MEMBRANE BIOREACTORS FOR THE EVALUATION OF MAINTENANCE PHENOMENA IN WASTE-WATER TREATMENT

A membrane bioreactor was used to calculate the maintenance coefficients ms, mo2; g · g-1h-1) and theoretical maximum yields (Yx/s, Yx/o2; g · g-1) of Pseudomonas fluorescens cultures taken as a model when grown on a limiting substrate complex medium, similar to a synthetic wastewater. The total control of the aerobic process of wastewater treatment in this type of reactor, and the perspective of the reduction of sludge production were directly related to this purpose. The operating conditions were either a total cell recycle or various imposed breeding rates; similar values of growth constants were obtained. It was established that the substrate mass flow (fixed by the dilution rate, Ds, independent of the breeding rate Db), had no influence on the values of m and Y. No deviation of the slope of the linear regressions serving to calculate these parameters was observed, even at low biomass breeding rates Db (<5% μmax). The concept of the maintenance energy coefficient and the advantages of this technical tool are discussed. © 1990.