Numerical modeling of aerobic bio-phosphorus removal by phosphorus accumulating organisms using coupled lattice Boltzmann method and cellular automata platform

The removal of phosphorus (P) from wastewater is important to reduce water pollution and potential eutrophication in surface waters. In previous studies, the multilateral interactions of biofilm growth and spatiotemporal concentrations of species were not considered or not affected by flow field and reaction rates. To fill some important parts of these gaps, an integrated platform of lattice Boltzmann method and cellular automata was developed to model the spatiotemporal nutrient transport and biofilm growth of an enhanced bio-phosphorus removal process in a T-shaped bioreactor. The model was validated against the data available in the literature. The effects of different dissolved oxygen concentrations and fluid velocities were investigated. The results showed that increasing the velocity ratio decreased the biofilm growth, leading to a decrease in the polyphosphate concentrations in the bioreactor. There was a difference of up to 33.9 % between the lowest normalized biofilm concentration and the highest one. Increasing dissolved oxygen concentrations through the primary inlet produced more biofilm in the bioreactor, especially in its bottom zone, than that through the secondary inlet. It is also found that there is a specific biofilm concentration threshold. After the threshold, the biofilm growth and the biochemical reaction rates decreased, leading to a decrease in the phosphorus removal rate and an increase in phosphorus concentration. This study demonstrates the LBM-CA model could improve our understanding of biological P-removal and help to optimize and improve the efficiency of such operations.