Source water for desalination has a significant content of naturally occurring inorganic ions, and the objective of treatment is to reduce the concentration of, or remove, these substances. These naturally occurring substances include some that would be of potential concern if present in sufficient concentrations after treatment. There are also many marine algae that can produce toxins of concern to human health. These issues are covered in detail in desalination technology: health and environmental impacts.
How Algae cause problems in Desalination Plants?
When source water quality varies widely, monitoring can help provide information for managing water withdrawals to minimize ingestion of constituents or contaminants. In addition, knowledge of potential contaminants is important for developing contingency plans to protect source water quality. Some algal species can cause problems if they reach sufficient numbers, either by producing toxins or by having a high concentration of biomass.
According to studies, bloom-producing algae include dinoflglates, diatoms, haptophytes, raphidophytes, and cyanobacteria. The latter, in particular, can cause dissolved oxygen depletion, foam on the beach, and toxic blooms (red or brown tide) when they proliferate greatly.
Membrane fouling and pre-treatment
There is growing evidence that algae are a major cause of operational problems in desalination plants. Many plants abstract raw water in coastal sources, where algal blooms frequently occur. Incidentally, HABs frequently occur in various areas where seawater desalination plants are installed. This makes the algae in one of the major affecting parameters in designing and operating the desalination plants.
The first point of control in minimising the entrainment of algae into the plant is the seawater intake. Better understanding the dynamic nature of HABs in coastal waters, their large spatial extent, and concerns about the environmental impacts of bloom control methods is essential.
In line with recommendations from the World Health Organization, moniotring the risks and hazards, monitoring the intake Point can be used to assure safe drinking water in the face of a toxic marine HAB, along with HAB Management Response Plans is included.
In order understandng the dynamic of the algae bloom around the deslination plant it is needed to plan for monitoring andmeasuring the algae concentrtion in different locations which normally faces with algae bloom like intakes and coastal area.
Intake of the Desalination plant.
In order being able to get information about suspecious increasement in the different algae classes and as an early warning indicator it is highly recommned to install bbe Algae Online Analyzer in the intake of the Deslaniation Plants. AOA will give real time information of algae concentration and important calasses of algae in the intake of plant.
The unique feated of the Sptectrofluoromteric method which is used in the AOA is Yellow Substances compensation. The instrument impresses due to its rapid analysis of chlorophyll concentrations. The chlorophyll concentration, the transmission and optionally the photosynthetic activity are determined simultaneously.
Algae bloom does not happen in a fixed place and it moves by waves and winds by the time, and also the algae changes its distribution in different depths to obtain enough food and suitable sun. Therefore measuring the algae concentration in different depths and locations is necessary. The bbe FluoroProbe is a highly sensitive measuring instrument for the analysis of chlorophyll with algae class determination. Individual profiles during the measurements are taken for green algae, blue-green algae/cyanobacteria, diatoms/dinoflagellates and cryptophytes. This enables the analysis of the occurrence and distribution of e.g. blue-green algae on site without the necessity of the laboratory. Possible interferences due to yellow substances are eliminated by an integrated CDOM correction factor.
The FluoroProbe can quickly and reliably determine the chlorophyll content of different algae classes down to a depth of 100m (optionally 1000 m). The measurement data can be displayed in real time on a PC or be stored in the probe for subsequent evaluation.