i m working on Sulfur and nitrate removal from wastewater treatment. during reviewing papers i observe that the researchers claim that during the autotrophic denitrification of Sulfur and nitrate in the reactor, ammonium (NH4) accumulated in the reactor. but the problem is that why it is accumulated, no one explain the reason. so i want to know why it is accumulated in the reactor. For example i will give one paper as a reference i.e. " Effect of S/N ratio on sulfide removal by autotrophic denitrification". if any one want to see the paragraph, i have highlight it in the paper and have added the paper here..

Need reasonable answers...