(393c) Optimization Based Selection of Industrial Biosolids Treatment and Valorization Pathways to Meet International Discharge Standards for Heavy Metals

Biosolids can be classified into residential or domestic sludge and industrial sludge. While residential sludge undergoes various reuse pathways, industrial bio-sludge typically ends up in landfill sites due to their heavy metal contamination. However, there exists multiple ways such as chemical extraction of heavy metals, absorption, microwave induced heavy metal removal, adsorption, and biosorption for treatment. At the same time, biosolids can be converted biochar, incinerated for energy production, or used in agriculture land application if it meets regulatory limits. These processes vary in cost, scale, efficiency of the process, energy, emissions, material, and energy demand. This work presents an optimization-based approach that screens different type of technologies for treatment and reuse of bio-sludge/biosolids with the objective of minimizing costs while adhering to the regulatory limits from various countries. A case study on industrial Gas-to-Liquid (GTL) waste biosolids was used to validate the proposed approach. The model identifies the cost optimal pathway of removing the heavy metal content off industrial biosolids to meet the ceiling concentration required. The biosolids then pass-through general treatment pathways which returns the biosolid contents as value added products which can be used as fertilizer or sold to other entities.