Development of an Off-Line Enricher-Reactor Process for Activated Sludge Degradation of Hazardous Wastes

The improvement in degradation of a hazardous chemical using a novel bioaugmentation scheme was studied. Bench-scale offline batch enricher-reactors (ERs) maintaining an enrichment culture were used to bioaugment bench-scale continuous-flow activated sludge reactors treating 1-naphthylamine (1NA). In batch experiments, onetime bioaugmentation inoculations of 1, 2, 5, 10, 20, and 50% by mass of a 1NA-degrading culture (mg mixed liquor volatile suspended solids [MLVSS] of 1NA-degrading culture/mg MLVSS of indigenous culture) increased degradation rates by approximately 0, 33, 100, 100, 100, and 300% respectively over an uninoculated control. In continuous-flow experiments, separate 13.7-L reactors received daily inoculations of 1.4, 2.5, 6.6, 11.4, and 18.3% by mass of 1NA-degrading culture. Cumulative target compound breakthrough reduction following a 50 mg 1NA/L spike was 13, 21, 11, 35, and 41% compared to an unacclimated control and 4, 13, 1, 27, and 35% compared to an acclimated control, respectively. Similarly, the reduction in breakthrough during reacclimation to 5 mg 1NA/L over six days was 66, 73, 85, 98, and 100%, respectively. A 6% bioaugmented continuous-flow reactor significantly reduced 1NA breakthrough following a step-loading increase from 1 to 5 mg 1NA/L compared to an uninoculated control. Effective bioaugmentation was achieved with additions of biomass equivalent to 14-25% of indigenous cell production rates.