PROCESS AND REACTOR FOR ANAEROBIC WASTE WATER PURIFICATION

The invention is directed to a process for the anaerobic purification of waste water using a sludge bed system, which process comprises feeding waste water and recycle water to the lower part of an upflow reactor containing mainly granular biomass thus producing biogas in the treatment passing the resulting gas/liquid/solid mixture upward and separating the gas and solid from the liquid in a three phase separator and thereby generating an anaerobic effluent that is withdrawn from the top of the separator, the improvement comprising withdrawing the recycle water separately from the effluent, either from the three phase separator or from the top of the reactor outside the three phase separator, and to an upflow reactor suitable for this process.