THE ROLES OF BIODEGRADATION AND ADSORPTION IN THE BIOLOGICAL ACTIVATED CARBON REACTOR

With an increased concern regarding potable water quality and protection of the aqueous environments, the increased use of granular activated carbon can be expected. One modification of this process is referred to as biological activated carbon. The previous literature has not resolved several questions regarding the mechanics behind this modification which, in turn, raises questions as to its applicability to water treatment. These questions principally concern the interaction of bacteria with granular activated carbon. The purpose of this project was to help clarify these mechanisms.; After examination of the literature, a study was undertaken so as to delineate biological and physicochemical interactions. This was achieved by developing synthetic waters having specific and measurable characteristics with regard to biodegradation and adsorption. The waters were individually applied to parallel, continuous-flow columns containing granular activated carbon or sand and having a biological population established on these media. The waters developed contained sodium acetate at differing levels as a nonadsorptive, biological substrate plus inorganic chemicals to provide for pH buffering and microbial nutrients. In addition, the waters used either dodecyl benzene sulfonate as a nonbiodegradable, adsorbable component or phenol as a chemical which both biodegrades and adsorbs.; The results of the investigation indicate that bacteria play a primary role in removing biodegradable materials but have the potential of significantly restricting or eliminating the adsorptive processes. Preliminary indications of a biosorptive mechanism were observed, but the capacity was small. This capacity was found to be an inverse relationship with the subtrate loading rate. Further, bioregeneration of carbon may be achieved through desorption of organics resulting from influent concentration variations, but distruction of generally nonbiodegradable organics through biochemical processes was not verified.; In summary, it appears that if a water contains a high level of biodegradable organics, the benefits of biological activated carbon become minimal compared to biological filtration. If not, the bacteria present within the reactor can provide improved adsorptive capacity and a degree of carbon regeneration; the latter benefit being aided by influent concentration variations.