how to design a corrosion pipe loop study
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Emily Tummons, PhD, PEBlack & Veatch
OAWWA Virtual Education SummitSeptember 29, 2020
How to Design a Corrosion Pipe Loop Study
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Agenda
• Purpose of Pipe Loop Testing • Harvesting Materials & Conditioning • Pipe Loop Case Studies
• Batch Systems (2)• Online Chemical Feed Systems• Multiple Pipe Loops Throughout a
System• Conclusions
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Purpose of Pipe Loop Testing
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• Captures hydraulic effects; reflects full-scale conditions
• Longer testing period, can capture seasonal results
• Can use new or harvested materials
• Increase confidence of the outcomes
EPA’s proposed LCR states that pipe loop testing would be required before changing corrosion control treatment
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Purpose of Pipe Loop Testing
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• Considering change in corrosion control treatment
• Changing coagulants, disinfectants, or other processes
• Optimize chemical use
• Adding a new source water
• Changing source waters
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Reasons for Pipe Loop Testing
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Harvesting Materials for Testing & Conditioning
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• Benefit of examining impact on existing pipe scale
• Analysis of scale could highlight analytes to test for
• Notes:• Limit disturbances to pipe
• Mark direction of flow
• Prepare for conditioning time
• Best to harvest and then install in pipe loop
Harvesting materials best mimics full-scale conditions
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Harvesting Materials
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• Pipe scale needs to equilibrate after harvesting
• Expose the pipes to the same water quality
• Stagnation and flowing periods (same as testing plan)
• Collect baseline samples
• Build pipe loop before harvesting materials to decrease conditioning
Conditioning length depends on care taken during harvestingTypically 1-3 months
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Conditioning is Critical
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Poll Question 1
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Case Study 1 – Batch Pipe Loop
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• Two water sources (only one available at pipe loop location)
• Examined impact of:• Seasonally switching sources
• Raising pH
• 4 replicate loops
• 3 months of conditioning
• 6 months of testing
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Case Study 1 – Batch Pipe Loop
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• Materials (triplicate):• Harvested ¾-inch galvanized iron
• Harvested brass meters (pre-2014)
• New ¾-inch copper pipe
• Timer controls created flowing & stagnation periods
• Weekly samples• Forward flow after materials
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Case Study 1 – Batch Pipe LoopBrass Meter
Copper Pipe
Galvanized Iron
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• 4 treatment conditions• 2 sources
• 2 sources with increased pH
• Water chemistry adjusted 2x/week• Target pH and Cl2
• Flowrate = 1 gpm
• Once through flow design
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Case Study 1 – Batch Pipe Loop
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Pipe Loop Testing Results
BBS = Control
Switching sources resulted in a 45% increase in copper
Increasing pH:• Mitigated source switch• Decreased copper
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Case Study 2 – Batch Pipe Loop
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• Adding new source & evaluating changes in chemistry
• New water not available at site• Examined impact of:
• Changing pH and calcium• Reversal of flow• Switching sources
• 2 sets of 4 replicate pipe loops• 3 months of conditioning • 6 months of testing
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Case Study 2 – Batch Pipe Loop
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• Materials (triplicate):• Harvested 2-inch galvanized iron• new ½-inch copper pipe with lead
solder
• Once through flow design
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Case Study 2 – Batch Pipe Loop
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• Materials (duplicate):• Harvested 6-inch cast iron (20 ft)
• Tested reversal of flow• Recirculated flow
• Limited water volume
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Case Study 2 – Batch Pipe Loop
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Poll Question 2
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Case Study 3 – Online Chemical Dosing Pipe Loop
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• Evaluating changes in treatment at WTP (only source)• Online chemical dosing improved consistency of water quality
• Examined impact of:• Changing pH and adding polyphosphate
• 2 replicate pipe loops• 2 months of conditioning • 8 months of testing
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Case Study 3 – Online Chemical Dosing Pipe Loop
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• Materials (triplicate):• Harvested ¾-inch galvanized iron• new ½-inch copper pipe with lead solder
• Weekly samples • Aesthetics and metals release
• Once through flow design
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Case Study 3 – Online Chemical Dosing Pipe Loop
Galvanized Iron
Copper Pipe with Lead
Solder
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• Online Chemical Feed System• Chemical Storage Tanks• Metering Pumps• Sample Ports
• Requires calibration and frequent monitoring
• Throttling valves minimized changes in flow
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Case Study 3 – Online Chemical Dosing Pipe Loop
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Pipe Loop Testing Results
Control• Fluctuations in
pH – increased copper
Increasing pH decreased copper
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Case Study 4 – Pipe Loops Throughout A Water System
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• 2 test materials (triplicate)• Copper pipe with lead solder
• Brass meter (harvested) and copper pipe
• No changes to water quality at pipe loops
• Evaluating impact of water age & reaction with pipe materials
• Captures seasonal results• 1 year testing period
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Case Study 4 – Pipe Loops Throughout A Water System
Brass Meter with Copper Pipe
Copper Pipe with Lead
Solder
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• Water Treatment Plant (WTP)
• Gezon Pump Station (Gezon)
• Clean Water Plant (CWP)
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3 Pipe Loop Locations
• Evaluate WQ changes throughout the system
• Same design and materials at each location
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• pH stable throughout distribution system
• Consistent pH through 6 months of testing
• Source water is Lake Michigan – prone to changes in pH
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pH at Pipe Loop Testing Locations
Preliminary Data
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Conclusions
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• Pipe loop testing increases confidence for full-scale implementation
• Harvesting materials provides ability to understand impacts on existing pipe scale
• Conditioning phase is critical to getting valuable results
• Online chemical dosing is preferable if water is available at site
• Analyte testing frequency should be more frequent around changes in treatment
• Replicate pipes allows for ability to identify outliers
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Conclusions
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