Extension and application of the three-phase weak acid/base kinetic model to the aeration treatment of anaerobic digester liquors

Abstract

The kinetic model for the carbonate (inorganic carbon) system in three phases and the phosphate, short chain fatty acid and ammonia mixed weak acid/base systems in single phase, based on modelling the kinetics of the forward and reverse dissociation processes of the weak acid/base species, is extended to model the three-phase mixed weak acid/base chemical reactions in anaerobic digester liquor aeration. The kinetic reactions for ion pairing, precipitation of struvite, newberyite, amorphous calcium phosphate, calcium and magnesium carbonate and stripping of NH3 gas are added to the model. A preliminary validation of the model was done by comparing model predictions with an equilibrium based struvite precipitation model; and equilibrium experimental results from the literature on simultaneous precipitation of calcium and magnesium carbonate and phosphate minerals.

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