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compost toilet
Compost toilet
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Sewage related services

Mains sewage is the norm in the UK, and there is much to recommend it. In general, if you can connect to the mains sewage system, then you should. It is cheap, safe and effective. However, there are some properties that are simply too isolated to make a connection to the mains appropriate.In these instances, you will need to treat your own sewage. But what exactly are we trying to do when we treat sewage, and how do we go about doing it?

What are we trying to achieve by treating sewage?
When we treat sewage we are trying to clean up the water we made dirty so that we can release it back into the natural environment. To do this, we need to remove three main things:
  • - pathogens (dangerous organisms that may cause disease)
  • - nutrients. If you release untreated sewage into the natural environment, the nutrients in sewage will act as a fertiliser. They will result in an increase in algae (small plants), and a process called eutrophication which can kill off many of the creatures living in the watercourse
  • - solids. These can be unsightly, but more importantly they are a major source of nutrients, so by removing them we are reducing the risk of eutrophication

How do we treat it?

The first stage of treating sewage is to separate the solids from the liquids and the easiest way of separating them is by leaving the sewage in a tank until the solids either float or sink. You can then draw the liquid away from the middle of the tank, and treat the solids separately.

There are a variety of ways of treating the liquids, but they all have one thing in common; they are all designed to make a pleasant home for the micro-organisms that break down sewage. These micro-organisms need food, air, warmth and water, so if you are treating your sewage at home, you will need to take care of the system so that the micro-organisms can do their job. The end result of the sewage treatment system is water that is clean enough to either discharge back into the environment (into the ground or a local water course), or to reuse for something else (such as to feed a wildlife pond or to irrigate a garden).

What about compost toilets?

We add water to sewage so we can move it along pipes to where we want to treat it. Sewage treatment consists of removing the solids from the water again and then cleaning the water to a high standard. In some instances it is simpler not to add water in the first place, and to have a compost toilet. You can then have a much simpler system for treating the water arising from baths, showers, sinks etc.

Want to know more?
A good introductory book on treating your own sewage is Sewage Solutions, available from the Centre for Alternative Technology. If you have a specific project in mind, Wales Water and Waste Services can help. We can visit your site and advise on how well any existing system is functioning and how it might be improved. We can design a system for you to install yourself, liaise with the Environment Agency and other regulators on your behalf, and show you how to maintain your treatment system.

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