Application of biofilms and biofilm support materials as a temporary sink and source

Wastewater treatment plants are typically subjected to variable influent lo ading conditions. Extreme variations of flow, composition and substrate con centration may occur in the influent of industrial wastewater treatment pla nts, but also at plants serving tourist areas. High rate reactors of low hy draulic buffer capacity are particularly affected. Exploitation of internal equalization capacities are proposed to dampen the fluctuations of biomass loading. In this context, the biomass itself and - in case of biofilm reac tors - the biofilm support media may be considered as a sink during peak lo ading situations, and as a source of substrate as soon as the influent load ing drops. Sequencing Batch Biofilm Reactors (SBBR) studies in laboratory a nd pilot scale were conducted to investigate the capacity of these internal sink and source terms. The reactors were packed with four types of biofilm carrier materials, blasted clay granules, granular activated carbon, zeoli te and small size plastic rings (Kaldnes). Temporary storage of substrates was achieved by means of adsorption, ion exchange and absorption processes. As the react phase proceeded, the bulk liquid concentration dropped and de sorption processes followed by metabolic reactions became dominant. From th e results achieved it can be concluded that thick biofilms, and biofilm sup port media with sorptive capacities are favorable to counteract peak loadin g fluctuations, and to keep the effluent concentration from exceeding set d ischarge levels.