water technology

resource water

Up to date, the ecological state of the surfacewater is one of the last hurdles in the general proces of setting up realtime monitoring systems of surface waters. Many urban area's have to rely on surface water resources for the provision of sufficient drinking water to the population. In the case of surface water being used for the preparation of drinking water, the real time monitoring may be of additional importance for control decisions such as intake of raw water to the buffer basins.

The CytoBuoy instruments for bench top, submersible and moored use are especially designed for fast analysis of the abundance, status and composition of phytoplankton including direct signalling of HAB species or species with morphology similar to certain HAB species. Species such as cyanobacteria (blue-green algae), can be identified, quantified and classified including the various colony formers such as filamentous species - Anabaena sp., Aphanizomenon sp., Microcystis etc. Autonomous systems allow a sufficiently high measuring frequency - and more: sudden events affecting phytoplankton viability and or physiology - caused by whatever agent / toxins - will be noticed immediately.
A CytoSense can be installed at a water intake station taking samples directly from the pipe line, or on a remote location on the resource lake or basin (buoy) or upstream river with telemetry of measuring data.

sediment transport

Generally, the phytoplankton in water samples is distinguished by their fluorescence. The non-fluorescing particles are detected also; these include the non-biological mineral and clay particles. In most river and estuarine waters we find 10 or 100 times (or more) nonfluorescing particles as compared to phytoplankton. The percentage phytoplankton increases in quite lakes or far enough off shore. The non-fluorescing particles are characterized according to their length and light scattering properties (forward and side scatter). Pure sand grains > appr. 100 um are not measured by the system since they are precipitating too fast to be drawn into the sample input tube at the low fluid speeds typically used. The rest is analyzed from a particle size of about 0.3 um and larger. The larger particles are, if assymetrical, oriented in their length axis so the sizes indicated are particle lengths. We were been analyzing some samples coming out of a sediment removal apparatus used to clean up the ballast water. We found a relatively small group of particles having different forward (lower) to sideward scattering properties. These particles had a relative mass <1, and probably of bio-organic origin.

marine optics

The availability of the CytoSense, -Sub and -Buoy flow cytometer systems opens up new possibilities for studying marine particles in situ, and the establishing of a link between single particle optics and bulk inherent optical properties. Potential applications include detecting thin layers of heterotrophic activity which are believed to exist close to major picnoclines, monitoring the physiological status of sinking algal blooms, investigating variations in diatom chain length under different physical conditions (e.g. turbulence regimes), and counting phytoplankton cells in waters which bear a heavy burden of other suspended particles. Application of flow cytometry to the determination of single particle optical characteristics may help to advance our understanding of the characteristics of mixed particle suspensions and hence, in an interesting contrast of physical scales, aid in the interpretation of satellite measurements of remote sensing reflectance.

As individual phytoplankton pigments are characterised by unique light absorption features, algal blooms may be detected 'remotely' by ocean colour remote sensing techniques. New satellites are often equipped with special ocean colour sensors, and it may therefore be expected that satellite ocean colour data will play an increasingly important role in detection and monitoring of algal blooms. However, reliable satellite remote sensing measurements of ocean colour rely on adequate and preferably simultaneous in-situ sea-truth measurements for calibration and validation of the sensor data. An adequate sea truth-measuring infrastructure should provide reliable information for calibration and validation of remote sensing data. The CytoBuoy systems yield a high level of information with high time resolution which can be dovetailed with satellite overpass times.