US PATENT SUBCLASS 210 / 621
.~.~.~ Recirculating to prior step

Current as of: June, 1999
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210 /   HD   LIQUID PURIFICATION OR SEPARATION

600  DF  PROCESSES {14}
601  DF  .~ Treatment by living organism {13}
620  DF  .~.~ Aerobic treatment {3}
621.~.~.~ Recirculating to prior step {2}
622  DF  .~.~.~.~> Of separated liquid
623  DF  .~.~.~.~> Of sludge or separated solid {3}

DEFINITION

Classification: 210/621

Recirculating to prior step:

(under subclass 620) Process wherein a portion of the stream is withdrawn subsequent to the aerobic treatment step and returned thereto.

(1) Note. This subclass provides for recirculation of a portion of the stream without a separation of the constituents. Recirculation of a constituent after separation is provided for in an indented subclass.

SEE OR SEARCH THIS CLASS, SUBCLASS:

194+, for apparatus including recirculating means.

603+, for collection and recirculation of a gaseous component to an aerobic treatment step.