Performance and Yeast Tracking in A Full-Scale Oil-Containing Paromomycin Production Wastewater Treatment System Using Yeast

High residual oil content in antibiotic production waste mother liquor makes solid–liquid separation of fermentation residue and wastewater difficult. A yeast-based pretreatment process was established for the removal of oil and promotion of solid–liquid separation in antibiotic production wastewater treatment systems. Six yeast strains acquired from different sources were inoculated into sequencing batch reactors (SBR) in pilot and full-scale wastewater treatment plants. Oil removal rates were 85.0%–92.0% and 61.4%–74.2%, and sludge settling velocities (SV) were 16.6%–21.3% and 22.6%–32.0% for the pilot and full-scale operations, respectively. 18S rRNA gene clone libraries were established to track the fates of the inoculated yeasts, which showed that Candida tropicalis was dominant in the full-scale plant. The fungi and bacteria gene copy ratio determined by quantitative polymerase chain reaction was 14.87 during stable field operation, indicating that yeast successfully colonized. Both the pilot and full-scale studies proved that yeast can be used to promote solid–liquid separation, and yeast systems are a stable and effective method for oil-containing fermentation antibiotic production wastewater pretreatment.