Modeling phosphate transport and removal in a compact bed filled with a mineral-based sorbent for domestic wastewater treatment

摘要

Phosphorus filter units containing mineral-based sorbents with a high phosphate (PO_4) binding capacity have been shown to be appropriate for removing PO_4 in the treatment of domestic wastewater in on-site facilities. However, a better understanding of their PO_4 removal mechanisms, and reactions that could lead to the formation of PO_4 compounds, is required to evaluate the potential utility of candidate sorbents. Models based on data obtained from laboratory-scale experiments with columns of selected materials can be valuable for acquiring such understanding. Thus, in this study the transport and removal of PO_4 in experiments with a laboratory-scale column filled with a commercial silicate-based sorbent were modeled, using the hydro-geochemical transport code PHREEQC. The resulting models, that incorporated the dissolution of calcite, kinetic constrains for the dissolution of calcium oxide (CaO) and wollastonite (CaSiO_3), and the precipitation of amorphous tricalcium phosphate, Ca_3(PO_4)_2, successfully simulated the removal of PO_4 observed in the experiments.