Energetic utilisation of biogenic fractions in residual waste as co-substrate in digesters of wastewater treatment plants (ENARA)

Funding:

The Department of Environmental Engineering - Waste Treatment and Resource Management at the University of Innsbruck is supporting Abfallwirtschaft Tirol-Mitte (ATM) GmbH in the implementation of the ENARA project, a sub-project of the STREFOWA programme within the Interreg Central Europe programme; co-financing comes from the European Regional Development Fund (ERDF). Additional funds are provided by the Province of Tyrol and the Packaging Coordination Centre (VKS).

Funding period: 01/08/2017 - 31/03/2018

Project partners:

  • ATM (lead partner), IKB and AAG (coordination and preparation of delivery and disposal of test materials)
  • UIBK (implementation of biological and chemical-physical test procedures and analyses, scientific support)
  • MCI (development and commissioning of the hydrocyclone prototype)
  • Regional wastewater treatment plants (ARA) (realisation of pilot tests)

Project objective:

The aim of the project is to develop a process concept for processing the organic-rich residual waste fraction into a co-substrate that can be fermented into biogas in the digestion towers of wastewater treatment plants. The results should serve as a basis for decision-making for a possible (large-scale) technical implementation.

Project description:

Despite the separate collection of biowaste, considerable quantities of biogenic waste, such as food waste, end up in residual waste (between 20 % and 40 %). According to EU legislation, residual waste must be pre-treated before being sent to landfill, either thermally (waste incineration plant) or biologically (MBT).

Some wastewater treatment plants (WWTPs) in Tyrol have been generously dimensioned and in some cases have considerable free digester capacity. In order to utilise these capacities, separately collected biowaste is currently co-treated as a co-substrate in some WWTPs in Tyrol. This can increase the sewage gas yield and thus improve the energy balance. At the end of the decomposition process, sewage sludge remains, which is usually sent for incineration. The ash is then landfilled, which means that the substances contained in the biowaste are lost as fertiliser for agricultural land.

The project aims to investigate how the biogenic components in residual waste can be processed into a high-quality co-substrate for digestion towers at the WWTP. This would allow separately collected biowaste to be treated to a higher standard and the nutrients to be fed back into regional agriculture. On the other hand, the energy balance of plants with free digester capacities could be greatly improved.

Sub-objectives:

  • Development of the most suitable process combinations for separating the organic substances from the low-calorific fraction of the residual waste from the Ahrental treatment plant;
  • Evaluation of the effects of any contaminants still contained in the processed residual waste on the facilities of the wastewater treatment plant, determination of any necessary adjustments;
  • Determination of the amount of biogas and thus the energy potential.
  • Assessment of the influence of the co-substrate on the degradation of the wastewater sludge, the reload from the fermentation into the wastewater line (in particular with nitrogen) and on the accumulation and composition of the fermentation residue (dewaterability, pollutant content (heavy metals), phosphorus content for possible recovery, etc.).
  • Analysis and evaluation of the technical and economic feasibility as well as the ecological effects of the overall process as a basis for decision-making for further large-scale implementation. The ecological effects are determined by means of a life cycle analysis.

Contact:

University of Innsbruck
Univ-Prof. Dr.-Ing. Anke Bockreis
Technikerstrasse 13
6020 Innsbruck
anke.bockreis@uibk.ac.at

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