COMBINED UASB REACTOR-SOLIDS ANAEROBIC DIGESTER DEVICE AND METHOD FOR TREATING UNSETTLED SEWAGE

The present invention relates to a one-stage device for treating wastewater, such as unsettled sewage, specially wastewater having sub-mesophilic temperatures and/or showing high fluctuations of temperatures over the year, the device being essentially made of a combination of a pulsating UASB reactor with a non-heated solids anaerobic digester located below the UASB reactor, comprising a baffle sloping partition element connecting both chambers; in such a way that the sludge produced during the process inside the UASB reactor is settled downwards to the digester, recycled and sent to the UASB reactor by a gas-lift pump that operates with the biogas generated in the anaerobic digester. The UASB reactor comprises a mixing and injecting device of wastewater that works by pulses, and that not only feeds and mixes the reactor, but it also mixes the sludge bed of the digester, in different operational modes. The invention also discloses the method for treating wastewater.