Soil is a key factor in the treatment of our wastewater. When you pick up a handful of soil most people don’t really realize what they are actually holding. Soil is an actual living system. Some even call it the skin of the earth. Like Franklin D. Roosevelt said, “a nation that destroys its soil destroys itself.” Soil has four important functions:
- Plant growth- this includes all vegetation that naturally grows as well as farmers’ crops, vegetable and fruit gardens.
- Water storage- through Pores of the soil water can be absorbed allowing there to be storage water.
- It is a modifier of the earth’s atmosphere- playing a key role in carbon cycling. 10% of the world’s carbon dioxide emissions are stored in soil.
- It is a habitat for organisms- Microorganisms all ranging in size. From microscopic cells that digest decaying organic material to small mammals that live mostly on other soil organisms. There are more microorganisms in a handful of soil than there are people on earth.
Using the four key functions, our wastewater is treated or filtered by the soil before it enters back into our water source.
Many people think that the septic tank is where most of the cleaning of the wastewater occurs but that is false. The septic tank is used for settling all the solids to the top or bottom before the liquids are moved into the soil to avoid clogging in the soils pores. The final treatment of most private wastewater systems is done with soil to complete treatment or cleaning of the wastewater and return the treated water back into the environment. This treatment is done with different types of systems such as treatment mounds or disposal fields, but all are using the soils as the final treatment. 95% of your wastewater treatment is done in the soil, the rest is evaporated into the air.
Soil is the most important factor to insure the filtration process is done to its full potential before reaching the groundwater, and is a huge factor in the designing process of your wastewater treatment system. Soil is made up of three characteristics; sand, silt and clay. Different textures of soil, or different pore size of soil, happens by having different percentages of the sand, silt, or clay. Different types of soil can handle different amounts of wastewater. Wastewater needs approximately a seven day period, or retention time, at an unsaturated flow condition to filter through the soil before going back into the water table. It is up to a professional designer or engineer to examine the soil and take all factors into consideration before concluding the amount of wastewater that can be applied to the soil.
The naturally occurring organisms that we find in our soil need steady diets and a comfortable living environment to flourish. Without proper conditions they wouldn’t be able do the work needed, consuming the organic matter and nutrients from our wastewater. The plants and other microorganisms in the soil recycle the organic matter portion of the wastewater to other substance that are then used by other life forms. Overloading the soil with wastewater will upset the microorganisms and deprive them of the oxygen they need to survive and is a part of the considerations of the designer or engineer. If overloading does happen it might appear that your wastewater system is working, but it is “pushing” untreated wastewater back to your groundwater before it has time to be fully treated. You could also see leaching or puddling above ground contaminating wildlife or creeks and ponds nearby.
It is amazing how strong but yet delicate soil is. We need to make sure that we give it the respect it deserves and not miss treat it. Soil is at the bottom of the food chain yet it is the cornerstone of life on earth. There is no avoiding the production of wastewater. We need to treat, or remove harmful containments, from our wastewater because we have the knowledge and proof that it can have a negative impact on the environment and health of both humans and animals and also our water sources. By treating our wastewater responsibly we are making it a reusable, renewable and recyclable product called WATER that everyone needs to live.
Written by, Amanda Opdendries