The toilets are attached to a biodigester.  Again it is a system that is mimicking a natural process. The solids and water enter the biodigester, a big underground tank. And in our case an external pump, pumps in air; although some accomplish a similar thing by agitating the “gloop” (technically it’s referred to as liquor). There are bacteria naturally present which multiply in this lovely airy, gloopy cocktail and eat all the nasties to such an extent that the liquid which comes out is clean enough to be allowed into a stream, pretty impressive eh! Of course over times the solids will build up until a man with a tank will need to come around and empty it. It costs around £140. You can, in theory, put this back on the land as fertilizer, but there is a risk that some nasties might still be lurking in the dark, so it's not allowed. However, a friend of mine who owns a farm in Truro was a part of a scheme, in which the local water authority used his land to spread composted human waste as fertilizer. He was chuffed to bits as it was free and the water authority did all the work. The smell, however, slowly drifted over the town and was so bad that it became the focus of the afternoon radio talk show. I don't think he phoned in. 

The biodigester cover in the garden!