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
