Throughout water and wastewater treatment operations, numerous opportunities exist to measure and improve process conditions. The use of effective level, flow and volume measurement technology can enhance your facility’s safety and environmental impact.
To handle your most complex measurement challenges, you need to implement accurate and reliable level and flow instrumentation throughout your facility. Here are a few applications where you can take advantage of water process controls to improve the efficiency of your operations.
Chemical Feed Tanks
In water and wastewater treatment facilities, chemicals are added from feed tanks for purposes that include water softening, pH adjustment, taste and odor control, coagulation and sedimentation, scale and corrosion treatment, pathogen control, neutralization and fluoridation.
Liquid solution storage and day tanks can be especially challenging, because they require stringent level monitoring to ensure ongoing chemical treatment. The nature of the chemical, the geometry of the holding vessel, and the presence of mixing systems or other hardware are factors that will help determine whether a pulse burst radar, guided wave radar, non-contact ultrasonic transmitter or magnetic level indicator (MLI) is the most suitable level control technology for your application.
Water Storage Tanks
Storage vessels for reclaimed water range from small tanks for potable and service water use to large, open or enclosed reservoirs. Large capacity storage – most commonly in open reservoirs – is necessary for off-line storage of peak flows, flow-through in-line storage and long-term storage of seasonal flows that are discharged during alternate seasons.
In this application, plant operators face the challenge of providing reliable level monitoring for large and small water storage tanks. In addition, level controls in open atmosphere reservoirs must frequently withstand punishing weather conditions. Controls, which can include pulse burst radar, guided wave radar or a non-contact ultrasonic transmitter, are specified according to the size and geometry of the bulk storage vessel.
Carbon Slurry Level
Carbon is employed in adsorption processes for the removal of organic, inorganic, taste and odor control compounds. granular activated carbon (GAC) and powder activated carbon (PAC) are two leading adsorption treatments, the former utilizing a carbon bed and the latter employing a contact basin. Carbon slurry tanks require level monitoring.
This process creates numerous challenges, including handling and safety problems due to the flyaway dust and difficult-to-wet characteristics of carbon. Because carbon buildup often chokes mechanical level controls, non-contact monitoring technologies and contact level sensing solutions that use single rod probes to avoid media buildup are popular. Some of the most frequently used water process controls for this application include pulse burst radar, guided wave radar, level switches and displacer level switches.
Flow measurement is accomplished by a transmitter programmed to convert a level reading into units of volume per time, as liquid passes through a flume or weir in an open channel. A flume is a specially shaped portion of the open channel, with an area or slope that is different from the channel’s slope or area. A weir resembles a dam placed across an open channel positioned so that liquid can flow over it.
Measurement devices are configured according to the geometry of the flume or weir. Flow control devices, which can include pulse burst radar, guided wave radar or a non-contact ultrasonic transmitter, must provide reliable measurement despite challenges that include turbulence, solids content, corrosive chemicals or varying flow velocities and flow depths. In addition, environmental requirements often mandate the use of a totalizer and data logger.
A centrifugal pump operating in a no-flow condition will quickly sustain damage. Whether caused by a closed valve or plugged line downstream – or by cavitation – restricted flow can overheat the media and cause seal damage. A flow switch along the pump’s discharge piping will shut down the pump when liquid flow drops below the minimum selectable flow rate.
Solid-state flow switches and mechanical flow switches provide a proven solution to this challenge, because they offer the highest level of reliability for pump protection by offering low flow sensitivity, wide temperature operation and high turndown.
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