Startup strategy for nitrogen removal via nitrite in a BAF system
A biological aerated filter (BAF) pilot plant consisting of two reactors (aerobic and anoxic one) was used to determine a strategy to remove nitrogen via nitrite. RNA/DNA analysis was performed to assess microbial activity and support chemical results. In less than 13 days the pilot plant was able to remove COD and suspended solids. Nitrogen removal via nitrite pathway could not be observed until day 130 when the empty bed contact time (EBCT) was set at 0.71 h. Nitrite was detected in the aerated BAF effluent but never nitrate. qPCR of amoA gene from RNA and DNA extracts of the aerobic biofilm confirmed that ammonia oxidizing bacteria (AOB) were present from the beginning of the operation but not active. AOB activity increased with time, reaching stability from operational day 124. The combination of both, low EBCT together with high OLR, has been demonstrated to be a feasible strategy to startup a BAF to achieve nitrogen removal via nitrite.
KeywordsRNA Nitrite Ammonia oxidizing bacteria Partial nitrification NGS
Authors would like to thank the valuable technical help of Aida Lopez during part of the experimental study as well as to the Caldes de Montbui WWTP workers Victor Mejias and Fran Cosano and the support given by the WWTP operator (Consorci de la Conca del Besòs). This work was funded by CDTI IDI-20140237 and PESA Medio Ambiente. The support of the CERCA Program and of the Consolidated Research Group TERRA (ref. 2017 SGR 1290), both from the Generalitat de Catalunya, is also acknowledged.
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