TWO-STAGE SBR SYSTEM MEETS CHALLENGES OF DUPONT'S ASTURIAS, SPAIN SITE

DuPont operates a world-class chemicals and fibers manufacturing complex on the north coast of Spain. Sequencing batch reactor (SBR) technology was selected to meet the challenging waste treatment needs for this growing site which has had environmental protection as a core objective and operating principle from its inception in 1991. The second expansion of the SBR system was completed in December 1999. Current COD treatment capacity is now approximately 15,000 kg/day which is 14 times that of the original system. The facility now has the capability to operate as a two-stage process with dual SBRs comprising each stage of treatment. Higher-strength wastes are “pretreated” in the first stage at a relatively high food:mass ratio. Lower-strength wastes are combined with the first-stage effluent for final treatment in the second-stage to comply with stringent effluent requirements. This paper describes the wastewater and treatability studies for the aramid fiber, nonwoven fiber, tetrahydrafuran and crop protection chemical processes at this manufacturing complex. Challenges from the various waste streams included very high salt levels, complex organic-nitrogen compounds and others that were potentially toxic or at least difficult to degrade. Emphasis is placed on the last study that demonstrated two-stage treatment would be required after startup of the fungicides unit. In addition to the laboratory studies, the conceptual design strategy of the overall collection and treatment system, as well as the startup and operational experiences to-date is discussed.