FATE AND EFFECTS OF SEMIVOLATILE ORGANIC POLLUTANTS DURING ANAEROBIC-DIGESTION OF SLUDGE

Anaerobic digestion of primary and secondary sludge containing selected semivolatile organic pollutants was investigated. Typical digester operation was simulated with three, complete-mix, bench-scale digesters maintained at 35.5-degrees-C with a 30 day solids retention time. Two digesters were fed a primary and secondary sludge mixture produced from wastewater spiked with twenty semivolatile organics from the CERCLA pollutant list. The remaining digester (the control) was fed a similar mixture of sludge, but with no added organics. Operational parameters were monitored to compare the test and control units. All parameters were found to be within the limits of normal operation. Performance was near identical. An isotope dilution GC/MS method was employed for organics analysis of influent and effluent streams for all reactors. Steady-state fates of the organics were determined by mass balance. Twelve of the chemicals appear consistently and at steady state. Degradation was apparent for all components, with at least 10% of each parent compound partially or completely transformed. Sorption onto digester solids was an important removal mechanism. Results of organic analysis for the control digester highlight the effects of metabolic interferences.