Diesel Fuel Quality Std & Filtration Service

My client wanted to reuse the diesel fuel that they are storing at an existing fuel storage tank for their new tank.

Can anyone recommend to me a standard of quality of diesel fuel for typical medium to large standby generators application?

If filtration service is available, can anyone recommend a typical filtration goal / std of quality that we normally have to achieve? I'm in South Florida, any particular vendor or service company that anyone can recommend for this type of fuel filtration service?