Stability of High-Rate Anaerobic Systems. II: Fuzzy Stability Index

Based on a fuzzy logic method, fuzzy stability index N was proposed to integrate the complex information contained in various system variables and explicitly indicate the departure of a system from normal state. The instability of a system subjected to a shock could be explicitly revealed by its variance of N. Based on the examination of variance of N, the stability of three high-rate anaerobic reactors in the presence of various shocks was quantitatively compared. The comparison results based on N coincided in general with the conclusions obtained from a direct examination of the reactorsʹ performance, but the N comparison method was proven to be much more convenient and explicit as compared with the method of direct examination of the reactorsʹ performance.