DuPont Dordrecht, Netherlands site is a multi-business industrial production site. One of the site businesses generates a saline, high strength organic containing wastewater with high fluoride concentrations. While the wastewater has been successfully treated biologically in the site's
extended aeration activated sludge system since the mid 1990's, it presents considerable operational challenges for complying with discharge permit limitations. This is primarily due to the inability of the microorganisms to form good flocs and subsequent high effluent solids levels.
A new permit requiring effluent total suspended solids (TSS) levels of less than 30 parts per million (ppm), total nitrogen of <10 ppm and less than 200 ppm of chemical oxygen demand (COD) provided the impetus for initiating an alternatives evaluation study. Consideration of the economic
and technical feasibility of various end of pipe and internal modifications led to a recommendation for a membrane bioreactor (MBR). The MBR provided numerous benefits over the other alternatives: assured low effluent suspended solids levels and resultant low total nitrogen and COD levels,
competitive costs, ability to reduce food to microorganism ratio (F/M) loading and subsequent effluent quality improvement through maintenance of higher mixed liquor levels, and improved ability to lower dilution water needs. Subsequent pilot testing confirmed flux rates, types of cleaning
materials and otherwise provided basic data for a full scale MBR slated to come on line by the end of 2003.
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