Online water analysers for process water and waste water industry
Process and waste water are the most challenging water for instrumentation. Mostly, these water are characterized by highly fluctuating loads, very high salt concentrations as well as a high particle density. Hence, the accurancy and speed of measurement depends on the measurement system itself and the used oxidation technique. Obviously, application-specific analysers provides huge advantages against standard analysers, that are used for every application.
Depending on the industry, there are different demands to water quality regarding the water influent, water effluent and discharge control. Limits are prescribed by law or defined by industry-specific associations.
Water that is supplied into an existing system, e.g. cooling water circuit, an industrial plant or waste water treatment plant (WWTP), is named as water influent. Depending on the application it may be necessary, that the water need to be treated before use.
Water, that is derived from a water system is known as a water effluent. Depending on the application, the water matrix may comprise a wide variety of characteristics. So, process water may have a high particle density. On the contrary, process water of a cooling water system is characterized by low particle density . However, it is mixed with chemicals.
Discharge control is the monitored effluent of water into a river or waste water treatment plant. Local law define limits for the effluent in public waters.
In the winter months aeroplanes, runways and landing strips are de-iced with the help of chemicals resulting in the pollution of storm water. Consequently, its disposal may have an extreme impact on waste water treatment plants or public water. Hence, the continuous monitoring of this storm water is of special importance.
Due to the large sealed surfaces at an airport, there is enormous amount of storm water when it rains. To ensure a fluent operating procedure this amount of water has to be discharged in the fastest possible way. During the summer months the water is usually treated with an oil extractor and discharged into the nearest discharge system or partially sprayed on green areas.
During the winter months aeroplanes, runways and landingstrips are de-iced with special de-icing agents which depositon sealed surfaces. However, on precipitation this effect leads to contamination of storm water. The disposal of such surface water, especially de-icing waste water, challenges not only airport operators but also planners and equipment suppliers. In order to monitor the contamination TOC (Total Organic Carbon) and COD (Chemical Oxygen Demand) are used as parameters.
Because of its adhesive characteristics de-icing water causes huge memory and carry-over effects with online monitoring systems. Hereby, residual traces of previous measurements falsify the results of the current measurement. Furthermore, due to this characteristic neither filtration nor transportation through thin tubing is recommended.
Another challenge is the strongly fluctuating loads. On one hand, the critical values for public discharge are very low, the discharge regulation for the river Rhein for example stipulates 150 mg/l O2. On the other hand, it must be possible to measure high concentrations of up to 50,000 mg/l C accurately. Therefore, a very fast and precise measurement technique is required in order to discharge most of the water into the discharge system in a costefficientway. Depending on the concentration/ load it can be discharged in a WWTP or storage basin.
In cooperation with airport operators LAR AG has developed an online TOC analyser that meets the high requirements of this application: LAR's QuickTOCairport.
Usually, waste water is characterized by suspended and dissolved pollutants. On the contrary to municipal waste water, it has a significantly more complex water composition.
Industrial waste water may involves toxic chemicals. These water needs a more intensive treatment than municipal waste water. Hence, the requirements on the measurements are enormous. Whether adhesive properties, high and fluctuating loads or a wide variety of water compositions, industrial waste water treatment plants are specialized to specific waste water to perform an optimally cleaning process.
The accurate online analysis of process water / industrial waste water allows conclusions about the functionality and effectiveness of the production facility. The right measurement technique enalbes the fast detection of product spills and provides the opportunity to take countermeasures.
For the toughest applications, LAR AG offers its Ultra series. The analysers QuickTOCultra, QuickCODultra or QuickTONultra provide reliable measurements of TOC, COD and TNb. Combinations of these parameters are possible. For a safe toxicity monitoring LAR offers its NitriTox. This online toximeter protects the biology of a waste water treatment plant against toxic loads.