Onsite wastewater treatment system (OWTS) is a privately owned and maintained sewage disposal system that treats wastewater and produces disinfected effluent, which is not harmful to humans and the environment.
In this system, certain mechanical components and natural processes perform the collection and treatment of sewage. The system plays a vital role in removing scum, nutrients, pathogens, grease, and settleable solids, thus protecting the living system.
This article explains the features and working of an onsite wastewater treatment system.
Features of Onsite Wastewater Treatment System
An onsite wastewater treatment system is a unique system that combines a septic tank and a soil absorption field. It is a simpler form of conventional septic system and hence is also known as a non-conventional septic system.
In a conventional septic tank system, the collected effluents in the tank flow to the soil adsorption field for final treatment and dispersal. The particulate matter present in the effluents settles down in the septic tank, while the effluent screen placed in the septic tank outlet filters out the suspended particles. In this way, large solid particles do not enter the drain field.
An OWTS system follows the same principle, but it has an advanced treatment arrangement to perform at a greater frequency. It is designed to treat and dispose of effluents on the same property that produces wastewater.
In rural areas where dwellings are spaced far apart, installing a sewer system is too expensive. In such situations, people decide to establish their own private sewage treatment plants. With the increase in population, it has been observed that the dependency on individual onsite treatment plants has also increased.
Stages of OWTS
The steps involved in the treatment of wastewater through OWTS are:
1. Identifying the Source of Wastewater
The sources of wastewater decide the strength and constituents of the sewage. Mainly, there are two sources of wastewater- domestic and commercial. Domestic wastewater is discharged from residences through plumbing fixtures, toilets, laundry, and dishwater. Commercial wastewater comes from restaurants, manufacturing plants, and businesses.
Before setting up an OWTS for a building, the homeowner must be aware of the system’s operation and maintenance. An adequately maintained OWTS can protect the public, environment, and property, and also increase the system’s life.
2. Collection and Storage of Wastewater
A solid rigid pipe is used for the collection of wastewater emerging from residential buildings. This rigid pipe collects wastewater from plumbing fixtures and appliances. The pipe is laid at a downward slope which leads to the pre-treatment plant. Just before the first pre-treatment component, a clean-out is provided in the pipe. Adequate sampling basins can be provided, depending on the sampling needs and requirements.
A broader version of the collection system uses pump tanks and holding tanks. Pump tanks collect the waste and transport it to the pre-treatment components. In certain situations, wastewater can be stored in storage tanks, whichare later collected and transported to a site for treatment and dispersal.
3. Pre-treatment of Wastewater
The pre-treatment method varies based on the environment from which the wastewater has come and its final use. This stage involves removing contaminants from the wastewater to prepare it for the final treatment. Some of the pre-treatment components include trash tanks, septic tanks and processing tanks. In this stage, the water is treated so that the soil carries a permissible level of impurities.
There are also advanced pre-treatment systems like aerobic treatment units, media filters and constructed wetlands.
4. Final Treatment and Dispersal of Wastewater
Here, the final removal of contaminants takes place. After the final treatment, the water can be safely dispersed into the environment.
Some of the final treatment methods include soil adsorption field, conventional drain field system, leaching chamber, etc. The treated wastewater can be distributed into the soil through different methods. One of the most widely used systems is the gravity flow system as it is the least expensive and requires less maintenance.
Another system used for distribution is pressurized distribution, which is used in areas with site limitations. Subsurface drip, low-pressure, and spray distribution systems are designed to function in difficult areas. A pressurized distribution system has additional operation and maintenance requirements.
FAQs
What is an Onsite Wastewater Treatment System (OWTS)? Onsite wastewater treatment is a privately owned and maintained sewage disposal system that treats wastewater and produces disinfected effluent, which is not harmful to humans and the environment. What is the need for an onsite wastewater treatment system (OWTS)? In rural areas where dwellings are spaced far apart, installing a sewer system is too expensive. In such situations, people decide to establish their own private sewage treatment plants. With the increase in population, it has been observed that the dependency on individual onsite treatment plants has also increased. How is water collected and stored for an onsite wastewater system (OWTS)? 1. A solid rigid pipe is used for the collection of wastewater emerging from residential buildings. This rigid pipe collects wastewater from plumbing fixtures and appliances. The pipe is laid at a downward slope which leads to the pre-treatment plant. 2. Just before the first pre-treatment component, a clean-out is provided in the pipe. Adequate sampling basins can be provided, depending on the sampling needs and requirements. 3. A broader version of the collection system uses pump tanks and holding tanks. Pump tanks collect the waste and transport it to the pre-treatment components. In certain situations, wastewater can be stored in storage tanks, which are later collected and transported to a site for treatment and dispersal.
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