Abstract: Disclosed are methods and devices useful for aerating and or adding additives to carbon-containing aqueous waste.

Abstract: Aerator kit comprising a body defining a fluid-flow channel, and a nozzle insert disposed inside said body as such forming together a venturi aerator which is useful for aerating aqueous waste. The aerator can be used submerged as a part of an aerobic digester, in which gas or air flow into the nozzle inlet while drawing liquid through a peripheral hole in the aerators body and cause mixing. The aerator can be also used as an above ground aerator in which liquid is pumped into the nozzle inlet while drawing air through said peripheral hole. In an another embodiment the aerator could be also used for adding additive to a gas or liquid.