FATE AND EFFECTS OF OLESTRA, A FAT SUBSTITUTE, DURING CONVENTIONAL WASTE-WATER TREATMENT

This study assessed the treatability of olestra, an edible oil and sho rtening replacement, during conventional wastewater treatment using la boratory and bench-scale testing. Results showed removal efficiencies for primary treatment to be similar to suspended solids removal (typic ally ranging from 45 to 65%) and removal during secondary activated sl udge treatment to be similar to 84%. Overall removal for primary and s econdary treatment was estimated to range from 91% to 94%. The removal during treatment occurred primarily by sorption onto wastewater solid s and settling during clarification, although some olestra was removed by biodegradation. Olestra exhibited no adverse effects on total susp ended solids (TSS) and chemical oxygen demand (GOD) removal during pri mary or secondary treatment. In addition, olestra caused no adverse ef fects on sludge dewatering as determined by filtration or gas producti on during the anaerobic digestion process. Under expected worst-case c onditions (that is, assuming that all conventional fat in savory snack s will be replaced with olestra) predicted U.S. average wastewater inf luent, effluent and 90th percentile receiving water concentrations und er mean flow conditions were 4.9, 0.7, and 0.2 mg/L, respectively. The concentration of olestra in anaerobically digested sludge under this worst-case scenario was predicted to be 1 281 mg/L(32.0 g/kg), with a corresponding sludge-amended soil concentration of olestra immediately after sludge application (37 mt/ha) estimated to be 656 mg/kg.