Kind of a gross and random question here, but would you ever expect the liquid from a septic holding tank to be pale green? It's from a facility with restrooms and a cafeteria. Thanks!
Do they have lots of 'little green men' from New Mexico as customers? I would pump it dry, then wash it down with a jet truck. Then go inside and see what they are flushing. Maybe lots of salad waste going through a very good garbage grinder. Or bimr may have your answer.