• Home
  • Search Results
  • Challenges in using allylthiourea and chlorate as specific nitrification inhibitors.

Challenges in using allylthiourea and chlorate as specific nitrification inhibitors.

Chemosphere (2017-05-16)
K Tatari, A Gülay, B Thamdrup, H-J Albrechtsen, B F Smets

Allylthiourea (ATU) and chlorate (ClO3-) are often used to selectively inhibit nitritation and nitratation. In this work we identified challenges with use of these compounds in inhibitory assays with filter material from a biological rapid sand filter for groundwater treatment. Inhibition was investigated in continuous-flow lab-scale columns, packed with filter material from a full-scale filter and supplied with NH4+ or NO2-. ATU concentrations of 0.1-0.5 mM interfered with the indophenol blue method for NH4+ quantification leading to underestimation of the measured NH4+ concentration. Interference was stronger at higher ATU levels and resulted in no NH4+ detection at 0.5 mM ATU. ClO3- at typical concentrations for inhibition assays (1-10 mM) inhibited nitratation by less than 6%, while nitritation was instead inhibited by 91% when NH4+ was supplied. On the other hand, nitratation was inhibited by 67-71% at 10-20 mM ClO3- when NO2- was supplied, suggesting significant nitratation inhibition at higher NO2- concentrations. No chlorite (ClO2-) was detected in the effluent, and thus we could not confirm that nitritation inhibition was caused by ClO3- reduction to ClO2-. In conclusion, ATU and ClO3- should be used with caution in inhibition assays, because analytical interference and poor selectivity for the targeted process may affect the experimental outcome and compromise result interpretation.

Product Number
Product Description

Hydrochloric acid, puriss. p.a., ACS reagent, reag. ISO, reag. Ph. Eur., fuming, ≥37%, APHA: ≤10
Ammonium chloride, 99.998% trace metals basis