A nine-point pH titration method to determine low-concentration VFA in municipal wastewater

Characterization of volatile fatty acid (VFA) in wastewater is significant for understanding the wastewater nature and the wastewater treatment process optimization based on the usage of Activated Sludge Models (ASMs). In this study, a nine-point pH titration method was developed for the determination of low-concentration VFA in municipal wastewater. The method was evaluated using synthetic wastewater containing VFA with the concentration of 10–50 mg/l and the possible interfering buffer systems of carbonate, phosphate and ammonium similar to those in real municipal wastewater. In addition, the further evaluation was conducted through the assay of real wastewater using chromatography as reference. The results showed that the recovery of VFA in the synthetic wastewater was 92%–102 and the coefficient of variance (CV) of reduplicate measurements 1.68%–4.72%. The changing content of the buffering substances had little effect on the accuracy of the method. Moreover, the titration method was agreed with chromatography in the determination of VFA in real municipal wastewater with R²= 0.9987 and CV =1.3-1.7. The nine-point pH titration method is capable of satisfied determination of low-concentration VFA in municipal wastewater.