AlgaeToximeter II

An instrument for the fast and sensitive detection of toxic substances in water

The bbe AlgaeToximeter II continuously monitors water for the presence of toxic substances. Standardised algae are mixed with the sample water and the instrument detects the photosynthetic activity of the algae. Damage to the algae, caused e.g. by herbicides, causes a reduction in algae activity and activates an alarm above a pre-defined threshold.

The bbe AlgaeToximeter II also serves as a measuring instrument for the precise determination of algal concentrations in water. Algae group differentiation – applied to the sample water – enables  the quantitative allocation to different spectral algal classes. This measurement principle corresponds to that of bbe’s tried and tested fluorometric instruments: the AlgaeOnlineAnalyser and AlgaeLabAnalyser.

The current version of the bbe AlgaeToximeter II works with a double test loop for sample incubation, short measuring intervals and a PC for online data analysis, which optionally allows a high temporal resolution of the water to be monitored. An alternative version of the AlgaeToximeter enables the incubation of the sample within the measuring chamber without sample loops thus resulting in less maintenance with longer measurement cycles.

Principles of the bbe AlgaeToximeter II

The cultivation of the algae takes place in a fermenter, which is regulated “turbidostatically” by a second fluorescence measurement. This regulation ensures that the algae and their activity are maintained.

The measurement procedure requires the water samples be almost continually pumped into the bbe AlgaeToximeter II, in which the concentration and the activity of the naturally occurring algae are determined. A precisely defined amount of algae from the fermenter is then added to the measuring chamber by way of a loop. The activity of the added algae remains constant as long as no toxic substances are present. If any toxic substance is present, its interaction with the photosynthesis centre leads to an inhibition of algal activity. The dimensions of the inhibition can be estimated by comparing the algal activity with and without water sample.

After each measurement, the measuring chamber is automatically cleaned by a piston. This prevents the growth of algae and biofilms within the measuring chamber.

Measurements

• direct chlorophyll fluorescence:
  corresponds to wet-chemical chlorophyll analysis
• active chlorophyll fluorescence in the sample (Genty method):
  determines the percentage of active chlorophyll under illumination and serves as a toxicity measurement
• differentiation of fluorometric algae classes:
  to simultaneously determine the content of chlorophyll according to green algae, blue-green algae, brown algae (diatoms and dinoflagellates) and cryptophytes
• transmission:
  takes place automatically during each analysis and, if necessary, can be used to compensate the influence of substances which cause turbidity