January 2005

New process cleans waste stream from DuPont’s manufacturing complex in Spain

The DuPont Corporation operates a world-class chemicals and fibers manufacturing complex on the north coast of Spain. ICEAS® Sequencing Batch Reactor (SBR) technology from ITT Industries’ Sanitarie unit 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 ICEAS (Intermittent Cycle Extension Aeration System) process is a variant of a sequential batch reactor (SBR) system where the processes of biological oxidation, nitrification, denitrification, phosphorus removal and liquids/solids separation are achieved continuously in a single basin. What makes the ICEAS process different is a continuous inflow, as opposed to conventional SBR processes, even during the settle and decant phases of the operating cycle.

The Sanitaire ICEAS SBR process can be used at both municipal and industrial wastewater treatment plants including biological nutrient removal. The process is a fully automatic, simple to operate, time-based system that responds to flow and load variations and is easily expanded.

Along the northwest coast of Spain is the principality of Asturias. To the north of this region of over one million inhabitants lies the Bay of Biscay, where the seacoast joins it to the European Atlantic arc. To the south lies the region of Castilla y León. There is a natural border between the two regions, along the ridges of the Cantabrian Mountains. Most of the population, industry and agriculture of Asturias found on the coastal plain. When viewing the green and blue of the mountains and the sea and the wilderness forests, it is easy to see why Asturias is known locally as the “Natural Paradise”.

In this natural paradise is a huge - and expanding - chemicals and fibers manufacturing complex operated by DuPont that has the protection of the environment at the top of its priorities. In 1991, DuPont began developing this manufacturing complex on a green-field site in a largely agricultural valley in Asturias. The nearly 350 hectare (850 acre) site is located was initially commissioned to produce Nomex® fiber, with plans calling for multiple production units to be constructed over a period of years for other products.

From the project’s inception, environmental protection of the site, the surrounding rural community, and the receiving waters from the plant was of crucial importance for DuPont. In light of the diversity of the products planned for the site and the complexity of the waste stream, the wastewater treatment for this industrial complex was foreseen as being a significant challenge. This was all the more so because of the stringent discharge requirements for protection of the downstream estuary.

The products manufactured currently at the DuPont site include Nomex® fiber, tetrahydrafuran (THF an intermediate chemical used for the manufacture of products such as DuPont Lycra® elastane), Sontara® spunlaced products, a new range of agricultural chemical products, and lastly, Corian®. All of these products have come on stream with plant expansions over the past decade.

After evaluating various biological treatment options, ITT Industries’ Sanitaire unit was chosen to provide the wastewater solution. Sanitaire’s ICEAS® variant of the sequencing batch reactor (SBR) technology was determined to be the best suited for this developing, multi-project manufacturing complex. The SBR system was selected primarily due to its capabilities to be expanded in a modular fashion, its automated operation, as well as its process flexibility to handle relatively low but variable flows.

The SBR system has since been expanded twice. The first expansion in the mid-1990’s involved the addition of a second, larger SBR to accommodate a significantly greater waste load from the next production unit, which manufactured THF.

The second expansion of the SBR system was completed in December 1999. This most recent expansion increased the treatment capacity of the plant by almost three-fold with the construction of two more SBR’s. The current treatment capacity is now approximately 15,000 kg/day, which is 14 times that of the original system.

The expanded facility now has the capability to operate as a two-stage process with dual SBRs comprising each stage of treatment. Higher-strength wastes are “pre-treated” in the first stage at a relatively high food-to-mass ratio. Lower-strength wastes are combined with the first-stage effluent for final treatment in the second-stage SBR to comply with stringent effluent requirements.

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