Transforming local waste into value: Activated carbon from brewery sludge for sustainable phosphate removal

Introduction
Phosphate pollution from industrial wastewater remains a critical threat to aquatic ecosystems due to eutrophication and nutrient imbalance. Addressing this challenge requires sustainable and locally adaptable solutions. This study presents an environmentally conscious approach to converting brewery sewage sludge—an abundant local waste in Gondar, Ethiopia—into activated carbon for phosphate removal. The concept integrates waste valorization with circular water management, reducing disposal burdens while producing efficient adsorbent materials.
Materials and Methods
Sewage sludge was chemically activated using phosphoric acid (H₃PO₄) and sodium hydroxide (NaOH), followed by controlled thermal treatment. Physicochemical properties were analyzed using FT-IR, BET surface area, pHₚzc, and proximate analysis. Batch adsorption tests were optimized via Response Surface Methodology (Design Expert 13.0.5) under varied pH (3–10), contact time (60–120 min), and adsorbent dosage (1–3 g).
Results
The H₃PO₄-activated carbon exhibited a highly porous structure (427.32 m²/g) and achieved 80.3% phosphate removal with an adsorption capacity of 13.6 mg/g at optimal conditions
(pH 3, 120 min, 2.6 g). Adsorption followed the Langmuir isotherm and pseudo-second-order kinetics, indicating chemisorption on a uniform surface. The regenerated adsorbent retained over 50% efficiency after three reuse cycles, confirming its operational stability.
Conclusions
This work demonstrates that brewery sludge—a problematic local waste—can be transformed into a high-value, reusable adsorbent for water purification. The approach supports both environmental protection and resource efficiency, offering a scalable, low-cost pathway toward cleaner water and circular economy practices. It exemplifies how local waste can become a local solution to global environmental challenges.