NOVELTY - A methanogenic digester (1) with a control panel is connected to an adjacent hydrolytic acidogenic digester (10) with outlets for water, biogas and biosolids, an effluent inlet (17), a biosolids recirculation pipe (14) and a homogenization vessel (15).    USE - For treating e.g. sewage, effluent from the agricultural or foodstuff industry or effluent from farms.    ADVANTAGE - The apparatus solves the problem of the incompatibility between acidogenic and methanogenic bacteria, especially with respect to pH, the presence of heavy metals, different reproduction rates and the effect on the bacteria supports. The result is a more efficient water purification and increased purification capacity with lower capital investment costs for the purification apparatus.    DETAILED DESCRIPTION - An apparatus for the biological purification of effluent by anaerobic hydrolytic and methanogenic digestion, useful for the treatment of e.g. sewage, effluent from the agricultural or foodstuff industry or effluent from farms, comprises at least two reactors or digesters. The first digester comprises round sepiolite tubes with a length of ca. 50 cm and diameter of ca. 20 cm, which have been fired in six-piece arrangements to form tubes with a contact surface area of 1 m2 for placing inside the reactor. The lower part of the digester has an inverted cone shape with a diameter of less than 3 inches at its bottom end. The digester has a programmable biosolid discharge valve. A recirculation opening is located halfway up the biosolids chamber or vessel and is connected via a pipe with a diameter of 2 inches to a pump for returning biosolids to the upper part of the chamber, the pipe between the pump and upper part of the chamber also having a diameter of 2 inches and being perforated over a length of 20 cm where it enters the chamber. The second digester has a volume capacity of several m3 approximately equal to twice the daily effluent intake. Effluent is supplied to the inverted cone-shaped base of the reactor via a 3 inch diameter pipe extending through the cone and terminating in round sprinklers. A methanogenic digester with a control panel is connected to an adjacent hydrolytic acidogenic digester with a biogas outlet (11), a water outlet (12), a biosolids outlet (16) connected via a pipe to a collection tank (13), a biosolids recirculation pipe, an effluent inlet and a homogenization vessel.    DESCRIPTION OF DRAWING(S) - Figure 1 shows the effluent purification apparatus.    Methanogenic digester (1)    Hydrolytic acidogenic digester (10)    Biogas outlet (11)    Water outlet (12)    Biosolids collection tank (13)    Recirculation pipe (14)    Homogenization tank (15)    Biosolids outlet (16)    Effluent inlet (17)