Biological treatment of the refractory gardenia-yellow-manufacturing wastewater and microbial community shift in A/O reactors.

Treatment of wastewater from natural-pigment-manufacturing process is a challenge due to its complex composition and recalcitrance. This study investigated the use of biological method to degrade high-concentration gardenia-yellow-manufacturing wastewater (GYMW) in a laboratory and then applied the anaerobic-aerobic (A/O) process in pilot- and full-scale plants. The maximum anaerobic volume load reached 6 kg chemical oxygen demand (COD) m_-3 d in laboratory and 5.5 kg COD m_-3 d in full-scale reactor, while the COD removal efficiency was consistently above 90%. Singlefactor control experiments were conducted in sequencing batch reactors to examine the factors that have an influence on the anaerobic treatment, which is responsible for the majority of COD removal. After adjusting the operating temperature, pH, and influent COD, the effluent COD further decreased by 300 mg L_-1. In addition, high-performance liquid chromatography, which was used to analyze the main contaminants in GYMW, confirmed that the toxic geniposide was considerably reduced. The high-throughput sequencing analysis illustrated that, under the selective pressure from GYMW, the microbial community structure can degrade biorefractory pollutants enriched in the A/O reactors and contributed to the satisfactory performance of GYMW treatment. [ABSTRACT FROM AUTHOR]