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Online control of fixed-bed reactors applied to aerobic wastewater treatment

Final Activity Report Summary - ONCOFIRE (Online control of fixed-bed reactors applied to aerobic wastewater treatment)

Biological wastewater treatment and other processes using microbes to degrade noxious effluents or to produce compounds of industrial interest are well developed in our industrial society. In comparison to other reactor designs, i.e. pieces of equipment where the biological reaction takes place, fixed-bed biological reactors are of major interest for treating wastewater. In this reactor design, the microbial biomass that is in charge of the process is fixed on an inorganic carrier. Fixed-bed reactors are difficult to characterise and control due to the complexity of the process and the sampling difficulty.

The aim of the project was to develop new methods for the characterisation of fixed-bed biomass. The proposed method was based on respirometry, which could be defined as the measurement of the oxygen uptake rate under controlled conditions. In particular, our project focussed on the measurement of the oxygen uptake rate after the injection of a pulse of substrate into the reactor. This method was called 'in-situ pulse respirometry'.

The main results obtained showed that the injection of substrate pulses was effectively achieved in suspended biomass reactors and allowed for the retrieval of seven stoichiometric and kinetic parameters which were all important for the process characterisation.

In case applied to fixed-bed reactors, the developed method was subject to some limitations. Indeed, we observed that the method could not be applied in reactors where the microbial growth generated non homogeneous hydrodynamic conditions. These application constraints were identified and were under analysis by the time of the project completion.