Whittier® L’eau Claire

Thanks to its high capacity for adapting to inlet conditions where the liquid stream is loaded with large amounts of suspended solids, L’Eau Claire® can remove up to three times the amount of solids captured by conventional downflow media filters. As a proven solution to the treatment of industrial water, Veolia’s L’Eau Claire® has an unmatched track record of attaining extremely fine filtration performance.
 

Benefits

• Reliability. High tolerance to operations with feed water under upset conditions delivering consistent effluent quality independently of inlet solids concentrations.
• No plugging thanks to upward flow through coarse media followed by fine filtration.
• Low CAPEX. Less expensive than conventional clarifiers and sedimentation basins that require costly flocculation, mixing, and filtration steps.
• Space efficient. Requires 75% less footprint than conventional alternatives.
• Downstream equipment protection. Longer life in demineralizer resin systems thanks to the absence of suspended solids and metal sulfates (e.g. alum).
• Less downtime. Eliminates costly maintenance of cleaning silica from turbine blades.
• Low OPEX. Total automation and minimal levels of chemical feed (typically 1 to 4 ppm) keep operating costs to a minimum.
   

Applications

Designed to operate at 6 gpm/ft2 across a wide range of applications, L’Eau Claire® is used extensively on river water as pretreatment and protection of demineralizing ion-exchange or membrane systems in cooling water or boiler makeup water systems. L’Eau Claire® is also used in seawater filtration, petrochemical and refinery process water and for the removal of hardness precipitation in brine service in the chlor-alkali industry.

Features

The L’Eau Claire™ filtration system consists of one or more vertical vessels which can be designed for pressurized or atmospheric operation. To ensure an even flow pattern and optimal removal efficiency, these filter units feature a deck plate with a multiplicity of flow nozzles that distribute the liquid through a media filtration bed consisting of coarse gravel, and various grades of sand. To minimize on-site costs and maximize installation efficiencies, L’Eau Claire™ filtration is provided as a packaged system with pre-assembled piping, valves, instrumentation and automatic controls which are skid-mounted along with polymer tanks and pumps, flush pumps and air scouring blowers.

L’Eau Claire™ filters, which are designed in a wide range of sizes and system arrangements to accommodate modular process capacity expansions, achieve up to 98% removal of particulate sized above 2 microns. Typical performance outcomes also demonstrate effluent turbidity of less than 1.0 NTU, suspended solids content below 1 mg/l, and colloidal silica not exceeding 0.1 mg/l.

Operation

The removal of particulate using L’Eau Claire™ filtration is achieved by the flow of the raw liquid stream in an upward direction through subsequent layers of granular filter media at rates of up to 6 gpm/sq.ft.

Two primary mechanisms allow for this unparalleled removal efficiency: entrapment and adhesion. Entrapment is achieved by straining and intercepting particles through powerful hydro-dynamic forces. Adhesion consists of combinations of chemical bonding, electrostatic forces, and mutual adsorption. The addition of a small concentration of cationic polyelectrolytes (i.e., polymers) to the raw water coats the surface of the suspended solids and coagulates them resulting in their adsorption onto the surface of the media grains throughout the media bed.

As the particulate matter is progressively captured by the sand grains, the media bed will gradually reach a point of saturation in its holding capacity. To free the particulate matter from the sand grains, the L’Eau Claire™ media bed is expanded by air scouring and introducing a stream of untreated water which fluidizes the bed with a powerful upward flow of water mixed with air bubbles. This cleaning cycle continues as the media circulation dislodges the attached solids thanks to the scrubbing action produced by the turbulent media fluidization until all of the solids are washed away.

As the operation of L’Eau Claire™ upflow filters alternate between a filtration cycle and a cleaning cycle, this flushed water volume can also be stored, decanted and reused in a closed loop cycle that eliminates the necessity for clean water tanks.