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Where does the dirty Water go?

In olden times, people threw the contents of their pottys out of the window onto the streets. It was a very smelly place to live!! Nowadays, all the waste water from our houses go through pipes, called sewers and is sent to the treatment works. Wastewater can be from your loo, your dirty bath water or from things like your washing machine. Factories, Hotels, Hospitals, Schools and Restaurants all use up lots of water that needs to be sent to the treatment works for cleaning.

When the wastewater arrives at the treatment plant, it first goes through a set of screens to take out rags, twigs, rocks and any other large objects that could break equipment in the plant. Grit is also taken out here. The screenings and the grit are taken away and washed separately, and afterwards they go for disposal, usually to a landfill site.

The sewage then goes to a big settlement tank, where all the sludgey stuff falls to the bottom of the tank. The sludge is pumped out of the bottom of the tank and then goes on to a sludge thickening tank. The sludge can then be dried and dewatered and used as fertiliser. People are looking into different ways of recycling the treated sludge.

In the meantime, the water part goes on to another tank where tiny little bacteria are added. These microscopic bacteria eat up any sewage that is left in the water to help clean it up. Any remaining sludge is taken off the bottom of the final settling tank. The clean water is then sent down an outfall pipe into the sea (or to a river if its inland).

Houses in the countryside that are not connected into the sewerage system use septic tanks or similar to take away the waste water from the house. It works like a mini-treatment works, and the sludge is pumped out by a tanker about once a year. Houses that use septic tanks and that have a groundwater well have to be very careful that their well does not get contaminated with sewage.

Here is a photo of the waste water treatment plant in Swords. There are also treatment plants in Malahide, Portrane and a new one in Skerries.

Water Treatment Plant in Swords (20Kb) PDF Water Treatment Plant in Swords (20Kb)