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Online Biomonitoring Using Green Algae - Algae Toximeter II

Online Biomonitoring Using Green Algae - Algae Toximeter II

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

The bbe Algae Toximeter 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 Algae Toximeter 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 Algae Toximeter 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 Algae Toximeter 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 Algae Toximeter

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 Algae Toximeter, 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

Advantages

• highly sensitive with regard to the detection of herbicides and their by-products
• sensitive to a wide range of toxic substances
• controlled independent cultivation of algae
• cultivation control due to active chlorophyll measurement
• no exclusion period after alarm
• anti-fouling system due to automatic cleaning of the measuring unit
• autostart function after power failure
• CE-sign

Applications

• drinking water supply
• dam monitoring
• waterway analysis and assessment
• general environmental assessment
• intake monitoring
• chemical analysis
• limnological work
• research and education

Software

The database software is used to record and analyse the data. The most important features are...

• saving of data and parameters at any time
• graphic display of all measurement values
• online display in LAN
• calibration of the instrument
• parameterisation of the measurement
• data export to EXCEL and to text files
• print function
• subsequent recalibration of algae classes





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