Biodegradation of wastes in a cyclically operated reactor: Theory, experimental verification and optimization studies

A cyclically operated biological reactor employed for treatment of liquid wastestreams containing a single pollutant was mathematically modeled and analyzed, using the principles of bifurcation theory for forced systems. The analysis showed that the system has two qualitatively different solutions (washout and culture survival), and that there are regions in the operating parameter space where multistability occurs. The theoretical predictions were experimentally verified with a 5-liter continuously operated reactor. Phenol was used as the model pollutant, and the biomass consisted of a pure culture of Pseudomonas putida (ATCC 31800). In all cases, an excellent agreement was found between experimental data and model predictions, both at a qualitative and a quantitative level. The model was subsequently used in numerical studies, the objective of which was to find optimal operating parameter values for maximizing the productivity (volumetric efficiency) of the reactor. The results indicate that in all cases, optimal parameter value sets exist. The system considered here is a variation of the sequencing batch reactors (SBRs) used in wastewater treatment applications. The results of this study suggest a methodology for optimal bioreactor design for environmental applications.