Sewer is a system of engineering networks, equipment and facilities intended to remove wastewaters. Unlike the water supply system dedicated to delivering fresh drinking or technical water, the sewerage system handles waste waters – sewage, meltwater, rainwater, industrial water. According to the scale and type of the system, the sewage can be treated, recycled and returned to water basins, or re-used.
The sewerage system should be selected appropriate to the operating conditions, size of the building or a facilities complex, kind of sewage, environment conditions, landscape, availability of surface waters and other case-specific particulars. To make the right choice, look into the classification of sewerage systems.
1. Domestic sewerage systems are intended to serve residential and auxiliary premises. A system covering a single building or a small group of buildings is called local, and a system covering a settlement, centralised.
2. Industrial sewerage systems are intended to treat wastewaters from massive industrial, manufacturing and agricultural sites.
3. Storm water/rain water systems drain the water accumulated through rains and other precipitations from the streets and roofs. Types of storm water/rain water systems:
- Open sewers with open channels and conduits
- Enclosed sewers with underground drainage networks and facilities
- Combined sewers with both open and enclosed elements
1. An indoor sewer is a system located inside a building. It consists of pipelines (risers and horizontal pipes), fittings and other valves, and connected domestic and sanitary appliances (washbasins, sinks, bathtubs, showers, urinals, bidets, toilets).
2. An outdoor sewer is a system beyond a building. It consists of pump plants, pipelines and treatment facilities.
An outdoor sewer can be arranged according to the following principles:
- Combined system carries all the waste waters by the same pipe
- Separate (completely separate) sewer carries sanitary sewerage separately from the storm water
- Semi-separate (incompletely separate) sewer brings all the wastes separately into a common interceptor to combine the flows
Different materials are used for various sections of a sewerage system, as the wastes differ by chemistry and impurities:
- Metals (cast iron, stainless steel, galvanised steel)
- Plastics (polyethylene, polypropylene, polyvinyl chloride, fibre-reinforced plastic)
- Non-polymers (reinforced concrete, asbestos cement, glass, ceramics)
- Cesspool: a pit or container in the ground, where all the drains are brought to by a sloping pipeline
- Dry closet: usually, a booth and a tank where wastewater is processed by dedicated biological agents
- Drainage system brings the wastewater by the drain pipes into a drainage well, where it is filtered and absorbed by the ground
- Septic tank – a system of several sealed drained chambers, where the wastewater undergoes step-by-step treatment. The outcome may be let into the surface waters or re-used for technical purposes
- Deep biological treatment plants – complex treatment facilities that combine several special treatment plants
Wastewater disposal methods
Gravity sewer utilises the gravitational operation principle: the wastewater is carried over the pipeline by its own weight.
Pump powered sewer contains pumps to remove wastewaters.