Biochar potential for long-term pharmaceutical remediation in flow-through tertiary wastewater systems

Wastewater treatment plants are not designed to remove pharmaceuticals from wastewater and upon release pharmaceuticals end up in the environment. This study investigated the adsorption capacity of five different biochar materials under dynamic flow conditions utilising a packed bed column test. Tertiary wastewater effluent was used to evaluate the breakthrough of the biochar columns. Two conditions were tested during this experiment: (i) biochar remediation under high pharmaceutical loads, where wastewater was spiked with 16 pharmaceuticals; and (ii) biochar remediation under normal working conditions, where 42 non-spiked pharmaceuticals were evaluated. The concentrations of pharmaceuticals were measured over 45 weeks (635 bed volumes), and the adsorption capacity was assessed by plotting relative concentration against bed volumes. The results show a high adsorption efficiency (>99 %) for the sewage sludge and forest biomass biochar, emphasising the role of packing density, feedstock and physicochemical properties of the biochar. Furthermore, fitted breakthrough curves allowed for the assessment of the adsorption capacity of individual pharmaceuticals. The results demonstrate a strong correlation between the charge and molecular size of pharmaceuticals and their adsorption capacity. This study provides key insights into the remediation potential of biochar for the removal of pharmaceuticals in wastewater effluent.