Feasibility of enhancing the DEnitrifying AMmonium OXidation (DEAMOX) process for nitrogen removal by seeding partial denitrification sludge

• The DEAMOX process was established for removing NH4+–N and NO3−–N simultaneously.
• Nitrite generated from nitrate was enhanced by seeding partial denitrification sludge.
• TN removal efficiency as high as 97% was achieved in DEAMOX process.
• ANAMMOX and denitrifying bacteria could coexist harmoniously in the DEAMOX system.

The recently proposed DEnitrifying AMmonium OXidation (DEAMOX) process combined anaerobic ammonia oxidation (ANAMMOX) with denitrification to convert nitrate to nitrite, which was a promising way for treating wastewater containing nitrate and ammonia. This study investigated the feasibility of establishing DEAMOX process by seeding partial denitrification sludge (NO3− → NO2−) using sodium acetate as an electron donor in a sequencing batch reactor. Results showed that the DEAMOX process was established successfully and operated stably in 114-days operation. The average effluent total nitrogen concentration was below 5 mg L−1 and TN removal efficiency reached up to 97% at COD/NO3− ratio of 3.0 under initial NH4+ concentration of 25 mg L−1 and NO3− of 30 mg L−1. It suggested that the presence of NO2− in the system supplied for ANAMMOX and the relatively long sludge retention time (SRT) for denitrifiers were attributed to commendable coexistence of ANAMMOX and denitrifying bacteria.