Patent ID: 7820047

Claim:
A wastewater treatment system comprising: a) a first processing vessel with inlet for receiving wastewater to be treated comprising: (i) an aerobic zone; (ii) at least one oxygen-depleted zone in communication with the aerobic zone; (iii) an aerator for introducing air or oxygen-containing gas into the aerobic zone; (iv) said aerobic zone, said oxygen-depleted zone, and said aerator being arranged such that the introduced air or oxygen-containing gas causes circulation of wastewater through the aerobic zone and the at least one oxygen depleted zone; and (v) a first clarification zone in communication with the at least one oxygen-depleted zone; and b) a second processing vessel separate from said first processing vessel comprising an anaerobic zone in a lower part thereof; c) first passage for permitting the transfer of material from the at least one oxygen-depleted zone to the anaerobic zone of said second processing vessel; and d) an outlet for processed wastewater.