Sustainable Wastewater Management via Biochar Derived from Industrial Sewage Sludge

Sewage sludge (SS), mainly the residual, semi-solid, or slurry, produced as an offshoot in sewage treatment plants comprises nutrients like nitrogen, phosphorous, potassium, and organic matter and can have traces of fatal toxins which cannot be eliminated by employing conventional techniques. The thermochemical conversion of SS into biochar is a potential approach with the goal of sustainable recovery of resources, promoting a circular economy and minimizing disposal costs. This carbonaceous material has broad applications in the textile, food, chemical, oil, mining, and pharmaceutical sectors due to its ease of application, accurate efficiency, and monetary feasibility. Moreover, owing to their elevated chemical and physical properties offering high porosity, pore volume (0.053 mLg−1), and an additional surface area (~ 69.7 m2g−1), they account for an efficient adsorbent, enabling a circular economy. The present review discusses the application of SS-derived biochar as an efficient system for removing various toxic and fatal pollutants from water. The main focus of this review can be classified as (1) various production techniques employed for the production of SS biochar; (2) the indication of various modification techniques employed to attain optimum physicochemical properties; (3) the application of SS-derived biochar as an adsorbent for the removal of various toxic effluents which include emerging contaminants, dyes, and organic molecules dealing with its kinetics and isotherms; and (4) characterization stating its morphology and mineralogy along with various stages involved in the life cycle analysis to assess the production and contribution of materials and energies associated with it from the cradle to the grave. Graphical Abstract