RESUMO
Non-reactive phosphorus (nRP) contains condensed phosphates and organic phosphorus (OP) species that are recalcitrant in secondary wastewater treatment and tend to remain in final effluents. To meet ultra-low effluent P discharge limits, persistent nRP must be removed. The objective of this study was to evaluate the use of an advanced oxidation process (AOP) which couples TiO2/UV photolysis with ultrafiltration to oxidize and remove nRP species. Initial tests utilized OP model compounds, adenosine triphosphate (ATP) and aminoethylphosphonate (AEP), in a binary mixture to evaluate AOP treatment and to elucidate possible mechanisms of phosphorus removal. The results were consistent with a model of preferential ATP binding to the TiO2 surface compared to AEP. On UV light exposure, AEP was removed from solution due to the photooxidation of ATP freeing up binding sites for AEP adsorption and subsequent oxidation. Orthophosphate released during AOP treatment was retained on the TiO2 solids. The AOP was applied to three municipal wastewaters and one automotive industry effluent for P removal. In all cases, phosphorus removal was found to occur through filtration, surface complexation and UV oxidation. Total phosphorus removal efficiencies between 90 and 97% were observed for the municipal wastewater effluents and 44% removal was observed in the industrial effluent after treatment using AOP.