Evaluation of influent prefermentation as a unit process upon biological nutrient removal

Area of Science:

• Environmental Engineering
• Wastewater Treatment Technologies
• Biological Nutrient Removal (BNR)

Background:

• Domestic wastewater treatment relies on Biological Nutrient Removal (BNR) processes.
• Prefermentation of primary influent is a potential strategy to enhance BNR efficiency.
• Understanding prefermentation's impact on Enhanced Biological Phosphorus Removal (EBPR) is crucial for design engineers.

Purpose of the Study:

• To quantitatively compare continuous flow BNR processes with and without prefermentation.
• To assess the impact of primary influent prefermentation on BNR treating septic domestic wastewater.
• To investigate prefermentation effects under both phosphorus-limited and COD-limited conditions.

Main Methods:

• Controlled comparison of identical continuous flow BNR processes.
• Two-phase study: bench-scale (P-limited wastewater) and pilot-scale (COD-limited wastewater).
• Analysis of readily biodegradable COD (RBCOD), slowly biodegradable COD (SBCOD), volatile fatty acids (VFAs), phosphorus (P), and nitrogen (N) removal.

Main Results:

• Prefermentation increased RBCOD, SBCOD, and VFA content in septic wastewater.
• Enhanced biological phosphorus removal was observed in septic, non-P-limited wastewater (TCOD:TP < 40:1).
• In P-limited wastewater (TCOD:TP > 40:1), P removal was suppressed despite affected P release and PHA content.
• Prefermentation increased specific anoxic denitrification rates in both COD- and P-limited wastewaters.
• Pilot study (COD-limited) showed increased system N removal with prefermentation.

Conclusions:

• Prefermentation positively impacts BNR by increasing biodegradable compounds and enhancing denitrification.
• The benefits of prefermentation for phosphorus removal are dependent on wastewater nutrient limitations.
• Prefermentation shows promise for improving both phosphorus and nitrogen removal in specific wastewater scenarios.