Anaerobic reactor UASB – recommended in Ukraine.
The UASB reactor is an anaerobic digester, which is filled up with granular biomass arranged into clusters, which consists of two kinds of bacteria referred to as oxidizing and methanogenic ones. The granular biomass reactors have been successfully applied in wastewater treatment for more than 30 years. A prominent feature of these reactors is the feasibility of using the biomass of lower quality in comparison with the EGSB reactor, which requires only high-quality granular biomass that is imported mainly from European states where the number of available treatment facilities with anaerobic reactors available in service hundred times exceeds the number of treatment facilities in Ukraine. Alternatively, taking into account the smaller volume of wastewater in terms of a kilo of COD/m3, the UASB reactor is many times larger and thus requires a large site area for construction. The reactor’s body, i.e. the cylindrical tank is made of monolithic reinforced concrete or round shaped metal.
Coagulants * flocculants * caustic * industrial effluents 1000m3/s * raw wastewater pumping room 2*75 m3/h * mechanical treatment * averaging tank * pumping room 2*45 m3/h * DAF * pumping room 2*45 m3/h * anaerobic reactor * denitrification * nitrification * secondary clarifier * discharge into receiving water * flotation sludge pumping room 2*5 m3/h * discharge pipe * basin/cogeneration unit * excess biomass * sludge collector * filtering press * organic and mineral fertilizer * fields
The scheme of anaerobic industrial wastewater treatment with the production of biogas.
To produce biogas, methanogenic bacteria absorb volatile fatty acids (mainly the acetic acid). Biogas is primarily a mixture of mainly methane and carbon dioxide with very small amount of hydrogen sulfide. This process can be described by the chemical reaction:
ChZT ? CH4 + CO2 + fresh sludge
Image 6 Granulated sludge
The produced biogas is separated from wastewaters in three-stage separators of the upper part of reactor.
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.
Image 7 Preinstalled three-stage separator of a UASB reactor
Separators are made of stainless steel and polypropylene (PP). 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 (referred to as the reactor’s profile). 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.
Anaerobic stage of wastewater treatment * biogas * treated effluents * industrial wastewaters
The scheme of a low-loaded UASB reactor
COD load is 5-7 kg COD/м3
UASB separators upon installation:
Example of treatment facilities with UASB reactor integrated with aerobic tank – image shows treatment facilities with a capacity of 1800m3/24h installed at brewery near the city of Rzesz?w (the Republic of Poland).