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When an engineer creates a wastewater treatment system that functions properly, many of the disposal schematics contain a leach field. Primary treatment is considered when wastewater leaves the standard septic tank. The first wastewater treatment is the separation of solids (as noted in other articles), Then the water is treated, biologically in the 2nd chamber. A “Standard United States Septic Tank” can treat to around fifty BOD, which is known as the biological oxygen demand, and the total suspended solids, also known as TSS, which is around 100, and having a load of total nitrogen at around forty-five milligrams per liter.

The septic tank water goes directly to the field. This is where the wastewater will be absorbed in nearby soil. This field is not just a living biological processing machine, but a liquid receptor as well. The biological processes will treat the wastewater further to achieve an acceptable concentration before the wastewater reaches groundwater, or any other potable drinking water source.

The general structure of the field has a layer of around four feet of 2-4 inch rock. From there, a line will be placed on top of the leach rock, and then will be covered with three inches of the same rock. There is a geo-textile barrier that is put on top of the rock to prevent any dirt and other foreign material from clogging up the rock below. Many times the rock is also covered up with twelve inches of soil.

The fields come in two different types: a leach bed or a leach trench. The trenches range from around one foot in diameter, to around three feet. The maximum length of a trench is around one hundred feet. The beds can range from twenty feet wide to a hundred feet long. Large industrial wastewater treatment disposal systems usually have leach beds. This is because the systems have a higher flow rate per day.

Many fields are supposed to be designed to function for a thirty year life span; which is in the worst of conditions. Leach fields are a biological processing plant that will break down into wastewater over time. When wastewater enters a field, the water has a high BOD, which is considered anoxic. Anoxic means that there is no oxygen present. While the waste water is flowing through the fields and in the soil, the biological oxygen demand dwindles down to the point that there is enough oxygen to move into an aerobic condition. Under this condition is when the bacteria levels are in a safe range.

One important factor to note, is the large amount of biological activity at the leach rock boundary, and the soil that continues on over the life span of the field. When the bacteria life cycle continues, the debris from the wastewater process settles in the soil-rock boundary. The foreign materials combines with clothing fibers that are not digestible. An example of this would be polyester, which forms a low permeable layer. This layer is known as the “matting”. Matting grows with age, which is the main reason why the life span of a leach field is thirty years.

When the field is old and is approaching the end of its life, it is usually expanded by adding more area to the field, or it can be replaced. This is quite costly to do, not to mention disruptive. People can buy products that promote the field health, and can rejuvenate it completely. One problem in septic tanks is that greases and oils flow to the field. These items increase the mat growth, which results in an early replacement of the line. There are two types of conditioners that consumers can buy for their septic tanks; liquid biologically active products, and dry enzymes such as RIDEX for septic tanks. Many waste water engineers swear by using the liquid biologically active conditioners. Either of the two types of conditioners will reduce matting growth, and extend the life of the field.

When a leach line has to be dealt with at the end of its life, usually from matting build-up, there are many products that make performance claims. Some of the products say that they can crack the soil matting with harsh chemicals, or through high pressure. Many of these techniques are only temporary, and often fail when the matting grows back. Some engineers add enzymes in the wastewater stream before the water reaches the field. The most effective way to perform this is by adding a tablet feeder to a leach line, which is between the leaching field and septic tank. This is when the wastewater is dosed by an active enzyme that is right before where it enters the leaching field. This enzyme is engineered to efficiently break down matting, and then restore the leach field to the original condition. If the matting has a lot of synthetic fibers, breaking down the matting will be very difficult to do. Many cases engineers will use a direct dosing of the stream to be effective.

In summary, you should try to take care of your complete septic system. Use good septic system conditioners and if you are in a failed leach line scenario, then I would recommend using both a conditioner and a continuous direct dosing approach. The combinations of both approaches should be quite effective and extend your complete septic system life. Also, the cost associated with septic tank pumping has escalated over the last five years or so, so a good septic tank conditioner can greatly reduce septic pumping frequency. I used to have to pump my septic tank every 2 to 3 years. Since I’ve been regularly using a conditioner, I have not pumped my septic tank for over 5 years. It saves you money.

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