Investigation of Para-nitrophenol Biodegradation in Shake Flasks and External Airlift Bioreactor by Alcaligenes faecalis

Abstract

In this study, removal of para-nitrophenol (PNP) from synthetic wastewater by Alcaligens faecalis was investigated for the first time in an external airlift bioreactor. The effect of factors such as pH (6, 7 and 8) and nitrogen source (yeast extract, peptone and urea) as well as initial PNP concentration (50, 75, 100 and 125 mg/lit) on PNP removal and bacterial growth was first examined in shake flask experiments. Then, performance of airlift bioreactor was studied at various aeration rates (1, 2 and 4 l/min) and initial PNP concentrations (50, 75 and 100 mg/lit). In shake flask experiments, yeast extract and pH value of 8 led to the highest bacterial growth and PNP removal. In all bioreactor experiments, PNP removal was higher and biodegradation time was lower compared to shake flask experiments. The maximum of 40 and 60% PNP removal were obtained in shake flask and bioreactor experiments at 50 mg/l initial PNP concentration respectively. Among examined aeration rates, 2 L/min resulted in the highest PNP removal percentage at all initial PNP concentration.