Patent ID: 6214228
Filing Date: 2001-04-10
Classification: C02F,Y02W

Abstract:
A process for the treatment of effluent comprising:(a) providing a first elongate vessel for anoxic metabolisation of effluent contained within the vessel, the first elongate vessel having a substantially vertical first downcomer zone for transport of effluent containing a population of aerobic and anoxic bacteria under substantially plug flow conditions towards a bottom region of the first elongate vessel, and a substantially vertical first riser zone for transport of effluent containing the population of aerobic and anoxic bacteria under substantially plug flow conditions towards a top region of the first elongate vessel, a bottom region of the first downcomer zone communicating with a bottom region of the first riser zone;(b) supplying to a top region of the first downcomer zone an effluent to be treated containing a population of aerobic and anoxic bacteria at a feed rate corresponding to a dwell time in the first elongate vessel of from about 90 seconds to about 5 minutes;(c) allowing the effluent to pass under substantially plug flow conditions through the first elongate vessel;(d) recovering from the top of the first riser zone effluent that has passed through the first downcomer zone and the first riser zone and containing aerobic and anoxic bacteria;(e) providing a second elongate vessel for aerobic metabolisation of effluent, the second elongate vessel having a substantially vertical second downcomer zone for transport of effluent containing aerobic and anoxic bacteria under substantially plug flow conditions towards a bottom region of the second elongate vessel, and a substantially vertical second riser zone for transport of effluent under substantially plug flow conditions towards a top region of the second elongate vessel, a bottom region of the second downcomer zone communicating with a bottom region of the second riser zone;(f) feeding effluent containing aerobic and anoxic bacteria from the first elongate vessel to a top region of the second downcomer zone;(g) injecting an oxygen-containing gas into the second elongate vessel so as at least in part to facilitate and maintain circulation of effluent through the second elongate vessel;(h) recovering effluent containing aerobic and anoxic bacteria from the top region of the second riser zone; and(i) recycling at least a part of the effluent containing aerobic and anoxic bacteria recovered from the top region of the second riser zone to the top region of the first downcomer zone.