At the NSF International (NSF) Wastewater Joint Committee Meeting in Ann Arbor, Mich., on Sept. 27-28, the committee chair established a task group to look into two reported areas of concern with effluent filters: The relationship of proven versus manufacturers’ reported service life of filters, and how filter design affects venting of septic tank gases.

The task group will investigate the need to add test parameters and criteria to the existing NSF/ANSI Standard 46, Evaluation of Components and Devices Used in Wastewater Treatment Systems for effluent filters, and whether to add effluent filters to NSF/ANSI Standard 360, Wastewater Treatment Systems – Field Performance Verification to evaluate service life claims made by manufacturers.

The new task group held its first meeting in December, and two issues were addressed. The first was how long screens and filters will actually go between service calls. At present, the regulatory community must rely on what manufacturers report in their literature about flow rates to determine service life. Some task group members feel a performance test to evaluate service life should be added to Standard 46 to protect homeowners’ investments.

The second issue is an emerging concern that some effluent screens and filters might be restricting the flow of gases out of the septic tank and potentially creating problems in the tanks themselves, or for the downstream treatment components and dispersal fields.

The history of Standard 46 as it relates to effluent filters began in 1997 when Florida became the first state to require them, followed by Georgia and North Carolina. It soon became clear that some minimum official standards were needed to protect homeowners, because products were being released that had not been tested in septic system environments or for actual screening capabilities in the waste stream.

An initial task group was formed, and from this group came standards requiring that effluent filters or screens:

At a minimum, remove solids larger than 3/16 inch

Pass a structural integrity test consisting of inserting and removing the filter from the case four times as a simulation of service stress

Allow no beads to pass through in a bypass test simulating a clogged filter

This became known as Standard 46, and the first effluent screens (filters) were certified to this Standard in early 2000.

A few years later, a second task group was formed to address a concern arising from field reports that some filters were dislodging from their housings once they became plugged and allowing solids to bypass out to the dispersal system.

At this same time, the second task group required that the particle size for certification be either 1/8 or 1/16 inch. This change brought the national Standard 46 more in line with state onsite codes, which usually specified one of these smaller sizes. Also, a more rigorous structural integrity test was added to the standard, where the filter was removed and inserted 100 times in liquid, and five times in a dry condition to simulate the stresses that might be placed on the filter during its service life.

To address the issue from field reports that some cartridges were becoming dislodged from their cases when plugged, an upward force test was added to the standard. This is a more demanding stress test, and only filters tested since 2010 have undergone this test as part of the certification process.

Currently, Standard 46 states that if a single bead of either the 1/16- or 1/8-inch size were to bypass the screen or filter cartridge, the product would fail and would not be certified to Standard 46. As of Jan. 31, 2012 all effluent screens and filters on the market had to pass this more stringent version or lose Standard 46 certification.

Certified products must carry the NSF Mark. Practitioners can view the status of any NSF-certified effluent screen or filter by visiting www.nsf.org/Certified/Wastewater/.

Onsite wastewater component manufacturers are constantly looking to improve their products, working with NSF International. Regulators, designers, and service providers who want to work on the new filter project may contact the third task group chairperson, Tom Konsler (tkonsler@co.orange.nc.us) or Mindy Costello (mcostello@nsf.org).