I'm about to set up a grey water experiment using a slow sand filter. The idea is to have a low tech filtration system for domestic grey water. The flitered water would then be stored for a short time before use. The water is not to be used for drinking but would be used for flushing a WC and for garden irrigation. I'm aware of the problems with grey water storage, which is why I wanted to give this a go.

The slow sand filters I've found on the internet use large volumes of sand, but are intended for wholesome drinking water. I'd like to know if I use a much smaller volume of sand (approx 250mm deep in plastic feed and expansion cistern) whether it will remove enough bacteria etc to make the resulting water safe and relatively odourless to store before use. Does anyone know the answer or where I might find it? Would I be better off trying a different approach altogether?

Thanks in advance,
Nick