Resource Recovery/ biogas plants

Up Flow Anaerobic Sludge Blanket Reactor
Up-flow anaerobic sludge blanket technology also known as UASB reactor is a form of anaerobic digester which is used in wastewater treatment. UASB reactor is a methane-producing digester, which uses an anaerobic process and forming a blanket of granular sludge and is processed by the anaerobic microorganisms. It is a single tank process where wastewater enters the reactor from the bottom and flows upward. A suspended sludge blanket filters and treats the wastewater as the wastewater flows through it. At the same time, biogas is formed in the reactor, which is collected from the top. Typically this technology is used for wastewater having a low level of solids. Industrial wastewater, as well as sewage, can be treated with UASB technology to reduce COD/BOD by 70-90%.Major Advantages

  • Less power required to reduce COD/BOD as compared to the Aerobic system
  • Reduce trade waste charges substantially (70-90% organics removal)
  • The utilisation of biogas as energy
  • Small footprint as compared to the aerobic system
Continuous Stirred Tank Reactor
The CSTR reactors are the most common low rate digesters for large scale application. The feed is introduced to a constantly stirred tank to ensure complete mixing of the reactor content. At the same time, an effluent flow is removed from the reactor. The CSTR reactor is continuously stirred so there aren’t any concentration or temperature gradient. Stirring also improves contact between anaerobic microorganisms and feedstock. The main characteristic of the CSTR reactor is that solids and liquid retention times on the reactor are equal. Feeds between 3-10% TS. This technology is used for high solids contents such as food, livestock industry waste and other waste. We have a database for various suppliers and thus we can choose the best suitable unit for the treatment plant. As an example, we intend to use Glass fused steel tanks that will save construction time by more than 4 months. Major Advantages

  • Better performance than other “low rate” digesters such plug-flow or covered lagoons.
  • Due to the mixing system, a CSTR reactor can decrease the hydraulic retention time of the waste from months to between 10 and 20 days, increasing the biogas production over 10-fold.
  • It is possible to treat a wide type of different wastes like slurries, swine, etc., making possible to mix different wastes to improve biogas production (codigestion).
Plug Flow Anaerobic Reactor
A plug flow digester vessel is a long, narrow, insulated and heated tank made of reinforced concrete, steel or fibreglass with a gas-tight cover to capture the biogas. Biogas produced by the digester is used to heat the digester to the desired temperature. Plug flow reactors are used in the treatment of wastes with high solid content 10-12% TS. An unmixed system that works on a semi-continuous mode by regularly receiving untreated wastes in one side of the reactor, and ejecting digested waste out at the end of the digester. Low maintenance and operational costs due to its simplicity and the heating system is the only mechanical components of the digester.
Major Advantages

  • Suitable for difficult feedstock that can’t be treated in any other digester (CSTR, UASB, anaerobic filter, etc.)
  • Secure sanitation. The risk of discharge un-decomposed substrate (shortcuts between inlet and outlet) is lower than in other digesters.
  • Due to its simplicity, plug flow reactors are widely used in developing countries, particularly India, Nepal, China and Vietnam, providing a cheap source of fuel, and reducing diseases caused by the use of untreated manure as fertilizer.
Anaerobic Baffled Reactor
An anaerobic baffled reactor (ABR) is an improved septic tank with a series of baffles under which the grey-, black- or the industrial wastewater is forced to flow under and offer the baffles from the inlet to the outlet. The increased contact time with the active biomass (sludge) results in improved treatment. ABRs are robust and can treat a wide range of wastewater, but both remaining sludge and effluents still need further treatment in order to be reused or discharged properly
Major Advantages

  • Resistant to organic and hydraulic shock loads
  • No electrical energy is required
  • Low operating costs
  • Long service life
  • High reduction of BOD
  • Low sludge production; the sludge is stabilized
  • Moderate area requirement (can be built underground)
  • Simple to operate