Abstract
Gibberellin wastewater cannot be directly discharged without treatment due to its high concentrations of sulfate and organic compounds and strong acidity. Therefore, multi-stage anaerobic bioreactor + micro-aerobic+ anoxic/aeration (A/O) + biological contact oxidation combined processes are used to treat gibberellin wastewater. However, knowledge of the treatment effects of the A/O process and bacterial community structure in the aeration tank reactors of such systems is sparse. Therefore, this study was conducted to investigate the treatment effects and operation of the A/O process on gibberellin wastewater, as well as changes in the bacterial community structure of activated sludge in the aeration tank during treatment. Moreover, removal was examined based on evaluation of effluent after A/O treatment. Although influent chemical oxygen demand (COD), NH3-N and total phosphorus (TP) fluctuated, effluent COD, NH3-N and TP remained stable. Moreover, average COD, NH3-N and TP removal efficiency were 68.41%, 93.67% and 45.82%, respectively, during the A/O process. At the phylum level, Proteobacteria was the dominant phylum in all samples, followed by Chloroflexi, Bacteroidetes and Actinobacteria. Proteobacteria played an important role in the removal of organic matter. Chloroflexi was found to be responsible for the degradation of carbohydrates and Bacteroidetes also had been found to be responsible for the degradation of complex organic matters. Actinobacteria are able to degrade a variety of environmental chemicals. Additionally, Anaerolineaceae_uncultured was the major genus in samples collected on May 25, 2015, while Novosphingobium and Nitrospira were dominant in most samples. Nitrosomonas are regarded as the dominant ammonia-oxidizing bacteria, while Nitrospira are the main nitrite-oxidizing bacteria. Bacterial community structure varied considerably with time, and a partial Mantel test showed a highly significant positive correlation between bacterial community structure and DO. The bacterial community structure was also positively correlated with temperature and SO42-.
Highlights
Plant hormones are essential intrinsic regulators of plant development and growth [1]
The highest influent chemical oxygen demand (COD) concentration of 772 mg/L was observed at 53 days
The effluent COD concentrations fluctuated between 50.29 and 76.45. These results indicate that removal efficiency changed with influent COD concentration
Summary
Plant hormones are essential intrinsic regulators of plant development and growth [1]. Gibberellins promote internode elongation and cambial activity of stems [2], and participate in the regulation of plant growth and development [3], including seed germination, stem elongation, flowering development, fruit growth, and root development. The raw materials and methods for production of gibberellin result in gibberellin wastewater containing high concentrations of sulfate, organic compounds, and NH3-N, as well as strong acidity. These features make wastewater difficult to treat; a highly efficient treatment is required before discharge to prevent pollution.
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