Development of simultaneous partial nitrification, anammox and denitrification (SNAD) in a non-aerated SBR

•Successful development of SNAD in a non-aerated SBR.•Major source of oxygen through diffusion from head space of reactor.•SNAD developed using flocculent type activated sludge from a tannery CETP.•Best removals of NH4-N (94%), COD (92%) and TN (82%) at COD/NH4-N equal to 1.•Low cost SNAD applications possible in anoxic and photo-resistant shallow ponds.

The objective of this work was to develop simultaneous partial nitrification, anammox and denitrification (SNAD) process in a twenty liter non-aerated sequencing batch reactor (SBR). Flocculent type activated sludge sourced from a tannery common effluent treatment plant was used as seed biomass. The SBR was operated for 161 days in 23 cycles with initial feed concentrations of NH4-N and COD as 250 ± 14.9 mg l−1 and 250 ± 4.6 mg l−1, respectively. The process was developed in a non-mixing condition in a dark room with no temperature control, but the temperature in SBR varied between 30 °C and 36 °C. The average HRT was 10.5 d with SBR cycle time of 7 d. The last three cycles gave the best average removals of NH4-N (94%), COD (92%) and TN (82%). The conversion ratio Y(NO2-N+ NO3-N)/(NH4-N) during the last 10 cycles remained below 0.11, confirming a stable SNAD process. Maximum specific substrate (NH4-N, COD and TN) utilization rates of SNAD biomass were determined as 185 mg NH4-N g−1 MLVSS d−1, 153 mg COD g−1 MLVSS d−1 and 172 mg N g−1 MLVSS d−1. These results contribute towards the application of SNAD process in shallow anoxic ponds/tanks/ditches in the absence of sunlight.