High Rate Filtration System

Abstract

A high rate, upflow filtration system is described in which a compressible, fibrous lump filtration media is compressed to adjust the porosity and collector size of the media in the bed and to provide a porosity gradient within the bed proceeding from more porous to less porous in a direction opposite to the flow of fluid so that filtration proceeds in a direction from a more porous to a less porous filter bed. Larger particles are removed by the more porous media and successively smaller particles are removed as the filter bed becomes less porous. The system is capable of reducing the turbidity of influent municipal wastewater from about 8 NTU to about 2 NTU at a wastewater flow rate of from about 820 to 1230 L / m2·min (20 to 30 gal / ft2·min), at a bed compression ration of from about 15 to 40 percent, and at a backwash rate of from about 1 to 6 percent based on the total wastewater passing through the filter.

Description

CROSS REFERENCE TO RELATED APPLICATION[0001]This application is a continuation of copending U.S. application Ser. No. 10 / 661,349, filed Sep. 12, 2003, which is a continuation of U.S. application Ser. No. 10 / 098,738, filed Mar. 15, 2002, which is a continuation of U.S. application Ser. No. 09 / 627,638, filed Jul. 28, 2000, which is a continuation-in-part of U.S. patent application Ser. No. 08 / 980,537, filed Dec. 1, 1997, each of which is incorporated herein in its entirety and claims the benefit of U.S. Provisional Application No. 60 / 032,643, filed Dec. 10, 1996.FIELD OF THE INVENTION[0002]This invention relates to filtration systems, including filtration systems used in connection with tertiary treatment of wastewater for reduction of suspended solids.BACKGROUND OF THE INVENTION[0003]Disposal and reuse of wastewater from raw municipal sewage is problematic. Stringent wastewater treatment requirements have been promulgated to protect human health, particularly in those areas having li...

AI Technical Summary

Benefits of technology

[0015]The invention provides a high rate filtration system in which the collector size and effective pore size of the filtration media can be adjusted according to influent conditions and to promote efficient cleaning of the media. The fluid travels through successive layers of filter media in which each layer becomes progressively more compressed with a smaller effective pore size and collector size for filtration and removes smaller and smaller particles. The compression gradient promotes more uniform loading of the media throughout the filter bed. The compression gradient can be altered during filtration to adjust head loss across the media and to extend the time for filtration while maintaining filtration efficiency within acceptable limits.

[0021]There is no necessity to provide a seal in an upper movable plate for a ram or screw that is designed to move the lower movable plate. Channelling can be reduced and the filter bed is not interrupted. There is no mechanical means in which the media can become entangled.

Problems solved by technology

However, the apparatus described in the Masuda et al. patent with the movable bottom plate has some difficulties associated with it.

The screw decreases the amount of room available for the media and potentially causes some channeling through the media in the region of the screw.

A seal is used where the screw passes through the top plate, further complicating the operation of the device.

The filter clogs up fast because large particles and fines are both trapped by the compressed initial layers of the filter media.

However, the flow rate of the wash water makes it difficult to achieve separation between the media and to obtain efficient cleaning.

Thus the overall efficiency of the apparatus described in the Masuda patent is greatly reduced.

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