Importance

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Abstract

Raw sewage ('black water' from toilets), wastewater from showers, sinks, kitchen facilities ('grey water') and oily water from the bilge of a host vessel ('oily water'), in combination, unexpectedly provide the essential nutrients for a live mass of mixed microorganisms which are peculiarly well-adapted to ingest the nutrients. To facilitate availability of oxygen to the microorganisms so as to provide growth of the microorganisms, and also, to allow them destroy to themselves, excess oxygen is discharged, in a combination of microbubbles and macrobubbles, into a membrane bioreactor ('MBR'). The mixture of bubbles is preferably generated with coarse (>2 mm) and fine (<20 .mu.m) bubble diffusers. An auxiliary stream, whether alone, or a recirculating stream into which air is drawn, may provide the coarse bubbles. The air is entrained, in a jet aerator or eductor, in a recirculating loop of activated sludge taken from the MBR. Another portion of the contents of the MBR is pumped to a semipermeable membrane which provides water (permeate) of excellent quality. The remaining concentrate is led to a gas micronizing means which produces a tail-jet of microaerated concentrate. The tail-jet is returned to the MBR to provide kinetic energy for maintaining a high velocity of liquid flow in the MBR. A portion of the concentrate is disposed of. Preferably the liquid waste to be treated on-board does not substantially exceed about 21 meters.sup.3 /day.

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First Claim