One of the first questions that homeowners ask when they have you out to investigate a system that has problems is: “If my system is broken, can I fix it?”
In this column, we will relate a few of our experiences with system restoration. You can’t answer the customer’s question until you have done the troubleshooting to determine the cause of the problem. Some typical causes of failure include:
• Using too much water.
• Discharging effluent too high in BOD and suspended solids.
• Designing the system too small based on soil conditions.
• A high water table.
• Soil smearing and compaction during installation.
Too much water
If the cause of the problem is using too much water, a solution is simply to cut back on the water usage to the point where it matches the system capacity. We like to highlight for clients or in our classes that systems have finite capacities and that soils can accept only so much water based on the texture and structure.
It is always interesting to speak with homeowners about water use. Most often they do not really know how much water they are using, and they almost always are way low in their estimates. We were involved in a research project about 30 years ago where we had a water meter installed. We were measuring flows in excess of 750 gpd for a three-bedroom house, and the system was designed for 450 gpd.
When we talked with the owners, they said they were not doing anything unusual, and it could not be that high. We recalibrated the meter and the numbers came out the same. This just means for their water use the system was half the size it needed to be. Restoration in this case involved cutting back water use and adding some treatment trenches to handle the flows.
Another somewhat amusing example was a case where the system was failing and we determined that water use may be a factor. To avoid cutting down trees to add to the system, the client put a timer on the shower, limiting the time his teenagers could use it. It had dramatic results after a month in eliminating the surfacing effluent. These examples are why we encourage the use of water meters.
Too much BOD
If the cause of the problem is organic overloading from neglected septic tank maintenance, the release of solids from the tank due to lack of a baffle, or the addition of a product that results in solids transport to the drainfield, there can be success in restoration.
Solutions here would involve fixing physical problems with the tank, getting the system on a regular maintenance routine, potentially resting the system or parts of it, or installing pretreatment devices such as a media filter or ATU.
Before we had all of the reliable products on the market today, the chief approach to restoration was to install at least another partial soil treatment unit, diverting the flow through a valve to the new part while resting the old system, getting the system on regular maintenance, and perhaps adding septic tank capacity by installing a second tank.
This strategy would make for an effluent with lower BOD and TSS and would provide some management options in the future, chiefly switching between parts of the system to provide resting and recovery, thus controlling biomat development.
We have been involved in research and demonstration projects over the years to look at whether adding pretreatment would have a positive impact. The answer is a resounding yes, provided the only problem with the system is organic overloading, or provided any other problems, such as hydraulic overloads, are also addressed.
One set of systems we worked on showed that using either ATUs or media filters to clean up the effluent brought immediate improvement in system performance. In one case, additional trenches, installed to provide a relief area for resting, were never used.
The one thing to remember when cleaning up the effluent to restore systems is that no matter how clean the effluent is, the soil still has a finite capacity to accept water, and if for any reason the flow meets or exceeds that capacity on a regular basis, the restoration will fail. We often see cases where pretreatment is tried without first investigating the soils. The results are generally disappointing.
Damaged soil
If the soil was damaged during installation by compaction or smearing, cleaning up the effluent will usually not improve performance greatly, and in that case a new soil treatment unit may be necessary. The same goes for lack of separation between the system and a zone of soil saturation. If the soil is already full of water, it simply will not be able to accept any more.
There are methods available that physically create cracks or add structure to the soil to help provide infiltration. These treatments can be successful in the short term, but if there are problems with organic loading, those new cracks and crevices will soon be plugged. So again, you need to know what the problems are before deciding on a solution.
One other thing to be aware of when using physical restoration techniques that create cracks is the risk of opening a crack directly to creviced bedrock or an aquifer. In that event, we get rid of the water, but we are not providing adequate treatment. This is why some states and localities have banned some of these techniques. Make sure you work with your regulators when trying to restore a system.
In the past, chemical methods have been employed to break down the biomat and restore some system infiltration. In general, any improvements are temporary if the real cause of the problem is not fixed. In addition, these chemicals (acids and peroxide) are dangerous to work with. Hydrogen peroxide has been shown to break down the biomat but also to oxidize the soil organic matter that is the binding agent for soil structure. The result is that it actually reduces infiltration capacity in the long run.
The bottom line is that systems can be and are being restored. Before you select a method, though, make sure you know why the system is not working properly. Fix all problems with the system, and then select the products or strategies that will work.
