixing
Turnover
is NOT
Enough
taste and
odor issues
temperature
stratification
bacteria
regrowth
loss of
chlorine
residual
disinfection
byproduct
spikes
Keep the Water Moving - Rehabilitation of a 1-million Gallon Water Storage Tank
Method No. 2 – Ensure Complete Mixing
Tideflex® Technologies
http://www.tideflex.com/tf/index.php/cfd-modeling
CFD Model Velocity Profile for Single Inlet in an
Elevated Tank (Duer M. , 2012)
Keep the Water Moving - Rehabilitation of a 1-million Gallon Water Storage Tank
TRENTON WATER WORKS AND
THE WHITEHORSE TANK
Trenton Water Works Water Supply System and
Pressure Gradients
Keep the Water Moving - Rehabilitation of a 1-million Gallon Water Storage Tank
The Whitehorse Tank
1-MG Multi-leg Steel
Elevated Potable Water
Storage Tank
Keep the Water Moving - Rehabilitation of a 1-million Gallon Water Storage Tank
The Whitehorse Tank
Steel Tank
Pedestal –
Typical of 8
Valve Vault
with Altitude
Valve
12-inch
Inlet/Outlet Pipe
1-MG
Whitehorse
Tank
96-inch
Diameter
Steel Riser
Distribution Main
on Hempstead Road
Keep the Water Moving - Rehabilitation of a 1-million Gallon Water Storage Tank
Trenton Water Works Tanks Operating Ranges
(historical data from 2009-2013)
Central Pumping Zone
Pressure Gradient
Minimum Turnover
in Whitehorse Tank
Keep the Water Moving - Rehabilitation of a 1-million Gallon Water Storage Tank
Potential for Water Quality Issues in the
Whitehorse Tank
Lack of adequate
daily turnover
Lack of adequate
Mixing
Keep the Water Moving - Rehabilitation of a 1 Million Gallon Water Storage Tank
ALTERNATIVES FOR IMPROVING WATER
QUALITY IN THE WHITEHORSE TANK
Improving Tank Turnover
Elevate
Existing
Tank
Install New
Elevated
Storage
Tank
Remove
Existing
Tank
Install
Booster
Pumps
Keep the Water Moving - Rehabilitation of a 1-million Gallon Water Storage Tank
Improving Tank Turnover: Elevate Existing Tank
Advantages
Disadvantages
• Increase local system
pressure
• No new equipment
• High capital cost
• Public perception
• Concerns with foundation
• Permitting challenges
Keep the Water Moving - Rehabilitation of a 1-million Gallon Water Storage Tank
Improving Tank Turnover: Install New
Elevated Storage Tank
Advantages
Disadvantages
• Increased life span
• Low maintenance
• High capital cost
• Major construction
• Permitting challenges
Keep the Water Moving - Rehabilitation of a 1-million Gallon Water Storage Tank
Improving Tank Turnover: Remove
Existing Tank
Advantages
Disadvantages
• Improved aesthetics to
neighborhood
• Eliminates maintenance
• Liability risk
• Decreased available
fire flow
• May impact insurance
ratings
• Permitting challenges
Keep the Water Moving - Rehabilitation of a 1-million Gallon Water Storage Tank
Improving Tank Turnover: Install
Booster Pumps
Advantages
• Low capital cost
• Minimize impact on local
residents
• Removes dependability
on system pressure for
turnover
Disadvantages
• O&M requirement
• Long term maintenance
• New equipment required
Keep the Water Moving - Rehabilitation of a 1-million Gallon Water Storage Tank
Improving Tank Circulation
Tideflex Mixing
System
SolarBee or
GridBee Mixing
System
PAX Mixing
System
Keep the Water Moving - Rehabilitation of a 1-million Gallon Water Storage Tank
Improving Tank Circulation: Tideflex
Mixing System
Advantages
Disadvantages
Tideflex mixing system installed in elevated storage tank (Duer M. , 2012)
• No maintenance required
• Achieves complete mixing
using Tideflex’s mix
design
• No operating costs
• Only mixes when tank
is filling
• Not effective if water
falls below nozzles
• Must take tank out of
service for installation
Keep the Water Moving - Rehabilitation of a 1-million Gallon Water Storage Tank
Improving Tank Circulation: SolarBee
Mixing System
SolarBee Flow Pattern(SolarBee SB500PWc v18 Owner’s Manual)
Advantages
• Provides constant mixing
• Low energy footprint
• Compatible with chlorine
injection systems
• Installed by supplier
Disadvantages
• New mechanical system
in an elevated tank
• Operating and
maintenance costs
Keep the Water Moving - Rehabilitation of a 1-million Gallon Water Storage Tank
Improving Tank Circulation: GridBee
Mixing System
Advantages
• Low initial cost
• Continuous mixing
• Removes dependability
on system pressure for
turnover
GS-12 120v submersible mixer (GridBee GS-12 120v Owner’s Manual)
Disadvantages
CFD modeling for GridBee GS-12 submersible mixer in 1.25-MG tank
(http://potablewater.medoraco.com/computational-fluid-dynamics-modeling)
• New mechanical
system in tank
• Risk with relatively
new product
• Must be anchored
to tank base
Keep the Water Moving - Rehabilitation of a 1-million Gallon Water Storage Tank
Improving Tank Circulation: PAX Mixing System
PAX Mixer (Image courtesy of PAX Mixing Technologies)
Advantages
• Continuous mixing
• Can be installed through
hatch
• Installation and startup
performed by supplier
Disadvantages
• Installation of new
mechanical device in
elevated storage tank
• Operating and
maintenance costs
• Custom mounting device
for irregular tank bottom
Keep the Water Moving - Rehabilitation of a 1-million Gallon Water Storage Tank
EVALUATION OF ALTERNATIVES AND
RECOMMENDATION
Keep the Water Moving Rehabilitation of a 1 Million Gallon Water storage Tank
Jonathan Reed/Bill Mitchell
03/19/2015
Recommended Combination of Alternatives
Pitless Booster Pumps
– Induce Turnover
Tideflex Mixing System
– Induce Mixing
Keep the Water Moving - Rehabilitation of a 1-million Gallon Water Storage Tank
OVERVIEW OF TANK IMPROVEMENTS
AND OPERATION
Overview of Tank Improvements
Keep the Water Moving - Rehabilitation of a 1-million Gallon Water Storage Tank
Operation – Draw Period
20-35%
Draw
Keep the Water Moving - Rehabilitation of a 1-million Gallon Water Storage Tank
Operation – Fill Periods
Complete Mixing
During Fill Periods
Keep the Water Moving - Rehabilitation of a 1-million Gallon Water Storage Tank
What did we achieve?
• Low cost solution, requiring no major structural
modifications to the Whitehorse Tank and no new
mechanical systems in the tank
• Reliable method for maintaining adequate turnover
in the Whitehorse Tank
• Sustainable method for maintaining adequate
circulation, requiring minimal maintenance
Keep the Water Moving - Rehabilitation of a 1-million Gallon Water Storage Tank
AMERICAN WATER WORKS ASSOCIATION
NEW JERSEY SECTION
2015 Annual Conference
QUESTIONS??
Keep the Water Moving –
Rehabilitation of a 1-million Gallon
Water Storage Tank
March 19, 2015
Jonathan T. Reed
CDM Smith
[email protected]
Bill Mitchell, P.E.
Trenton Water Works
[email protected]