ABSTRACT
This chapter describes the technical feasibility of single stage autotrophic nitrogen removal over nitrite using sponge-bed trickling filters (STF) under natural air convection. The research is focused on developing autotrophic nitrogen removal using activated sludge as inoculum, achieving a short start-up period. After a successful start-up, the STF reactors may be operated without mechanical aeration control systems, whereas a high nitrogen removal at a small footprint is expected. Activated sludge from the Harnaschpolder wastewater treatment plant was used for the inoculation of STF reactors. The sponge layers were properly saturated with synthetic wastewater and the activated sludge was aerated during 10 minutes prior to inoculation. The STF or “extended down-flow hanging sponge” bioreactor is a promising technology that could be coupled to an Upflow Anaerobic Sludge Blanket reactor to develop a cost-effective post-treatment system for ammonium removal provided extensive organic matter removal is achieved upstream.
