North of Scotland Water has now kindly supplied information on the perils of a school's sewerage system being linked to that of a hotel. Fat has been slipping through traps into the sewers and preventing friendly bacteria and funghi breaking down waste, it seems. Hence the niff.
The answer is a septic tank and reed beds. Obvious, really. A spokesman for the water authority said: "They use a similar principle: bacteria in the septic tank break down waste and produce sludge, which is removed for further treatment and recycling.
"What's left is best described as grey water, which flows to the reed bed, where reeds and flowers thrive on remaining nutrients."
We thought budding scientists would want to know.