This paper presents an investigation of the barium sulfate inhibition performance of diethylenetriamine penta (methylene phosphonic acid), DETPMP, in a brine containing iron ions in both aerated and anaerobic systems. A test apparatus was designed to achieve truly anaerobic conditions (zero oxygen level in the test brine), under which a range of
ferrous iron Fe(II) concentrations (0 to 40 mg/L) were dosed into the test brine and barium sulfate inhibition efficiencies of DETPMP were determined. Parallel experiments were performed under ambient/aerated conditions. The barium sulfate inhibition performances of DETPMP under aerated conditions and anaerobic conditions were then compared. This experimental study reveals that Fe(ll) did not result in reduction of the barium sulfate inhibition efficacy of DETPMP. On the contrary, it appeared to enhance the DETPMP performance. This finding contradicts the previous reports by other researchers, which showed a detrimental effect of the presence of iron on the performance of scale inhibitors, including that of DETPMP. However, there was no clear evidence that, in the previous studies, the test brines were maintained truly anaerobic. In fact, this investigation did demonstrate that, under aerated conditions, the barium sulfate inhibition performances of DETPMP in presence of iron (initially dosed as ferrous iron) was severely impaired by ferric iron (Fe(lll)) which was transformed from ferrous iron Fe(II) by oxidation.