Robustness of ANAMMOX granule sludge bed reactor: Effect and mechanism of organic matter interference

The organic matter together with ammonium has become a major concern in the applications of ANaerobic AMMonium OXidation (ANAMMOX) process because of its possible adverse influences. The robustness of ANAMMOX against organic matter interference was found by accident in the ANAMMOX Granule Sludge Bed (GSB) reactor. Under inorganic conditions, Autotrophic ANAMMOX Granular Sludge (AGS) was cultivated, in which ANAMMOX accounted for 89.7% of the total nitrite removal. The bioreactor based on AGS showed an intriguing resistance to organic matter interference, with a stable volumetric nitrogen removal rate (NRR) for a surprisingly long time (vertical bar Delta ANR vertical bar <= 10% for 33 days). Under organic conditions, however, AGS gradually shifted to mixotrophic ANAMMOX granular sludge (MGS), in which ANAMMOX accounted for 51.9% of the total nitrite removal. The bioreactor based on MGS was sensitive to organic matter interference, with a decrease by 20.9% in NRR when the volumetric organic loading rate was 7.5 kg CODI(m(3) d). Beneath the threshold CODIN02--N ratio of 1.71, ANAMMOX played its dominant role in MGS (contributed to 68.9% of the total nitrite removal). While above the threshold ratio, ANAMMOX was dramatically inhibited (contributed to less than 34.1% of the total nitrite removal), but it did not disappear completely as expected. The discovery of ANAMMOX robustness in AGS is significant for the development of new ANAMMOX process suitable for the treatment of ammonium-containing wastewaters with coexistence of organic matter. (C) 2016 Elsevier B.V. All rights reserved.