Corrosion immersion testing case study – Chloramine conversion project results

Background

In Spring 2020, the City of Craig switched disinfection treatment from free chlorine to chloramines to address frequently low free disinfectant residuals in their distribution system. Low disinfectant residuals increase risk of pathogen presence in tap water, which can lead to waterborne disease outbreaks. Since this treatment change could potentially affect water corrosivity, the City and the Department teamed up to conduct a proactive immersion study to simulate whether the chloramines would impact lead and copper levels in the distribution system. In the last article, we discussed the setup of the City of Craig’s corrosion immersion study.

The experiment tested two water scenarios: the free chlorine potable water (control scenario) and chloramine water (chloramine test scenario). Since individual home plumbing materials vary in the distribution system, three materials were tested: lead, copper with lead solder, and brass. Each material was tested under both water conditions with the water in the jars being changed out three times per week.

Figure 1: Jars with copper with lead solder and brass coupons. The experiment took place from early October 2019 to late January 2020, over approximately 13 weeks. For the first 6 weeks, all the sample jars were filled with the free chlorine water. This stabilized the metal samples and     simulated the current conditions of the distribution system pipes. The second 7 weeks, half of the jars were filled with the free chlorine water        (control scenario) and half the jars were filled with the future chloramine water (chloramine test scenario).

Craig water treatment staff created the test chloramines water by dosing ammonia to the free chlorine water and checking the total chlorine and ammonia concentrations. The staff refreshed the water in the jars three times per week. Water from each jar was collected and the three samples combined into a single sample per week per jar, which is called taking a weekly composite sample. The composite samples were analyzed for lead and/or copper at the State laboratory. 

Lead results

Composite lead concentrations were analyzed weekly from jars containing one of two types of metal coupons. Immersion test results are shown in the four graphs below. The free chlorine (control) scenario is the blue-dashed line and the future chloramine scenario is the red line. 

 Figure 2: Weekly lead concentrations from jars with immersed lead coupons. Note: The December 11, 2019 data only has one sample per scenario due to a compositing issue.

  Figure 3: Weekly lead concentrations from jars with immersed copper with lead solder coupons. 

Immersion tests are imperfect and the cause of the lead concentration spike in the control scenario in mid-January is unknown. The median lead concentration between the test condition scenario (chloramines) and the control scenario (free chlorine) with both types of coupons was similar. Based on the immersion tests results, we don’t expect introducing chloramines into Craig’s distribution system to meaningfully affect the existing lead concentrations at customer’s taps. Craig’s 90th percentile average lead concentration from 2018 and 2019 was 0.0026 mg/L. The lead action level is 0.015 mg/L and the maximum contaminant level goal is 0.0 mg/L. The EPA and the Centers for Disease Control and Prevention (CDC) agree that there is no known safe level of lead in a child's blood. Lead is harmful to health, especially for children, therefore it is always advisable to minimize lead concentrations in water to the extent possible.

Copper results

Composite copper concentrations were analyzed weekly from jars containing one of two types of metal coupons. Figure 4 is the copper with lead solder coupon results and Figure 5 is the brass coupon results. 

 Figure 4: Weekly copper concentrations from jars with immersed copper with lead solder coupons. 

 Figure 5: Weekly copper concentrations from jars with brass coupons. 

Conclusions and Next Steps 

The median copper concentration between the test condition scenario (chloramines) and the control scenario (free chlorine) with both types of coupons indicate that some copper release may be expected. The immersion tests results indicate that introducing chloramines could increase copper concentrations by approximately 17% for the copper with lead solder coupons to 36% for the brass coupons. The immersion test is an experimental simulation and the model results may not be linearly correlated to the actual 90th percentile lead and copper results in the distribution system (e.g., a 36% jar results may not be a 36% increase in the 90th percentile). 

Craig will be monitoring lead and copper every 6-months for at least a year to ensure that the actual 90th percentile lead and copper results do not exceed the action levels. The copper action level and maximum contaminant level goal is 1.3 mg/L. In 2018 and 2019, Craig’s 90th percentile average copper concentration was 0.21 mg/L. Copper does not have the same health impacts as lead and is not a concern for developmental effects in children. Even though there may be a slight copper increase, based on the 2018/2019 customer tap sample results combined with the immersion study results, the potential copper concentration increase at customer’s taps should not affect public health. 

For more information on immersion testing please see the department’s Lead and Copper Corrosion Bench-Scale Testing Guidance Manual. 

Verifying an Operator's Certificate

Avoiding a Close Call! 

A water utility recently dodged a bullet. With an operator in responsible charge position coming open soon, the water district began accepting applications to fill the vacancy. One applicant was a current employee who included a Colorado Water Treatment Class A certificate with the application. The human resources department did its due diligence by going to the public operator search feature of the CCWP Portal to verify the certification. Unfortunately, the operator could not be found. The district called the CCWP Office, which performed a deeper search for the operator under the applicant’s name and other names used by the applicant in the past. The applicant was not found in Colorado’s certified operator base. 

The water utility sent the CCWP Office a copy of the applicant’s certificate and it was immediately apparent that the certificate submitted by the applicant was a fraudulent document. This triggered legal action against the individual. It is illegal in Colorado to present yourself as a certified operator when you are not certified. This includes calling yourself a certified operator after your certificate has expired. It is also against the law to falsify state records, such as operator certification.

The water district’s efforts to confirm the certification paid off. It ensured the district didn’t put an unqualified person in charge of the facility, which could have had disastrous consequences for public health and the integrity of the facility.

How to Protect Your System with an Easy Search?

It is an easy thing to verify an applicant’s certificate if you have the certificate number, the operator ID number, or the operator’s name. On the public search page, you simply enter one of the three data points and click the search button. The public operator search should return the operator’s ID number, name, certificate number, certificate type and class, the expiration date of the certificate and the status of the certificate. 

If no information is returned, you should contact the CCWP Office for confirmation of your search results. 

➽Nancy Horan, Operator Certification Board Liaison 

Ask Aqua Man

Dear Concerned:

Thank you for your question! We are also concerned about the impacts of COVID-19 and compliance rates with both the Backflow Prevention and Cross-Connection Control Rule as well as the Storage Tank Rule. The division worked with stakeholders since April to propose some important updates to the rules. On April 10, 2020, the division proposed the rule to the Water Quality Control Commission and they approved them! We have a web page dedicated to this effort. Below are some highlights of the proposed changes.

Cross-Connections:

• Make failing to achieve an adequate distribution system survey ratio a Tier 3 violation. This is mostly due to the outstanding effort that water districts have made over the last few years of implementation. So many water systems have performed surveys of their distribution systems to the extent that the division now has confidence a very high percentage of systems have been surveyed.
• Extend out the final compliance deadlines by a year for the rule given the major impact COVID had on assembly testing.
• Extend the allowable window to repair the assembly from 60 days to 120 days once an assembly fails. 

Storage Tanks:

• Allow two inspections per year before assessing a violation rather than the current four per year. This is primarily due to the outstanding performance of systems and the dozens of acceptable alternative schedules showing proper tank inspections twice a year adequately protect public health. However, the division still strongly recommends performing monthly or quarterly inspections as best practice.  
• A single missed inspection will result in a Tier 3 violation rather than a Tier 2 violation. However, if a system does not complete a periodic inspection over an entire 12- month window, a Tier 2 violation is warranted because that length of time constitutes neglect of storage tanks.

Please check out the web page for more details. Any questions about that can go to Tyson Ingels, lead drinking water engineer at tyson.ingels@state.co.us. 

-Aqua Man

New Toxic Algae Resources

It's the Season for Toxic Algae!

During summer months, most water treatment professionals are well aware of the challenges of algae in surface water bodies. They cause a myriad of issues relating to lake management and water aesthetics. Algal blooms cause many customer complaints and public outcry about water quality. However, in recent years, more awareness has been raised about possible immediate health risks from certain types of algae.

New Resources!

We have published a webpage with guidance on harmful algal toxins and what a utility can do about it. As we approach the height of algae season - please stay diligent in monitoring lakes and reservoirs for signs of harmful algae.