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-1 for 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.

Keywords: Multiple pH-point titration, volatile fatty acids, wastewater, full-scale, primary sludge hydrolysis