Removal of nitrate from industrial wastewaters in a pilot plant by nitrate-tolerant klebsiella oxytoca CECT 4460 and arthrobacter globiformis CECT 4500

Degradation of different wastewater by a biological sponge iron system: microbial growth and influencing factors

The bio-ZVI process has undergone widespread development in wastewater treatment in recent years. However, there has been limited examination of the growth and degradation characteristics of functional microorganisms within the system. In the present research, strains were isolated and identified from the bio-ZVI system constructed by sponge iron (encoded as SFe-M). The consistency of operating conditions in treating different wastewater was explored. Three SFe-acclimated microorganisms exhibiting characteristics of degrading organic pollutants and participating in the nitrogen removal process were isolated. The adaptation time of these microorganisms prolonged as the substrate toxicity increased, while the pollutant degradation was related to their metabolic rate in the logarithmic phase. All these functional bacteria exhibited the ability to treat wastewater in a wide pH range (5-8). However, the improper temperature (such as 10 °C and 40 °C) significantly inhibited their growth, and the optimal working temperature was identified as 30 °C. The iron dosage had a significant impact on these function bacteria, ranging from 1 g L-1 to 150 g L-1. It was inferred that the SFe-acclimated microorganisms are capable of resisting the poison of excessive iron, that is, they all have strong adaptability. The results provide compelling evidence for further understanding of the degradation mechanism involved in the bio-ZVI process.

Interactions between nitrate assimilation and 2,4-dinitrophenol cometabolism in Rhodobacter capsulatus E1F1

The phototrophic, nitrate-photoassimilating bacterium Rhodobacter capsulatus E1F1 cometabolizes 2,4-dinitrophenol (DNP) by photoreducing it to 2-amino-4-nitrophenol under anaerobic conditions. DNP uptake and nitrate metabolism share some biochemical features, and in this article we show that both processes are influenced by each other. Thus, as was demonstrated for nitrate assimilation, DNP uptake requires a thermolabile periplasmic component. Nitrate assimilation is inhibited by DNP, which probably affects the nitrite reduction step because neither nitrate reductase activity nor the transport of nitrate or nitrite is inhibited. On the other hand, DNP uptake is competitively inhibited by nitrate, probably at the transport level, because the nitroreductase activity is not inhibited in vitro by nitrate, nitrite, or ammonium. In addition, the decrease in the intracellular DNP concentration in the presence of nitrate probably inactivates the nitroreductase. These results allow prediction of a negative environmental effect if nitrate and DNP are released together to natural habitats, because it may lead to a lower rate of DNP metabolism and to nitrite accumulation.