Disposal of sewage sludge can be by
The chosen means of disposal is strongly influenced by the amount of heavy metals in the sludge. Sludge that is rich in heavy metals is not suitable for use as a fertiliser since the heavy metals could quite easily enter the food chain and accumulate there.
Disposal by dumping at sea is becoming less common and should cease entirely by the end of 1998 when new EU guidelines come into force strongly discouraging it.