The EGSB reactor is a highly loaded anaerobic reactor, which is filled up with granular biomass consisting of two kinds of bacteria – the oxidizing and methanogenic bacteria. To produce biogas methanogenic bacteria absorb volatile fatty acids (mainly the acetic acid). Biogas is primarily a mixture of methane and carbon dioxide (IV) with a very small amount of hydrogen sulfide. This process can be described by the chemical reaction:
ХСК ? CH4 + CO2 + fresh sludge
The main features of EGSB (expanded granular sludge bed) reactor are high settling velocity of granular sludge and high methanogenic activity. Because of its high settling velocity it is possible to ensure a high upflow velocity in a reactor. High velocity and upflow direction of biogas allows the sludge to be equally distributed in the reactor. It results in the best possible junction of sludge and effluents and thus a greater performance can be achieved contrary to standard UASB-type or single-stage reactors. Therefore, EGSB reactors require a smaller area for construction.
Most of anaerobic reactors on the market are equipped with only one gas/liquid/sludge phase separator, which presupposes a far more limited capacity, and makes them more sensitive to load variation. Therefore, under higher loads the reactors with one separator are at risk of biomass washout, which as a result can negatively affect the reactor’s performance and cause the necessity to refill reactor with fresh sludge.
The produced biogas is separated from wastewaters in the separator’s basin located in the upper part of reactor and can be used in industry.
The intensity of recycle flow caused by the biogas upflow depends on the wastewater COD concentration level. It resulted in automatic adjustment; thus, if the COD concentration is higher, the rate of recycle of the inlet wastewater flow is also higher; if the COD concentration is lower, the sludge recycle is lowered as well.
Wastewaters are recycled simultaneously with the granular sludge that ensures a strong junction of sludge and wastewaters. The uptake header has special convergent points, which create an eddying upflow resulting in the enhanced separation of biogas from a biomass.
The anaerobic reactor is protected against the pressure rise and vacuum processing. The applied safety technology ensures continuous pH and temperature measurement. In addition, it is possible to monitor the state of biomass by sampling from extractors located at various high levels of the reactor. The excess anaerobic sludge is periodically removed and directly delivered for dewatering or is recycled by other types of treatment facilities. It should be mentioned that the given reactor is hermetically sealed and thus there is no chance for any smell to waft into the environment.
The reactor’s body is made of high-alloyed enameled steel, accessory parts are hot dipped galvanized (stainless steel or PP on request); separators’ body is made of polypropylene sheets and fittings are made of special sealants produced by SIKA or BASF.
UASB-type highly loaded reactor
COD load is 10-20 kg COD/м3
Installation of the reactor and separators: ENZYM Company, PJSC, city of Lviv