Climatic changes and extensive agriculture activties endanger drinking water reservoirs in many countries . Eutrophication turns the drinking water dams to a suitable environment for harmful algae blooms. Controlling blooms of phytoplankton, including cyanobacteria, is a high priority for managers of aquatic systems especially for drinking water, recreation activities and aquaculture production in these days.
Moreover, some cyanobacteria produce taste and odor compounds, such as geosmin and 2-Methylisoborneol (MIB). The effort to drinking water reservoirs with the unpleasant musty flavors and odors gets every year worldwide bigger and bigger. Beside algae and cyanobacteria are well known to synthetisize biotoxins. These toxinsreleased from cell lyses, have negative effects to human health and are quite often the reason for a high fish mortality.
The management of lakes, reservoirs and rivers to monitor cyanobacterial blooms is critical to protect human health.
The harmful cyanobacteria Planktothrix rubesence has been identified as a dominant bloom-forming genus, as well as a frequent toxin producer. Planktothrix rubescens belongs to the class of cyanobacteria with a specific pigment composition and is a thread-like many other cyanobacteria. This cyanobacteria has a red pigment phycoerythrin inside the. Therefore the cells appear red (Fig. 1). Planktothrix rubescens can produce the toxic peptide microcystin, which can lead to liver damage and cancer . Lifestock s and dogs are highly sensitive for the biotoxin and can immediately die after water intake from toxic dam water.
The Sengbach dam located in the Nordrhein-Westfalen province in Germany provide around 17,9 million population. In total there is a demand of drinking water of around 2.3 Mio.m3. The dam reservoir has 20 ha area and the capacity of the dam is 2,8 Mio. m3. The maximum depth of the reservoir is 36 m.
In the spring 2013 dogs died after dinking the water in this big dam area. Further investigations furnished the proof of Planktothrix rubescens increase and later on a big algae bloom was reported in the Sengbach dam waterworks.
The water production was interrupted for three month after this event with extensive laboratory tests carried out daily and supplementary by continuous monitoring in the intake with an bbe AlgaeOnlineAnalyser since the beginning of May 2013. Below is a picture of the AlgaeOnlineAnalyser which installed in the intake monitoring station.
By use of the AlgaeOnlineAnalyser the time consuming microscopic analysis was reduced drastically. massively. Additionally an alarm threshold was implemented to monitor harmful algae continuously 24/7.
In an extra approach the algae concentration of different water samples collected from the surrounding lakes and rivers of the dam, have been tested weekly faster and more accurately in the laboratory of the waterworks using the bbe AlgaeLabAnalyser - shown in below.
Cyanobacteria like Planktothrix rubescens thernm often show an accumulation at the thermocline of the dam or lake. To obtain information about the distribution depth of the algae, the profile measurement with the bbe FluoroProbe instructs the operators to figure out the best depth for the water inlet in order getting the best quality water with lowest algae content (around 12 m depth). Below pictures shows some of the measurement of Fluorporobe in 2014.
The fluorometric measurement is the a reliable method where algae concentration can be determined in real time and in-situ. Comparision of the laboratory analysis (cell counting) and the AlgaeOnlineAnalyser measurements are good accordance - below picture.
The AlgaeOnlineAnalyser measures also the activity of the Algae to get the information if the bloom dynamics. This information helps to optimise drinking water processing.
After a while the algae concentration decreased again and reached a continous low - below the alarm value proposed by the WHO. The WHO recommends in a guideline that the observation value for the total cyanobacteria should be less than the 1 µg/l for drinking water production. Below picture is a screenshot of the WHO guidelines:
In peak times it became more than 20 µg/l measured in the waterworks. The AlgaeOnlineAnalyzer is a great tool for the safety of the drinking water supply optimacing there treatment efforts.
You can watch a video about this application in youtube below link: