초록 ▼

The outer surfaces of hollow fiber membranes in a skein, or a bank or cassette of stacked skeins, are kept essentially free of solids by maintaining a substantially uniform flow of a stream of coarse bubbles through each of plural orifices in an aerator disposed beneath the fibers. Aerators for skei

The outer surfaces of hollow fiber membranes in a skein, or a bank or cassette of stacked skeins, are kept essentially free of solids by maintaining a substantially uniform flow of a stream of coarse bubbles through each of plural orifices in an aerator disposed beneath the fibers. Aerators for skeins used in microfiltration of wastewater in a tank are periodically flushed by injecting flushing air into permeate returned to the tank over a short period. The air is injected into returning permeate for less than 1 minute, preferably less than 20 sec so as to produce discrete masses of water which are flowed laterally through the body of the aerator, cleaning its walls and maintaining the orifices essentially free from plugging.

대표청구항 ▼

[ We claim:] [1.] In a method for maintaining production of permeate at equilibrium flux, in a skein submerged in a solids-containing substrate held in a tank, continuously, by scrubbing hollow fiber membranes ("fibers") of said skein with bubbles generated from scrubbing gas flowed into an aerator,

[ We claim:] [1.] In a method for maintaining production of permeate at equilibrium flux, in a skein submerged in a solids-containing substrate held in a tank, continuously, by scrubbing hollow fiber membranes ("fibers") of said skein with bubbles generated from scrubbing gas flowed into an aerator, the improvement comprising,supplying said scrubbing gas to said aerator's air plenum at a pressure greater than the liquid head between the surface of substrate in the tank and the surface of the substrate in the plenum;maintaining a substantially uniform flow of a stream of said bubbles through each of plural orifices in lateral walls of said aerator, in which stream the majority are coarse bubbles having an effective diameter in excess of 3 mm and rise at a velocity in the range from about 5 ft/sec to 10 ft/sec (1.5 m/sec to 3 m/sec); periodically returning permeate to said aerator through a conduit means connected thereto;injecting a desired amount of said flushing gas into said permeate in said conduit means within an injection period of less than 10 min so as to flush said aerator with a two-phase mixture of flushing gas and permeate flowing laterally through said aerator, in a volumetric ratio of flushing gas:permeate in the range from about 1:2 to about 25:1, said gas in said mixture being at elevated pressure, above that of permeate flowing in said permeate line, and in addition, sufficient to overcome a hydrostatic head above said aerator, so as to provide discrete dispersed masses of permeate which impinge against internal walls of said aerator;maintaining flow of said two-phase mixture for less than 10 min; and, returning loosened solid deposits from within said aerator into said substrate; and, re-establishing flow of said scrubbing gas.