Aerobic biological sludge blowdown from the clarifier in the wastewater treatment system previously had been discharged to solar ponds. However, this procedure became environmentally unsuitable. Hoechst Celanese then tried a belt-filter press, but because the product solids content averaged only about 20%, it was slow to dry in the landfill and couldn't support the equipment used to spread it. It also became readily rehydrated by rain and took too much of the limited landfill space that was available. The company tried combining the material with other waste solids and drying with compression type equipment or a number of gas fired units that required backfeeding. None of these techniques proved satisfactory.

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