Challenges With Onsite Treatment Systems at Assisted Living Homes

Challenges With Onsite Treatment Systems at Assisted Living Homes
Septic tanks at an adult care facility.

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Adult foster homes provide assisted-living services — including nursing and 24/7 care — for individuals requiring special medical and behavioral needs. Wastewater from these homes and the corresponding effects on conventional onsite sewage treatment systems differs from average residential sources. Assisted living homes have reported various issues with their septic system operation and performance, including surface discharge of wastewater and premature system failure.

A short-term study of six foster homes and one non-foster system (for comparison) was conducted, that included laboratory and field data. Several issues were observed that likely contribute to decreased septic system performance and operation at the properties. Wastewater characteristics, onsite practices and septic system attributes varied considerably between sites. Nonetheless, common conclusions can be drawn and remedial actions recommended for improved system performance and stability at all sites.

Waste characteristics are difficult to change without fundamentally altering waste sources (and habits) in the home. Waste strength was generally normal at all sites, with the only notable exception being two sites that had high BOD. All sites had slightly elevated nutrient ratios (carbon to nitrogen), which may be attributable to the unique nature of these homes — namely, that many residents are wearing adult briefs (diapers) and do not contribute solid waste to the treatment system. Elevated carbon-to-nitrogen ratios are associated with excessive biological accumulation in the soil treatment zone. This may shorten the life expectancy of a soil treatment area but may be an unavoidable characteristic of these systems.

Some waste sources, such as pharmaceuticals and personal care products, are essential to the health and quality of living for residents. Four sites were analyzed for contaminants of emerging concern, and numerous drugs and synthetic compounds were detected. This is likely a unique and unavoidable characteristic of waste streams from assisted living homes. The amounts and types of certain products, however, such as hand soaps and detergents, could reasonably be addressed. Milder or more environmentally conscience alternatives (such as dye- or perfume-free and non-antibacterial brands) are generally less stressful for septic system microbial communities. Overuse of these products may be an issue. For example, the presence of unusually strong fragrances/perfumes was observed on more than one visit. Likewise, surfactant concentrations (associated with soaps and detergents) were fairly high at all sites, with the exception of one site.

Another issue was the observed presence of wet wipes (disposable cloths) at three of the sites. These cloths actually clogged sampling equipment on several occasions and pose a risk to the septic systems. Care should be taken when flushing anything down the toilet. A simple discussion about this issue with staff, as well as visitors, could prevent serious issues in the future.

Water usage was an issue at several sites. Three sites had notably high flows. A high flow, which is any flow greater than 70 percent of the design flow, can upset solids or prevent settling in the pretreatment tanks and contribute to ponding in the soil treatment area. One in particular had flows near or above the design flow.

Water conservation practices, including low-flow showerheads and water-efficient front-loading laundry machines, could substantially decrease water use at all sites. The homes reported abnormally high frequencies of laundry washing, which suggests that water patterns at assisted living homes are unique compared to typical residences. This could be a problem if septic systems are designed using normal flow estimates based on the number of bedrooms in a home. This is not a new observation. For example, one site had issues with high flow, which required the addition of an extra tank and a second mound in 2002.

Septic system integrity was an issue or potential issue at several sites. Soil treatment areas should be mowed regularly and plants removed. Roots can grow into the soil treatment area and cause structural damage. Two sites had notable vegetation growing on their mounds, although one of them was mowed midsummer. Another site had holes from burrowing animals on the south side of the system, which is also a cause for concern.

There were several tank issues that needed to be addressed. Manhole covers needed to be secured at two locations. One site had significant soil intrusion in the pump tank, while another had manholes that needed to be brought to grade to prevent soil and water intrusion. Soil adds to the solids concentration of wastewater and can damage pumps, clog plumbing fixtures, and hinder soil treatment infiltration.

Three sites appeared to have insufficient soil separation. One location had a tank leaking below designed operating depth, suggesting it is a risk to groundwater. Also, pump conduits and electrical work are a potential hazard and need to be sealed or reinstalled at all sites with the exception of one location.

The full report summarizes the project findings and recommends septic system management practices that may help prevent future problems, which can be found at

About the author
Sara Heger, Ph.D., is an engineer, researcher and instructor in the Onsite Sewage Treatment Program in the Water Resources Center at the University of Minnesota. She presents at many local and national training events regarding the design, installation and management of septic systems and related research. Heger is education chair of the Minnesota Onsite Wastewater Association (MOWA) and the National Onsite Wastewater Recycling Association (NOWRA), and serves on the NSF International Committee on Wastewater Treatment Systems. Send her questions about septic system maintenance and operation by email to


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