Aerobic Granules and Activated Sludge Biomass Exposed to Lead and Erythromycin: A Comparative Study of Toxicity Assessment and Removal Efficiency

The present study was conducted to perform a comparative toxicity assessment on two configurations of activated sludge processes; one running in conventional sequencing batch (SBR) mode and the other operated in an aerobic granular SBR mode. The biomasses from both the reactors were subjected to synthetic wastewater consisting of 50 and 100 ppm of erythromycin and lead respectively. Further, both the systems were fed with diluted landfill leachate and struvite precipitated diluted leachate to check for removal of dissolved organics. When exposed to lead, granular system had a 14.3 % higher NH3; 99% higher PO43--P and 13.87% higher COD removal in comparison with conventional system. Toxicity effect of erythromycin was more evident in conventional system which was proven by 13.9% NH3 lesser; 98% lesser PO43--P and 37.3% COD lesser removal in comparison with granular system. Overall, conventional system was adversely affected during the shock loading. Activity of ammonia oxidizing bacteria (AOB) and polyphosphate accumulating bacteria (PAO) seemed to be inhibited by the presence of erythromycin incase of conventional system. Before spiking the biomasses with lead and erythromycin, microbial community analysis revealed a greater abundance of phylum Proteobacteria and Bacteroidetes in granular system. Fluorescent In-situ hybridization (FISH) analysis visually revealed the abundance of PAOs in both the systems responsible for phosphorous removal. Further, both the biomasses were tested against the landfill leachate toxicity and checked for removal of organics. Both the experiments depicted high level of sturdiness exhibited by granular system towards effect of external perturbations in comparison with the conventional system. It was also able to sustain and remove organics from the landfill leachate more effectively.