ANAEROBIC TREATMENT APPLICATIONS AND FUNDAMENTALS - SUBSTRATE-SPECIFICITY DURING PHASE-SEPARATION

The effect of phase separation on anaerobic biodegradation was evaluated in terms of thermodynamic principles. Individual components of common wastewaters were considered, and results indicate that the response of different substrates to phase-separated anaerobic treatment is diverse. A key element is the response of soluble substrates to acidification when syntrophic relationships are eliminated and biological reactions that require syntrophic relationships are altered. The acidification of carbohydrates and some proteins is thermodynamically favorable. In contrast, the acidification of fatty acids and aromatics is not thermodynamically favorable unless a sink for reducing equivalents is available. Reported data are consistent with this analysis and phase separation has been observed to enhance the treatment of carbohydrate wastewaters. In addition. the potential for detoxification of specific inhibitory compounds under acidifying conditions has been observed. Whether or not treatment of certain substrates will be enhanced by phase separation should be considered in the choice of reactor design, recognizing that various reactor designs exhibit different degrees of phase separation. This paper presents an overview on how phase-separated treatment affects the biodegradation of specific substrates and relates this to the selection of reactor designs.