Origin and nature of refractory organic compounds produced during anaerobic treatment of easily biodegradable substrate
Résumé
Anaerobic processes used for wastewater treatment produce soluble residual microbial products (SMPR) which are both easily degradable and difficult to biodegrade. Reducing these residual organic matters requires the knowledge of their origin and nature. Anaerobic batch cultivations of readily degradable substrate (14C-glucose) were performed and 14C flows in soluble and insoluble liquid fractions and in gaseous fractions were investigated. Results of experiments indicated that the soluble residual microbial products represented 1.0 ± 0.1 % of the initial carbon concentration for a ratio of the initial substrate concentration to the initial biomass concentration (S0/X0 as COD/VSS) of between 0.1 and 1.6. Biodegradability level of anaerobic SMPR was estimated in aerobic cultivation with activated sludge. Biodegradability tests showed that half of the anaerobic SMPR were biodegradable and that the anaerobic SMP produced during lysis and degradation of microorganisms was completely oxidized in 14CO2.