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Anthracene and phenanthrene belong to a group of persistent environmental contaminants called PAHs. Evaluation of the structure of two selected PAHs i.e. anthracene and phenanthrene on their resistance to destruction by UV-activated PDS was the aim of this study. The authors focused on two aspects of this problem: - the role of the so-called ‘bay-region’, in the structure of phenanthrene, during PDS/UV oxidation - formation of substituted forms of these PAHs in the absence and presence of three nitrogen-containing compounds i.e. ammonia and nitrite or nitrate ions. Even though phenanthrene and anthracene have the same molecular formula, the difference in their ring assessment influences their degradability. Considering all the results, in all the cases anthracene was degraded faster and/or had a higher degradation rate. That proves phenanthrene to be more stable and resistant for degradation however comparison of PDS/UV systems vs. UV– irradiation alone confirms that the addition of PDS accelerates the degradation of anthracene and phenanthrene. Comparison of PDS/UV with the addition of three different nitrogen-containing compounds showed a significant difference between anthracene and phenanthrene. In the experiments with phenanthrene were observed additional peaks with an absorption maximum between 230-240 cm-1 which is characteristic of the nitro-group. Based on their absorption maximum and the addition of nitrogen-containing compounds, emerging by-products are assumed to be nitro-derivatives of phenanthrene. The results of GC/MS analysis suggest the possibility of formation of many compounds which can be formed from phenanthrene and are embedded on its skeleton. These analyzes also suggest the rearrangement of phenanthrene’s aromatic rings and formation new compounds.

In this study, the aerobic and anaerobic biodegradability of the industrial wastewater from the vegetable tanning process were evaluated. Water from a food wastewater treatment system was used as seed inoculum for the aerobic process and mature granular methanogenic sludge from a brewery industrial wastewater plant was used for the anaerobic process. The water from the tanning industry had a biological to chemical oxygen demand ratio of 33% with values of total chemical oxygen demand (COD) in the range of 342000 mg O2/L and total dissolved solids of 506595 mg/L. The assay of the tannery effluent under aerobic conditions resulted in a decrease of COD of 39.2% and a degradation of tannins lower than 12% after 26 days, while the anaerobic degradation showed a COD reduction of 65% with a 39% of degradation of tannins. The production of methane and Volatile Fatty Acids, during the anaerobic treatment, suggests a potential adaptation of biological organisms present in the mature anaerobic granular methanogenic sludge.

In the current study, three different photo-assisted sources were used to evaluate the photo-Fenton oxidation process for the pollutant degradation of mature landfill leachate. Solar, UV, and LED visible light photo sources were adopted in this Fenton process. Fenton dosages (FeSO4 : H2O2) 1:30, 1.5:30, 2:30, and 2.5:30g/L were used in the investigation, which was conducted under a variety of pH settings (2 to 3.5) and at experimental reaction duration of 30, 60, 90, and 120 minutes. To analyze and compare the efficiency of the solar, UV, and LED visible light photo Fenton processes for pollutant degradation, Taguchi experimental design orthogonal arrays (L16) was employed. To analyse the significance of this experimental design for landfill leachate treatment, Larger the Better was selected. The highest levels of pollutant degradation in the Solar Photo Fenton method was identified when compared to UV, and LED visible light photo Fenton processes. The maximum removal of 95% color, 83% COD, 89% TSS, 94% Cr, 86% Cd, and 93% Cu was achieved in Solar Photo Fenton process at pH-3, Fenton dosage 1.5:30 g/L and reaction period 60 minutes.

Biosorption of hexavalent chromium ions from the synthetic solution was performed using activated Ziziphus jujube seeds powder as an adsorbent material. A chemical synthesis process prepared the adsorbent, and various methods have evaluated its characteristics. FTIR, SEM and EDX analysis was conducted to check the ability of hexavalent chromium uptake from the synthetic solutions. Batch mode of adsorption process was performed and the adsorption parameters of pH, concentration, dose, contact time and temperature were found in various operating conditions. The entire adsorption process was evaluated by isotherm and kinetic models to check the nature of the adsorption process and its chemical reactions. Thermodynamic studies were conducted, desorption studies were used to recover the spent adsorbent using concentrated hydrochloric acid.