Some maintenance calls for the manufacturer or designer to weigh in, but there are some problems you can diagnose on your own first.
As always for maintenance requirements, the manufacturer or designer should be consulted. However, as a service provider there are a few things to look for or look at to determine if things are operating properly. If there are required permit values for performance, such as fecal coliform levels or total nitrogen, these samples should be taken and analyzed. If they do not meet the requirements, then some work will need to be done in conjunction with the manufacturer or designer to bring the system into compliance. Some visual observations can be made, though, that can also indicate current or future problems.
The surface of the filter should be inspected to see if there is any evidence of effluent ponding or lack of equal distribution over the filter surface. In no filter should there be any evidence of ponding at the surface. If the filter is not already broken in terms of performance, it will be soon. It will require some detective work with the homeowner to determine the cause of the problem. If there is ponding, it can be due to overloading the system either hydraulically (the amount of water) or organically, which means a higher-strength waste than expected. Working with the homeowner is key here, either to reduce water use or to address what is causing the increased levels of BOD and TSS to the system, causing plugging at the surface. People’s diets and how they cook can have a large impact on BOD levels in the effluent.
For those filters that have pump basins and are located at the base of the filter to supply the final treatment and dispersal drainfield, the level of effluent should be measured to make sure it is not so high that it is coming into contact with the filter media. This can result in wicking and interfere with the movement of effluent through the filter as well as impacting oxygen levels in the filter, resulting in less treatment and causing ponding at the surface.
Distal head pressures should be measured in the distribution system, which can be done by measuring squirt height in a clear viewing tube. If the squirt height is higher than the design specifications, it indicates that there is plugging in the distribution system and the system should be cleaned. This is usually done on a yearly schedule, but in some systems it may need to be done more often since orifices tend to be smaller in media filter pressure systems than for pressurized trenches or mounds.
Many media filters come in self-contained modules with lids. The condition of the containers should be evaluated for integrity and any problems, such as damage where surface water or animals could enter the container. Any soil settling around the container or evidence of surface water entering the system or ponding around the container should be addressed.
In a future series we will look more directly at filter-specific maintenance requirements and problems.
About the Author
Jim Anderson is connected with the University of Minnesota onsite wastewater treatment education program, is an emeritus professor in the university’s department of soil water and climate, and education coordinator for the National Association of Wastewater Technicians. Send him questions about septic system maintenance and operation by email to firstname.lastname@example.org.