Evaluating 5 and 8 pH-point titrations for measuring VFA in full-scale primary sludge hydrolysate

Abstract

An evaluation of 5 and 8 pH-point titrimetric methods for determining volatile fatty acids (VFAs) was conducted, and the results were compared for tap water and primary treated wastewater at the laboratory scale. These techniques were then applied to full-scale primary sludge hydrolysate, and the results were compared with those obtained via gas chromatography. The comparison showed that the VFA concentrations measured with the two titration methods were higher than those obtained via gas chromatography, differing by 9 and 13 mg COD•ℓ -1 for the hydrolysate and by 5 and 6 mg COD•ℓ -1for the ordinary primary settler effluent. No improvement in the accuracy of VFA concentration measurement was obtained from applying the 8 pH-point titration method instead of the 5 point method. The 5 pH-point method was successfully applied to determine VFA in full-scale primary sludge hydrolysate and was shown to be equally efficient to the methods that are routinely-used for this purpose.

Integration of complete elemental mass-balanced stoichiometry and aqueous phase chemistry for bioprocess modelling of liquid and solid waste treatment systems – Part 4: Aligning the modelled and measured aqueous phases

“…The 5-point titration has been demonstrated in several studies to be an accurate method for determining the H 2 CO 3 alk and VFA concentrations in mixed weak acid/base samples (Lahav et al, 2002;Hey et al, 2013;Vannecke et al, 2015).…”

Monitoring Volatile Fatty Acids and Carbonate Alkalinity in Anaerobic Digestion: Titration Methodologies

“…Hey et al 28 evaluated the accuracy of five‐ and eight‐pH point titrimetric methods by determining the recovery of VFAs in both tap water and primary settled effluent. The precision and applicability of both methods were assessed by comparing the results of measuring the content of VFAs in hydrolysate to GC analysis.…”

“…Titration methods are considered superior for the purpose of routine full‐scale AD monitoring and control due to their simplicity, cost‐effectiveness, and robustness. In addition, the alkalinity of the AD will also be determined simultaneously 8, 28.…”

“…However, there are large differences in the approaches and in the results obtained from each method 8. Systematic evaluation and comparison of these methods have not been carried out in sufficient depth to date 1, 12, 27–30. Moreover, there are also many new methods which have been proposed in recent years 1, 31–33.…”

A Headspace Gas Chromatographic Method for Determination of Formic Acid Content in Isosulfan Blue and Various Drug Substances

“…Moreover, formic acid has accelerated the degradation of the experimental drug FK480 by optical isomerization from the desired S-enantiomer to undesired R-enantiomer 6 . So many analytical methods have been applied for analysis of formic and acetic acids, including titration methods 7 , HPLC 8 , IC 9 and GC 10 . The outdated titration methods are normally not selective, and they show content of total acids 11,12 .…”