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What is a sewer system?

A sewer system, also called a sanitation system, is the infrastructure that’s designed to collect and dispose of stormwater and wastewater, thereby preventing stagnation and flooding. They are essential to maintaining healthiness and hydrological balance.

What elements make up a sewer system?

Sewer systems can be quite simple or complex, and they may be composed of a varying number of parts; however, some of the most common include:

  • Sewer network, or just sewers: these are the most visible parts of a sewer system. This is a channeling system that’s usually underground with openings on the surface. The mouths may be connected to the piping system of a building (residential connection or intake) or found on public roads. Sewer accesses, called drains, are protected by covers or grilles to prevent accidents, large objects falling into the system that could cause obstructions, or animals or people entering.
  • Storm drains: they are responsible for channeling, collecting, and managing rainwater. In urban areas, storm drains lead to sewers, but in rural areas, they can channel water for a dual purpose: to prevent waterlogging and to harness the water resource. Some components of the storm drain system are the ditches, the channels, and the culverts, small structures that act together to allow the drainage of surface waters below other infrastructures, usually roadways, such as highways or railways.
  • Sustainable Urban Drainage Systems (SUDS): these are surface elements that aim to use rainwater. They are usually permeable and are generally part of green infrastructure. The goal is retaining, transporting, and reusing stormwater, as well as filtering and infiltrating it into the ground while maintaining or restoring water quality in the process.
  • Collectors: these collect water from various branches of the network to direct it to sanitation plants.
  • Wet wells or underground wells: these store wastewater, which accumulates until it reaches a certain level. Normally, they are equipped with detection systems that make it possible to pump water to treatment plants when a certain level is reached.
  • Pumping stations: sewer systems usually work by gravity; however, not all terrains allow for this. Pumping stations are points at which pumps are installed to allow the flow of water to points of higher elevation.
  • Wastewater treatment plants: at these specialized infrastructures, wastewater is subjected to different processes, usually physical-chemical ones, to remove polluting elements before redirecting it to new uses or reintroducing it into the environment.

What types of sewer systems are there?

Broadly speaking, the types of sewers can be divided into:

  • Urban drainage: manages water in cities. This is important because, due to its characteristics, urbanized land has a lower water absorption capacity.
  • Agricultural drainage: helps remove excess water in the soil to maintain its quality and ensure an adequate water supply for crops.
  • Road drainage: collects and channels rainwater to prevent waterlogging and flooding, thus guaranteeing road safety.
  • Building drainage: implemented in all types of buildings (residential, commercial, and industrial) and used to channel storm water and especially wastewater.
  • Industrial drainage: although this formally belongs to the domain of building drains, industrial drainage should be treated separately. Each industry presents different demands and challenges in terms of drainage. The management and treatment of industrial wastewater are particularly important to prevent environmental pollution (soil, groundwater, etc.) and the appropriate disposal of hazardous or particularly toxic waste.

What importance do sewer systems have?

Sewer systems are important for reasons that have already been mentioned, such as:

  • Flood control.
  • Rainwater management.
  • Sanitation.
  • Wastewater treatment.
  • Preservation of soils and groundwater from possible pollutants.

They are also important for:

  • Erosion control: the free flow of water through the terrain causes soil erosion; this can lead to the loss of nutrients in the soil in rural contexts and the destabilization of foundations in more urban contexts.
  • Integrated water management: proper water management has an impact on maximizing the use of water and the proper reintegration of wastewater into the water cycle.

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