Hydrodynamic behaviour of full scale trickling filters

In the trickling filter process, knowledge of the hydrodynamic behaviour is essential for accurate mechanistic modelling. Numerous measurements includ ing the mean residence time, the free draining volume and the residence tim e distribution (RTD) have been performed in other studies. However, these r esults have often been obtained at pilot scale, and there is still a lack o f data for the full-scale process. In the present work, eight full scale pl astic-packed or stone-packed trickling filters receiving urban wastewater a re studied. The free draining volume and the mean residence time obtained a re used together with the literature data to find correlations. Despite the variety of operating conditions of the filters, correlations are establish ed for the stone-packed filters as well as for the vertical and random plas tic-packed filters. The RTDs were assessed from tracer experiments using in jections of lithium chloride. In order to explain the observed RTDs, an hyd rodynamic model is developed assuming that the tracer is transported by an axially dispersed plug flow and by diffusion in and out of the biomass. Mod el fitting permits to identify the volume of biomass and circulating liquid in the filter. (C) 2000 Elsevier Science Ltd. Ail rights reserved.