The competitive adsorption of pharmaceuticals on granular activated carbon in secondary effluent

The competitive adsorption characteristics of four pharmaceutical compounds, including clofibric acid (CA), carbamazepine (CBZ), naproxen (NAP), and diclofenac (DCF), were evaluated on granular activated carbon in secondary effluent. In ultrapure water (UW), the adsorption efficiencies of CA, CBZ, NAP, and DCF on coconut shell-based carbon were 63.0, 85.5, 79.1, and 68.8%, respectively, at initial concentration of 500g/L and carbon dosage of 133mg/L. All the substrates could be removed completely when carbon dosage was increased to 250mg/L. In the secondary effluent from a real wastewater treatment plant, the removal of four pharmaceuticals were decreased to 26.9, 57.9, 44.7, and 31.0%, respectively, with carbon dosage of 250mg/L, which recovered to 39.6, 67.1, 53.4, and 48.1% after solution filtration by 0.22-m hydrophilic membrane. The suspended solids and soluble organic compounds in wastewater were considered as the key inhibited factors for pharmaceuticals adsorption by activated carbon. The differences of adsorption efficiency between spiked UW and secondary effluent demonstrate that further purification for secondary effluent is necessary in practical wastewater treatment, when activated carbon is used as adsorbent for pharmaceuticals removal and wastewater advanced treatment.