Key factors related to drinking water treatment residue selection for adsorptive properties tuning via oxygen-limited heat treatment

The beneficial recycling of drinking water treatment residue (DWTR) for environmental remediation has attracted growing attention, and oxygen-limited heat treatment has a high potential to improve DWTR adsorptive properties for better recycling. In this study, physicochemical property variation induced by oxygen-limited heat treatment was evaluated for six DWTR obtained from different drinking water treatment plants in Australia, China, and Ireland. The results showed that the changes in many properties, typically amorphous Al and Fe contents, mesopores, specific surface area (SSA), and total pore volume (TPV) of DWTR after treatment, showed inconsistent trends. The treatment also led to the varied lability of metals and As in DWTR although the human bioaccessibility and plant bioavailability of most metals decreased. Accordingly, oxygen-limited heat treatment may not be applicable for all DWTR improvement. Based on these findings, pre-screening processes to evaluate adsorptive properties and metal and metalloid lability were determined. Oxygen-limited heat treatment was more applicable to DWTR with neutral and weak alkaline properties (pH 7.0-7.8), low humic acid (HA) content (<2.09 mg g−1), and high amorphous Fe and HA ratio (>5.93), as well as with relatively high amorphous Al and HA ratio and high humin content.