UK Focus - Water/Wastewater xiii Water Quality Monitors Now Have Ammonium and Fluoride Capability
Intellitect Water (UK) has announced that ammonium and fluoride sensors have been added to the range of parameters available on the company's Intellisonde™ water quality monitors.
Recent advances in monitoring technology have enabled the measurement of water quality at the point of delivery through the direct insertion of specially designed 'Intellisondes™' into distribution pipes. Initial units were able to measure a range of water quality parameters (including chlorine) but both fluoride and ammonium have now been added to the list.
Intellitect's Technical Director, David Vincent believes that this new facility will be of great value to water companies, adding, "Both species are naturally present in drinking water, however, fluoride levels in drinking water are tightly regulated for oral health purposes and ammonium levels are of interest for two reasons. Firstly, they can indicate contamination of sanitary significance and secondly, they can form part of a disinfection process to form chloramine which maintains chlorine in the distribution system.
"The key feature of the new sensors is their size; the whole sonde, containing all of the sensors, fits inside a 1½ inch valve so the sensors, which are Ion Selective Electrodes, are very small."
It was from observing different patterns of dental decay in areas of differing levels of naturally fluoridated water that the benefits of fluoride were first observed. Currently around six million people in England receive water which either has had its level of fluoride adjusted to, or has a natural fluoride content of around 1 mg/l. The Guideline Value suggested by the World Health Organisation, dependent on local conditions, is 1.5mg/l of Fluoride.
At present, drinking water quality is mostly measured at the treatment plant, but with the arrival of Intellisondes™, real-time measurements can now be taken at any point in the distribution network and with the addition of both Fluoride and Ammonium to the choice of sensors, Water Companies will be able to further improve both the efficiency of treatment processes and the reliability of the delivered product.
Optical Dissolved Oxygen Technology Outperforms Traditional Methods
Three methods are generally used to measure dissolved oxygen (DO) in surface waters: Winkler titration, membrane-covered electrochemical sensors (polarographic or galvanic cell), and optical-based sensors. The optical technology for measuring DO levels in water has quickly become a well-accepted method due to many advantages over membrane sensors, and its close correlation to Winkler titrations.
Optical DO sensors rely on lifetime-based luminescence technology to accurately measure DO levels in- situ. If an oxygen-specific lumiphore is illuminated with a blue LED, it causes the lumiphore molecules embedded in the
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gas-permeable sensing foil to emit red photons. DO acts as a dynamic luminescence quencher, therefore the lifetime of luminescence is inversely proportional to the DO concentration. Optical sensors are especially accurate below 2 ppm—a range in which most membrane sensors routinely give poor results. When monitoring anoxia in open bodies of water, achieving accurate readings below 2 ppm allows researchers to reliably characterise nutrient-related hypoxic zones. Optical DO sensors do not consume oxygen as part of an electrochemical reaction, and do not require sample flow for accurate readings.
COD in 10 Minutes
Camlab (UK) has launched a revolutionary instrument from Aqua Diagnostic, which is capable of accurate, sensitive, real-time analysis of Chemical Oxygen Demand. The new green technology requires no hazard- ous chemicals, produces fast results and eliminates the time consuming digestion step. The core of the technology is the PeCOD™ sensor which has a number of practical advantages compared with the traditional methods of COD analysis. PeCOD's ability to analyse samples containing chloride is significantly better than the dichromate method, and does not require the addition of toxic reagents like mercury and silver salts. The increased sensitivity of the method enables the measurement of clean water samples with low ppm levels of COD. Typical analysis times of less than 10 minutes are easily achieved. The sensor consists of a UV-activated titanium dioxide film coupled to an external circuit. The high oxidising power of the sensor gives the analyser a significant advantage compared with the traditional dichromate method. The PeCOD™ COD analyser exhaust- ively oxidises all organics, and counts the electrons that are liberated to provide a direct measure of equivalent COD. The PeCOD™ analyser is avail- able as a true on-line monitor or can be supplied as a benchtop labora-tory instrument, which has an optional battery pack for field use. The PeCOD™ technology allows the user to rapidly measure COD online in real time and enables a reading to be generated every 15 minutes to give unrivalled data on a waste or discharge stream. The online real time capability means that processes can be adjusted to reduce energy use or to make treat- ment more cost effective.
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Optical sensing technology has been proven in multiple field studies to give accurate data over long deployment periods—with minimal maintenance and calibration requirements. Maintenance and material costs are drastically reduced, and site visits are minimised. Data is especially accurate in anoxic conditions with accuracy in normal environmental DO ranges as good or better than traditional membrane sensors. Additionally, sensor response time is faster, and the sensing element is more durable and has a longer operational life than an oxygen permeable membrane.
According to the American Society for Testing and Materials (ASTM) International, the luminescence-based DO sensor method (D888-05, Test Method C) is an acceptable method for measuring DO. For more information on optical DO technology and on robust, accurate RDO®
sensors for groundwater, surface water, and process applications, please visit
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Reliable, accurate water level monitoring
Instrument Family
Application/technical notes and product specifications available at
www.in-situ.com
From the Water Level Experts: In-Situ® Inc. CALL 07958 236100 TO ARRANGE A DEMONSTRATION
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