Patent ID: 8066878

Claim:
An anaerobic purification device for purification of influent fluid, the anaerobic purification device comprising: a) a reactor tank; b) an influent inlet for introducing influent fluid into the tank, the influent inlet being located in a lower section of the tank; c) a water collecting device for collecting purified water, the water collecting device being provided at an upper section of the tank and defining a liquid surface in the reactor tank; d) at least one gas collecting system for collecting gas from the fluid contained in the reactor tank, the at least one gas collecting system being arranged at a level below the water collecting device; e) a gas-liquid separation device arranged at a level above the water collecting device; f) at least one riser having a discharge opening debouching into the separation device, the at least one riser being connected to the at least one gas collecting system for raising fluid contained in the tank by gas lift action caused by gas collected in the at least one gas collection system; and g) a downer having a downer inlet commencing into the separation device and a downer outlet debouching in the lower section of the tank for returning liquid separated in the separation device, into the lower section of the tank; wherein the purification device is arranged to define, in the downer at the level of the liquid surface, a head pressure of, at least, approximately 1.4 m water column (approximately 0.14 bar), and wherein the at least one riser has a top part, which is defined as that part of the riser extending upwards from the liquid surface, and wherein the top part has a length which is, at least, approximately 1.2 m.