Biomass fermentation to augment biological phosphorus removal.

Area of Science:

• Environmental Engineering
• Biotechnology
• Wastewater Treatment

Background:

• Biological nutrient removal processes are essential for wastewater treatment.
• Enhancing phosphorus removal often requires optimizing volatile fatty acid (VFA) supply.
• Biomass fermentation offers a potential source of VFAs.

Purpose of the Study:

• To evaluate the effectiveness of recirculating fermented biomass as a volatile fatty acid (VFA) supplement in a sequencing batch reactor (SBR) for enhanced biological phosphorus removal.
• To investigate the impact of VFA addition on phosphorus removal, nitrification, and ammonium levels.
• To optimize phosphorus and ammonium removal through process modifications.

Main Methods:

• A lab-scale sequencing batch reactor (SBR) coupled with a side-stream biomass fermenter was utilized.
• Fermented biomass effluent was recirculated as a VFA supplement to the SBR.
• Process parameters, including VFA addition timing and solid-liquid separation, were manipulated.
• Magnesium oxide (MgO) was added for phosphate and ammonium precipitation.

Main Results:

• Recirculating fermented biomass as VFA supplement decreased effluent phosphate from 6 to 4.5 mg/L.
• Initial VFA addition led to increased phosphate and ammonium loads, impairing nitrification.
• Separating fermented solids and adding MgO to the supernatant improved phosphorus and ammonium removal.
• Delaying VFA addition post-denitrification further enhanced phosphorus removal.
• Biomass fermentation yielded 157 mg VFA-COD/g biomass, primarily acetate (78%) and propionic acid (10%).

Conclusions:

• Biomass fermentation can augment biological nutrient removal processes by providing VFAs.
• Effective phosphorus and ammonium removal necessitates managing the products of fermentation, such as through struvite precipitation.
• Optimizing VFA addition timing and employing solid-liquid separation are critical for successful implementation.