Aqua Answers: Bag and Cartridge Filters in Surface Water Treatment

Dear Aqua Answers,

I’m the operator for a surface water treatment system that uses bag and cartridge filters, and I have a few questions!

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Question 1: What’s the difference between compliance filters and other bag or cartridge filters at my plant?

For suppliers of surface water or groundwater under the direct influence of surface water (SW/GWUDI), the treatment system must be designed to meet the requirements of Section 11.8 of Regulation 11, also known as the Surface Water Treatment Rule (SWTR). This rule requires the treatment process to remove specific levels of Giardia and Cryptosporidium to ensure public health protection.

One way to meet these requirements is by using bag or cartridge filtration. These filters use a straining process where water passes through a disposable bag or cartridge housed in a permanently installed filter housing. Each filter and housing combination used for compliance filtration must be approved by the Colorado Department of Public Health and Environment (the Department) through the alternative technology approval process. Typically, this approval is obtained by the filter manufacturer rather than through a site-specific approval.

Every installation of bag or cartridge filters at a public water system (PWS) must also be reviewed by the Department as part of a design submittal.

Additional filters, sometimes called “roughing filters” may be installed upstream of the compliance filters. These do not require separate Department alternative technology approval but usually still require review as part of the design submittal.

For more details on design requirements, see the State of Colorado Design Criteria for Potable Water Systems (DCPWS), Section 4.3.9.

Question 2: How do I know which cartridges or bags I should use in my compliance filters?

Many SW/GWUDI suppliers have been issued a Record of Approved Waterworks (RAW) that lists all the supplier’s approved treatment and storage facilities and water sources. To find your facility’s RAW, visit the Department’s RAW webpage and enter your PWSID or facility name.

If you don’t have a RAW, you can find this information in the approval letter issued by the Department for your filtration system, or you can contact the Engineering Section for assistance.

Your RAW (or approval letter) will specify the approved filter manufacturer, model number, and the Department’s alternative technology acceptance letter. You can find the acceptance letter on our drinking water alternative technology website.

Important: Many bag and cartridge filters on the market have not been approved by the Department. Using unapproved filters or filter/housing combinations for compliance filtration can result in a treatment technique violation or a significant deficiency noted during a sanitary survey—both of which would require the supplier to issue a public notice.

Question 3: I have a sanitary survey coming up. Is there anything I should know about my bag or cartridge filters?

Yes! Suppliers using alternative filtration technology must continuously meet the design, performance, and operation and maintenance requirements in Sections 4.3.9.6 – 4.3.9.8 of the DCPWS and in the Department’s acceptance letter for the specific filtration technology.

For bag and cartridge filtration systems, this typically includes:

• Not exceeding the maximum specified pressure differential.
• Keeping daily records of pressure differentials and filter change-outs. These records will be reviewed during the sanitary survey.
• Maintaining specific spare parts on-site, which may also be checked during the survey.

Be sure to review your RAW and acceptance letter to understand all conditions of approval and ensure you’re keeping the required records. Both your RAW conditions and site-specific records will be evaluated during the sanitary survey.

Question 4: I’m a contract operator managing multiple public water systems. Do the requirements for bag and cartridge filters differ by system type?

Yes, the requirements can vary based on system size and type (e.g., community, non-community, or transient systems). These differences may include NSF 61 certification, the number of redundant filters required, and other system-specific considerations. The DCPWS outlines these requirements in detail, but if you have any questions, please reach out to the Department’s Engineering Section for assistance.

Sincerely,

Aqua Answers

History of Disinfection Waivers and Where We Go From Here

 Hello everyone, 

In the Fall 2013 issue of Aqua Talk we ran a brief article regarding the history of disinfection waivers in Colorado and where we were planning to go in the future. We thought it would be a good time now to provide an update. 

In 1955 the State Board of Health recognized the tremendous risk reduction from waterborne disease that results from disinfecting drinking water, and adopted a resolution recommending that all drinking water supplied to the public contain at least 0.1 parts per million of free available chlorine. In 1967 the State Board of Health required disinfection of all drinking water unless that requirement was specifically waived by the Colorado Department of Public Health and Environment based on evidence that the drinking water was free of contamination.  

Over the years from 1967 to about 2000, approximately 126 disinfection waivers were granted across the state including 62 community water systems serving 60,695 people. The department lacked a systematic process for reviewing the status of these waivers on a periodic basis. The department began to review the status of disinfection waivers in about 2007, which was before the 2008 Alamosa waterborne disease outbreak. We found that many of these systems had already begun to disinfect their drinking water. 

In 2010, the Water Quality Control Commission banned new disinfection waivers and imposed more appropriate requirements on systems with disinfection waivers if they wished to retain them. After that, the division began systematically reviewing all the disinfection waivers in the state to make sure that they complied with the requirements and working with systems to get disinfection installed if their disinfection waiver was withdrawn. We continued implementing this rule, and systems that struggled with bacterial contamination had their waivers withdrawn. We also started to periodically review the waivers every year. By late 2010, the number of disinfection waivers fell to less than 40 public water systems. 

From late 2010 through about 2013, the division implemented the new requirements regarding disinfection waivers and many systems chose to begin disinfecting while several disinfection waivers were withdrawn as well. By late 2013 only about 15 disinfection waivers remained in place. Since then, the division continued to review disinfection waivers and withdraw waivers when circumstances merited, typically when multiple positive total coliform or E. coli events occurred without there being an adequate way to assure that such events would not recur.

As of 2023, only two (2) of the approximately 2,075 public drinking water systems in Colorado have disinfection waivers, and they are both at community water systems. The systems are the Towns of Ward in Boulder county serving about 230 people and Sanford in Conejos county serving about 850 people. Without further regulatory changes, those systems will retain their waivers as long as they continue to meet the regulatory requirements. We review the status of disinfection waivers annually, whenever there are total coliform rule violations or positive bacterial tests, and during sanitary surveys. The graph below displays the history of disinfection waivers in Colorado from the high point of 2007 to 2023.

➽ Ron Falco, P.E. Safe Drinking Water Program Manager

➽ Bryan Pilson, Technical and Regulatory Implementation and Coordination Unit manager

Disinfection of Drinking Water Promotes a Culture of Health

How does disinfection of drinking water relate to a culture of health:

In Colorado, all public drinking water systems are required to have continuous chemical disinfection, except for a few rare systems that meet strict standards to retain disinfection waivers and hand-pumped wells at campgrounds. Most folks understand that surface water sources used for drinking water are filtered and disinfected to remove and kill harmful organisms such as Giardia lamblia or Cryptosporidium. However, some may question the need to disinfect groundwater and spring sources. Why? Perhaps they believe that a groundwater source or a spring must be pure and free of harmful organisms by nature.

News Flash! Springs and groundwater can be contaminated with viruses and bacteria from any number of sources - from animal waste, septic systems, from the influence of a stream just across the road, from a dead animal 100 yards upstream, and on and on. Even if the water from the well or spring is not contaminated, contamination can enter the distribution system due to line breaks, leaks in pipelines, low pressure events, backflow events, or storage tank contamination, just to name a few. Yuck! 

Additionally, there are regions in Colorado where nitrate, arsenic, uranium and other acute or chronic contaminants are known to occur naturally in groundwater. Thus, it would be a mistake to assume that it’s safe to consume untreated water from a well or a spring. Arsenic and E. coli are “natural” but they can also be harmful or even deadly. 

Some common examples of unprotected openings are inadequately protected access hatches, overflow pipes and air vents at storage tanks as well as unprotected well caps (check for holes or cracks in electrical conduits and vents where critters could enter).

The photos below show an unprotected opening into a storage tank (left) and a well cap with unprotected openings (right).

Multiple Lines of Defense:

Disinfection of drinking water supplies effectively inactivates bacteria and viruses. Continuous disinfection of drinking water sources is one of the best lines of defense in the multiple barrier approach to providing safe drinking water. Even if water from a groundwater source meets safe drinking water standards, unprotected openings can allow contamination to enter storage tanks, wells, spring boxes or distribution systems. Frequently, unprotected openings and sanitary defects are found at storage tanks and wells by Field Service Section staff during sanitary surveys. 

Disinfection with chlorine or chloramines provides a persistent disinfectant residual. Maintaining a sufficient disinfectant residual throughout the distribution system is an important second line of defense against harmful organisms that can unknowingly enter a water system at unprotected openings.

The photos below show a storage tank with significant deficiencies. 

Case Study:

Positive total coliform (TC) samples were collected from the distribution system of a previously unregistered community water system in Costilla County, indicating contamination in the water system. Upon investigation it was found that the system was using two wells which were not being properly disinfected. In addition, unprotected openings into the supplier’s wells and storage tanks were found during a sanitary survey. Although the exact source of the contamination was not determined, it is noteworthy that the supplier’s TC samples came back clean after the supplier began disinfecting the system with chlorine. 

The photo to the right is a close-up of a significant deficiency - the tank’s overflow pipe is unprotected. 

Conclusion: 

Lack of appropriate disinfection can lead to positive bacteria (TC) samples in the distribution system, which points to a source of bacteriological contamination and a pathway for contamination to enter the water. Chemical disinfection is a critical part of the multiple barrier approach to providing safe drinking water and is a safe and effective way of protecting our communities and promoting a culture of health. 

The photo below demonstrates another significant deficiency - the tank has an inadequately protected access hatch with debris inside the tank. 

Guidance & Resources:  

• Quick guide: Disinfectant residual and 
• Quick guide: Minimum disinfection for groundwater 
• Additional information about disinfection is available at the division's Revised Total Coliform Website
• Please feel free to reach out to the field services section at cdphe_wqcd_fss_questions@state.co.us with any related questions.

➽ Monique Morey, PE, field services section

Cybersecurity: Threats on the Rise, Take Action Today!

Take Action Today to Protect Your System Against Cyber Attacks! 

A cyber attack is not something any utility should experience especially when these are already tough times with COVID-19. Take measures to help prevent your system from being attacked.  

If your utility experiences a cybersecurity incident, please coordinate with your local law enforcement, the department, and report the incident to the DHS Cybersecurity and Infrastructure Security Agency and WaterISAC. 

For department coordination, please note the following:

• If you experience a Cybersecurity threat or attack fill out a Tampering Threat and Incident Report and submit to cdphe.wqacutes@state.co.us.
• If the cyberattack will result in an acute drinking water incident (e.g. turbidity exceedance, positive E. coli sample, line break, actual/potential backflow contamination, etc.) contact the CDPHE 24-hr Acute line: 1-877-518-5608.
• If there is no potential for an acute drinking water incident, contact your system’s  compliance officer.

Design Criteria Update Project - 2020 - 2021

Design and update critical drinking water infrastructure!

The Design Criteria for Potable Water Systems (Safe Drinking Water Program Policy 5) serves as a key policy document for the department to make decisions on approval of new designs for water sources, treatment, and storage facilities. The document also serves as a guideline for repairing or upgrading waterworks that are cited as significant deficiencies during the department’s sanitary surveys. While systems are not required to modify their waterworks to meet the design criteria, they are required to consider the criteria as acceptable fixes whenever their current waterworks are found to be deficient. 

The department intends to update the document regularly, approximately every 4 years with input from stakeholders. To assist with updates, we keep a running list of errors and enhancements. The last update was in 2017. At this time, the department is initiating a criteria update project in late 2020 to be completed in 2021. The Department has identified the following three key areas of focus for this project but is open to other stakeholder recommendations:

1. Updates of known errors and enhancements since 2017 - including such items as wetwells at pump stations being considered finished water storage, typos, etc.
2. Updates to sections that pertain to corrosion control and the lead and copper rule.
3. Addition of sections pertaining to direct potable reuse and requirements for pertinent treatment processes (e.g. advanced oxidation, ozone/biological filtration, adsorption, etc)

More communication will follow and the department encourages stakeholders to participate as they are able to ensure we have the best design criteria policy we can.  For more information, please contact Tyson Ingels at 303-692-3002 or tyson.ingels@state.co.us. 

➽Tyson Ingels, Lead Drinking Water Engineer

Ask Aqua Man

COVID-19 and Water Operation Concerns

Dear Worried, 

Great questions! We are also concerned about the impacts of COVID-19. In fact, we have prepared an Frequently Asked Questions (FAQ) document about exactly your concerns. Please read through it. 

FAQ Highlights

During any type of emergency, the most powerful tool for public utilities is other utilities lending a hand. This was true in the large-scale flooding of 2013 as well as major forest fires and blizzards. Having a network of other utilities that you can rely on is highly valuable. 

Our primary recommendation to utilities is to make both your needs and your resources known on the CoWARN network. CoWARN is an organization that facilitates mutual aid and resource sharing between water and wastewater utilities, and it is free to join. READ MORE ABOUT IT IN THE FAQ.

If you are short-staffed, you would still need to sample, but please contact CDPHE during any specific emergency where sampling will be disrupted. We also recommend sampling early in the month (or monitoring period). That way, if staff become ill later in the month, at least there will be one less thing to worry about for that month. We are more than happy to help you prioritize and also to warn potentially impacted people. Also, it is important to announce your labor shortages during an emergency through the CoWARN network. 

Please check out the FAQ. If you have concerns that are not addressed in the FAQ, please let us know! It’s very likely that someone else has the same question, so we want to add it to the FAQ. You can also check out the news updates on our department COVID-19 webpage for the latest information on Colorado's COVID-19 efforts. 

Best of luck, 
-Aqua Man

Contacts

Drinking water  
Tyson Ingels | tyson.ingels@state.co.us 
Lead Drinking Water Engineer

Wastewater 
David Kurz | david.kurz@state.co.us
Lead Wastewater Engineer

Success stories

Bringing a recently regulated public water system into compliance

Wellhouse before design approval and modifications

During the year, the department routinely activates anywhere between 10 to 30 “unregistered” public water systems. These are systems that have been in routine operation, but have not been regulated. Many of these systems struggle with meeting the drinking water regulatory requirements (e.g. installing disinfection, hiring an operator, developing a monitoring plan, sampling, etc.). In 2017, due to customer complaints, the department activated an unregistered system in Teller County that is a year-round campground and serves approximately 20 residents and 50 transients. Initially, the owners feared the cost of installing treatment and ensuring compliance with the drinking water regulations would force them to shut the campground down.

In July 2017, the system was placed on a boil water advisory due to confirmed E. coli in the distribution system and lack of chlorination for their groundwater well. The advisory was escalated to a bottled water advisory in October 2017 due to high levels of nitrate in addition to the detected E. coli in the drinking water. The system was issued a formal enforcement order in April 2018 for numerous unresolved violations, including ongoing failure to disinfect the drinking water.

The system contacted the department’s local assistance unit in late March 2018 for assistance with completing plans and specifications for a new treatment system and well/wellhouse upgrades. During five separate coaching visits, the coach worked with the campground owners to complete a design submittal for a new treatment system, ensure proper chlorinator installation, and inspect the final project after completion. As of October 2018, the system has an approved chlorination system installed and in operation. This project would not have been possible without the extensive collaboration between the water system owners and the department’s drinking water compliance assurance section, the engineering section, the field services section, and the assistance coach. Through the collaboration efforts, the water system realized the compliance issues were solvable and could be completed without hindering their business.

Wellhouse after design approval and installation of treatment system

The system’s disinfection treatment project also included wellhead and source water protection improvements to address both nitrate and E. coli issues, and expansion of the existing treatment building to accommodate a contact time pipeline. After over 16 months of being on a boil water advisory due to E. coli in the distribution system, the advisory was rescinded in early November 2018 as the department determined the system is operating properly and providing safe drinking water to the public. The department is continuing to work with system to meet the drinking water regulatory requirements and to close the enforcement order in the near future.

➽ Haley Orahood, compliance assistance and Mike Bacon, local assistance coach