The increasing discharge of emerging contaminants (ECs) such as zinc oxide nanoparticles (ZnO NPs) and degradable microplastics (DMPs) into aquatic environments poses a growing challenge for next-generation wastewater treatment technologies. This study investigates the individual and combined effects of ZnO NPs, polylactic acid (PLA), and polycaprolactone (PCL) microplastics on microalgal-bacterial granular sludge (MBGS), a promising low-energy biotechnological system. Using photosequencing batch reactors, changes in extracellular polymeric substances (EPS), chlorophyll content, and microbial activity were monitored across multiple exposure scenarios. The results revealed significant, concentration-dependent alterations. While low-dose exposures (5 mg/L) to individual contaminants marginally stimulated ammonia oxidation or algal growth, combined exposures, especially ZnO+PCL and ZnO+PLA+PCL, induced synergistic inhibitory effects. EPS protein fractions decreased by up to 82%; chlorophyll content decreased by 52%, and specific ammonia and phosphorus uptake rates were reduced by more than 60% at a concentration of 10 mg/L. Principal coordinate analysis (PCoA) confirmed the pronounced system-level perturbations under mixed contaminant stress. These findings underscore the ecological vulnerability of MBGS to co-occurring ECs and highlight the need for pollutant-specific resilience strategies in the design and operation of sustainable wastewater technologies.
Kedves et al. (Fri,) studied this question.