A review of the adsorption-biological hybrid processes for the abatement of emerging pollutants: Removal efficiencies, physicochemical analysis, and economic evaluation

Highlights: • Adsorption/biological hybrid technologies enhance micropollutants removal. • Considered configurations: PAC-MBR, PACT/GAC-CAS and BAC • Partition coefficient and polarity influence the performance of hybrid techniques. • PAC-MBR and PACT have the highest efficiencies, although PACT is more cost effective. • Removal percentages above 80% were achieved for most of the studied compounds. The limited efficiency of conventional wastewater treatment plants (WWTPs) in emerging pollutants (EPs) removal encourages the development of alternative technologies for the adequate treatment of wastewater, due to its adverse effects on human health and ecosystems. The biological, physical or chemical hybrid technologies to treat EPs results interesting since they can enhance the performance of WWTPs. Among them, hybrid adsorption/biological technology could offer different possibilities that are explored in this work (PAC-MBR, PACT/GAC-CAS, BAC configurations). In this way, different variations in the adsorption process have been considered: the form of the adsorbent, the feed to the system, and the type of biological process, either conventional activated sludge (CAS), membrane bioreactor (MBR) or biofilm systems. For each combination, the removal efficiency of micropollutants, classified according to their use into pharmaceuticals, personal care products (PCPs) and other micropollutants (mainly benzotriazoles) was analysed. From reported data, it was observed a beneficial synergistic effect of dipole moment and octanol–water partition coefficient on the removal efficiency of micropollutants by adsorption/biological hybrid technology. Finally, a preliminary economic evaluation of the powdered activated carbon in a conventional activated sludge reactor (PACT), powdered activated carbon-membrane bioreactor (PAC-MBR) and biological activated carbon (BAC) hybrid systems was carried out by analysing the capital expenditure (CAPEX) of plants for capacities up to 75,000 m³d⁻¹. Likewise, estimations of adsorbent concentration for a hypothetical plant with a capacity of 10,000 m³d⁻¹ is presented. Among these hybrid configurations, PAC-MBR achieved the highest micropollutant elimination percentages; however, it presents the highest CAPEX and activated carbon requirements.