Once you get past the sewage systems the water is sent to settlement tanks, where the water and the waste is left to sit motionless for some time. This allows time for the solid waste to sink to the bottom, where it is removed by scrapers. This waste is then taken away and sometimes used as fertilisers or composted. Following this, the water flows over the top of the tanks and moves onto the next stage.
Despite the removal of the solid waste, the water is still not clean at this point in the process. There are many dangerous microorganisms that can be found in the water, and so the next stage is to send the water to aeration tanks where oxygen is pumped into the water. This encourages any ‘friendly’ bacteria in the water to grow and eradicate the dangerous bacteria. Following this, the water is sent to another settlement process where the dangerous bacteria that has been killed sinks to the bottom to form sludge, and is removed.
In most sewage systems there is one final stage where the water is passed through sand to filter any remaining waste that was not eliminated in one of the previous steps. At the end of this, the water is sent out into natural bodies of water such as rivers or oceans, where it re-enters the ecosystem. But this is the best case scenario. Remember: it doesn’t always go this way. That’s why blocked drains Bath are always on call – to make sure this happens.