MONITORING AND METERING
sensor head, new blanket detectors are capable of locating and tracking even very thin sludge blankets, for example on clean water clarifiers. Reliable radio communications also allow operators to install multi-point systems without the need for expensive interconnection cables. Using this new sludge blanket technology, a multi-point system is installed on four rectangular primary tanks and four circular secondary tanks. Sensors communicate via a mesh radio network to a centrally located processor and controller. The blanket level detectors allow the operator to maintain and control blanket levels which helps the plant meet its final ammonia and suspended solids consents.
Picket fence thickeners Picket fence thickeners are used to thicken sludge prior to digestion. De- sludging of these tanks is often controlled on a timer basis. Traditionally it has been very difficult to measure sludge blankets in picket fence thickeners because of the poor interface, there is a high solids content in the supernatant which make detection of the top of the blanket difficult, however recent advances in technology have made this possible.
Energy saving Wastewater treatment plants require reliable and cost-effective sludge blanket level detectors. New technology supplied by Sludge Blanket UK focuses on providing automated and continuous detectors. This latest generation of ultrasonic sludge blanket level detectors can be used in primary and final tanks as well as picket fence thickeners, and are capable of de-sludging tanks based on level rather than time, which save energy and cost while ensuring compliance with discharge consents. ■■■
www.sludgeblanketuk.com the window
rotor excite a static Hall Effect sensor located in the body. This generates a series of voltage pulses; the output pulse voltage is equivalent to input (4.5 - 24VDC), with a frequency proportional to the flow rate. Digital rate meters, totalisers, and other electronic controllers then use the output signal. A subset of the RFO sensors is the RotorFlow Analog (RFA) Type. These use the same operating principle, but instead of outputting a voltage pulse they are conditioned to provide an analog output signal of 0-10VDC. RotorFlow sensors monitor fluids with flow rates ranging from 0.4 - 227l/minute. Accuracy is dependent on model and flow range selected. RotorFlow sensors combine their high visibility rotors with solid-state
electronics that are packaged into panel mountable housings. Housing bodies are available in brass, stainless steel or polypropylene. ■■■
www.gemssensors.com
September 2010 Water & Wastewater Treatment 23
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