Municipal Sewage Sludge Treatment

Currently 60% of total municipal sewage sludge produced in the USA remains unused and went to landfilling which contains high concentration of toxic heavy metals and pathogens. Because of the need for sustainable treatment of sewage sludge, I have investigated the hydrothermal liquefaction (HTL) of sewage sludge to transform this waste material into liquid fuel grade chemicals called biocrude oil. It was the initial work to open my research notebook for Ph.D. Journey. To improve the biocrude quality, I have synthesized a catalyst from red mud, an iron enriched industrial waste produced in alumina production process. .Another very important scientific contribution of this project was the use of gaseous hydrocarbon: ethylene, as reaction atmosphere for HTL reaction. Ethylene gas has increased biocrude production with greater stability which was not shown by any research work before. I have conducted all the HTL experiments with sludge, characterized the biocrudes and later documented all the results to publish in scientific journal. The next part of the project was to evaluate the effect of different solvents in biocrude extraction after sludge liquefaction with a subsequent upgrading process called hydrotreatment. Me and my colleagues worked closely on this part of project where I contributed by conducting HTL experiments, extracting biocrudes by different solvents and characterization of the products. We found that a widely used solvent named dichloromethane made the hydrotreatment process quite challenging due to catalyst deactivation, polymerization of biocrude, and equipment corrosion. Our recommended solvent was hexane which produced less biocrude but induced better fuel properties . The third part of this project was about the purification of the aqueous by product from sludge HTL by biochar from pyrolysis process. Here, I have provided the aqueous phase to my colleagues by running numerous HTL experiments, collected the data under his guidance and later contributed to his research article writing. We investigated the effect of temperature, pH, bio-char concentration, and mixing speed on two types of bio-char sorption of phenolic compounds. We have concluded biochar is a remarkable, low-cost sorbent for phenolic compound removal from wastewater.

Check the resulted publications:
- Hydrothermal liquefaction of municipal sewage sludge: Effect of red mud catalyst in ethylene and inert ambiences’, Energy Conversion and Management, Volume 245,01 October 2021, 114615. DOI: https://doi.org/10.1016/j.enconman.2021.114615

- Hydrotreatment of solvent-extracted biocrude from hydrothermal liquefaction of municipal sewage sludge’, Energy Conversion and Management, Volume 263, 01 July 2022, 115719. DOI: https://doi.org/10.1016/j.enconman.2022.115719

- Sorption and recovery of phenolic compounds from aqueous phase of sewage sludge hydrothermal liquefaction using bio-char’, Chemosphere, Volume 287, Part 1, January 2022, 131934. DOI: https://doi.org/10.1016/j.chemosphere.2021.131934