Method of maintaining clean vertical skeins of hollow fiber membranes and system therefor

A method for removing concentrated solids from within a vertical skein of shell-less, immersed hollow fiber membranes used for the filtration of water containing suspended solids, said method comprising;

• i) assembling multiple skeins in side-by-side relationship in a cassette in an unrestrictive reservoir, each skein comprising multiple generally parallel arrays of vertical fiber membranes;
• ii) concentrating solids within skeins of the cassette by creating a differential pressure across walls of the hollow fibers to filter the water flowing in tangential flow, parallel to the surface of the membranes;
• and,
• iii) generating an oscillating movement of the cassette about its central transverse axis located above the skeins causing the cassette to travel in an arc, at a frequency sufficient to renew water around the skeins by inducing a substantially vertical flow of the water upwards or downwards through the skeins, and flow of permeate through the fibers parallel to the bubble-generated flow when the angulating vertical axis of the oscillating cassette passes through the central vertical axis.