Substrate Inhibition and Recovery Strategies for Anammox Process

Ammonium and nitrite are the two substrates of anaerobic ammonium-oxidizing (Anammox) bacteria,but they are potential inhibitors when their concentrations surpass the threshold inhibition values.The inhibition characteristics of the two substrates(nitrite and ammonia) were investigated by raising the influent substrate concentrations of an Anammox UASB bioreactor.Subsequently,different recovery strategies were carried out based on the inhibition characteristics of the two substrates.Results showed that nitrite was more toxic than ammonium.When the nitrite inhibition was relatively slighter,characterized by effluent nitrite concentration lower than the inhibition parameter(K_(IH,NO_2~--N),632mg/L),nitrogen removal performance completely recovered within 15 days(recovery degree,100%) by decreasing the influent nitrite concentration.However,severer nitrite inhibition(effluent nitrite concentration was higher than 632mg/L),resulted in worse recovery performance.The recovery degree only achieved 89%after 39 days by applying slow-recovery strategy.Besides,inhibition caused by free ammonia(FA) was also observed when the free ammonia concentration reached 83—130mg N/L.The recovery degree achieved 100%after 1 day by decreasing the pH to 6.8—7.0.