This study investigates the potential of a synergistic co-culture of microalgae (M) and activated sludge (AS) for the bioremediation of agro-industrial wastewater and the valorization of resulting biomass for biofertilizer production. Co-cultures were established with inoculation ratios of 1:1, 1:3, 1:0, and 0:1 (M:AS) and cultivated under two photoperiod regimes (24L:0D and 16L:8D) for 14 days. The highest removal efficiencies were observed in the 1:1 and 1:3 treatments under the 24L:0D regime, achieving up to 90.61% COD, 100% nitrogen, and 99.8% phosphorus removal. Biomass analysis revealed substantial macromolecular content, including lipids (24.2% and 16.2%), proteins (39.5% and 43.2%), and carbohydrates (70.8% and 53.7%) under 24L:0D and 16L:8D, respectively. The biofertilizer potential of the biomass was assessed using Cucumis sativus seeds, showing improved germination and growth, particularly at 25% dilution, with a 90% germination index, an average of 4 ± 0 leaves, and shoot length of 5.05 ± 2.07 cm. These findings highlight the dual benefit of pollutant removal and biomass valorization in integrated wastewater management.

Arsenic is a carcinogenic metalloid prevalent in groundwater, predominantly as As (III), the most toxic and recalcitrant species. This study evaluates a hybrid strategy coupling hydrodynamic cavitation (HC) oxidation of As (III) to As (V) with subsequent adsorption on FeCl ₃ ‐modified activated carbon. HC oxidation followed a pseudo‐first‐order kinetic model ( k = 3.02 × 10 ⁻² min ⁻¹ ; R ² = 0.9754), with optimal conditions of 4 bar inlet pressure and pH 4. Adsorption equilibria were described by the Langmuir model for commercial carbon (CC), q _max = 1.99 mg·g ⁻¹ , and by the Freundlich model for modified commercial carbon (MCC), K _F = 0.49055 (mg·g ⁻¹ ) (L mg ⁻¹ ) ^1/n . Kinetics for both adsorbents were best fitted by the pseudo‐first‐order model ( k ₁ = 0.08876 min ⁻¹ for CC and 0.1674 min ⁻¹ for MCC). The integrated process, HC pre‐oxidation followed by MCC adsorption, improved arsenic removal by 34.68% relative to conventional adsorption. Findings support HC‐assisted oxidation coupled with adsorption on Fe‐modified carbon as an efficient, eco‐friendly, and cost‐effective option for treating waters with elevated As (III)/As (V) levels.

Hydrogels (HGs) have emerged as promising multifunctional materials for sustainable agriculture due to their high water retention capacity and their ability to act as controlled-release platforms for agrochemicals, nutrients, microorganisms, and bioactive compounds. Their application has gained increasing attention in response to global challenges associated with climate change, water scarcity, soil salinization, and the low efficiency of conventional fertilizers, which contribute to environmental degradation and reduce crop productivity. This review provides a critical overview of hydrogel-based systems for agricultural applications, with particular emphasis on the encapsulation of bioactive components for soil remediation and crop protection under abiotic stress conditions. A systematic literature review following PRISMA guidelines was conducted using the Scopus database, resulting in the analysis of 548 studies published between 2003 and 2024. Bibliometric analysis revealed a marked increase in research activity since 2021, mainly driven by advances in water-retention technologies, nanocomposite hydrogels, controlled-release systems, and bioactive encapsulation strategies. The review discusses the main factors governing hydrogel functionality, including swelling behavior, crosslinking density, biodegradability, and interactions with soil–plant systems. Particular attention is given to recent developments involving the incorporation of microorganisms, nanoparticles, micronutrients, and agrochemicals into biodegradable hydrogel matrices to improve nutrient availability, mitigate salinity stress, and reduce agrochemical losses. Finally, the challenges associated with scalability, environmental stability, and field validation are discussed, highlighting the potential of hydrogel-based bioactive delivery systems for developing resilient and resource-efficient agricultural systems.