High-performance combined nitrification/denitrification processes: Scaling-up and modelling

Nitrification in airlift reactors on an industrial scale as well as the combination of nitrification and denitrification with immobilized systems (airlift/fluidized bed) have so far not been investigated. This paper looks at the preconditions for translating the results of basic laboratory and pilot plant studies on the subject into industry practice. This involves, in particular, taking into account the effects resulting from the combination of the two partial processes (e.g. introduction of biomass, COD and CO2 in nitrification, introduction of O2 in denitrification). The selection of a suitable substrate for nitrification, the performance curve of the nitrifiers in a combined plant, the activity loss caused by the stoppages inevitable in a food industry, and the identification of the bases for system modelling and scaling-up are discussed. Following the initial experiences with a pilot plant in the 1996 campaign, the plant was optimized and operated again in 1997. Moreover, a technical airlift reactor for the nitrification of sugar factory waste waters is presented. Concentration gradients, specific degradation performance and energy consumption are calculated for this reactor and its optimization potential considered. The reliability of the model is tested by varying the parameters.