Biological treatment of effluents from a coal tar refinery using immobilized biomass

Abstract

AbstractAn airlift‐loop reactor with a fluidized bed was used for the microbiological removal of a complex mixture of aromatic substances originating from coal tar process waters. A specially adapted mixed microbial culture derived from several soil and sludge samples was immobilized on fluidized sand particles and retained in a reactor at high biomas concentrations of 3 to 16 g dry matter per liter, depending on the COD‐load. In a two‐stage pilot plant, those aromatic substances which passed through the first stage either unaltered or only partially oxidized were effectively eliminated by the immobilized biomass in the second stage. Whereas most of the waste water components such as phenols and quinoline were already degraded by a conventional activated sludge system in the first stage, the majority of nitrogen‐containing aromatic bases could be sufficiently eliminated with specially adapted micro‐organisms in the second stage. Although the COD‐feed load was increased to 12 and 15 kg m−3 d−1 in the first and second stages, respectively, it was removed to the extent of 87% on the average with an overall residence time varying between 11.5 and 29 h.