Methods and apparatus for treating wastewater are described, one method
embodiment including the steps of flowing a mixed liquor suspended solids
to a high rate clarification stage, forming a clarifier effluent, a first
waste activated sludge stream, and a return waste activated sludge
stream. The high rate clarifier effluent stream then flows to a membrane
stage that includes a membrane media, producing a membrane reject
(retentate) stream and a treated effluent (permeate) stream. Optionally,
the methods include routing a screened raw wastewater to an anaerobic
and/or aerated anoxic stage and introducing a gas comprising oxygen to
the wastewater during the aerated anoxic stage, and optionally allowing
the product of this stage to flow to an aeration stage prior to the high
rate clarification stage.