Wastewater treatment is processing water from household and industrial use to make it safe to reintroduce into the ecosystem. From your drainpipes it it transported through sewage systems to the water treatment plant operator who undergoes a serious of processes before it is recycled or disposed of. In a combined sewage system it can also include storm water runoff.
There are three main stages of the wastewater operations, aptly known as primary, secondary and tertiary water treatment. In some applications, more advanced treatment is required, known as quaternary water treatment. This stage deals with part per million to part per billion levels of contamination and often involves oxidation or fine filtration processes. Each of these stages tackles different pollutants, with water becoming cleaner as it moves through the phases.