Algae Toximeter II
Online Biomonitoring Using Green Algae
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.
- 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
takes place automatically during each analysis and, if necessary, can be used to compensate the influence of substances which cause turbidity
THE online instrument for drinking water protection
Quick and reliable detection of toxins in the water supply
The ToxProtect is an automated monitoring system to protect a drinking water supply from accidental or malicious contamination due to harmful substances. The characteristic of these threats is a relatively high concentration of dangerous substances that occurs suddenly. Such situations must be detected quickly and safely. False alarms are reduced to an absolute minimum using the ToxProtect. This improves the trust of the operators and reduces unnecessary expenditure.
The Measurement Principle
The ToxProtect monitors the swimming activity of fish in an aquarium fed with drinking or mains water. The location of up to 10 fish and their activity is monitored continuously. Fish react sensitively to the presence of toxins and change their behaviour. The use of fish to detect toxins is an established method.
The test organisms react sensitively to most substances harmful to humans. Toxicity data are available for almost every combination of fish and toxin. To use the ToxProtect to monitor chlorinated drinking water, a dechlorination substance can be added.
The movements of the fish lead to interruptions in light barriers located in the instrument which register the entire volume of the aquarium. The activity of the fish (interrupts per minute per fish) is calculated from these interruptions. If these values fall below a pre-defined threshold, an alarm verification system is activated. In addition, immobile fish at the bottom and top of the aquarium are also registered.
The fish species can be determined by the user, the fish should be however active and have a length of 4-6 cm.
The ToxProtect detects changes in the swimming activity of the fish due to intoxication and evaluates the measurement data for alarm events. The thresholds for the alarm triggers can be set individually. High priority of the alarm emission is given to fish at the top and bottom of the aquarium, which could indicate mortality.
The ToxProtect detects for example the respiratory toxin potassium cyanide within 10 minutes at a concentration of 1 ppm.
Due to naturally occurring random variations in fish behaviour, each alarm criterion is fulfilled from time to time by accident. Hence, in order to prevent false alarms, a verification system is required. This is achieved by decreasing the illumination (turning the light off) inside the aquarium during the verification period.
Normally, this leads to a dramatic increase in fish activity. Under toxic conditions, however, this may be different. Hence, by monitoring the "increase" in activity or lack of it during modified illumination, it is possible to accept or reject the initial alarm automatically.
Operation Monitoring (Hardware Alarm)
The ToxProtect is equipped with internal sensors which refer to possible error functions. The following parameters are monitored:
- sample flow
- drain blockage
- temperature decrease
- accidental or unauthorised ambient light in the aquarium
- high chlorine concentration
Continuous analysis of fish behavioural patterns for the detection of toxins in water.
The bbe Fish Toximeter observes the behaviour of fish in a tank under the influence of a stream of "sample" water with the aid of a camera and continuous computer-assisted image analysis. This uncomplicated but highly sensitive instrument is designed to detect toxic substances in e.g. rivers, reservoirs, water supply systems, water treatment plant intakes and sewers.
The instrument is based on the development of Extended Dynamic Daphnia Tests (EDDT), a tried and tested detection method in Europe and other parts of the world. Continuous biological monitoring with the bbe Fish Toximeter enables rapid detection of toxic substances in water and provides a real-time, online early warning system.
This unique instrument enables the user to observe and analyse toxic contaminations, record them and react quickly to them. The bbe Fish Toximeter is well-suited for the rapid detection of wilful or negligent damage to water systems. It is also conceived as a long-term monitor of water quality during "strategic" analysis.
Features & Informations
Technology for water-quality monitoring
Continuous analysis of live video images enables rapid determination of the behaviour and health of the fish. Toxicity computations and assessments are based on the measurement of the following behavioural parameters:
- swim speed
- behaviour (height, turns, circular motion, etc.)
- determination of size
- number of active fish
- location of fish in the aquarium
Each type of change in behaviour of the fish is investigated and analysed. The so-called "Toxic Index", summarised from all behavioural parameters, is calculated permanently. If the toxic index exceeds a pre-determined value for a certain amount of time, an alarm is triggered. For this, several behavioural parameters must show deviations.
Advantages of the Fish Toximeter
- test results with fish can be used for comparisons with humans
- evaluation of 10 behavioural parameters means an error-free alarm detection
- no sample preparation necessary
- optional dechlorination for use with chlorinated drinking water
- effective public relations presentation
- splash-protected touch screen monitor
- multiple possibilities of connection to a control centre