Development of a continuous protein and polysaccharide measurement method by Sequential Injection Analysis for application in membrane bioreactor systems

Polysaccharides and proteins are the main components of extracellular polymeric substances, which are considered to give a major contribution to the overall fouling potential of the MBR system. This work focuses on the automation of spectrophotometrical assays for protein and polysaccharide determination for on-line measurement in MBR. Sequential Injection Analysis (SIA) was identified as more suitable for continuous measurements. In screening tests the selection of an appropriate assay for the successful automation by means of SIA was carried out. Lowry Assay and Dubois Assay were chosen for protein and polysaccharide determination. Lowry Assay could be successfully automated by means of SIA. The automated method shows a lower sensitivity than the manual Lowry method, what can be contributed to specific characteristic of SIA. The confidence limit was calculated to 2.8 mg/L. The automated method shows in validation tests good correspondence with protein concentrations measured with the manual assay (R²=0.971). The successful establishment of the Dubois Assay for polysaccharides failed so far due to sensitivity problems.