Characterisation, remediation and valorisation of contaminated sediments: a critical review

The constraints associated with the availability of huge amounts of natural resources for infrastructure and agricultural development call for the reuse and recycling of anthropogenically created geomaterials, which is in line with the UN Sustainable Development Goals. In this context, valorisation of dredged sediments (DSs), obtained from water bodies such as rivers, lakes and oceans, as a resource material is worth considering. Unfortunately, DSs might be contaminated and exhibit a higher moisture-holding capacity due to higher contents of organic matter and clay minerals/colloids. These attributes pose a serious question towards dumping of DSs in the deep sea (in the case of marine sediments), a practice that prevails presently despite endangering marine life. Hence, the way forward would be to characterise them holistically, followed by adequate treatment to make them ecologically synergetic before developing a strategy for their valorisation. In this regard, many studies have been focused on the characterisation and treatment of DSs to make them an environmentally safe man-made resource. With this in mind, a critical synthesis of the published literature pertaining to the (a) characterisation; (b) treatment, remediation and immobilisation of contaminants; and (c) utilisation of DS was conducted, and the salient findings are presented in this paper. Based on this study, it was observed that DS acts as a sink for emerging contaminants for which no remediation strategies are available. Moreover, the study emphasised the lacuna in upscaling the existing treatment and stabilisation techniques to field conditions while highlighting the concept of circular economy.