Fig. 3.

Changes in nitrogen species (NH₄⁺-N, NO₂⁻-N, and NO₃⁻-N) concentration with time under anoxic conditions and in the presence of different PhACs initial concentrations [(a) 0.16 mg L⁻¹, (b) 0.40 mg L⁻¹, (c) 1.48 mg L⁻¹, and (d) 1.78 mg L⁻¹].