City septic tanks need to be cleaned regularly, where do the vacuum trucks transport the feces after sucking it out? How to deal with it?

Transported to the countryside, as organic fertilizer, mainly used for vegetable fertilizer applied to the vegetable field inside there is a directional treatment of manure, biogas can be done gas, residue can be done fertilizer, but the cost of doing so is high, so the government sector only a small number of people in this way, if an individual, it is not necessarily, there are no hard and fast rules.