Patent ID: 6811702
Filing Date: 2004-11-02
Classification: C02F,Y02W

Abstract:
A process for treating a polluted aqueous liquid having a COD value caused by organic compounds present therein and a BOD/COD ratio smaller than 0.2, whereinthe polluted aqueous liquid is percolated through a packed filter bed of a carrier material which is colonized with a first concentration of aerobic bacteria, enabling degrading of at least part of said organic compounds under aerobic conditions, and which forms an adsorbent for at least part of said organic compounds, the percolate which has passed through the filter bed is collected and separated with a membrane filter into a first portion of the collected percolate which is recirculated to the filter bed, and a second portion of the collected percolate which is removed as treated effluent showing a reduced COD value, wherein said filter bed is kept at most only partially submerged in the liquid percolating therethrough, wherein said second portion is removed from the collected percolate has a second concentration of aerobic bacteria which is smaller than 10% of the first concentration of aerobic bacteria; and wherein an oxygen-containing gas is supplied to the collected percolate, and said oxygen containing gas is allowed to rise in the collected permeate along said membrane filter.