Corrosion Control Studies
The lead and copper rule (LCR) requires that many community and non-transient, non-community public water systems have optimal corrosion control treatment (OCCT) to minimize lead and copper concentrations at customers’ taps. 
Under the lead and copper rule, approved corrosion control treatment processes include the following:
- pH/alkalinity adjustment
- Calcium hardness adjustment
- Addition of a phosphate or silicate based inhibitor
Corrosion control studies (CCS) are an experimental approach to determine the most effective corrosion treatment process. These studies are hands-on experiments designed to evaluate treatment methods and/or the impact of new water sources or treatment changes. They are not intended to model the lead and copper concentrations at customer’s taps. Instead, CCS can be used to identify the most effective strategy to optimize corrosion control treatment and reduce lead and copper release to drinking water. CCS can also be used to model how distribution system materials will react to treatment and source changes.
There are multiple reasons that a system could be required to do a CCS or may elect to do a CCS type evaluation. All systems serving over 50,000 people are required to have operational OCCT so if the population grows over 50,000 people, then a system must conduct a CCS to determine their OCCT. Systems that are evaluating their OCCT due to an action level exceedance may elect to do a study to help select their treatment process, or they may be required to do a CCS due to complicated water chemistry and/or history of exceedances. Systems that are making treatment modifications or adding new sources may use a CCS type of evaluation to determine the corrosion impacts of their project prior to construction.
 |
| Example of metal coupons used in testing for corrosion. (Courtesy sciepub.com) |
Testing approaches
Various testing approaches are available to evaluate corrosion. Some approaches use a small sample of metal (known as a “coupon”) that is either placed in various test waters or within a pipe loop. More complicated corrosion studies may use harvested service lines or pipe loops to study impacts on existing scale and/or more closely mimic distribution system conditions.The typical approaches are summarized in the table below (modified from Table 3-2. Summary of Corrosion Testing Strategies in Lead and Copper Corrosion Bench-Scale Testing Guidance Manual).
Table 1 - modified from Table 3-2: Lead and Copper Corrosion Bench-Scale Testing Guidance Manual
|
Method |
Description |
Best
Applications |
Potential
Drawbacks |
|
Coupon Testing |
Coupon testing involves a sample of metal (known as a “coupon”)
placed in a flowing pipe rack, often located at a water treatment plant or at
key locations in the distribution system. |
·
Overall corrosion rate; ·
Monitoring of infrastructure
degradation |
·
Does not monitor metal
release to drinking water; ·
Does not include
representative materials; ·
Not recommended for LCR compliance purposes |
|
Immersion Testing |
Immersion testing is a bench-scale strategy involves subjecting
metal samples to specific test waters and measuring the concentration of lead
or copper released to the test water |
·
Screening of CCT strategies for reducing metals release; ·
Understanding corrosion mechanisms |
·
Does not consider the
effects of flow; ·
New materials (not
representative of distribution system scales); ·
Not suited for testing of
lead service lines, cast iron mains, or copper pitting |
|
Recirculation Pipe Loop |
Pipe loop testing is a pilot-scale strategy with pipe sections
in a flowing loop. In a recirculating pipe loop, batches of test water are
prepared and used to fill a reservoir, from which water is
pumped through the pipe section according to a predetermined schedule.
. |
·
Testing CCT
with batches of test water in flowing conditions; ·
Can use harvested
materials; ·
Can perform scale analysis |
·
Challenges in sample
collection; ·
Water quality changes in
recirculation reservoir |
|
Flow-Through Pipe Loop |
Pipe loop testing is a pilot-scale strategy with pipe sections
in a flowing loop. In a flow through pipe loop system, each set of pipe
sections is connected to a continuous supply of test
water. To test alternate corrosion control treatment
strategies, a pilot-scale chemical feed system is needed for each loop
to adjust pH/alkalinity or add a corrosion inhibitor. |
·
Pilot-scale demonstration
testing of CCT; ·
Can use harvested
materials; ·
Can perform scale
analysis; ·
Long-term monitoring |
·
Complex and costly to implement; ·
Large footprint; ·
Challenges in operation
and maintenance; |
Guidance available
To assist systems conducting corrosion control studies, the department hired the engineering consulting firm Hazen and Sawyer to develop a guidance manual and immersion testing protocol. These will help public water systems, whether they have existing corrosion issues or are making a long term treatment or source water change. The guidance manual builds on existing EPA guidance and published literature. It helps water systems determine potentially beneficial corrosion control strategies, understand available corrosion control inhibitors, and help determine if a bench-scale testing is appropriate.The corrosion testing protocol focuses on a four phase bench-scale testing approach including planning, preparation, performing and analysis. The protocol document summarizes testing approaches used in prior studies and published literature to justify key aspects of the testing protocol. The guidance document discusses the advantages, disadvantages, and limitations of the bench-scale testing approach that should be considered in planning the tests and interpreting the results. The information is available on the lead and copper webpage.
Still have questions?
For more information on corrosion control studies please contact:Melanie Criswell, corrosion control engineer
melanie.criswell@state.co.us
303-692-3603
➽ Melanie Criswell, corrosion control engineer
