The effect of organic pollution on the seasonal dynamics of water quality in a semi-arid zone: case of the Hammam Boughrara Dam, Tlemcen (Algeria).

The present study aims to assess the impact of human activities on the water quality of the Hammam Boughrara dam. It also highlights the crucial importance of sustainable management of water resources in the face of persistent challenges related to various forms of pollution. The study is based on an exhaustive database covering a period spread over 16 years, with monthly measurements of organic pollution indicator parameters, namely BOD5, COD, [Formula: see text],[Formula: see text], [Formula: see text], [Formula: see text], Organic Matter (OM), TDS, Dissolved Oxygen (DO) and pH. The box plots showed an asymmetric distribution of almost all the parameters, with significant seasonal variations in the interquartile (IQR) range. The IQR ranges for [Formula: see text] extends from 0.575 mg/l (summer) to 4.445 mg/l (spring), and for [Formula: see text] from 1.3075 mg/l (autumn) to 1.8625 mg/l (spring). This led to the use of the Spearman method for the analysis of correlations between different parameters. The seasonal study of the five categories of water quality, according to the Organic Pollution Index (OPI), revealed considerable organic pollution. At the 1% significance level, the seasonal correlation between OPI and [Formula: see text] varies between -0.71 and -0.85, while that with [Formula: see text] fluctuates between -0.69 and -0.86. During the period analyzed, the COD/BOD Ratio (CBR) reveals two dominant categories with seasonal variations, i.e. the Moderately Biodegradable Effluents (MBE), with 96 cases, reaching 29 in autumn and 20 in spring. The Difficult to Biodegrade or Non-Biodegradable Effluents (DBE or NBE) category records 94 cases, with a maximum frequency of 26 in winter and minimum of 21 in autumn. These results therefore show the persistence of organic pollution, which had an impact on water quality over the four seasons and throughout the period studied. The results indicate persistent organic pollution affecting water quality. Therefore, prompt actions and sustainable strategies are deemed necessary to mitigate these harmful impacts and to ensure the sustainability of the water resource.

Adsorptive removal of P(V) and Cr(VI) by calcined Zn-Al-Fe ternary LDHs.

The present study deals with the preparation and structural and adsorbent characterization of the ternary layered double hydroxides (LDHs; ZFA-HT) with molar ratio Zn2+/Al3+/Fe3+ = 2/0.5/0.5 and its product calcined (ZFA-350) at 350 °C, which is examined for the removal of phosphate P(V) and chromate Cr(VI) from aqueous media. The as-obtained materials are characterized by X-ray diffraction (XRD), Fourier-transform infrared (FT-IR), thermogravimetric analysis-differential scanning calorimetry (TGA-DSC), scanning electron microscopy-X-ray energy dispersion (SEM-EDX) and Brunauer-Emmett-Teller (BET). Structural characterizations show that the LDHs is successfully synthesized and its calcined product is a mixed oxide. Batch sorption studies are conducted to investigate the effects of various experimental parameters such as contact time, solution pH, adsorbent amount, initial P(V) or Cr(VI) concentration and temperature. The isotherms, kinetics and thermodynamic parameters of adsorption of phosphate and chromium are studied. The adsorption processes are well described by the pseudo-second-order kinetic model than the other models examined. The adsorption isotherms data fit best to the Langmuir isotherm model instead of Freundlich and Dubinin-Radushkevich models. The maximum monolayer adsorption capacity of ZFA-350 was found to be 140.85 mg/g for P(V) and 52.63 mg/g for Cr(VI). The positive ΔH and ΔS and negative ΔG values reveal that the P(V) and Cr(VI) sorption onto ZFA-350 is endothermic, irreversible and spontaneous in nature.

Synthesis, Characterization and Photocatalytic Performance of Calcined ZnCr-Layered Double Hydroxides.

The development of new materials for performing photocatalytic processes to remove contaminants is an interesting and important research line due to the ever-increasing number of contaminants on our planet. In this sense, we developed a layered double hydroxide material based on Zn and Cr, which was transformed into the corresponding oxide by heat treatment at 500 °C. Both materials were widely characterized for their elemental composition, and structural, morphological, optical and textural properties using several experimental techniques such as x-ray diffraction, x-ray photoelectron spectroscopy, scanning and transmission electron microscopy, Fourier transform infrared spectroscopy, UV-vis spectroscopy and physisorption techniques. In addition, the photocatalytic activity of both materials was analysed. The calcined one showed interesting photocatalytic activity in photodegradation tests using crystal violet dye. The operational parameters for the photocatalytic process using the calcined material were optimised, considering the pH, the initial concentration of the dye, the catalyst load, and the regeneration of the catalyst. The catalyst showed good photocatalytic activity, reaching a degradation of 100% in the optimised conditions and showing good performance after five photodegradation cycles.