Refineries face risks to supply water, slow permits, tighter limits, drought, or expansions outpacing supply – pushing them to reuse effluent as their only option. Reuse means RO, and RO on this variable mix of blowdown, desalter effluent, and sour water means removing oil, grease, and organics first – via coagulation, flocculation, flotation, then a bioreactor.