Very little is known about the interaction between dissolved and particulate organics in the fixed-film biological process used for wastewater purification, although this process has been used for many decades. The mechanisms for the removal of dissolved and particulate organics differ and it has been found that a large fraction of the organics in most wastewaters exists in particulate form.

In the experiments described here, the influence of particulate organics on the removal of glucose was studied in laboratory-scale fixed-film reactors. The particles used were starch particles and particles obtained from digested sewage sludge. The result of the experiments showed that for high glucose concentrations and high temperatures the removal of glucose was reduced when particles were adsorbed on the biofilm surface. A dramatic reduction was observed when large amounts of particles were adsorbed. This effect has also been observed in a full-scale trickling filter plant and in pilot trickling filters. At low glucose concentrations and low temperatures, however, a slight increase in glucose removal was observed when organic particles were adsorbed on the biofilm surface.

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