Protecting Public Health and the Environment.

Extended Treatment Package Systems (Aerobic Treatment Units)

Extended treatment package systems (ETPSs) are manufactured and packaged mechanical treatment devices that provide biological treatment to septic tank effluent before the effluent’s discharge to a drainfield. ETPSs are also commonly referred to as aerobic treatment units. The biological treatment provided by ETPSs is done under aerobic conditions that facilitate the growth of aerobic bacteria. The aerobic conditions and bacterial growth are made possible by extended aeration, contact stabilization, rotating biological contact, trickling filters, attached growth media, other approved methods, or combination of any of these methods. The enhanced treatment provided by ETPSs occurs after primary clarification of wastewater in an appropriately sized septic tank.

Enhanced Treatment

Enhanced treatment of septic tank effluent through use of an ETPS may be required for certain parcels based on certain site features such as, but not limited to, the following:

  • Shallow soil depths
  • Predominance of coarse- or very coarse-grained soils
  • Shallow ground water depth
  • Outcome of a nutrient-pathogen evaluation

ETPSs are capable of providing an 85% reduction or better in total suspended solids (TSS) and carbonaceous biological oxygen demand (CBOD5) in septic tank effluent. Additionally, some ETPSs are also capable of providing a reduction of total nitrogen (TN) in septic tank effluent. These improvements in effluent quality are necessary to protect sensitive environmental areas and the function of the drainfield. To ensure an ETPS unit is capable of providing enhanced treatment to septic tank effluent, specific operation and maintenance procedures must be performed.

Operation, Maintenance, and Monitoring

Operation and maintenance procedures for ETPS units vary among the manufacturers. Each manufacturer has specific operation and maintenance procedures that need to be followed. As part of the septic permit issued for an ETPS unit, Idaho requires that a minimum of one operation and maintenance event occurs for each ETPS unit annually. This requirement is allowed by DEQ’s Individual/Subsurface Sewage Disposal Rules (IDAPA 58.01.03) as a condition of issuing a subsurface sewage disposal permit (septic permit) (IDAPA To ensure the effluent discharged from an ETPS unit is meeting the required reduction levels, annual monitoring is also required.

Monitoring refers to the testing of effluent quality discharged from an ETPS unit. Monitoring is also a requirement allowed by IDAPA 58.01.03 as a condition of issuing a septic permit. Monitoring is required annually and is typically performed after annual operation and maintenance is performed on an ETPS unit. Effluent samples are submitted to a laboratory capable of meeting the effluent analysis standards for ETPSs specified in the Technical Guidance Manual for Individual and Subsurface Disposal Systems (TGM). Effluent is analyzed for concentrations of TSS, CBOD5, and if required TN. All ETPS units must produce effluent meeting the quality standards of 45 milligrams per liter (mg/L) (parts per million [ppm]) TSS and 40 mg/L (ppm) CBOD5. Effluent standards for TN are specific to each septic permit issued with TN reduction requirements. If any of the effluent samples fail to meet the minimum quality standards, then additional ETPS maintenance and monitoring are required to be performed until the effluent quality meets the minimum septic permit requirements. Operation, maintenance, and monitoring are required to be performed by a certified service provider.

Operation and Maintenance Entities – No Longer Required

Beginning July 1, 2017, real property owners served by an ETPS are no longer required to be members of a nonprofit operation and maintenance entity. To meet the operations, maintenance, and monitoring (OMM) requirements of their ETPS, real property owners shall retain the services of a service provider approved by DEQ (IDAPA Real property owners with member agreements and easements recorded with their county as a condition of subsurface sewage disposal permit issuance, may seek to remove those recorded documents at their own expense.

Service Provider

A service provider is any person, corporation, or firm engaged in the business of providing operations, maintenance, and monitoring of the following specific complex alternative systems in Idaho (IDAPA

Complex alternative systems requiring service providers for OMM:

  • Extended Treatment Package Systems
  • Recirculating Gravel Filters

Property owners may use a certified service provider of their choosing that is manufacturer-trained to perform the annual operation, maintenance, and monitoring. It is the property owner’s responsibility to ensure the requirements of the septic permit are met on an annual basis. The property owner’s responsibilities are defined in IDAPA These responsibilities include not only that the operation, maintenance, and monitoring are performed but also that these activities are reported to the septic permit-issuing public health district on an annual basis.

As people, corporations, or firms meeting the new requirements become certified, DEQ will maintain a list of approved service providers. In addition, your local health district will have a list of approved service providers.

Service Provider Certification Requirements

Any licensed complex installer in the state of Idaho can be certified as a service provider. The complex installer must pass the service provider examination administered by the Health District with a score of 70% or higher (IDAPA A study guide and FAQ for the examination are available under DEQ Resources. Service provider certification is valid upon submitting annual documentation of manufacturing specific training of each manufactured and packaged treatment system to the local health district (IDAPA Service provider certifications expire annually on the first (1st) day of January (IDAPA Service providers must attend one (1) service provider refresher course approved by DEQ every three years.  NOTE: The refresher course for a complex installer will not substitute for the service provider refresher course and are two separate courses.

Annual Reporting

To ensure that a property owner is fulfilling the operation, maintenance, and monitoring requirements associated with their ETPS unit and septic permit, the property owner is responsible for submitting an annual report to the public health district that issued their septic permit. The annual report documents all of the operation and maintenance activities that occurred during the reporting year for the property owner’s ETPS unit. Additionally, the annual report contains all of the laboratory analysis results related to the effluent sampling for the property owner’s ETPS unit. This annual report may either be submitted by the property owner or their contracted service provider, but the responsibility of ensuring the annual reporting requirements are fulfilled lies with the property owner. Annual reports are required to be submitted to the public health district that an ETPS unit is located within no later than July 31 every year.

Additional Information

An in-depth description of ETPS operation, maintenance, monitoring, and annual reporting requirements is found in the Extended Treatment Package System section of the TGM. Property owners are encouraged to educate themselves regarding ETPS units and their associated septic permit requirements before installing one.

ETPS units must have a constant supply of electricity to function property. Shutting off the power supply to any of an ETPS unit’s electrical components will compromise the unit’s function and will result in additional operation, maintenance, and monitoring costs for the property owner. The savings in an electrical bill by shutting off an ETPS unit’s power supply will be greatly outweighed in the additional operation, maintenance, and monitoring costs. Property owners should contact their service provider before altering an ETPS unit or any of the unit’s associated components.

Aerobic bacterial growth within an ETPS unit is vital to the unit’s function. Bacteria are living organisms and are sensitive to their environment. Any products that a property owner puts down the drain will impact the function of their ETPS unit. Care should be taken not to overload a septic system with household cleaning products (chemicals), unconsumed medicine, or trash. Household cleaning products poured down a drain or placed in a toilet should be limited and diluted. Unconsumed medicine should be destroyed and disposed of in the garbage. Any non-toilet paper-related trash should also be disposed of in the garbage. Garbage disposals also impact the function of ETPS units and their use should be extremely limited. Kitchen sinks should be strained and all byproducts should be disposed of in the garbage. Property owners should contact their service provider regarding household water use practices to ensure the best possible function of their ETPS unit.

Septic tanks require pumping on a semiregular basis (every 3–5 years) to remove the fats, oil, grease, and settled solids from the tank. ETPS units may also require more frequent periodic pumping. Any pumping of the ETPS unit should occur under the direction of a property owner’s service provider. The service provider’s supervision will help to ensure that the ETPS unit continues to function properly and may prevent any damage to the unit from the pumping process. Service providers should inform the property owner of the need to pump the ETPS unit. Property owners should not allow a permitted pumper to pump their ETPS unit without approval from their service provider.

Staff Contacts

On-Site Wastewater Analyst
Peter Adams
DEQ State Office
Water Quality Division
1410 N. Hilton
Boise, ID 83706
(208) 373-0464

Health District Contacts

For questions regarding a proposed or existing on-site wastewater system permit or inspection, please contact your local public health district.

DEQ Resources

More Information

Related Pages

Technical Guidance Manual for Individual and Subsurface Sewage Disposal Systems

Nutrient-Pathogen Evaluations

On-Site Wastewater Systems (Septic Systems)