Sewage sludge valorization via phytohormones production: Parameter regulation and process evaluation

Area of Science:

• Environmental Science
• Chemical Engineering
• Sustainable Materials

Background:

• Sludge treatment is critical for environmental protection but current methods struggle with carbon emissions, efficiency, and resource recovery.
• Alkaline hydrothermal treatment offers a potential solution for sludge valorization, aiming for high-value product generation.

Purpose of the Study:

• To investigate the impact of treatment duration, temperature, and solid content on alkaline hydrothermal treatment of sludge.
• To optimize conditions for synthesizing high-value products from sludge for agricultural use.
• To assess the environmental benefits and resource recovery potential of the developed process.

Main Methods:

• Alkaline hydrothermal treatment was applied to sludge under varying conditions (duration, temperature, solid content).
• Analysis of solid and liquid phases to identify and quantify synthesized high-value products.
• Evaluation of heavy metal content, biological stability, and volume reduction.
• Energy efficiency comparison with conventional anaerobic digestion.

Main Results:

• Optimized conditions identified as 2 h, 160 °C, and 14% solid content.
• Synthesized products include phytohormones (up to 10^4 μg/L), humic substances, and essential nutrients (C, N, P, K).
• Achieved significant sludge volume reduction (60%), low heavy metal content, and biological stability.
• Demonstrated a 42.12 times higher energy efficiency compared to anaerobic digestion.

Conclusions:

• Alkaline hydrothermal treatment provides an efficient, low-energy method for sludge valorization.
• The process yields valuable agricultural inputs, supporting waste resource recycling and sustainable urban management.
• This approach offers a promising alternative to conventional sludge treatment methods.