Development and calibration of a new model for designing and optimising a new passive aeration system for the treatment of municipal wastewater.

Biofilm-based passive aeration systems (PAS) have attracted recent attention as alternative energy efficient and low maintenance technologies for the treatment of municipal wastewater. However the modelling of biofilm-based PAS offers unique challenges for modellers particularly where new technologies are not easily modelled using existing commercial modelling software. However, if the modeller is concerned only with modelling the effluent from the system it may be possible to model these technologies using surrogate unit process systems (eg using an activated sludge process to model a biofilm process). The pumped flow biofilm reactor (PFBR); a batch biofilm technology, is one such example of a passive aeration system. The PFBR is a two reactor technology that employs a unique hydraulic regime and enables aerobic, anoxic and anaerobic conditions to be sequenced. Biofilm, growing on plastic media modules within the two reactors, is aerated passively as wastewater is moved alternately between the reactors during an aeration sequence. Thus as the two reactors empty and fill a number of times during a typical aeration sequence, the biofilm is exposed, in turn, to atmospheric air and wastewater. Furthermore while the PFBR has many of the features of a sequencing batch reactor the fill and discharge from the system typically take place in Reactors 1 and 2 respectively.