Baffle for conversion of fine bubbles to coarse while filtering with a vertical skein of hollow fibers

In a gas-scrubbed assembly comprising, a filtration membrane device in combination with a gas-distribution means adapted concurrently to provide a growth environment for microorganisms and to minimize build-up of particulate deposits only the surfaces of hollow fiber membranes ("fibers") in said device, and to recover permeate from a multicomponent liquid substrate while leaving particulate matter therein, said membrane device comprising,

• a multiplicity of fibers secured at opposed ends in first and second headers disposed in spaced-apart relationship within said substrate, all said fibers extending from a face of each said header and essentially all said fibers being open at their ends;
• said fibers being sealingly secured with open ends thereof secured in fluid-tight relationship with each other in each of said headers;
• permeate collection means to collect said permeate, sealingly connected in open fluid communication with a permeate-discharging face of each of said headers;
• means for withdrawing said permeate;
• and,
• said gas-distribution means is located within a zone beneath said skein, said gas-distribution means discharges gas to generate enough bubbles flowing in a column of rising bubbles through and around said skein fibers, to keep surfaces of said fibers awash in bubbles;
• said fibers, said headers and said permeate collection means together forming a skein wherein said fibers are essentially vertically disposed;
• said first header being upper and disposed in vertically spaced-apart relationship above said second header at a fixed distance;
• each of said fibers having substantially the same length,
• the improvement comprising,
• a foraminous conversion baffle removably secured to said second header at the permeate discharging face thereof, said baffle being adapted to trap and discharge said gas flowing under said baffle in a vertically upward direction, said baffle having through-openings therein sized to discharge said gas as coarse bubbles in a size range effective to scrub outer surfaces of said fibers;
• and,
• said gas-distribution means is adapted to discharge fine bubbles directly beneath said baffle in a size range adapted to provide a desirable utilization rate by microorganisms in said substrate;
• whereby said permeate is essentially continuously withdrawn while concentration of said particulate matter in said substrate is increased.

In a process for maintaining the outer surfaces of hollow fiber membranes of a vertical skein having fibers of substantially the same length secured at opposed ends in first and second headers, essentially free from a build-up of deposits of particulate material while separating a permeate from a multi component liquid substrate having growing microorganisms therein requiring an environment of gas by submerging skein fibers in a reservoir of said substrate,

• said process comprising,
• flowing said gas through a gas-distribution means disposed beneath said skein,
• collecting said permeate in said collection means;
• and, withdrawing said permeate,
• the improvement comprising,
• introducing said gas as fine bubbles, in a size range adapted to provide a desirable utilization rate by microorganism in said substrate, beneath a fine-bubble trapping zone bounded by a foraminous conversion baffle under said second header near the permeate discharging face thereof;
• and,
• discharging said gas from said baffle adjacent a major portion of said second header's periphery, as coarse bubbles in a size range effective to scrub outer surfaces of said fibers.