Thinking back through the haze to when I ran an airport and sold fuel to all comers, if we defuelled an aircraft the removed fuel was put back into the storage upstream of filters etc, in other words exactly as the fuel arriving on site by road in a 23,000 ltr bridger. I don't recall any procedures about direct transfer between one company's aircraft, and I cannot imagine how that could be done without using an airport supplier's tanker to do it, which I would never have allowed had it been requested, for all sorts of reasons, liability being top of the list.
However if the removed fuel was found to be contaminated it was kept quarantined until treated or maybe just left to settle, I don't remember; usually in a tanker.
Because of the time it took, and the problems of dealing with and storing the fuel, we charged so much that it was better for the airline to offload some passengers or freight, which was exactly our intention. We really did not want to know! Getting down to a maximum RTOW (or another weight, if limiting; forgive the old-fashioned terminology) was almost always the purpose of the defuel. The reason was usually either tankering in too much (by cheapskate airlines who didn't like our very reasonable prices), or crew miscalculation when ordering the uplift.
The reference CAP 748 seems to be engraved on my heart, but may be something else entirely. In any case, EASA has probably produced a 1,000 page document on the subject, saying the roughly the same as the UK CAA said in about 20 succinct and totally adequate pages. They've done that for everything else, why should fuel storage and delivery be spared?
Last edited by Capot; 1st Feb 2016 at 12:28.