The answers you have ...
Published by Chetan Shukla, Clean Environmental Technologies Pvt. Ltd. - Director
The answers you have received here are not reflecting the entire aspect of grey water. If you are using only grey water, i.e. water from bathing, washing, and from clothes washer then it is perfectly safe.
Presence of phosphates in the grey water are an ideal source for the plants. Additionally the bacteria in the soil assist in breakdown of the wastewater and uptake of the nutrients to the plants.
It is very clear that the grey water should have no presence of black water, as black water is full of pathogens. Black water is used in several parts of the world as irrigation water but there are 2 fears, firstly presence of heavy metals in the black water and the other is presence of pathogens. Both of these need to be removed before using for gardening.