Performance and Life Cycle Assessment of Bioreactors Packed with Recycled PVC Granules and Luffa Fibers for Dairy Wastewater Treatment

Conventional biological systems increasingly struggle with stricter discharge limits, high energy consumption, and carbon footprint, creating an urgent need for advanced sustainable wastewater treatment technologies. Thereby, the current study addresses this critical gap by conducting a holistic comparative assessment of innovative systems, a luffa fiber-packed bioreactor (LFPB), and a recycled PVC granule-packed bioreactor (RGPB). The operational parameters, including hydraulic retention time (HRT), aeration time, aeration intensity, and the COD/P ratio, were systematically optimized for COD, nitrate, and phosphorus removal from dairy wastewater. Their life cycle assessment (LCA) and carbon footprint were also quantified, ensuring alignment with sustainability goals. The RGPB illustrated superior stability and attained maximum removals of 82.44, 57, and 54.98% for COD, nitrate, and phosphorus under low-energy conditions, HRT of 3 h, 25 min aeration time, and a COD/P ratio of 75. However, the LFPB at the same HRT and COD/P ratio required a high aeration intensity and 35 min aeration time to achieve comparable COD removal of 82.4%, resulting in 76% higher energy consumption. In the pursuit of environmental sustainability, the RGPB significantly outperformed the LFPB across all environmental impact categories, indicating 55.6% lower global warming potential and 59.3% lower fossil resource scarcity, owing to its reduced energy demand. The RGPB benefited from 14 to 56% lower negative impacts on human health and resources, which was confirmed with uncertainty analysis. The findings substantially underscored a sustainable pathway toward circular wastewater treatment management and waste recycling using recycled PVC waste as a high-performance biocarrier.