Preparation of Waterworks Sludge Based Ceramsite for Phosphorus Removal in Constructed Wetlands with Non-Sintering Method

Harmless disposal and reutilization of municipal solid attract growing interest due to the increasing waterworks sludge and limited landfill space. As a solid waste produced in the process of tap water treatment, waterworks sludge has been found to have excellent phosphorus adsorption capacity. However, it is often faced with problems such as difficult recovery and easy blockage in practical application. In this study, waterworks sludges composite ceramsite (WSCC) was made with waterworks sludges as main material, mixed with mineral powder, fly ash, and steel slag, and using cement as binder. The optimal ratio of WSCC was determined by mixture design: waterworks sludge=48,92%, cement=34.01%, mineral powder=8.35%, fly ash=5.69%, steel slag=2.85%. The SEM results showed the microporous structure of WSCC. Phosphorus adsorption of WSCC was more consistent with the pseudo-second-order kinetic model and Freundlich model. The calculated maximum P adsorption capacity of WSCC according to the freundlich model was 45.8mg/g. The morphological analysis of adsorbed phosphorus showed that Ca2+ and Al3+ play a significant part in phosphorus adsorption of ceramsite. In dynamic adsorption experiment, about 90% of the phosphorus was removed by WSCC with a hydraulic retention time (HRT) of 6 h. This study proposed a new preparation method of highly efficient phosphorus adsorption material and provided theoretical guidance for the harmless and resource utilization of urban sludge