Start-up of a sequential anaerobic/aerobic batch reactor for the mineralization of p-nitrophenol

Abstract

The start-up of a sequencing batch biofilter integrating anaerobic and aerobic conditions, for the mineralization of P-nitrophenol (PNP) was studied. In this study a reactor packed with volcanic stones and inoculated with microorganisms from activated sludge processes treating municipal and industrial wastewater was used. The reactor was acclimated with a concentration of PNP of 25 mg/l during 75 days (25 cycles). The duration of the first two operation cycles was 8 days. As the bacterial population acclimated to the anaerobic/aerobics conditions, cycles duration was reduced to 40 h (30 h anaerobic stage and 10 h aerobic one). The PNP was transformed to p-aminophenol (PAP) in the anaerobic phase. The mineralization of PAP was found in the oxidative phase. Removal efficiencies of 100% were obtained for initial concentrations of 25 and 55 mg/l of PNP. In the reductive phase (anaerobic) 60% of biotransformation of the PNP to PAP was observed. In the aerobic phase the amines mineralization was 100%.