Which Characteristics Make Drinking Water Treatment Residuals a Low-Cost Adsorbent?

Millions of tons of Drinking Water Treatment Residuals (DWTR) are daily produced globally that mainly end up in landfills. The use of DWTR as an adsorbent for nutrients and emerging pollutants may become a sustainable option for this waste that can become a by-product. The aim of this study was to analyse seven DWTR with significant activated carbon content as adsorbents of phosphate ( \({\text{P}}{\text{O}}_{4}^{3-}\) ) and trimethoprim antibiotic (TMP). DWTR characterization showed that although all samples incorporated the same water treatment chemical reagents, the amount of it and the raw water characteristics resulted in differences in their chemical and physical characteristics. The \({\text{P}}{\text{O}}_{4}^{3-}\) adsorption studies showed that for a solid/liquid (S/L) ratio of 1.18 g/L, uptake capacities higher than 9 mg/g were achieved for most of the DWTR, while for TMP a S/L of 0.29 g/L achieved uptake capacities higher than 1 mg/g for some DWTR samples. In this study, it was possible to conclude that the \({\text{P}}{\text{O}}_{4}^{3-}\) adsorption is influenced by the Al and Ca content and the pHPZC, suggesting that highly alkaline DWTR have greater adsorption capacity. For TMP adsorption, DWTR surface area is important, however, further studies are required to identify key characteristics for TMP adsorption, including optimal dosage for removal optimization. The adsorption experiments in real samples demonstrated the potential of DWTR as an adsorbent for wastewater treatment.