Pathogen reduction in an algal-based wastewater treatment system employing Galdieria sulphuraria

The feasibility of an algal-based wastewater treatment system employing an extremophilic alga, Galdieria sulphuraria, in removing dissolved organic carbon and nutrients from primary-settled wastewater has been demonstrated at pilot scale. Here, pathogen-reduction capability of this system was assessed and compared against that of an existing traditional wastewater treatment system (WWTS). While total coliform in the influent (2.3 x 10(7) CFU/100 mL) was reduced by 3.3 log units in the WWTS, no total or fecal coliform were detected in the algal effluent. Results of qPCR analysis confirmed 98% removal of total bacteria and complete removal of Enterococcus faecalis and Escherichia coli in the algal system. Illumina MiSeq sequencing showed diverse bacteria phyla (> 10 classifications) in the WWTS-effluent; but, only two classifications in the algal effluent. Bacteria kingdom relative to the entire microbial population declined from 99% to 83% in the WWTS; and to 17% in the algal system. Proteobacteria phylum (which includes mostly putative pathogenic bacterial genera) dominated the WWTS-effluent (abundance = 35%). Substantial alteration of the bacterial profile was observed in the algal system: Acidobacteria phylum being the most dominant (98%), and Proteobacteria, the least (2%). At the genus level, enteritis-causing Arcobacter species were detected only in the WWTS-effluent with a relative abundance of 0.9%.