BIOMASS GROWTH MONITORING USING PRESSURE-DROP IN A COCURRENT BIOFILTER

The possibility of following the biomass growth by pressure drop measu rement was investigated in an aerated cocurrent upflow fixed-bed biore actor continuously fed with wastewater containing industrial organic p ollutants. The experiments were carried out in a biological filtration oxygenated reactor (Biofor) pilot plant packed with expanded clay bal ls (Biolite) of 2.7-mm diameter, which served as biomass carriers. The column was equipped for on-line pressure drop measurements. Correlati on between pressure drop measurements and Reynolds numbers of air and water were determined in experiments carried out without biomass. Unde r operating conditions with biomass, it was demonstrated that column c logging and the operating time between washing cycles can be predicted depending on the volumetric organic load for a given total organic ca rbon inlet concentration. The biological activity of the fixed biomass was estimated from the oxygen consumption rate per unit time and carr ier area. The oxygen consumption rate measurements demonstrated that t he biological activity depends on the inlet substrate concentration, a nd that the Biofor column was most efficient between 75 and 100 g m(-3 ) of total organic carbon inlet concentration. In the course of the wa stewater treatment, using pressure drop measurements, the equivalent d iameter of the Biolite particles, the reduced column macroporosity, an d the biofilm thickness were calculated. An expression correlating bio film density and biofilm thickness, as determined from the pressure dr op measurements, was proposed. Good agreement was found between the fi xed biomass in the reactor, determined as volatile suspended solids, a nd the biologically active biomass, estimated by respirometry. (C) 199 8 John Wiley & Sons, Inc.