Integrated Electrodes for Nutrient Removal from Municipal Wastewater Using Electrocoagulation Technology
Published August 2, 2025, in Scientific Reports
Municipal wastewater discharge remains a significant environmental challenge worldwide due to the excessive nutrients it contains—primarily nitrogen and phosphorus—which can lead to eutrophication and deteriorate water quality, affecting human health and aquatic ecosystems. Addressing this problem, researchers Bilisa Bulti Emana and Tsehay Bulti Bulge have recently advanced the field of wastewater treatment by evaluating the efficiency of electrocoagulation (EC) technology using integrated electrodes to remove these harmful nutrients.
Background
Nutrients such as nitrate nitrogen (NO₃⁻-N), ammonia nitrogen (NH₃–N), and orthophosphate (PO₄³⁻-P) are abundant in municipal wastewater. When released untreated into water bodies, they stimulate excessive growth of algae and aquatic plants, causing eutrophication that disrupts ecosystems. Traditional treatment methods—like ion-exchange, chemical oxidation, coagulation-flocculation, adsorption, and membrane technologies—present challenges including high chemical use, operational complexity, and sludge production.
Electrokinetic technologies, particularly electrocoagulation (EC), are emerging as sustainable alternatives. EC generates coagulants electrochemically from sacrificial electrodes (aluminum or iron), avoiding the need for added chemicals and reducing sludge generation. These coagulants destabilize and aggregate pollutants, facilitating their removal from wastewater.
The Study
Conducted as an experimental investigation, the study tested integrated electrode systems—Al-Al (aluminum-aluminum), Fe-Fe (iron-iron), and Al-Fe (aluminum-iron)—to optimize nutrient removal from municipal wastewater. Key parameters studied included current density (20, 60, and 80 A/m²) and operating time (5, 60, and 90 minutes), while maintaining constant pH (7), electrode distance (0.2 cm), and voltage (30 V).
The experimental setup featured a 2-liter glass beaker reactor holding 1.5 liters of wastewater, powered by a direct current source and equipped with aluminum electrodes measuring 6 cm by 8 cm by 0.6 cm, providing an active surface area of 48 cm².
Results
The highest nutrient removal efficiencies were observed at the longest operating time (90 minutes) and highest current density (80 A/m²):
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Al-Al electrodes:
- Nitrate nitrogen removal: 95.59%
- Ammonia nitrogen removal: 97.56%
- Orthophosphate removal: 96.74%
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Fe-Fe electrodes:
- Nitrate nitrogen removal: 96.08%
- Ammonia nitrogen removal: 98.54%
- Orthophosphate removal: 97.78%
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Al-Fe electrodes:
- Nitrate nitrogen removal: 95.83%
- Ammonia nitrogen removal: 98.05%
- Orthophosphate removal: 97.31%
These results indicate that increasing current density and reaction time significantly enhances pollutant removal efficiency in the electrocoagulation process. The iron-based electrodes (Fe-Fe) exhibited a slight edge in performance, suggesting their particular effectiveness for nutrient removal in municipal wastewater treatment.
Mechanism of Electrocoagulation Nutrient Removal
During electrocoagulation, metal ions (Al³⁺ or Fe²⁺/Fe³⁺) are released into the solution via anodic dissolution. These ions undergo hydrolysis to form metal hydroxides such as aluminum hydroxide (Al(OH)₃) and iron hydroxide (Fe(OH)₂), which act as coagulants. These coagulants adsorb and destabilize pollutants, leading to the formation of larger flocs that can be separated effectively.
Additionally, hydrogen gas bubbles generated at the cathode promote turbulence and aid flotation by attaching to particles, decreasing their density and facilitating separation from the treated water.
The relevant electrochemical reactions at the electrodes include:
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Iron electrodes:
- Anode: Fe(s) → Fe²⁺(aq) + 2e⁻
- Cathode: 2H₂O(l) + 2e⁻ → H₂(g) + 2OH⁻(aq)
- Overall: Fe(s) + 2H₂O(l) → Fe(OH)₂(s) + H₂(g)
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Aluminum electrodes:
- Anode: Al(s) → Al³⁺(aq) + 3e⁻
- Cathode: 3H₂O(l) + 3e⁻ → 3/2 H₂(g) + 3OH⁻(aq)
- Overall: Al³⁺(aq) + 3H₂O(l) → Al(OH)₃(s) + 3H⁺(aq)
Implications and Conclusion
The study confirms electrocoagulation using integrated aluminum and iron electrodes as an effective, economical, and environmentally friendly technology to remove nitrogen and phosphorus nutrients from municipal wastewater. This method minimizes chemical inputs and sludge generation compared to conventional treatments.
Adopting such technologies at wastewater treatment facilities could make a substantial contribution to reducing nutrient pollution, mitigating eutrophication, and improving overall water quality. The findings provide valuable insights for designing optimized EC systems, promoting sustainable water management, and safeguarding aquatic ecosystems.
For researchers and practitioners interested in advanced wastewater treatment technologies, this work highlights the practical advantages of electrocoagulation with integrated electrodes and contributes to the global effort to develop cleaner, greener, and more efficient treatment methods.
Reference:
Emana, B. B., & Bulge, T. B. (2025). Integrated electrodes for the nutrient removal from municipal wastewater using electrocoagulation technology. Scientific Reports, 15, 28244. https://doi.org/10.1038/s41598-025-28244
