Sustainable approach to biotransform industrial sludge into organic fertilizer via vermicomposting: a mini-review

Currently, industrial sludge is generated in large amounts. Industrial sludge is a solid or semi-solid material consisting of all compounds removed from wastewater, as well as any substances added to the biological and chemical operation units during the treatment process. The composition of sludge may vary considerably. Furthermore, distinctive treatment and disposal methods are necessary as sludge produced from different industries has different characteristics. Therefore, processing and disposing of industrial sludge is a challenging and complex environmental problem. Landfilling, incineration and agricultural land application are the three most commonly employed methods for the disposal of industrial sludge. Among the three methods, the agricultural land application is a convenient and economical disposal alternative for industrial sludge. However, industrial sludge could have high putrescible content and pathogenic hazards. One possible way to ensure that the industrial sludge could be reused on agricultural land is by conditioning and stabilizing the sludge using a pretreatment process. One of the pretreatment processes which could be employed in this context is vermicomposting. Vermicomposting is an alternative for biological stabilization of organic wastes, with the addition of earthworms. Through vermicomposting, industrial sludge could be transformed into matured organic fertilizer or vermicompost in a shorter period. Thus, this work reviewed the recent literature on utilizing the vermicomposting process to manage industrial sludge in order to assess the feasibility of this technology. The present review also provides a brief overview of the production and treatment methods of industrial sludge.