Online (source) water monitoring

Aquatic ecosystems like lakes, rivers, seas and oceans play a vital role in global and human health and prosperity.  Although maintaining biodiversity and good ecosystem conditions may seem a longterm goal only, many human activities are hampered or jeopardized immediately by sudden occurrence of substances, microscopic particles or organisms that are harmful.   Besides recreation activities like swimming and bathing, food provision like fishing and aqua farming, many urban area’s rely on surface water resources for the production drinking water. In such cases, high frequency or realtime monitoring is important for timely migitation measures and control decisions, such as warning the public or stopping the intake of raw water into the buffer basins.

A logistic and financial hurdle is caused by onsite taking of samples for transport to the lab for analysis, followed by lengthy manual microscopical determinations.  Insitu sensors and remote sensing do provide realtime data but their information, especially the biological, is often not specific enough. CytoSense and CytoSub technology can be used insitu, and by their optical analysis on the individual particle level they provide a surprisingly high level of information. Not only it generates a direct link to bulk optical parameters such as turbidity, chlorophyll load, bluegreen algae etc, it allows analysis at the microscope level – of particulate and microbial composition, detection of individual species, and by a trained software model it may even provide an alert for toxic pollution e.g. herbicides.

Typically monitored organisms are cyanobacteria aka blue-gree algae which are possibly toxin producers and therefore pose a threat also for bathing/swimming/recreation waters.  Bulk optical sensors may provide a crude amount of total blue-green as a simple and fast result. However, not all species are equally nuisant which makes it advantageous to know more about their composition.  The scanning and imaging capabilities of CytoSense allow high level characterization, with determination often to the genus and sometimes even species level, as well as the abundances and cell/colony size distributions for each of those groups. Gas vacuolated species are also detected. The images and scans also provide insight in cell damage or lysis for instance by oxidation processes in drinking water production. The total averaged data corresponds to the bulk optical data again, and may serve to add significance to aerial images.  

Real-time data processing and reporting

The combination of CytoSense or CytoSub and EasyClus software (Thomas Rutten Projects, NL) provides a unique way of real-time data processing and reporting directly to a central system (link to  You can benefit from a “warning tool” mode EasyClus LIVE which gives online alert (or email alert) upon certain basic parameter reaches a pre-defined level (e.g. x particles/mL).

the ‘dash board’


In-situ plankton dynamics monitoring in the river Meuse 

The Meuse river has important functions including the provision of drinking water.  A floating measuring station  continuously performs physical and chemical analyses.  A CytoSense on this station runs since 2013 (click here to see results in a near real-time) for biological analysis (phytoplankton and other particles). The project is led by the Dutch Ministry of Infrastructure and the Environment, in close collaboration with CytoBuoy.  The river water is analysed 24/7 by the CytoSense for 30 minutes on and 30 minutes off continuously. Data files are automatically transferred to HQ and processed by EasyClus software (Thomas Rutten Projects). The CytoSense runs unattended and is serviced once per year.  The hourly flow cytometric data is also used for an early warning system for water quality (below).

CytoSense – C  in continuous operation on the River Meuse monitoring platform
automated data clustering
automated categorisation of the plankton, scans and images

Mussel larvae 

Mussel larvae may be a nuisance for the functioning of mechanical microsieves in the first line of river water filtering for drinking water production. The picture shows mussel larvae as detected and photographed by CytoSense. They form a distinct group (cluster) in the analysis of the scans resulting in photo collection.

Source: river water Afgedamde Maas, near the intake for drinking water by Dunea water (The Hague).

Free liths and other microparticles

In several methods of drinking water production, filters play a crucial role. The functioning of these may be hampered by the presence of high loads of very small particles.  Sometimes such nuisance particles are billions of small liths, rigid calcium discs, freely suspensed particularly when a bloom of coccolithophores occurs. Their light scattering is an important property to interpret aerial photo’s or readings from bulk optical sensors.  However,  similarly sized particle types may be vastly different in terms of light scattering and absorption.  Therefore such methods can not differentiate sufficiently to the type and amounts of particles present like a single cell analysis technology such as CytoSense, combining light scatter, fluorescence scans and images.  This generates a high level of insight in the types of particles present in the source water, in terms of size, nature and shape.  Shown are results of insitu detection with CytoSense on a moving ship, each analysis ca. 10 mins apart.  The cyanobacterium Synechococcus sp. and the freely suspended liths are similarly sized particles and they were similarly abundant. From the lower panel it is clear that the light scattering of an individual lith is ca. 100x more intense as compared to that of an individual Synechococcus cell.  Therefore, from a bulk optical scattering analysis or aerial photo or satellite image alone the cause of the turbidity as well as the presence of Synechococcus would remain unclear.   

SEM image of Emiliania huxleyi coccolith
Top Panel: numbers of cells and particles. Lower panel: the average detected light scattering per particle for each group. 

Damacy: a warning system for water quality control, based on CytoSense data of algal populations

Freshwater phytoplankton form a complex community. The species and phenotypes may be influenced by environmental water quality changes like acute freshwater toxicity of known and unknown toxicants. Full continuous microscopical characterization and taxonomic identification is practically impossible. However, with thousands of phytoplankton sampled on a hourly basis by a CytoSense, a huge amount of data is gathered. A Discriminant Analysis of Multi-Aspect CYtometry (DAMACY) method was adapted to extract normal environmental conditions imposed by diurnal, meteorological and other exogenous influences, from this data.  After sufficient training, and by realtime analysis of new CytoSense data, deviations from the predicted normal environmental conditions could detect when phytoplankton are affected by non-natural contaminants in the river water like herbicides.  Such a model was built by the Dept. of Analytical Chemistry, Radboud University, Nijmegen, The Netherlands, and subsequently automated by Thomas Rutten Projects called EasyDamacy ( The system performs initial trials on CytoSense data from the River Meuse measuring station operated by Rijkswaterstaat, Ministry of Infrastructure and Public Works.   This turns the CytoSense flow cytometer from an unsurpassed technology for algae characterization into a monitoring solution for freshwater quality.

Thresholds for alarm determination
Damacy simplified alarm output