A comparison between exogenous carriers enhanced aerobic granulation under low organic loading in the aspect of sludge characteristics, extracellular polymeric substances and microbial communities

In this study, polymeric ferric sulfate (PFS), aluminum sulfate (AS) and diatomite were added to enhance the aerobic granulation under low organic loading rate (OLR) of 0.6 kg.COD/(m(3).d), and their effects of aerobic granule formation, extracellular polymeric substances (EPS) secretion and microbial community were investigated. The results showed that adding carriers could facilitated the growth of aerobic granules and improve the sludge settleability and biomass retention. Nutrient removal efficiencies were also enhanced. Compared with diatomite, adding PFS and AS resulted in more significant increase in EPS production, especially for the extracellular proteins. For microbial community, the dominated bacteria (Zoogloea, 18.47-23.95%) in the mature granular consortia were similar. Moreover, the introduction of PFS and diatomite contributed to the enrichment of Paracoccus, which was responsible for denitrification. Adding carriers potentially activated the functional genes related to metabolism and genetic information processing, and PFS had the most significant effects.

Automated summary

Adding polymeric ferric sulfate, aluminum sulfate, and diatomite can enhance aerobic granulation and improve wastewater treatment efficiency under low organic loading conditions. These carriers also increase the production of extracellular polymeric substances and influence the composition of microbial communities.