By Drain Doctor on 12/01/2016


Do you ever stop to think where all the water from your toilet and sinks goes to?  Probably not!  However, it is an interesting and pretty complex process.

Sewage is the waste water which runs through the drainage network.  It is kept separate from rainwater drainage and remains fully enclosed between your house and the treatment works. In cities in particular, parts of the sewerage network are connected to the rainwater runoff and this is the most common cause of issues when flooding occurs and the sewage overspills.

As soon as you pull the plug from your sink, your waste water enters the sewage process and must travel through a cleaning process to transform it into a sanitary state so it can be re-introduced back into the rivers.

Here’s what happens -

- the water is screened and all non-biodegradable items are removed.

- a primary treatment removes solid waste from the water.  This is done by putting the sewage into large settlement tanks.  The primary sludge is collected and lays at the bottom of the tank.  This means the water at the top of the tanks has a greatly reduced amount of solids in it than before this primary process.  The sludge is pumped away for further treatment or disposal.  It is often turned into an energy generator and turned into electricity or sometimes is turned into an organic fertiliser.

- the water is sent onto a secondary process which is a biological treatment known as the activated sludge treatment.  Oxygen is pumped into the water providing an environment for good bacteria cells to grow, which then consume the sewage and breakdown unwanted micro-organisms within the water.

- the final treatment sees the water being pumped into another settlement tank where the bacteria cells form another sludge similar to stage one.  The water may then be filtered through a bed of sand to provide a further sanitisation before it is pumped back into the rivers and reservoirs. 

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