EGSB Reactor

Expanded Granular Sludge Bed reactor for wastewater treatment

Expanded Granular Sludge Bed (EGSB) reactor is a variant of the UASB concept. The distinguishing feature is that a faster rate of upward-flow velocity is designed for the wastewater passing through the sludge bed.The increased flux permits partial expansion (fluidization) of the granular sludge bed, improving wastewater-sludge contact as well as enhancing segregation of small inactive suspended particle from the sludge bed. The increased flow velocity is either accomplished by utilizing tall reactors, or by incorporating an effluent recycle (or both).

The EGSB design is appropriate for low strength soluble wastewaters or for wastewaters that contain inert or poorly biodegradable suspended particles which should not be allowed to accumulate in the sludge bed.

The difference of EGSB from UASB process is operation capability in higher loadings and accordingly the reactor of EGSB is taller and slender. In both systems, the wastewater prepared in conditioning tank via mixing with nutrients and anaerobic effluent is controlled by means of pH and temperature and pumped into the reactor. The required upflow velocity and homogeny of the pumped wastewater is accomplished by a specially FARAN designed distribution system. The organic substances in the wastewater are decomposed to biogas as they are flowing through several meters of biomass in granular bacteria bed. Together upwards movement of produced biogas and wastewater accelerated by the distribution system blends the whole reactor volume without any mechanical mixing device. The three phase separator (settler) at the top of the reactor ensures an excellent separation of treated water, biogas and biomass. The relatively higher density of the biomass eases the return to the sludge bed, where the treated water is returned into the conditioning tank in order to prepare the raw wastewater and will be discharged or transferred into the next treatment step. The biogas is collected on top of the reactor and used in production of energy or burned in the flare without any fan required after reducing the sulphur concentration if necessary . The corrosion possibility is minimized for the reactor working oxygen free and hermetically closed conditions, which is partially in UASB and completely in EGSB.

FARAN’s EGSB steel components are protected against corrosion with special paint system.