What is waste water?
Waste water is water that has been contaminated after use and is discharged via the drainage system to a sewage treatment works. In building services, several types of waste water are distinguished, each with its own drainage arrangement.
Types of waste water
- Foul water (black water) — waste water from the toilet, heavily contaminated
- Grey water — lightly contaminated water from the shower, basin, washing machine and kitchen
- Surface water — rainwater that runs off roofs and paved areas (technically not waste water, but often drained via the same system)
- Industrial effluent — water contaminated by manufacturing processes
Drainage systems
Two main sewer systems are used:
- Combined system — foul water and surface water are drained together. In heavy rain the sewer can overflow (combined sewer overflow, CSO)
- Separate system — foul water and surface water each have their own pipe. Surface water goes to a watercourse; foul water goes to the treatment works
Applications
- Building services — all sanitary fittings are connected to the internal drainage system
- Drainage design — a correctly sized drainage system prevents blockages and flooding
- Sustainable construction — grey-water recycling (e.g. reusing shower water for toilet flushing) saves potable water
- Construction site — waste water from concrete operations must be collected and must not enter watercourses
- Sewer connection — new buildings require a connection to the public sewer
Related terms
- Drainage
- Rainwater downpipe
- Sanitary ware
- Sewerage
- Separate drainage system
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