Online fluorescence measurements for monitoring of raw waters and drinking water treatment processes from algae like waters < Back

The aim of the project was the use of fluorescence spectroscopy as a tool of early warning against cyanotoxins in drinking water treatment. The indicator function of the fluorescence signals of the cyanopigments phycocyanin and phycoerythrin as early warning parameters against the microcystins in drinking water was investigated by lab- and pilot-scale studies. The early warning function of the fluorescence signals was examined with regard to the signals real-time character, their sensitivity, and the behaviour of the cyanopigments in different treatment stages in comparison to microcystins. Fluorescence measurements have real-time character, because they can be carried out on-site without any pre-concentration of pigments contained in cyanobacteria-like samples. The limit of detection of phycoerythrine is determined at 0.7 µg/L and of phycocyanin at 5.3µg/L respectively. If the pigment-/microcystin-ratio is known and calculated to be higher than 1, a microcystin concentration lower than 0.1 can be estimated by the fluorescence signals in drinking water. The compared behaviour of both pigments and selected microcystins (MC-LR and MC-RR) during water treatment shows that pigments have an early warning function against microcystins in nearly all water treatment options like, conventional treatment stages using pre-oxidation with permanganate, ozone, application of powdered-activated carbon, disinfection like chlorination and UF-membranefiltration In contrast, cynopigments do not have an early warning function if chlorine dioxide is used as a pre-oxidant or final disinfection agent.

In addition to cyanopigment measurements by fluorescence technique it could be found that the raw and drinking waters are characterized by 2D-Exitation/Emission fingerprints. As a result of the project a software for the design of the 2D-matrix in the range from 200 till 700 nm was developed. The algae like sector of the matrix formed by the protein-fluorescence at 280/340 nm and pigment fluorescence at 520/685 nm was calibrated.

The results show that the method is extremely sensitive and changes of DOC-fractions can be detected in a range which is not possible by other adequate DOC-measurements. Because of the quick measurements, the method can be used as a early warning tool for water monitoring and process management. This requires a mathematical software for quantification as well as robust equipment.

In this field the research of future should be orientated. The TZW will accompany this way by 1. development of an online fluorescence sensor, 2. mathematical separation of the 2D-matric as pseudochromatographic method, 3. calibration of the several matrix sectors and 4. application of that method for solution of special problems in drinking water treatment, e.g. the formation of taste and odor.