Ceramsite made from drinking water treatment residue for water treatment: A critical review in association with typical ceramsite making

The use of ceramsite to construct filtration systems (e.g., biofilters) is a common method for water treatment. To promote such applications, the development of low-cost, high-performance, and environmentally friendly ceramsites has received increasing attention from scientists, and a critical step in the development is the preparation of raw materials. As an inevitable and non-hazardous by-product during potable water production, drinking water treatment residue (DWTR) is typically recycled to make water treatment ceramsite to promote recycling in filtration systems. This study aims to bridge the knowledge gap regarding DWTR in making ceramsites for water treatment. The results suggest that the fabrication methods for DWTR-based ceramsite can be generally classified into sintering and non-sintering procedures. For the sintering method, owing to the heterogeneous properties (especially aluminum, iron, and calcium), DWTR has been applied as various sub-ingredients for raw materials preparations. In contrast, for the non-sintering method, DWTR is commonly applied as the main ingredient, and natural curing, physical crosslinking, and thermal treatment methods have been typically adopted to make ceramsite. However, DWTR-based ceramsites tend to have a high adsorption capability and favorable microbial effects to control different kinds of pollution (e.g., phosphorus, nitrogen, and organic matter). Future work is typically recommended to thoroughly evaluate the performance of DWTR-based ceramsite-constructed filtration systems to control water pollution concerning the making procedures, the potential to control pollution, the stability, and the safety of raw DWTR-based ceramsite, providing systematic information to design more proper planning for beneficial recycling.