It is well-established that aquatic wildlife is exposed to natural and synthetic endocrine disrupting compounds which are able to interfere with the hormonal system. Although advanced oxidation processes (AOPs) have shown to be effective, their application is limited by a relatively high operational cost. In order to reduce the cost of energy consumed in the AOPs, widely available solar energy instead of UV light may be applied either as photocatalytic oxidation or as photosensitized oxidation. The main goal of the present study was to investigate the sunlight photodegradation of paraben mixture. Two processes, namely the photocatalytic oxidation with modified TiO2 nanoparticles and photosensitized oxidation with photosensitive chitosan beads, were applied. The oxidants were identified as singlet oxygen and hydroxyl radicals for photosensitized and photocatalytic oxidation, respectively. The toxicity, as well as ability to water disinfection of both processes under natural sunlight, has been investigated. Application of sunlight for the processes led to degradation of parabens. The efficiency of both processes was comparable. Despite the fact that singlet oxygen is weaker oxidant than hydroxyl radicals, the photosensitized oxidation seems to be more promising for wastewater purification, due to the possibility of chitosan bead reuse and more effective water disinfection. Graphical Abstractᅟ Electronic supplementary materialThe online version of this article (10.1007/s11270-018-3991-y) contains supplementary material, which is available to authorized users.

The aim of this study was to investigate the effect of hydrogen peroxide on the UVC photolysis of diclofenac (DCF) in aqueous solution. The experimental results confirmed very high effectivity of UVC direct photolysis of diclofenac. Moreover, it was found that H2O2/UV only slightly improved photodegradation; however, the addition of hydrogen peroxide into the reaction system affected the mechanism of DCF decomposition. Kinetics of the DCF reaction with ⋅OH radicals in the UV/H2O2 process was determined. For both processes, namely, photolysis and UV/H2O2, an in-depth analysis focused on the formation of phototransformation products of DCF (TPs) was performed. To the best of our knowledge, such comprehensive comparison of diclofenac photodegradation via UVC photolysis and UV/H2O2 has not been presented so far. Although there were no significant differences with regard to the rate of diclofenac degradation by photolysis and UV/H2O2, different oxidation products were found to be associated with the two considered processes. Furthermore, the H2O2/UV treatment increased toxicity towards Vibrio fischeri, while direct UVC photolysis had no significant effect on toxicity. The increase in toxicity can be attributed to the breakdown of DCF and formation of much more toxic TPs in the course of the H2O2/UVC process.

It is well established that aquatic wildlife in marine and freshwater of the European Union is exposed to natural and synthetic endocrine disruptor compounds (EDCs) which are able to interfere with the hormonal system causing adverse effects on the intact physiology of organisms. The traditional wastewater treatment processes are inefficient on the removal of EDCs in low concentration. Moreover, not only the efficiency of treatment must be considered but also toxicological aspects. Taking into account all these aspects, the main goal of the study was to investigate the photochemical decomposition of hazardous phenolic compounds under simulated as well as natural sunlight from the toxicity point of view. The studies were focused on photodegradation of 2,4-dichlorophenol as well as mixture of phenol, 2-chlorophenol and 2,4-dichlorophenol. Photosensitized oxidation process was carried out in homogeneous and heterogeneous system. V. fischeri luminescence inhibition was used to determine the changes of toxicity in mixture during simulated and natural irradiation. The photodegradation was carried out in three kinds of water matrix; moreover, the influence of presence of inorganic matter on the treatment process was investigated. The experiments with natural sunlight proved applicability of photosensitive chitosan for visible-light water pollutant degradation. The results of toxicity investigation show that using photosensitive chitosan for visible-light, the toxicity of reaction mixture towards V. fischeri has significantly decreased. The EC 50 was found to increase over the irradiation time; this increase was not proportional to the transformation of the parent compounds.