Anaerobic biological processes

CSTR (Continuously Stirred Tank Reactor)

The CSTR reactor is a completely mixed reactor operating in the absence of oxygen. The uniform mixing is achieved either by several side-entry or top-entry stirrers. Compared to high-load reactors, this process operates at lower space loads between 1 and 5 kg COD/m³.d and can be used at lower and fluctuating wastewater temperatures down to a minimum of 20°C. This robust process also has the advantage that it can be used for wastewater with increased suspended and dissolved substance concentrations. As this type of reactor allows to work with suspended flocculated sludge in addition to granulated biomass. The larger footprint compared to anaerobic high-load reactors also allows the roof area to be used as an integrated biogas storage, which reduces the investment costs for further biogas treatment.

The CSTR is therefore ideal for industries such as breweries and distilleries that produce wastewater with average temperatures between 20° and 35°C and have sufficient space available on the production site.

UASB (Upflow Anaerobic Sludge Blanket) reactor

This high-load anaerobic reactor has been used since the 1980s to reduce heavily organically polluted wastewater. An even distribution of the wastewater to be treated over several distribution lines at the bottom of the reactor allows granulated biomass, which has a high settling velocity, to be kept in suspension. This dense biomass allows the organic matter to be converted into biogas quickly and efficiently. So-called 3-phase separators are installed near the top of the tank to separate the pretreated wastewater, the granulated biomass and the biogas from each other. The continuous solids retention achieved in this way within the reactor allows higher room loads of 8 to 9 kg COD/m³.d at wastewater temperatures of 35 to 39°C. The biogas produced can be processed. The biogas produced can be upgraded and used, among other things, to heat the feed water in the UASB reactor or, if possible, fed into the gas grid.

The UASB reactor is therefore ideally suited for production plants with limited available space. The higher investment costs are amortised within a few years due to the operating cost savings in energy costs for aeration and the lower excess sludge production. With over 20 UASB reactors in operation, CUSS is your trusted partner for the construction and operation of anaerobic high-load reactors. Another advantage for our customers is that the granulated biomass required for operation is available for delivery worldwide.

EGSB (Expanded Granular Sludge Bed) Reactor

The EGSB reactor stimulates an anaerobic biological treatment process and is a further development of the UASB reactor. This high-load reactor is used for the elimination of high organic loads of wastewater and creates a more extended sludge bed due to both its increased upflow velocity and its high design, resulting in more intensive and longer contact between granulated biomass and wastewater to be treated. The reactors are up to 20 m high and run at high space loads of 20 kg COD/m³.d. The slim design in height enables the space requirement of the treatment plant to be greatly reduced - ideal for our customers who would like to use their limited available space on the production site for their core business while simultaneously complying with the sometimes strict environmental standards specified.