Saturday, 19 September 2015 10:13

DESDÉMONA: Development of an energetically self-sufficient urban wastewater treatment plant through autotrophic nitrogen removal in the mainstream and phosphorus recovery

 A current wastewater treatment plant (WWTP) requires a minimum of 8-15 kWh/inh/year to meet the legal requirements of effluent organic matter, nitrogen and phosphorus. The research challenge of DESDEMONA is, thus, to redesign and to operate current urban WWTPs so that they become energy-producers rather than energy consumers without affecting its performance. DESDEMONA aims at demonstrating, at lab scale and with real urban wastewater, that the energetic balance of an urban WWTP can be severely improved at both, high and low temperatures.

The first step in this direction will be the use of most of the entering organic matter for biogas production purposes by designing a first biological step with low oxygen consumption and high biomass production, i.e. with low sludge residence time. In addition, this biomass would have a very favourable methane production potential by anaerobic digestion. Then, the DESDEMONA WWTP should be able to remove nitrogen without the need of organic matter. Autotrophic biological nitrogen removal will be implemented for this aim using a two-step approach of partial nitritation followed by anammox. This approach will reduce severely the aeration costs and, contrary to one-step approach, will be able to work at low temperatures. Therefore, the outcomes of this work can be generalized worldwide. Finally, DESDEMONA aims at recovering part of the influent P as struvite, a commercial fertilizer, from the anaerobic digestate via a hybrid bio-chemical methodology.

The feasibility of DESDEMONA will be shown at lab-scale plant fed with real wastewater that comprises all the subsystems of the proposed WWTP. In the first period of the project, the different parts of the WWTP will be implemented and operated individually, whereas an integrated long-term operation of the DESDEMONA plant will be ran during the last year of the project. Both, the benefits and the impacts of this new conceptual plant will be quantified and compared to conventional WWTP configurations using life cycle analysis. The research group has a lot of experience in this field and has pioneered some of the current biological removal advances. Thus, most of the equipment and analytical methods needed to run the project are already in the group facilities and know-how.

The implementation of DESDEMONA versus current WWTP configurations will result in significant positive impacts such as: i) converting current WWTP from energy consumers to net energy producers, ii) reducing CO2 emissions and the associated carbon footprint, and iii) reducing operational costs. Moreover, phosphorus recovery as struvite will result in: iv) the obtainment of a valued by-product, v) the decrease of the operational costs and vi) the reduction of mineral phosphorus dependency. If DESDEMONA was applied to all current Spanish WWTPs, the annual benefits could reach up to 80-90 million €/year whereas in Europe could be ten times higher.

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