Patent ID: 7537693

Claim:
A reactor comprising: a wastewater inlet at the bottom of the reactor; a first-stage reaction zone in fluid communication with and above the inlet; at least one first-stage three-phase separator in the first-stage reaction zone; a sludge inlet in fluid communication with the first-stage reaction zone; a second-stage reaction zone in fluid communication with and above the first-stage reaction zone; at least one second-stage three-phase separator in the second-stage reaction zone; a separation zone comprising a gas/liquid separator above the second-stage reaction zone; a first-stage upflow pipe in fluid communication with the upper portion of the first-stage reaction zone and the gas/liquid separator; a second-stage upflow pipe in fluid communication with the upper portion of the second-stage reaction zone and the gas/liquid separator; a gravity-fed downflow pipe in fluid communication with the bottom portion of the first-stage reaction zone and the gas/liquid separator; a treated effluent outlet in the separation zone; a pump in fluid communication with the gas/liquid separator and a water tank, the pump capable of providing continuous internal circulation of liquid in the reactor; a biogas outlet in fluid communication with the gas/liquid separator; biogas; organics-laden wastewater within the inlet; sludge; and anaerobic biological organisms.