Technical Publication Liquid Level/Interface Monitoring in Flocculant/Sludge Control By Steven Craig, Sr. Member Technical Staff Fluid Components International (FCI) Visit FCI on the Worldwide Web g www.fluidcomponents.com Headquarters g 1755 La Costa Meadows Drive San Marcos, California 92078 USA Phone 760-744-6950 g Toll Free 800-854-1993 g Fax 760-736-6250 European Office g Persephonestraat 3-01 5047 TT Tilburg, The Netherlands Phone 31-13-5159989 g Fax 31-13-5799036 FCI is ISO 9001:2000 and AS9100 certified

In municipal and industrial wastewater treatment plants, sludge clarifiers are utilized to separate solids from the water treatment effluent system by introducing air and flocculants. This process results in the sludge rising to the top of the pond or tank and spilling over a weir into a separate collection area. The amount of air and flocculants are controlled by measuring the liquid level interface between the sludge and water. Flocculants are used in both the treatment of municipal sewage and industrial wastewater. There are many different types of flocculant chemicals and wastewater treatment...

stream. One RTD is heated while the other senses the actual process temperature. The temperature difference between these two sensors is measured and is directly proportional to the flow rate of the liquid (Figure 2). When a liquid-to-liquid interface change occurs, for example in oil to water, large changes in natural convection and thermal properties will cause substantial changes in the temperature. The liquid level/interface switch point may be factory pre-set by the manufacturer or field adjusted by the plant operator. Similarly when clear liquid is present, the natural convection heat transfer...

With its advanced thermal dispersion mass flow sensor, the FLT features built-in temperature compensation which ensures repeatable and reliable operation, even in dirty or extreme environments, such as those found in municipal and industrial wastewater treatment. This automatic compensation adjusts the instrument for changes in operating environment temperatures to ensure the trip points will remain accurate and will prevent false alarms or alarm failures to improve end-product quality, to maximize safety and to allow alarms to be set within a narrower set point range. A wide selection of standard...