Overview of aerobic single tank system
The aerobic single tank system uses a single unit divided into chambers with two manholes. The alternative system is called an aerobic multi tank system.
The main function of the Aerobic Single Tank System treatment unit is to collect and treat household wastewater, which includes all water from toilets, bathtubs, showers, sinks, and laundry. Aerobic units themselves come in many sizes and shapes-rectangular, conical, and some shapes that defy classification. There are two typical aerobic treatment designs: (1) suspended growth units and (2) attached growth units.
The process most aerobic units use to treat wastewater is referred to as suspended growth. These units include a main compartment called an aeration chamber in which air is mixed with the wastewater. Since most home aerobic units are buried underground like septic tanks, the air must be forced into the aeration chamber by an air blower or through liquid agitation.
The forced air mixes with wastewater in the aeration chamber, and the oxygen supports the growth of aerobic bacterial that digests the solids in the wastewater. This mixture of wastewater and oxygen is called the mixed liquor. Unfortunately, the bacterial cannot digest all of the solids in the mixed liquor, and these solids eventually settle out as sludge. Many aerobic units include a secondary chamber called a settling chamber or clarifier where excess solids can settle. Other designs allow the sludge to accumulate at the bottom of the tank.
Aerobic systems designed with a separate settling compartment, the sludge returns to the aeration chamber. The sludge contains bacterial that also aid in the treatment process. Although, in theory, the aerobic treatment process should eventually be able to consume the sludge completely, in practice, the sludge does build up in most units and will need to be pumped out periodically so that solids don’t clog the unit. Once the wastewater has passed through the aerobic unit, it will be disinfected with some type of disinfection, most commonly chlorine tablets. However, there are alternatives to the chlorine tablets, ultraviolet light and liquid bleach chlorinators.