Septic drainfield restoration is a newer and frequently overlooked possibility because the standard fix is installing an entirely new drain field. If you want some more background info on the problem, check out: drainfield failure.
Types of Failure
There are three basic types of failure that would necessitate restoration: mechanical, physical, and biological.
- Mechanical failure would be something like a truck driving across the yard and crushing the distribution line columns or the lines themselves.
- Physical failure refers to physical solids like washing machine line actually clogging the distribution lines and/or soil.
- Biological failure, the most common and expensive, refers to instability in the septic drainfield biomat; mechanical and physical also lead to biological failure. In this post, I’ll discuss several forms of restoration to deal with biological failure.
Influence of the Biomat
The biomat is a colony of anaerobic bacteria that form a black, sticky layer of slime to hold themselves together. Water from the septic tank passes through the biomat very slowly giving the bacteria time to digest harmful pollutants. Under ideal conditions, the biomat forms an equilibrium with the amount of sewage coming from the house; however, if they’re exposed to too much or too organically rich sewage, they’ll grow too thick leading to a biomat that won’t allow water to pass. Once the biomat reaches this thickness along the bottom and sides of the distribution ditch, then effluent will no longer seep into the soil and will be forced to the surface.
At the risk of getting too scientific, the anaerobic bacteria in the biomat use sulfur to create energy leading to the release of large amount of sulfides that usually react with iron in the ground to form iron sulfide. Iron sulfide gives the biomass it’s black appearance and slow water absorption. As long as oxygen can reach the iron sulfide, it converts into a soluble substance and washes away; however, as less water seeps into the soil, less air is drawn into the drainfield. Less air in the drainfield leads to increasingly anaerobic conditions and becomes a vicious cycle of increasing iron sulfide until the soil is completely clogged and effluent overflows onto the yard.
Septic Drain Field Restoration Possibilities
- Chemical: Some products claim to have ingredients that will oxidize the iron sulfide turning it into a more soluble material. Theoretically, this reaction should break down the overgrown bookstores and return the drainfield to equilibrium. Two of the main products in this category are septic seep and septic scrub.
- Physical: This type of septic drain fields restoration refers to physical aeration of the ground using a piece of equipment that forces pressurized air into the ground causing cracks that allow oxygen to get to the biomat. At this point, the iron sulfide in the biomat should react and begin to dissolve into the soil, thereby restoring the soil’s ability to absorb effluent. The machine is called a terra-lift.
- Aerobic (or, partial aerobic) Conversion: The final method for restoring the septic field is the most drastic and expensive but still much less expensive than a new field. Adding a piece of equipment called an aerator to the septic tank will allow aerobic bacteria to grow inside the tank; these bacteria digest organic material inside the effluent 20 to 30 times faster than anaerobic bacteria. After a short time of being aerated, the biomat should begin to shrink significantly because their food supply is being cut-off, the oxygen in the effluent is toxic to them and dissolves their iron sulfide, and the aerobic bacteria will feed on them as well. On the down side, the aerator needs power to work, so by adding one the system is no longer completely natural; furthermore, local governments usually have regulations on septic system conversions making it important to check before installing new equipment. There are many options, but the one that comes to mind is aero-stream.
In order to try the chemical solution, the distribution box needs to be dug up so the solutions can be poured in directly. The physical solution requires a large piece of equipment. And, the aerobic solution requires the installation of new equipment. Unless you’re really handy, the ideal situation would be to hire a contractor who advertizes their use of the treatment you’re looking for. The above methods for septic field restoration start with the least expensive, so it would probably be best to try chemical, then physical, then consider aerobic conversion if nothing else works.