Aerobic septic system
Aerobic Septic System is also known as Aerobic Treatment System (ATS) is a small sewage treatment system similar to the septic system. But it uses an aerobic process for digestion opposite to the septic system that uses an anaerobic process. Most commonly aerobic septic systems are used in rural areas where no sewerage system is available. Generally, it is used for a single residence or group of homes.
In contrast with the traditional septic tank system, the aerobic septic system generates high-quality effluent. This effluent can be used for irrigation purposes. Hence the needed length of the drain field becomes about half of the normal septic drain field.
Working procedure of aerobic septic system:
The term aerobic refers to the process that involves oxygen. The aerobic septic system adds up the extra oxygen (O2) into the tank. The excessive amount of O2 increases the natural efficiency of the bacterial ecosystem in the tank. Some aerobic septic systems consist of two tanks. One is the pre-treatment tank and the other is the final treatment tank. The final treatment tank includes the disinfection of pathogens.
The aerobic septic system uses mechanical components for the treatment of waste. The treated sewage is then discharged into the absorption area or leach field. There are aerobic bacteria in the tank that need excess of oxygen for the breakdown of organic waste. These bacteria can’t work and can’t even live without oxygen. This oxygen is provided from pumped air with the help diffusion aerator. The diffusion aerator provides excessive oxygen and organic product to the aerobic bacteria in the tank. The aerobic bacteria eat the sewage and produce carbon dioxide (CO2) as a waste product.
Generally, the Aerobic septic system process consists of the following 4 steps:
Pre-treatment stage: In this step, the large solids and other undesirable substances are removed with the help of the Aerobic Treatment Unit (ATU).
Aeration stage: In this step, the air is compressed into the tank with the help of an air pump. This air gets mixed into the wastewater. Here the growth of aerobic bacteria increases to digest biological wastes.
Settling stage: In this stage, the undigested solid wastes settle down at the bottom of the tank. These solid wastes then produce sludge that must be removed periodically.
Disinfecting stage: In this step, the leaving wastewater from the tank is further treated. UV radiation or chlorine or similar disinfectants are used to treat the water, to produce an antiseptic output. After this step, the disinfected water goes into the pump tank. This stage is optional and is used when sterile effluent is required.
Types of aerobic treatment systems
Generally, there are two designs used by small-scale aerobic systems. One is a fixed-film system and the other is a Continuous-flow suspended growth aerobic system (CFSGAS). In both stages, the difference only lies in the aeration stage. The pre-treatment and effluent handling stages are the same for both types.
Fixed film systems
Fixed film systems are the porous systems that provide a medium to the biomass film to digest waste material. Fixed film system is further divided into two categories. In the first one, the bacterial film moves relative to the wastewater. The air exposes the film from an alternate side. The other one uses stationary bacterial films. These bacterial films are submerged in the alternate direction of the water and exposed to air. In both categories, bacterial films are exposed to both wastewater and air for the aerobic digestion process. The film may be made up of plastic, peat moss, or any porous material.
Mostly, the simple septic systems use stationary media. Moreover, these systems depend upon gravity forces. In these systems, wastewater and air are provided with periodic exposure. Also, these systems have a Rotating Biological Contractor (RBC). In RBC disk is rotating slowly on a horizontal shaft. About 40 percent of the disks are submerged at any given time. Furthermore, the shaft rotates at a rate of one or two revolutions per minute.
Continuous flow, suspended growth aerobic systems
As the name signifies, these systems are designed to control continuous flow. They have no bacterial film involved. In these systems, the bacteria are directly suspended into the wastewater. Generally, the air exposure is provided with the help of an air pump that pumps air through the aeration chamber.
Portable aerobic systems
A portable aerobic system or retrofit aerobic system is another increasingly used type of ATS. Usually, this system is the remediation of a failed anaerobic septic system. In this system, the existing anaerobic system is retrofitted with aerobic features. The process is known as aerobic remediation. It is designed to remediate the biologically failed anaerobic septic systems. In this process, the biochemical oxygen demand and total suspended solids are reduced. It results in the development of an aerobic environment. Furthermore, the effluents with high amounts of oxygen and aerobic bacteria flow to the distribution component or leach field.
Components of Aerobic septic system:
The aerobic septic system is a little bit different from the anaerobic septic system. It mainly consists of the following 4 components:
1) Trash Tank
The trash tank works in the same manner as a septic tank. It separates the waste into three different layers.
- The solid wastes or sludge layer at the bottom
- A layer of liquid at the center
- A layer of scum at the top
The wastewater then flows through a T-shaped baffle into an aerobic treatment unit.
2) Aerobic treatment unit (ATU)
In this part of the aerobic septic system, aerobic bacteria are used to treat wastewater. These aerobic bacteria grow in air rich environment provided with the help of a pump. These bacteria are responsible for the breakdown of dangerous pathogens in the wastewater.
3) Disinfection Chamber
Flowing from ATU the wastewater then enters into the disinfection chamber. In this chamber, the wastewater is subjected to UV radiations or other disinfecting products like chlorine or bleach, etc. These products further treat the wastewater before it gets entered into the pump tank.
4) Pump Tank
Generally, this part of the aerobic septic system regulates the drainage of wastewater. When the sewage level rises in the tank, an alarm will notify you about the maintenance. As the water is much treated, so it’s safe to discharge into drainage fields.
For further queries, visit: UAESTC
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