Nitrogen removal using ELAN® technology and stripping technology
NewsAqualia assess the results of two nitrogen removal innovative systems from the UMBRELLA prototype
Liquid fractions coming from the treatment of urban waste usually have high concentrations of nitrogen in the form of ammonium (NH4). In the case of Ecoparc 2 (Montcada i Reixac, Barcelona) this concentration reaches 5 g N / L. This compound must be eliminated before reaching the natural environment, since it causes eutrophication.
In LIFE Methamorphosis Aqualia is leading an action aimed at evaluating two nitrogen removal treatments in an innovative and efficient way, when compared with the system most widely used in sewage treatment plants (WWTPs): conventional nitrification - denitrification (N-DN).
1. 1. The first treatment to be evaluated is the ELAN® technology (Spanish acronym for Autotrophic Nitrogen Elimination), a system patented by Aqualia (EP2740713 A1) and based on the development of granular biomass.
The ELAN® process consumes less than half the energy consumed by the conventional N-DN system. In addition, it doesn't require biodegradable organic matter and the production of excess sludge is insignificant.
The liquor from the digestate in Ecoparc 2 presents some suitable conditions to be treated by the ELAN® process, since it has temperatures around 35ºC and low carbon / nitrogen ratios.
Prior to the ELAN®, the Anaerobic Membrane Bioreactor (AnMBR) of the UMBRELLA prototype removes the suspended matter as well as most of the soluble organic matter. If these fractions are not eliminated, they would interfere in the subsequent Anammox process or hinder the operation with the granular sludge from the ELAN® technology.
After heating the reactor to 35ºC and inoculating with Anammox granular biomass, the ELAN® reactor in UMBRELLA is ready to start to be fed during the month of April.
The liquor from the digestate in Ecoparc 2 presents some suitable conditions to be treated by the ELAN® process, since it has temperatures around 35ºC and low carbon / nitrogen ratios.
Prior to the ELAN®, the Anaerobic Membrane Bioreactor (AnMBR) of the UMBRELLA prototype removes the suspended matter as well as most of the soluble organic matter. If these fractions are not eliminated, they would interfere in the subsequent Anammox process or hinder the operation with the granular sludge from the ELAN® technology.
After heating the reactor to 35ºC and inoculating with Anammox granular biomass, the ELAN® reactor in UMBRELLA is ready to start to be fed during the month of April.
2. 2. The second treatment to be evaluated is stripping, a physical-chemical process consisting of an ammonium removal with an air stream. It is a simple treatment and especially adapted for currents with high concentrations of ammonium, high temperatures and high values of pH. The digestate effluent has a pH around 8.0; an insufficient value to obtain satisfactory performances by means of stripping. However, in a discontinuous process, the actual aeration used in the process causes the elimination of alkalinity, which increases the pH without the need to add alkalizing chemicals.
In UMBRELLA a stripping tower has been installed aimed at carry out batch tests at various temperatures. Using permeate of the AnMBR, the results to date are promising: at 55ºC, after 6 hours of recirculation, 69% of the initial ammonium has been eliminated. The ammonia transferred to the air stream can be easily precipitated with sulfuric acid, generating a fertilizer (ammonium sulphate) that can be used in agriculture, becoming a good example of circular economy.
