Extended Treatment Package Systems
From: Ed Marugg, SE District Health, August, 2000
Description: Manufactured and "packaged" mechanical treatment devices that provide additional biological treatment to sewage producing an effluent of significantly better quality than that of septic tank effluent. Such units may use extended aeration, contact stabilization, rotating biological contact, trickling filters, or other methods to achieve treatment.
There are several systems that are approved in the State of Idaho. They must be NSF approved or specified by a professional engineer licensed in Idaho.
However, there are strict conditions for approval, including the requirement for a maintenance entity to be available to provide continuing operation and maintenance of the device. An approvable maintenance entity could be the following:
If an 85% reduction or better in biological oxygen demand and suspended solids can be achieved, then the effluent may be discharged to a drainfield meeting the criteria in the Sand filter-Intermittant Gravity disposal trenches section. Otherwise, the effluent must be discharged to a standard drainfield.
Any extended treatment package systems being installed within the jurisdiction of the Southeastern District Health Department could require monitoring by the maintenance entity for the following:
Results for BOD and TSS that exceed 30 mg/l indicate the pretreatment device is not achieving the required 85% reduction. Additional O&M would be required for devices that fail to achieve the 85% reduction and additional sampling is required to demonstrate the additional O&M was successful in restoring the treatment device to normal operational conditions.
If the Portneuf Valley Aquifer were re-designated a Sensitive Resource Aquifer, one of the requirements would be to implement Best Available Technology. This would include subsurface sewage disposal. Extended Treatment packages could play an integral role in this type of environment. Theoretically, these types of systems drastically remove a large percentage of nitrogen from normal septic effluent. If the county and cities changed their ordinances to a "performance based" approach to septic effluent, requiring a higher quality effluent to be discharged to a subsurface sewage disposal system, we might be able to address the nitrate/nitrite issue.
However, as mentioned above, there are some additional requirements for these types of systems. A major requirement is the maintenance entity. Other areas of the state have experienced problems with maintenance entities that are corporations. A viable alternative might be to explore the option of having the City of Pocatello wastewater department serve as the maintenance entity on any extended treatment systems that are installed. This would serve the purpose of allowing the City of Pocatello/Bannock County to ensure that these systems are functioning at their properly designed level, and reduce the nitrogen loading going into groundwater. It would also ensure they are inspected periodically. The county and City could require some type of an agreement, through ordinance, of homeowners to sign up for the maintenance program, or to go with another such as provided by a corporation. Or, in areas close enough to the city, they could require connection to the citys treatment plant.
Research could be done to see what a good baseline performance standard could entail. Since there are already standards in place for extended treatment systems for BOD and TSS, those could be included as is. Additions could be for the other monitoring requirements, nitrogen, nitrates/nitrites.