Evaluation of the 5 and 8 pH point titration methods for monitoring anaerobic digesters treating solid waste
Environmental Technology (United Kingdom)
Department of Biosystems Engineering, Ghent University, Ghent, Belgium; Water Research Group, Department of Civil Engineering, University of Cape Town, Cape Town, South Africa
Simple titration methods certainly deserve consideration for on-site routine monitoring of volatile fatty acid (VFA) concentration and alkalinity during anaerobic digestion (AD), because of their simplicity, speed and cost-effectiveness. In this study, the 5 and 8 pH point titration methods for measuring the VFA concentration and carbonate system alkalinity (H2CO3∗-alkalinity) were assessed and compared. For this purpose, synthetic solutions with known H2CO3∗-alkalinity and VFA concentration as well as samples from anaerobic digesters treating three different kind of solid wastes were analysed. The results of these two related titration methods were verified with photometric and high-pressure liquid chromatography measurements. It was shown that photometric measurements lead to overestimations of the VFA concentration in the case of coloured samples. In contrast, the 5 pH point titration method provides an accurate estimation of the VFA concentration, clearly corresponding with the true value. Concerning the H2CO3∗-alkalinity, the most accurate and precise estimations, showing very similar results for repeated measurements, were obtained using the 8 pH point titration. Overall, it was concluded that the 5 pH point titration method is the preferred method for the practical monitoring of AD of solid wastes due to its robustness, cost efficiency and user-friendliness. © 2014 Taylor and Francis.
acetic acid; bicarbonate; butyric acid; isobutyric acid; propionic acid; alkalinity; anoxic conditions; fatty acid; measurement method; monitoring; pH; solid waste; volatile substance; alkalinity; anaerobic digestion; Article; concentration (parameters); continuous stirred tank reactor; flow rate; high performance liquid chromatography; monitoring; municipal solid waste; pH; photometry; solid waste management; titrimetry