Patent Application
20070210017
The present invention is directed to water and/or wastewater filter systems for filtering impurities from a liquid. More particularly, the present invention is directed to a filter system having active filtering particles and a method of operating the filter system.
The Harberer process is a know method of producing and operating active filters to remove various organic and inorganic dissolved solids from water and wastewater. The Harberer process is disclosed in U.S. Pat. No. 4,208,281 the entire contents of which are hereby incorporated by reference. The filter bed includes buoyant plastic balls that are coated with an active material. Specifically, a liquid containing the active material is directed upwardly through the filter bed to cause the active material to be distributed on and adhere to the surfaces of the plastic balls at a predetermined flow rate. The active material is a carbon (sometimes referred to as powdered activated carbon or PAC) or other powdered material such as aluminum oxide that is maintained on the plastic balls through static electrical attraction. Subsequently, a liquid to be purified is directed upwardly through the active filter bed at a flow rate lower than the predetermined flow rate for the application of the active material to the plastic balls of the filter bed. Overtime, the performance capacity of the active material is degraded through a combination of adsorption of dissolved solids and blinding by accumulation of solid material at the surface. The spent or exhausted active material must be removed from the buoyant plastic balls and a new coating reapplied to the buoyant plastic balls. In prior applications, the removal of the active coating was accomplished by directing high volumes of treated or filtered water downwardly through the filter bed. The velocity of the filtered water is higher than the velocities of the liquid in the application step to expand the filter bed downward and flush out the spent carbon. This method is very inefficient as it uses high volumes of treated water that is directed to waste rather than provided for service.
An object of the present invention is to provide a novel and unobvious active filter system and method of operating the active filter system to filter water or wastewater.
Another object of a preferred embodiment of the present invention is to provide a method of operating an active filter system that does not require a washing fluid to be directed in a direction opposite to the flow of influent during filtration thus considerably simplifying operation and structure of the filter system.
A further object of a preferred embodiment of the present invention is to obviate the need to use filtered water to remove the coating of active materials from the plastic media particles.
Yet another object of a preferred embodiment of the present invention is to provide a method of operating an active filter system that does not require high volumes of washing fluid to expand the filter bed downwardly to remove the coating of active material from the plastic media particles.
Still another object of a preferred embodiment of the present invention is to provide a method of operating an active filter system that effectively and efficiently removes spent coating of active material from the plastic media particles.
It must be understood that no one embodiment of the present invention need include all of the aforementioned objects of the present invention. Rather, a given embodiment may include one or none of the aforementioned objects. Accordingly, these objects are not to be used to limit the scope of the claims of the present invention.
In summary, one embodiment of the present invention is directed to a method of clarifying a liquid. The method comprises the steps of: (a) providing a filter having at least one layer of filter media for removing impurities from a liquid, the at least one layer of filter media being formed from particles having a specific gravity less than a specific gravity of the liquid being filtered such that the at least one layer of filter media remains buoyant during filtration; and, (b) during washing, passing a washing fluid upwardly through the at least one layer of filter media, the washing fluid having a specific gravity greater than the particles forming the at least one layer of filter media such that the at least one layer of filter media remains buoyant during washing.
Another embodiment of the present invention is directed to a method of washing a filter for filtering liquids. The method of washing comprises the steps of: (a) providing a filter having at least one layer of filter media; and, (b) during a stage of a washing cycle, directing a combination of air and a washing liquid through the at least one layer of filter media, the combination of air and washing liquid having a specific gravity greater than the particles forming the at least one layer of filter media such that the at least one layer of filter media remains buoyant as the combination of air and washing liquid passes through the at least one layer of filter media.
A further embodiment of the present invention is directed to a method of washing a filter having at least one layer of filter media formed from a plurality of buoyant particles coated with an active material. The method comprises the step of: (a) directing a washing fluid upwardly through the at least one layer of filter media to remove at least some of the active carbon from the buoyant particles. The washing fluid has a specific gravity greater than the buoyant particles coated with the active material so that the at least one layer of filter media remains buoyant during washing of the filter.
The preferred forms of the invention will now be described with reference to
Referring to FIGS. 1 to 3, a portion of a filter system A is illustrated in one of many possible configurations. The filter system A includes a filter housing A′, a filter bed B, an air conduit C, an influent distribution manifold D, an effluent discharge port E, a waste discharge port F, a carbon slurry container G and a media retaining screen H.
The effluent discharge port E and waste discharge port F are typically opposing ports on a T (not shown) that extends outwardly from the filter housing A′. When liquid is to flow to waste the T is adjusted so that flow is only through the waste discharge port F. When liquid is to be used in service, the T is adjusted so that flow is only through the effluent discharge port E. However, it will be readily appreciated that numerous other configurations could be used.
The filter bed B includes at least one layer of filter media formed from buoyant plastic particles that are coated with an active material. Preferably, the filter media is formed from polystyrene. The active material is preferably a powdered adsorbent held on to the plastic material by static electrical attraction. It should be noted that powdered carbon (sometimes referred to as powered activated carbon or PAC) can be used as the active material. However, it will be readily appreciated that any suitable coating can be used including but not limited to aluminum oxide. Preferably, the coated buoyant plastic particles have a specific gravity less than the specific gravity of the washing fluid combination of air and liquid. Most preferably, the specific gravity of the coated buoyant particles is in the range of approximately 0.5 to approximately 0.8. The low specific gravity of the coated buoyant particles allow the filter bed to remain buoyant in the filtration cycle and washing cycle.
During a filtration cycle, as seen in
Overtime, the performance of the filter bed B becomes degraded through a combination of adsorption of dissolved solids and blinding by the accumulation of solid material at the surface. The spent coating must be removed. To accomplish the removal of the spent coating, influent is directed upwardly by the influent manifold D through the filter bed B to waste through waste discharge conduit F for a predetermined period of time as seen in
As seen in
Referring to
While this invention has been described as having a preferred design, it is understood that the preferred design can be further modified or adapted following in general the principles of the invention and including but not limited to such departures from the present invention as come within the known or customary practice in the art to which the invention pertains. The claims are not limited to the preferred embodiment and have been written to preclude such a narrow construction using the principles of claim differentiation.
