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Secondary Treatment

long reservoirs of water under metal railings at sunset
Environment, Great Lakes, and Energy

Secondary Treatment

Contact

EGLE-ST@Michigan.gov

A facility with a secondary treatment system is one that receives water from a public water supply and adds chemicals to provide additional treatment to their potable water. Often these facilities are hospitals and healthcare centers that are using chemicals to control pathogens such as Legionella. Adding corrosion control chemicals to potable water to reduce exposure to lead, copper, or other metals is also a form of secondary treatment.

Using such chemical treatment causes a facility to meet the definition of a public water supply and to be subject to regulation under the Michigan Safe Drinking Water Act (Act 399). These facilities, designated as Secondary Treatment Public Water Supplies, are required to complete the items listed below to maintain compliance with Act 399.

Facilities intending to use copper silver ionization treatment must also submit a Copper Silver Treatment Efficacy Requirements form. 

Program information

  • The facility must submit to EGLE the treatment system design plans and specifications prepared by a licensed professional engineer in accordance with Section 4 of Act 399. Alterations to water systems must meet the standards of the 2022 addition of Recommended Standards for Water Works.
  • The facility is required to submit the following three applications:
  • The facility is required to have a water management program based on the ASHRAE 188 standard. A copy of the program must be submitted with form EQP2231.
  • If the facility is licensed by the Michigan Department of Licensing and Regulatory Affairs (LARA), a copy of the license must be submitted with form EQP2231.
  • The facility is required to retain a certified drinking water operator with the appropriate certification level to operate and oversee the treatment system. For treatment systems that use sodium hypochlorite (chlorine), the required certification level is D5. For treatment systems that use monochloramine or chlorine dioxide, the required certification level is D5+. The D5 certification is granted to examinees who pass the D5 exam. The D5+ certification is granted to examinees who pass both the D5 exam and D5 lab. See the Operator Training and Certification Program for more information.
  • The operator is required to conduct on-site monitoring in accordance with the schedule of EGLE’s operations oversight policy (ODWMA-399-017). The standard frequency for operator site visits is weekly.
  • The facility is required to become part of Michigan’s public water inventory and pay an annual fee to EGLE.
  • The facility is required to conduct sampling for various water quality indicators based on the type of treatment employed. Depending on the specific indicator, these samples will need to be collected on a weekly, monthly, quarterly, semi-annual, or annual basis. Sample results which indicate water quality problems, such as the presence of total coliform bacteria, may prompt repeat samples to be taken.  The facility will need to identify appropriate sampling locations and submit to EGLE a sample siting plan (SSP). A Secondary Treatment Sample Siting Plan (EQP2248) template is available to use.
  • The facility is required to submit monthly operation reports to EGLE. Water system data for these reports may need to be collected daily.  The certified operator is required to complete and sign the monthly reports.
  • The facility is required to make available water quality results, including information on lead and copper levels, to consumers of the drinking water.
  • The facility is required to inform the wholesale public water supply of their intent to install a secondary treatment system and separate their water treatment system from the wholesale public water supply with an approved cross connection control assembly.  The wholesale water supply must approve the back flow prevention methods.
  • For a facility with a wholesale supply that sources its water from groundwater, the facility will be required to comply with the groundwater supply rules. In general, this will require the facility to report any positive lab results for bacteria to the wholesale supply within 24 hours.
  • The facility is required to develop a cross connection control plan which will include the periodic inspection of the building’s entire plumbing system for the presence of cross connections.

A facility’s water quality goals may be attainable through water management practices, such as flushing, or by working with the wholesale water supply to affect the incoming water quality. This may be more economical for the facility and reduce the regulatory oversight, risks, and liabilities associated with chemical treatment. EGLE is open to facilitating discussions between facilities and wholesale supplies for achieving the desired objectives.