Biovalorization of biosolid from wastewater treatment plant for production of biofuels and biomaterials

Abstract

Wastewater treatment plant (WWTP) sludge, once considered waste, is now recognized for its potential in bioenergy production, bioremediation, and catalytic applications due to its neutral pH, high organic content, and presence of essential nutrients and trace metals. This study investigates the use of WWTP sludge by isolating microbial strains and developing innovative catalytic materials. Bacterial strains such as Bacillus circulans and Burkholderia sp., enriched in minimal salt medium (MSM), demonstrated the ability to degrade complex polymers like lignin, cellulose, and hemicellulose, which are essential for biofuel production. The Tedlar bag method was used to analyse biogas from medium-scale digesters, confirming methane-rich biogas, supporting the use of anaerobic digestion for renewable energy. A novel heterogeneous catalyst was developed by immobilizing lipase on calcite and DigSBiochar for biodiesel production via transesterification. The materials were characterized using Fourier transform infrared spectroscopy (FTIR) for functional groups, energy dispersive spectroscopy (EDS) for elemental composition, and field emission scanning electron microscopy (FESEM) for surface morphology. The results showed improved stability and reusability of the catalyst, making it suitable for biodiesel production. Additionally, the fatty acid methyl ester (FAME) profile of the sludge revealed a high cetane number and an optimal ratio of monounsaturated to polyunsaturated fatty acids, confirming its viability for biodiesel. Furthermore, a bio-composite (DigSBiochar + calcite + Burkholderia sp.) achieved 95% efficiency in decolorizing methyl red dye under optimal conditions (pH 9, 40°C, 500 ppm). These results demonstrate the significant potential of WWTP sludge for sustainable bioenergy and environmental remediation. Future research should aim to enhance catalyst durability and recyclability in biofuel production. newline