Lahav Ori, Morgan Barak E, Loewenthal Richard E
Faculty of Agricultural Engineering, Technion--Israel Institute of Technology, Haifa.
Environ Sci Technol. 2002 Jun 15;36(12):2736-41. doi: 10.1021/es011169v.
This paper presents a new simple, rapid, and accurate method suitable for on-site measurement of volatile fatty acids (VFA) and carbonate alkalinity in anaerobic reactors. This titrimetric method involves eight pH observations, and typically, the full procedure takes approximately 15 min. An important feature of the method is a built-in quality control mechanism allowing the user a rapid means of assessing the reliability of the experimental procedure. To evaluate the accuracy of the method, both laboratory-made waters and industrial UASB effluent were tested. High accuracy for both VFA and carbonate alkalinity measurements (error within 2% and 1%, respectively) plus good repetition (average standard deviation of 6.7% and 1.45%, respectively) was obtained. The method takes into account the effects of the phosphate, ammonium, and sulfide weak acid subsystems. Appraisal of the effect of an input error in these subsystems revealed that VFA measurement is fairly insensitive to phosphate and ammonium concentrations. It is, however, sensitive to H2S loss during titration where the sulfide concentration is higher than approximately 10 mg/Las S. With regard to the carbonate alkalinity measurement, error in concentration of either phosphate or sulfide or H2S loss might result in a significant error. Short guidelines for correct execution of the method are given in an appendix.
本文提出了一种适用于现场测量厌氧反应器中挥发性脂肪酸（VFA）和碳酸盐碱度的简单、快速且准确的新方法。这种滴定法涉及八个pH值观测点，通常整个过程大约需要15分钟。该方法的一个重要特点是内置了质量控制机制，使用户能够快速评估实验过程的可靠性。为了评估该方法的准确性，对实验室配制的水样和工业UASB出水进行了测试。VFA和碳酸盐碱度测量均具有高精度（误差分别在2%和1%以内），且重复性良好（平均标准偏差分别为6.7%和1.45%）。该方法考虑了磷酸盐、铵和硫化物弱酸子系统的影响。对这些子系统输入误差影响的评估表明，VFA测量对磷酸盐和铵浓度相当不敏感。然而，当硫化物浓度高于约10mg/L（以S计）时，它对滴定过程中的H2S损失敏感。关于碳酸盐碱度测量，磷酸盐或硫化物浓度误差或H2S损失可能会导致显著误差。附录中给出了正确执行该方法的简短指南。
