Valorization of undervalued aluminum-based waterworks sludge waste for the science of “The 5 Rs’ criteria”

Abstract

Alum sludge (AS) is an underrated by-product waste resulted from treating raw water through conventional water treatment plants. Water is attained from various reservoirs such as rivers and aquifers, and it may contain a wide variety of contaminants as drinking water processing systems produce “waste” sludge as a residual material that causes significant environmental issues. Hence, numerous efforts aimed to sustainable reuses of such sludge. This article illustrates the beneficial reuses of the aluminum-based sludge to close the loop between the sludge waste generation and the sustainable environment with providing past, current and updated knowledge with the introduced uses with their advantages and challenges. Alum sludge as a resource not as a “waste” for reuse facilities is considered a value-added alternative for management achieving the legislation requirements and proposing “end-of-waste” concept. 5Rs, including “Reduce, Reprocess, Reuse, Recycle and Recover,” are providing sustainable solution to fulfill present and future aspects for green environment and safe sludge disposal. In this regard, now, it is essential to focus and adopt the 5Rs criteria for the concept of circular economy that replaces the “end-of-life” principal with restoration.