Effects of size and spacing of basalt fiber carrier media on performance, extracellular polymeric substances and microbial community of hybrid biological reactors

Carrier media play a key role in microbial activity, biomass amount, microbial community and mass transfer, and hence the process performance in biological wastewater treatment. In this work, a green basalt fiber (BF) carrier medium was introduced into hybrid sequencing batch reactors (SBR) to determine the effects of two important engineering parameters (carrier size and spacing) on the wastewater treatment performance. Extracellular polymeric substances (EPS) and deoxyribonucleic acid (DNA) extracted from the BF-based bio-nest were analyzed to give further insight into the mechanisms. The results show that with a carrier size of 15.0 cm and spacing of 14.0 cm the reactor had more nitrifying and denitrifying bacteria as well as an appropriate protein/polysaccharide ratio (PN/PS), leading to slightly higher removal efficiencies of chemical oxygen demand (COD) and total nitrogen (TN) in wastewater. This study on the effects of carrier size and spacing provides implications for bioreactor construction when using BF carrier media in wastewater treatment.