ESTIMATION OF BODST, RESPIRATION RATE AND KINETICS OF ACTIVATED-SLUDGE

Tight control of activated sludge processes is hampered by the lack of reliable information about important process characteristics. Some of those important characteristics are sludge kinetics, short-term bioch emical oxygen demand (BODst) and respiration rate in the aeration tank , Spanjers et al. (1994) developed a technique to estimate those chara cteristics from data collected from a continuously fed respirometer wi th a specially developed operation strategy. Essential in their estima tion technique is the instable backward integration of a forwardly sta ble differential equation. In this paper, an improved on-lint implemen table estimation methodology is presented. The estimation problem is f ormulated as a non-linear optimization problem, avoiding backward inte gration and estimating the respirometer flow. This novel methodology h as been applied to the data set of Spanjers ct ol, (1994), and the res ulting estimates turn out to be comparable. But, contrary to expectati on, the estimates still suffer from unacceptable inaccuracy due to lar ge parameter correlation. However, a slight modification in the measur ement strategy is proposed which will eliminate the problem of paramet er correlation to a large extent and so enable more accurate estimatio n, The new measurement strategy is only advantageous when combined wit h the novel estimation methodology presented in this paper. (C) 1997 E lsevier Science Ltd.