Anaerobic-aerobic sequential treatment: Temperature optimization and cost implications.

Area of Science:

• Environmental Engineering
• Waste Management
• Biotechnology

Background:

• Anaerobic digestion (AD) is a common waste treatment, but post-processing is crucial for effluent quality.
• Aerobic polishing is typically operated at ambient temperatures.
• Optimizing aerobic treatment can enhance overall waste management efficiency.

Purpose of the Study:

• To investigate the impact of psychrophilic versus mesophilic temperatures in the aerobic stage of an anaerobic-aerobic sequential system (AASS).
• To evaluate the effect of temperature optimization on effluent quality, nutrient removal, and operational costs.
• To assess the co-digestion of raw wastewater and food waste within the AASS.

Main Methods:

• An anaerobic-aerobic sequential system (AASS) was used for co-digesting raw wastewater and food waste.
• The aerobic compartment was operated under both psychrophilic and mesophilic temperature conditions.
• Key performance indicators including volatile solids (VS), chemical oxygen demand (COD), nitrification, and denitrification were monitored.

Main Results:

• The anaerobic digester achieved high removal efficiencies for VS (85%) and COD (84%).
• Operating the aerobic reactor at mesophilic temperatures halved effluent COD and solids concentrations compared to psychrophilic conditions.
• Mesophilic operation increased nitrification from 68% to 91% and denitrification from 10% to 16%.

Conclusions:

• Raising the aerobic reactor temperature to the mesophilic range significantly enhances effluent quality from AASS treating food waste and wastewater.
• Mesophilic operation leads to substantial reductions in effluent solids and COD, alongside improved nutrient removal.
• The optimized aerobic stage presents favorable operational costs, considering sludge disposal and energy revenues, making it a viable strategy for urban waste management.