Biomass accumulation modelling in a highly loaded biotrickling filter for hydrogen sulphide removal

A pilot scale test on a biotrickling filter packed with polyurethane foam cubes was carried out for 110 d at high volumetric mass load (up to 280 g m(bed)(-3) h(-1)) with the aim of studying the accumulation of solids in the treatment of H(2)S. Removal rate up to 245 g m(bed)(-3) h(-1) was obtained; however, an accumulation of gypsum, elemental sulphur and, above all, inert biomass was identified as the cause of an increased pressure drop over the long term. A mathematical model was applied and calibrated with the experimental results to describe the accumulation of biomass. The model was capable of describing the accumulation of solids and, corresponding to a solids retention time of 50 d, the observed yield resulted in 0.07 g of solids produced g(-1) H(2)S removed. Respirometric tests showed that heterotrophic activity is inhibited at low pH (pH < 2.3), and the contribution to biomass removal through decay was negligible.