Decrease of inhibitory effect of 2-chlorophenol on nitrification in sequencing batch reactors

Area of Science:

• Environmental Microbiology
• Biotechnology
• Wastewater Treatment

Background:

• Nitrification is crucial for removing ammonia from wastewater.
• Phenolic compounds like 2-chlorophenol (2-CP) can inhibit nitrification processes.
• Acclimation of nitrifying sludge to contaminants is a strategy to enhance treatment efficiency.

Purpose of the Study:

• To evaluate the metabolic and kinetic behavior of nitrification in the presence of 2-chlorophenol (2-CP).
• To compare the performance of sequencing batch reactors (SBRs) using nitrifying sludge pre-exposed to 2-CP versus p-cresol.
• To assess the simultaneous removal of ammonium and 2-CP.

Main Methods:

• Two SBRs (SBR1, SBR2) were operated with nitrifying sludge.
• SBR1 sludge was pre-exposed to 2-CP; SBR2 sludge was pre-exposed to p-cresol.
• The impact of 20 mg 2-CP-C/L on nitrification rates and efficiency was monitored over multiple cycles.

Main Results:

• An initial inhibitory effect of 2-CP on nitrification was observed in both reactors.
• SBR1 (2-CP adapted sludge) achieved stable nitrification with 99.6% ammonium consumption and high nitrate yield by cycle 6.
• SBR2 (p-cresol adapted sludge) showed complete ammonium consumption but partial nitrification with nitrite accumulation.
• Both sludges demonstrated complete 2-CP consumption.

Conclusions:

• Nitrifying sludge pre-exposed to 2-CP in SBR systems offers a robust alternative for simultaneous ammonium and 2-CP removal.
• Adaptation strategies are key to overcoming inhibitory effects of phenolic compounds in biological wastewater treatment.
• SBR technology is effective for treating wastewater containing both ammonium and phenolic contaminants.