Slightly heavy particle system for wastewater treatment

A slightly heavy particle fluidized bed system for wastewater treatment, comprising:

• a contactor enclosing a chamber, a liquid wastewater inlet near a bottom of the chamber for flowing liquid wastewater into said chamber, said chamber enclosing a gas-liquid-solid three phase region within said chamber when gas is being injected into said chamber when liquid wastewater is flowing into said chamber and when a solid phase is located in the liquid wastewater, said liquid wastewater being a continuous phase and said solid phase comprised of slightly heavy particles, said slightly heavy particles having microorganisms on their surfaces;
• and
• a gas injection system which includes a gas source and a plurality of aeration tubes connected to said gas source for injecting gas into said chamber located at a bottom of said chamber and below the liquid wastewater inlet to give a uniform array of aeration tubes extending across the chamber to inject gas upwardly into said liquid wastewater phase containing said slightly heavy particles located in said chamber, the gas being injected at a gas flow rate that allows the slightly heavy particles to be generally uniformly dispersed in the chamber by the injecting gas, and wherein said plurality of aeration tubes are configured so that the gas phase flows upwardly in said chamber continuously or intermittently to form a fluidized bed with the slightly heavy particles uniformly dispersed therein;
• and
• wherein the gas injected upwardly into the liquid phase containing the slightly heavy particles causes the slightly heavy particles to be uniformly dispersed and suspended in the liquid phase and not undergoing directional flow circulation.