[Role of Borate and Phosphate Buffers in the Degradation of Organic Compounds in a PMS/Co2+ System: Influencing Factors and Mechanisms].

Peroxymonosulfate(PMS)-based advanced oxidation processes were widely used for the degradation of organic pollutants. Electron-rich azo dye Acid Orange 7(AO7) was selected as the target organic matter in this work. The differences, influencing factors, efficiency, and mechanisms of a PMS/Co2+ homogeneous system in the degradation of organic pollutants with two different buffers of boric acid(Lewis acid) and phosphoric acid(Bronstede acid) were investigated. The k value of AO7 degradation in the PMS/Co2+ homogeneous system with phosphate buffer was greater than that with borate buffer, but the degradation percentage during the first 10 seconds of the reaction was lower in the former case. These differences were affected by buffer concentration, the PMS and Co2+ dosages, and pH. In the phosphate buffer, ·OH or SO4-· contributed to organic degradation in the PMS/Co2+ system, while in the borate buffer, the nonradical pathway(1O2) made a critical contribution to the removal of organics. This study provides a reference for the application of different types of buffers in the homogeneous catalysis of PMS.

Efficient inactivation of bacteria in ballast water by adding potassium peroxymonosulfate alone: Role of halide ions.

In recent years, ballast water disinfection has been paid much more attention due to the untreated discharged ballast water posing threaten of biological invasion and health related consequences. In this study, an effective and simple approach for ballast water disinfection by just adding potassium peroxymonosulfate (PMS) was assessed, and the role of halide ions in seawater on the enhancement of inactivation was revealed. The reactive species responsible for inactivation, the leakage of intracellular materials, and changes of cellular morphology after inactivation were evaluated to explore the inactivation mechanism. The results showed that Escherichia coli and Bacillus subtilis in ballast water could be totally inactivated within 10 min by adding 0.2 mM PMS alone. The inactivation of bacteria in ballast water fitted to the delayed Chick-Watson model. Chloride and bromide ion in seawater were found to play a crucial role in inactivating bacteria, while the effect of iodide ion could be negligible due to its relative lower concentration in seawater. Chlorine and bromine, produced by the reaction of PMS with chloride and bromide ion, were proved to be the main reactive components that were responsible for the inactivation of bacteria. The extracellular ATP and total nitrogen concentration increased after inactivation which indicated that cell membrane was destroyed by reactive oxidants produced by the reaction between PMS and halide ions. The change of cell morphology confirmed that bacteria were seriously damaged after inactivation. The results suggest that PMS is an attractive alternative disinfectant for ballast water disinfection and this application deserved further research.

Reactivation of fungal spores in water following UV disinfection: Effect of temperature, dark delay, and real water matrices.

The occurrence of fungi in water supply systems causes many environmental problems (e.g., odor, taste, turbidity, formation of mycotoxins); it has been an area of increasing concern in recent years. Ultraviolet irradiation can inactivate fungi efficiently. However, its reactivation poses further challenges in water purification. The reactivation characteristics of waterborne fungi under different environmental conditions have rarely been reported. In this study, the effects of temperatures and dark delay on the reactivation of three genera of fungal spores (Trichoderma harzianum, Aspergillus niger, Penicillium polonicum) were evaluated. The reactivation levels among these fungal spores were compared in phosphate buffer solution (PBS) and in real groundwater. It was found that lower temperature can inhibit the photoreactivation of fungi, whereas higher temperatures would promote the process. A long-term dark delay can inhibit the photoreactivation of fungi effectively. The dark repair of fungal spores almost do not occur neither in PBS nor in real groundwater. Finally, the photoreactivation percentage in real groundwater was higher than that in PBS. This study will provide a basis for controlling the reactivation of fungi in water.