As part of the LIFE RESEAU project, VCS Denmark has been retrofitting existing conventional activated sludge tank with Membrane Aerated Biofilm Reactors (MABR) to increase its capacity and reduce energy consumption, as a demonstration test. In spring 2023, five new Zeelung. MABR cassettes delivered by SUEZ Water A/S together with pre-owned cassettes were installed at Søndersø wastewater treatment plant (WWTP), located at the northern part of Funen.
The existing configuration at Søndersø before the retrofitting consisted of phase-isolated oxidation ditches, consisting of two separate trains (LT1 + LT2 and LT3 + LT4). To accommodate the best environments for the MABRs, which has the highest nitrification rate at a higher ammonia concentration, the MABR train was changed into serial configuration.
Future capacity test of the MABR Train
The performance of the MABRs is dependent on the load in the reactor. The configuration at the treatment plan has been 50/50 distribution to the two trains in the past two years. Results for the two years have shown an average conversion of 30% of the NH₄-N load to WWTP, for the six MABR cassettes. This means a relatively high conversion in a lower volume.
Now, the capacity of the MABR train is being tested by changing the distribution to 100/0 in dry weather by closing the inlet to Control train. With this capacity test is expected to achieve the same effluent quality in half of the volume, as well as to observe that the MABR train can handle the entire flow of NH₄-N to Søndersø WWTP.
This demonstration during the RESEAU project makes MABR installation highly relevant for future refurbishments of new and existing WWTPs where capacity and energy are an important factor.
About the MABR
MABRs are a newer technology with promising results in both energy savings and space optimization regarding nutrient removal in wastewater treatment plants. They are typically based on hollow-fibre, gas permeable membranes utilizing a bubble-free intermediate in the process of oxygen transfer and are designed to support biofilm growth directly on the membrane. This can result in reduced loss of gas and optimized oxygen transfer efficiency.
The MABR supports the process of simultaneous nitrification and denitrification through its biofilm arrangement. It will arrange itself in a gradient with the highest electron donor concentration near the biofilm-bulk interface and the highest oxygen concentration near the membrane-biofilm interface creating an environment with niches for the different microorganisms and theoretically allowing for reduced N2O-emissions as a result, having a positive effect on greenhouse gas emissions as well.