Howgate, 2004; Houle et al., 2011) but how to remove them, or how to decrease their occurrence, is still under investigation (Schrader et al., 2010) without much success. Guttman and van Rijn (2008) have proved that having anaerobic conditions within the system
could be a possible solution for the mitigation of this problem. Likewise, denitrification devices, although presently not very common, are being used where high levels of nitrate, high stocking densities and high levels of C/N interact (van Rijn et al., 2006). Thus,
adding a non-aerobic denitrification stage after the aerobic nitrification (i.e. biofilter) could likely mitigate both water quality and off-flavors issues at the same time; however, this will need further investigation.