NOVELTY - The wastewater treatment process comprises measuring a concentration in a liquid phase zone connected to a biological reactor (100) having bacterial species by a reaction product inhibiting the bacterial species, extracting a fraction contained in the reactor when the concentration exceeds the predefined threshold value of 200 mg/L, separating the fraction into first and second sub-fractions, and recirculating the first sub-fraction in the reactor. The first sub-fraction is impoverished in the reactional product.    USE - The process is useful for anaerobic treatment of wastewater in a biological reactor having a bacterial species, where the wastewater is an effluent obtained agri-food industry or urban industry (claimed) and the biological reactor is useful for production of methane.    ADVANTAGE - The process ensures economical anaerobic treatment of wastewater in the biological reactor with high efficiency and less consumption of energy and without clogging of the membranes and formation of biogas in the reaction mixture, and provides easy, larger and industrial production of methane without generating any toxic gases.    DETAILED DESCRIPTION - The wastewater treatment process comprises measuring a concentration in a liquid phase zone connected to a biological reactor (100) having bacterial species by a reaction product inhibiting the bacterial species, extracting a fraction contained in the reactor when the concentration exceeds the predefined threshold value of 200 mg/L, separating the fraction into first and second sub-fractions, and recirculating the first sub-fraction in the reactor. The first sub-fraction is impoverished in the reactional product. The zone connected to the reactor comprises an inner area of the reactor and a wastewater supply conduit (110), and an outlet conduit (135) or recirculation conduit. The reactor is fixed bed reactor or fluidized bed reactor and mesophilic or thermophilic reactor, and free of biomass. The wastewater is filtered with a ceramic membrane having pore size of lower than 5 mu m and a diameter of 1.2 mu m, between the extraction and separation steps. The reactional product comprises an assembly of volatile fatty acids. The separation is carried out using an electrodialyzer comprising a cation exchange membrane and/or an anion exchange membrane. The reactor maintains a pH value of 6.5-7.5. The recirculation conduit is adapted for doping the reactor with the second sub-fraction. An INDEPENDENT CLAIM is included for a device for anaerobic treatment of wastewater in a biological reactor.    DESCRIPTION OF DRAWING(S) - The figure shows a schematic view of a process for anaerobic treatment of wastewater in a biological reactor.    Reactor (100)    Wastewater supply conduit (110)    Supply tank (120)    Effluent (130)    Outlet conduit for methane (135)    Measure point. (150)