Chlorine dioxide as a potable water disinfectant: Application, residuals, and by-products monitoring

The objectives of this work where to study the effectiveness of the standard DPD (N, N-diethyl-p-phenylenediamine) method's for the detection of chlorine dioxide. This included evaluating calibration using potassium permanganate and alternative free chlorine masking agents, diethanolamine and triethanolamine. Additional objectives included the development of suitable spectrophotometric methods alternative to DPD from which a new detection platform could be established. Candidates such as N,N,N',N'-tetramethyl-p-phenylenediamine (TMPD), alizarin red S (ARS), and copper(II) sulfate were selected.;Results suggest that calibration of DPD using a potassium permanganate surrogate is susceptible to temporal changes, whereas use of diethanolamine and triethanolamine as a free available chlorine mask proved to interfere with DPD chlorine dioxide testing. Use of Alizarin red S provided a detection mechanism for chlorine dioxide (0-4 ppm) in the presence of low concentrations of chlorite ion (0.2 and 0.5 ppm). Detection of chlorite concentrations using copper(II) sulfate were established for chlorite concentrations ranging from to 6 ppm to 10 ppm which is much higher than regulated residual concentrations in drinking water. Lastly, the combination of TMPD and cerium(IV) provided for residual chlorine dioxide analysis in concentrations less than 1 ppm.