Abstract
The adaptation of commercially available ion-selective electrodes (ISEs) for use in wastewater matrices was demonstrated using
multivariate analysis and optimization with the Microsoft Excel Solver tool. The electrodes were characterized in pure analyte
solutions, and their parameters were estimated using multivariate analysis and Solver optimization. The ammonium, nitrate, and
nitrite ions were measured in model systems that were designed to simulate wastewater. The accuracy of the measurements
(95.3% - 101.0%) was satisfactory for the determination of ammonium, nitrate, and nitrite in complex matrices. The adapted ISEs
were then successfully used for bioprocess (synthetic wastewater treatment) dynamics and efficiency studies in a horizontal
rotating tubular bioreactor (HRTB) by monitoring the concentrations of the substrates and intermediates in the samples collected
from the bioreactor. The simultaneous determination of ammonium, nitrate, and nitrite in the samples through the use of adapted
ISEs considerably shortened the time required for ion determination.