provides a process for the biological anaerobic treatment of wastewater by converting constituents into gaseous compounds said process comprising a intense mixing of influent with reactor liquor extracted from the bottom section of the reaction vessel without damaging bacteria present b intense contacting of wastewater with the reactor sludge c demoting of sludge granulation to increase the contact area between bacteria and constituents to be converted into gaseous compounds without damaging the bacteria d dispersing floating sludge into the reactor without damaging the biocatalysts by injecting liquid into at least one downer e liberating encapsulated gaseous compounds by applying low shear stress f mixing of reactor contents through a natural gas lift effect induced by the production of gaseous compounds h separating solids from purified water using a separation step thus retaining sludge inside the reactor vessel and maintaining activity i removing purified water from the reaction vessel after said separation step j removing sludge as required from the vessel k preventing excessive foaming by spraying treated water onto the floating sludge layer l provision of influent either in a continuous mode or in a fed batch mode in an embodiment of the present invention the constituents to be removed from the water are lipidic compounds long chain fatty acids lcfa which induce sludge floatation after being adsorbed onto.