Practitioner's Tool / Technology and Operation 1 Overview

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Pretreatment and Grease Management

Pretreatment or grease management is necessary in several fields of wastewater treatment. Below is a list of such circumstances:


Sewers transport waste away from businesses, homes and other sources to septic tanks, other treatment systems, or community sewers. They are constructed out of plastic, clay or iron pipe and laid at a constant grade of 2% that helps to maintain proper speed of the sewage in the pipeline to minimize clogging. Proper design, installation and maintenance are critical for proper operation.

View a comparison of all sewer systems.

Primary Treatment

Septic tanks and anaerobic baffled reactors are low-cost components that remove much of the pollution from sewage. These must be desludged periodically to function properly.

Summary table of primary treatment methods.

  • Septic Tanks: A septic system is a small wastewater treatment system designed to treat and dispose of household sanitary waste using a septic tank as the primary component. The septic tank is the first stage in a private wastewater treatment system. Sewage from the building flows to the septic tank where solids are separated from the wastewater flow. The heavier solids sink to the bottom of the tank to form sludge, while the lighter particles, such as hair and grease, rise to the top to form a scum layer.
  • Vermicomposting digesters: This system provides aerobic primary treatment by providing an enclosed environment in which worms transform solid effluent into humus. Liquid is separated from solids by draining through a filtration medium that retains solids. Aerobic digestion is faster and generates less smell than septic tanks.
  • Anaerobic Baffled Reactors: An anaerobic baffled reactor (ABR) is a tank with several compartments that is designed to reduce the organic and suspended matter in the wastewater by about 70%. Raw wastewater enters the ABR tank through the inlet structure, which directs the flow to the bottom of the first compartment. Due to the nature of wastewater under anaerobic conditions, a granulated sludge blanket is formed. As the wastewater flows up through the sludge granules, the solids are trapped in the sludge blanket where anaerobic bacteria consume the organics as food.
  • Sewage Lagoons: Sewage lagoons are lined ponds or basins that treat wastewater through the physical action of settling and the biological action of microbial digestion. Also known as waste stabilization ponds, sewage lagoons are popular because they are relatively inexpensive and easy to design, install and maintain and can produce a good quality effluent. They do, however, require large land areas. See also:
  • Biogas Systems, Biogas Reactor, Biogas Combustion: A biogas reactor or anaerobic digester is an anaerobic treatment technology that produces (a) a digested slurry (digestate) that can be used as a fertilizer and (b) biogas that can be used for energy. Biogas is a mix of methane, carbon dioxide and other trace gases which can be converted to heat, electricity or light.
  • Interceptor Tanks: A settler is a primary treatment technology for wastewater; it is designed to remove suspended solids by sedimentation. It may also be referred to as a sedimentation or settling basin/tank, or clarifier. The low flow velocity in a settler allows settleable particles to sink to the bottom, while constituents lighter than water float to the surface.