Example from literature:  Acetoclastic methanogenic activity (in g COD CH4.g VSS-1.day-1 at different TAN (bottom axis) and FAN (top axis) at 25 °C and pH 7.7 .  A  ∼40% inhibition of the methanogenic activity wwas found at FAN concentration of 4000 mg.L-1 when compared to 1200 mg,L-1. Reproduced with permission (ASK) from \cite{Garcia_2009}. Copyright Elsevier.