A 5 PH Point Titration Measurement For The Volatile Fatty Acids Of Low Concentrations In Wastewater

The volatile fatty acids (VFA) in wastewater are precursors for formed intracellularβ-hydroxy-n-Salts (PHB), have an important impact in biological phosphorus removal. Understanding and mastering of the VFA in wastewater have significant value to optimization of biological waste water treatment project design and operation management, are also the current water treatment issues to be resolved. Measurement methods for volatile fatty acids include distillation, colorimetry, gas chromatography and various titration techniques. In terms of routine monitoring and control, it is generally accepted that titration methods are simplicity, saving time and cost-effectiveness. Titration methods for VFA includ four point titration, five point titration and eight point titration. These titration methods were mainly applied for the measurement of high VFA concentration in anaerobic reactors. The characteristic of VFA in municipal wastewater is low concentration, great variability, and has various inorganic and organic weak acid and weak base components.The accuracy, stability and the main factors titration of used titration measuring low concentrations VFA in wastewater has not yet reasearched.In this paper the method of 5 pH titration measurements using for the determination of VFA was studied in the Lab systemically, and the main work and conclusion includes the following three aspects:1. The 5-pH titration measurements were used to determinate the synthesized acid wastewater with known different concentrations. And the recovery efficiency and coefficients of variation were calculated to reflect the accuracy and precise of the methods. The test results of the measurement values is lower 3mg/L than theroetical values , the values of RE is lower with the acetic acids concentration increased,between -14.55%～-4.41% and coefficients of variation is less 6%.2. The influence of NH4Cl on the determination of VFA by titration are checked further. The results shown when acetic acids concentration is 10～100 mg/L, added 20 and 40mg/L NH₄⁺-N, the average values of HAC is lower with NH₄⁺-N concentration increased. 20mg/L NH₄⁺-N added the measurement average values is lower 3.5mg/L than theroetical values, 40mg/L NH₄⁺-N added the measurement average values is lower 3.6mg/L than theroetical values. The values of RE is lower with the acetic acids concentration increased,but it is higher with NH₄⁺-N concentration increased, between -16.55%～-5.06%. The coefficients of variation are less 6% and it is lower with the acetic acids concentration increased.3. The influence of KH₂PO₄ on the determination of VFA by titration are checked. The results shown when acetic acids concentration is 10～100 mg/L, added 3 and10mg/L PO₄^3-–P, the average values of HAC is lower with PO₄^3-–P concentration increased. 3mg/L PO₄^3-–P added the measurement average values is lower 3.8mg/L than theroetical values, 10mg/L PO₄^3-–P added the measurement average values is lower 3.86mg/L than theroetical values. The values of RE is lower with the acetic acids concentration increased,but it is higher with PO₄^3-–P concentration increased, between -14.25%～-4.86%. The coefficients of variation are less 6%and it is lower with the acetic acids concentration increased.4. The influence of NH₄⁺-N and PO₄^3-–P on the determination of VFA by titration are checked. The results shown when acetic acids concentration is 10～100 mg/L, added 20mg/L NH₄⁺–N+3mg/L PO₄^3-–P and 40mg/L NH₄⁺–N+10mg/L PO₄^3-–P, the average values of HAC is lower with NH₄⁺–N and PO₄^3-–P concentration increased. 20mg/L NH₄⁺–N+3mg/L PO₄^3-–P added the measurement average values is lower 4.4mg/L than theroetical values, 40mg/L NH₄⁺–N+10mg/L PO₄^3-–P added the measurement average values is lower 4.44mg/L than theroetical values. The values of RE is lower with the acetic acids concentration increased,but it is higher with NH₄⁺–N and PO₄^3-–P concentration increased, between -15.13%～-5.69%. The coefficients of variation are less 6% and it is lower with the acetic acids concentration increased.5. The influence of alkalinity concentrations on the determination of VFA by titration are checked. The results shown when acetic acids concentration is 20 and 30 mg/L, added 20～100mg/L alkalinity, the average values of HAC is lower with alkalinity concentration increased. Acetic acids concentration is 20 and 30 mg/L added 20～100mg/L alkalinity the measurement average values is lower 5.00 and 5.14 mg/L than theroetical values. The values of RE is lower with alkalinity concentrations increased, between -26.10%～-12.93%. The coefficients of variation are less 7% and it is lower with alkalinity concentrations increased increased.