Treatment of drinking water sludge through co-calcination with calcium carbide residue

Drinking water sludge (DWS) is a byproduct of urban water production, generated in large quantities. Utilizing DWS in building materials through calcination offers a sustainable solution. However, DWS calcined alone shows low reactivity, limiting its effectiveness. To overcome this limitation, this study examines the co-calcination of DWS with a calcium-rich industrial byproduct, calcium carbide residue (CCR), enhancing the transformation of DWS into active components. This study investigated the effects of calcination duration, temperature, and the DWS/CCR ratio on the production of active ingredients. Additionally, the performance of Portland cement (OPC) paste containing a 10 % calcined DWS-CCR mixture was evaluated. Results suggest that co-calcination generated reactive, calcium-rich amorphous phases , with an optimal calcination temperature of 1000–1100 °C. Extending calcination from 0.5 to 1.0 h significantly increased reactivity. Incorporating a 10 % calcined DWS-CCR mixture into OPC paste improved compressive strength by 10.6 % after 90 days, reduced large pores, and promoted formation ettringite and C-A-S-H gels. Moreover, DWS-CCR mixture shows a reduced CO₂ intensity and approximately 64.2 % lower costs compared to OPC, underscoring the positive environmental impact and market potential of utilizing the calcined DWS-CCR mixture. This study has identified a new direction for the treatment of DWS. • A novel co-calcination method for treating drinking water sludge (DWS) is proposed • Co-calcining DWS and calcium carbide residue (CCR) forms more reactive phases • 10 wt% DWS-CCR addition raises cement paste strength by ∼10 % after 90 days • DWS-CCR reduces cement pore volume, promoting ettringite and C-A-S-H formation • DWS-CCR yields lower CO₂ intensity, reducing concrete CO₂ emissions