Characterisation of trickling filter effluent by particle size distribution and high performance size exclusion chromatography

Wastewater treatment objectives are still typically defined in terms of non specific parameters such as biochemical oxygen demand and total suspended s olids. However, wastewaters are a heterogeneous mixture of materials with a wide range of particle size and molecular weight, and most processes invol ved in treatment (sedimentation, mass transfer, adsorption, diffusion, bioc hemical reactions, filtration) are effected by particle dimension. This stu dy deals with the evolution;of the particular and dissolved content of synt hetic sewage during treatment. The experimental system consisted of a pilot -scale low-rate trickling filter, with and without secondary settlement, fo llowed by crossflow microfiltration (CFMF). In terms of particle size distr ibution (PSD), results show a shift towards larger particle sizes through b iological filtration, most of which can then be removed by settlement. Some fine particles remain and these can be removed by CFMF with a 0.1 mu m por e size membrane. High performance size exclusion chromatography (HPSEC) was used to study the evolution of the dissolved fraction of wastewater throug h treatment. Both PSD and HPSEC are shown to be valuable tools to assess th e performance of wastewater treatment processes. (C) 1999 Elsevier Science Ltd. All rights reserved.