Tech Tips For Diluting Pharmaceuticals In Wastewater

Trace amounts of chemicals – the byproduct of prescription medicine usage – can linger in onsite systems. Septic service best practices can help solve this groundwater issue.
Tech Tips For Diluting Pharmaceuticals In Wastewater
Jim Anderson, Ph.D., is an emeritus professor at the University of Minnesota Department of Soil, Water and Climate, education coordinator for the National Association of Wastewater Technicians, and recipient of the pumping industry’s Ralph Macchio Lifetime Achievement Award. Email Jim questions about septic system maintenance and operation at

QUESTION: How well do our systems treat pharmaceuticals and other contaminants?

ANSWER: I hear this question often during workshops, and it will be a continuing issue of concern for the industry. Pharmaceuticals are regarded as contaminants of emerging concern from both an environmental and human health perspective. Research has been limited on these compounds due to their trace levels – in the low parts per billion. Treatment for the compounds in wastewater treatment plants is very costly even though there are available technologies such as ozonation, reverse osmosis and process optimization.

Each compound is an entity with a particular organic structure, which means it is almost impossible to generalize levels of treatment or how long they exist in our particular environments. Recently a number of studies were commissioned to look at these contaminants in wastewater treatment plants because these compounds have been found in surface water and in fish below the outfalls from the plants. So there is a continuing environmental and health concern over the effects of long-term low-level contamination. I expect we will see continuing reports on the results of various studies and, in particular, some specifically looking at our onsite treatment systems.

I have seen a few studies that may give us a clue to the treatment effectiveness within our soil-based treatment systems. First was a study of sand filters and constructed wetlands (both technologies used in decentralized systems). For ibuprofen and some other organic pharmaceuticals studied, a drain and fill operation of the subsurface wetlands significantly enhanced the elimination of the compounds over the continuous flow operation. This increase in treatment was attributed to allowing oxygen into the system, which stimulated biological activity and led to the breakdown and dissipation of the compounds. The study also noted that the presence of higher aquatic plants also enhanced the treatment of the compounds.

Another study looked at land application of biosolids in eastern Colorado. Here they found that some of the compounds dissipated after six months from the time of application, while others persisted longer than 18 months and some moved downward in the soil profile even given the semiarid environment. After a year and a half, though, most detects were actually below the minimum reporting levels for the compounds. The compounds they degrade to are not fully understood and the authors conclude further research should be conducted on the transformations occurring, taking a closer look at any long-term accumulation.

I also remember University of Illinois studies in the late 1980s looking at organic pesticides in septic systems. They showed pesticides were tied up in the organic material from wastewater and soil in the highly biologically active zone where they slowly degraded.

While we are bound to hear more in the coming months about these compounds and issues, the best onsite practices we employ should effectively tie up these compounds and hold them in place while they degrade or dissipate.

Practices like keeping the systems as shallow as possible should be put in place, utilizing parts of the soil profile with the highest biological activity and usually the most permeable to water and air. This allows oxygen to be in the soil around the system, allowing aerobic soil organisms to function and assist in the breakdown of organic compounds. This should sound like the KISS (Keep it Shallow …) principle. Nevertheless, just more evidence that keeping systems shallow is the way to go even if it means having to add a pump into the system.

The other aspect to shallow is it maximizes the separation distance in a biologically active zone so if some compounds do move somewhat downward, they are not out of the zone where treatment can occur.

Employing dosing of our systems through pressure distribution – whether it is in pretreatment devices such as media filters or the final soil treatment system – again provides the opportunity to tie up the compounds until they are dissipated. This approach has been demonstrated to help make sure water movement through the soil is unsaturated and allows for oxygen to be present in the system – both major ingredients in the wetland study that resulted in the best treatment.

This furthers the argument that undisturbed natural soil is the best final treatment media. This means that the soil should not be disturbed, graded, compacted, smeared or otherwise compromised before, during or after the installation of the final soil treatment unit. If this sounds suspiciously like KINN (Keep it Natural …), that’s because it is!

For years we have talked about these two underlying principles as being key to quality, long-lasting systems that treat our wastewater indefinitely. Study after study confirms the value of these principles, yet I still see instances where these simple guidelines are violated with the predictable bad results. When we do our jobs right and install our systems correctly, we have the best treatment system possible and better than any wastewater treatment plant. When we don’t do things properly, we get a bad name and people look away from us as being part of the wastewater solution and see us as part of the problem. Let’s demonstrate that we are the solution for the future, regardless of the compounds or the problems encountered.


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