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Managing Water Age in the Distribution System
SE District PA AWWA / Eastern Section WWOAPSpring 2016 Joint Technical Conference
April 7, 2016
WHO ARE WE?
WHO AM I?
Civil Engineering since 1998 Drafting / Surveying and Land Development Started with Aqua in 2007 Learned Hydraulics under experienced
leadership and expertise at AquaHave had the privilege to work one on one
with Dr. Tom Walski, Bentley Systems
MY KIDS – JINX AND PUMPKIN
AGENDA• Modeling Overview• Modeling Benefits• Case Study Examples• Summary
WATER AGE MODELING (It’s always young at heart)
WHAT IS WATER AGE?
Water age refers to the time it takes for water to travel from it’s source to consumers and is influenced by distribution system flow velocities and pipe lengths.
Residence time in reservoirs is probably the most important contributor to age.
WHY MODEL WATER AGE?
Gives an idea of the oldest areas of water in the system
The age of the water affects chlorine levels Chlorine decay = Bacterial Growth
Areas of low demand create low velocity = increased water age
Helps us size proposed pipe (is it too large?) Helps us locate areas where extra treatment may
be needed Simpler than modeling chlorine decay
RUN A WATER AGE MODEL
‘Extended Period Simulation’ Scenario Set model to run a Water Age Calculation Diurnal Curve applied to Demands Use Off-Peak or Average Day Demands Set ‘Duration’ to allow tanks to establish
accurate fill/drain patterns
TANK MOVEMENTMODEL TANKS IN THE RANGE THEY MOVE
AND COMPARE RESULTS WITH ACTUAL DATA
TANKS ADD AGESet ‘Tank Mixing’ to the appropriate type for each tank
- Completely Mixed (Solar Bee, Shark, Etc…)- 2 Compartment (Level 1 full – mixes with Level 2)- FIFO – First In First Out (Simultaneous Inflow & Outflow)- LIFO – Last In First Out (Typical Tall Narrow Standpipe)
WATER AGE DURATIONA 7 DAY RUN MIGHT NOT CUT IT,
YOU MAY NEED TO RUN 15 OR 31 DAYS
MODELING BENEFITS
PLOT THE RESULTS (MAX AGE)
AGE CONTINUES TO GROWWater moves through the system depending on demand and velocity
Water ages as it goes and sits in tanks
MODELING BENEFITSHELPS TO IDENTIFY OLDER WATER AREAS IN YOUR SYSTEM
CASE STUDYEXAMPLES
CASE STUDY 1ACTUAL WATER AGE ISSUE IN ONE OF OUR GREATER PENNSYLVANIA SYSTEMS
• Water supplied from the plant traveled and aged in several tanks through 4 pressure zones & 4 storage tanks
SOLUTION (CASE STUDY 1)IT WORKED!
• Removed 1 large tank (1.0 MG)• Removed 1 Booster Station• Relocated and updated a booster station• Bypassed a pressure zone (blue zone direct to the green zone)
CASE STUDY 2
FLUSHING
Conventional flushing can remove aged water and help bring in fresh water
You just have to decide where are the best locations?
CASE STUDY 3
PROBLEM TANKS
IDENTIFY PROBLEM STORAGE TANKS IN YOUR SYSTEM• We target 20% to 30% of turnover daily in our
storage tanks – the more turnover the better.• Acceptable ‘Days Old’ can vary depending on the
chlorine decay of the area it serves and the type of treatment it recieved
• This opens the discussion on operations and effective value of the tank
IN SUMMARY
Water age is a simple surrogate for evaluating some water quality issues in your distribution system
Tanks are a major contributor to water age Hydraulic modeling is a valuable tool for
examining water age Hydraulic modeling can be used to identify
problem areas and evaluate solutions
