The increase in organic load greatly affected the removal efficiency
of TKN as a result of the competition for oxygen between
heterotrophic and nitrifying microorganisms: heterotrophic
bacteria compete with autotrophic ones for dissolved oxygen and inhabitation area, causing nitrification inhibition (Liu et al., 2008).
Hence, a decrease in the removal was observed, from quite
complete removal during phase 1 to a value lower than 80% at
maximum in phase 4.