Sustainable management of water treatment sludge through 3'R' concept

The handling and disposal of voluminous sludge produced from water treatment plant poses difficulty to environmental scientists and engineers. In fact, its environmental friendly management and disposal is a challenging task and requires careful consideration. This article covers the physicochemical characteristics of water treatment sludge and its toxicity to environment and explores various options of constructive sludge application that may reform the handling of such waste sustainably. Several reuse options have been identified and investigated globally such as; coagulant recovery and reuse, as coagulant in wastewater treatment, as adsorbent for contaminants and heavy metals, as substrate in constructed wetlands, in co-conditioning and dewatering of sewage sludge, in cement production, in brick and ceramic making, in manufacturing artificial lightweight aggregate, as cementitious material and sand substitute in preparing concrete and mortar, in agriculture practice and in land based applications. However, the properties of water treatment sludge in majority depend on the chemical compositions that are important while deciding its potential reuse. It is also important to note that the sludge generated at different processing steps of a treatment plant varies in physicochemical characteristics. Therefore, an updated database on quantitative and qualitative analysis results of water treatment sludge produced along with their current disposal practices is needed to prepare sustainable application guidelines for various reuse options. Further extensive investigations are required to find a steady and reliable source of the sludge, with minimal compositional variability for fearless and optimum utilization. Present review is focused on the beneficial reuse in various environmental settings. Wide and variable sludge utilization methods have been reviewed in depth with associated pros and cons. This document may help in developing some ideas of suitable sludge management strategies for sustainable development under stringent environmental norms.