Model-based design and operation of biotrickling filters for foul air H2S removal at wastewater networks

Biotrickling filters (BTFs) are odour control technologies that utilise the action of sulfur oxidising bacteria to treat foul air contaminated with H 2 S. BTFs are complex systems where an immobilised biofilm is allowed to grow on a supportive solid media, while the foul air flows counter-currently with a stream of trickling liquid. In this work, a mechanistic model is developed, based on first principles where applicable, that describes the interphase mass transfer and biological oxidation kinetics. The model also focuses on the spatial discretisation of a BTF bed and describes the competition between sulfur oxidising bacteria (SOB) and aerobic heterotrophs growing within different niches of the bed. The model successfully produced concentration profiles over time and space of all relevant chemical and biological species within the bed. The model was then used to theoretically investigate the effect of design and operating parameters on the bed performance. It was found that the optimum liquid rate could vary significantly based on other factors such as bed size and inlet H 2 S concentrations but a typical value lies between 0.3 and 1.3 m/hr, with a larger bed and/or higher H 2 S loads requiring higher loading rates to achieve the same treatment levels. The model also predicted that bed shape has no significant impact on H 2 S removal, provided all other conditions are the same. The model successfully allowed for more detailed design of industrial BTF units in terms of both sizing and tuning of operational parameters. • Mechanistic model describes dynamic profiles along biotrickling filters bed depth. • The model uses first principles, mass transfer and microbial kinetic competition. • The model describes the effect of changing design parameters on process performance. • An optimum liquid seems to exist interdependent on factors such as H 2 S load. • A tradeoff appears between bed volume and liquid loading with no bed shape effects.