P-nitrophenol biodegradation by aerobic microbial granules

Area of Science:

• Environmental microbiology
• Biotechnology
• Wastewater treatment

Background:

• Aerobic microbial granules (AMG) are effective for xenobiotic degradation.
• Developing AMG for specific pollutants like p-nitrophenol (PNP) can be challenging.
• Two methods for AMG cultivation were explored: direct from activated sludge and adaptation of pre-grown granules.

Purpose of the Study:

• To investigate the cultivation of AMG for p-nitrophenol (PNP) biodegradation.
• To compare the effectiveness of activated sludge versus pre-grown granules for PNP degradation.
• To assess the impact of PNP concentration and co-substrates on granule stability and function.

Main Methods:

• Cultivation of AMG using sequencing batch reactors (SBRs).
• Comparison of reactors fed PNP alone, acetate alone, or both acetate and PNP.
• Monitoring of PNP mineralization, acetate mineralization, and nitrification.

Main Results:

• Direct cultivation from activated sludge with PNP failed.
• PNP biodegradation was established in SBRs with pre-grown AMG fed PNP with or without acetate.
• PNP removal rates were high (47-55 mg/g VSS/h), but higher PNP concentrations (>50 mg/L) caused granule disintegration.
• A labile co-substrate (acetate) was crucial for maintaining the structural and functional integrity of AMG during PNP degradation.

Conclusions:

• A labile co-substrate is essential for maintaining the physical and functional integrity of aerobic microbial granules during the degradation of toxic compounds like PNP.
• PNP alone inhibits AMG development and causes disintegration, while co-feeding with acetate supports granule stability and nitrification.
• The findings are critical for designing effective bioreactors for toxic waste degradation using granular sludge technology.