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Rapid urbanisation has had a significant negative influence on the water bodies that flow through and around urban areas. This study aims to evaluate the water quality and analyse the suitability for drinking and irrigation uses. This study envisaged assessing the water quality status of the groundwater using the pollution index of groundwater (PIG), ecological risk index (ERI) and multivariate statistical techniques, namely cluster analysis (CA) and principal component analysis (PCA), that were applied to differentiate the sources of water quality variation and determine the cause of pollution in the study area. Most groundwater is unsuitable for drinking and irrigation consumption, depending on analyses. PIG values indicated high pollution levels in the studied water body, rendering it unsuitable for any practical purpose. CA results showed the impact of surface water and treatment plant on groundwater. PCA was used to identify four important factors in the groundwater, including mineral and nutrient pollution, heavy metal pollution, organic pollution and faecal contamination. The deteriorating water quality of the groundwater was demonstrated to originate from vast sources of anthropogenic activities, especially municipal sewage discharge. Study wells had greater concentrations of Cl − and Na + in their water because seawater flows into the aquifer system and mixes with the marine aquifer matrix. Thus, the current work reveals how to employ the PIG and multivariate statistical approaches to obtain more accessible and more meaningful information about the water quality of groundwater and to identify the sources of pollution.

The Quaternary alluvial, Miocene sandstone and Lower Cretaceous sandstone aquifers represent the main source of water in Wadi Dara basin. The three aquifers are hydraulically connected through faults. The groundwater of the Quaternary aquifer is saline and exists at great depths from the ground surface, while the other two aquifers are between brackish to slightly saline and occur at relatively shallow depths. The groundwater salinity of the Quaternary aquifer varies from 4171 to 21,124 mg/l. The groundwater salinity of the Miocene aquifer varies from 6512 to 10,088 mg/l. The Lower Cretaceous aquifer represents the main source of water in the study area, its thickness ranges from 150 to about 450 m, and the groundwater salinity ranges from 2094 to 4380 mg/l. The hydrochemical results, application of inverse geochemical model in addition to the obtained water quality indices were used to recognize the source of groundwater salinization in the investigated area. The variation of groundwater salinities among the three investigated aquifers are mainly attributed to the nature of the aquifer matrix (lithofacies) as well as the recharging sources. The detected hypothetical salts reflect meteoric water origin (affected by leaching and dissolution of terrestrial salts) and paleo-water origin of the mature stage of chemical evolution. The chemical similarity between the three aquifers supports the presence of the hydraulic connection between them, and Quaternary alluvial aquifer at the downstream portion of Wadi Dara is influenced by seawater intrusion. The groundwater chemistry is mainly affected by the evaporation process during surface runoff and partially by the rock–water interaction. Carbonate, halite and sulfate minerals represent the main sources of salinity (mineralization) due to the leaching and dissolution processes. The quality of the investigated groundwater for the three aquifers is unsuitable for drinking purpose; only the groundwater of the Lower Cretaceous sandstone aquifer is suitable for irrigation with respect to salt-tolerant plants. Finally, some recommendations are given to develop the investigated area.

Several approaches have been used to reduce the accumulation of heavy metals in aqueous solutions, including adsorption to the surface of agricultural waste. Batch studies have been performed in this study to explore the adsorption of Fe2+, Mn2+ on olive pomace (OP), and moringa seed husk (MSH). Fourier transform infrared and scanning electron microscopy also characterized the prepared adsorbent. Batch adsorption studies were performed, and the effects of adsorbent chemical structure, adsorbent dosage, pH, contact time, and initial ion concentration were investigated on Fe and Mn ions sorption and mechanism in order to maximize the removal efficiency of Fe and Mn. It was shown that the removal percentage of Fe2+ and Mn2+ were 83% and 91%, respectively, at optimum pH 5 and optimum time of 120 min at 5 g of OP. Although the removal percentage of Fe2+ and Mn2+ were 80.5% and 93%, respectively, at 5 g of MSH. The pseudo-second-order model was followed by the adsorption kinetics of Fe2+ and Mn2+ on OP and MSH, and the Langmuir model worked well with the adsorption isotherms. Based on their adsorption/desorption processes, OP and MSH adsorbents may be regenerated by DI water more than five times. The overall adsorption power of the OP adsorbent for Fe2+ and Mn2+ was 10.406 and 10.460 mg/g, and the MSH was 10.28 and 11.641 mg/g for Fe2+ and Mn2+, respectively.

The present work focuses on the photocatalytic degradation of methylene blue (MB) on erbium ion (Er 3+ ) doped TiO 2 under visible light. Pure TiO 2 nanoparticles and erbium (Er 3+ ) doped TiO 2 nanocomposite (Er 3+ /TiO 2 ) NCs were synthesized using the sol–gel method. The synthesized (Er 3+ /TiO 2 ) NCs were characterized using Fourier transform infrared spectroscopy (FTIR), high resolution scanning electron microscopy (HR-SEM), elementary dispersive X-ray (EDX), X-ray diffraction (XRD), and X-ray photoelectron spectra (XPS), specific surface area (BET), zeta potential, and particle size. Different parameters were used to study their efficiency for the photoreactor (PR) and the synthesized catalyst. These parameters include pH of the feed solution, the rate of flow, the presence of an oxidizing agent (aeration pump), different ratios of nanoparticles, the amount of catalyst, and the concentrations of pollutants. An example of an organic contaminant was the dye methylene blue (MB). The result achieved using the synthesized nanoparticles (I) under ultraviolet light pure TiO 2 was found to have degraded by 85%. For (Er 3+ /TiO 2 ) NCs under visible light, dye removal increased with pH to a maximum of 77% degradation at pH 5. Furthermore, photocatalytic efficiency improves to 80% at 40 rpm (3 l/h) low motor speed. The degradation efficiency decreased to 70% when the MB concentration was increased from 5 to 30 mg/L. When oxygen content was increased using an air pump, and deterioration reached 85% under visible light, it improved performance.