Influence of pH and temperature on soluble substrate generation with primary sludge fermentation

Area of Science:

• Environmental Science
• Biotechnology
• Wastewater Treatment

Background:

• Primary sludge fermentation generates soluble products that can increase biodegradable organic matter.
• Understanding factors influencing fermentation is key to optimizing wastewater treatment processes.

Purpose of the Study:

• To evaluate the impact of pH and temperature control on soluble fermentation product generation from primary sludge.
• To quantify the release of soluble chemical oxygen demand (COD) and volatile fatty acids (VFAs) under controlled and uncontrolled conditions.

Main Methods:

• Parallel experiments were conducted comparing controlled and uncontrolled pH and temperature conditions.
• Fermentation experiments were performed at various temperatures (10-24°C) and VFA concentrations.
• Analysis included soluble COD, VFA generation, nutrient release (nitrogen and phosphorus), and VFA composition.

Main Results:

• Uncontrolled fermentation at 20°C yielded 14 mg/L soluble COD release and 9.2 mg COD/L VFA generation.
• Nutrient release (nitrogen and phosphorus) was minimal.
• VFA generation was significantly influenced by temperature control, with a five-fold increase observed between 10°C and 24°C.
• Acetic acid was the primary VFA, its proportion decreasing with higher VSS concentrations and pH levels.

Conclusions:

• pH and temperature control are critical for maximizing soluble fermentation product generation from primary sludge.
• Optimized fermentation can increase the biodegradable COD content of wastewater effluents.
• Temperature has a more pronounced effect on VFA generation than previously assumed.