Response of anammox to organics with different degradation characteristics and exposure time: Performance, sludge characteristics and bacterial community.

The effects of typical organic compounds including easily degradable organic matters sodium acetate, yeast and methanol, and refractory organic matter (ROM) humic acid on anaerobic ammonium oxidation (anammox) systems in short-term and medium-term exposure time were studied. During short-term experiments, nitrogen removal activity (NRA) was inhibited at sodium acetate level of 150 mg L total organic carbon (TOC) and methanol level of 30-150 mg L TOC, but humic acid and yeast (≤150 mg L TOC) enhanced nitrogen removal in anammox systems. The greatest NRA of 30.10 mg TN g VSS h was recorded at yeast level of 90 mg L TOC. In medium-term experiments, organics significantly inhibited the nitrogen removal ability. As a ROM, humic acid enhanced sludge aggregation and biological diversity, but decreased the bioactivity and extracellular polymeric substances levels. Due to the endogenous denitrification, the relative abundance of anammox bacteria (AnAOB) was decreased. Candidatus Kuenenia is still dominant in sludge with methanol and humid acid, but AnAOB are not dominant due to the addition of sodium acetate and yeast. This research would be beneficial for the full-scale application of the anammox process in treating real wastewater with organics and ammonia.