Dinitrogen oxide detection for nitrification failure early warning systems

Experiments were conducted in order to establish whether N₂O could be used to predict nitrification failure (through non-invasive means). Previous research had shown a strong correlation between N₂O gas and NH₃ in the effluent, giving rise to the possibility N₂O can be used as an indicator for failure in the nitrification process. Two pilot-scale activated sludge plants were used, each with two lanes. The smaller consisted of a 60l aeration tank and a 20l clarifier; the larger pilot plant had an aeration tank of 315l and a clarifier of 100l. The small pilot plant experiments showed that N₂O gas was given off almost immediately from O₂ deprivation/NH₃ shock loads, but did not follow the expected trend of the time lag of NH₃ in the effluent. This led to further investigation in the hydrodynamics and mixing characteristics of aeration basins, where a second larger pilot plant was used. Further experiments were conducted of high NH₃ loadings and O₂ deprivation, showed that work of was reproducible. However, it was also shown that with partial nitrification failure, a different N₂O response of a continual rise was observed.