- a new intelligent Dissolved Air Flotation (i-DAF) technique for reducing the volume of sewage sludge,
- a series of improved sewage sludge treatment techniques,
- high added value sludge treatment derivatives, including an Organo-Mineral-Fertiliser (OMF), Biopolymers and new tools for sludge management planning.
Sludge management systems have critical impacts on …. Each year, 9.4 million tons of sewage sludge are generated in the European Union. In this context, the major challenges addressed include:
- material reuse and disposal,
- environmental and health impacts of sludge management practice and
- regulatory compliance and public perception.
END-O-SLUDG has addressed these challenges by setting up a holistic approach, i.e. by taking into account technologies, long-term planning issues and commercial exploitation of outcomes.
END-O-SLUDG was a trans-European project which started in January 2011 and ended in December 2013. It was coordinated by United Utilities Water PLC (United Kingdom), a company supplying water and wastewater services to 9.2 million (population equivalents) in the North West of England. END-O-SLUDG was a multi-million euros project, co-financed by the EU FP 7 grant funding programme.
The major objective was the development of wastewater and sludge treatment processes and approaches for recovering valuable materials from the sludge. This overarching goal was broken down into the following sub-objectives:
1. Reduction of sewage sludge volume produced:
A new intelligent Dissolved Air Flotation (i-DAF) technique was developed. i-DAF consisted of injecting a flow of micro-bubbles into the wastewater. It could perform a physical separation by making suspended matter adhere to these air bubbles. An i-DAF pilot-scale plant was set up in the Netherlands. By combining i-DAF with primary sedimentation, the pilot-plant showed a total suspended solid (TSS) removal over 99%.
2. Improvement of sewage sludge treatment:
Partners of the project focused on improving:
- techniques with regard to enzymatic hydrolysis, in order to improve biogas production, and
- probiotic techniques in order to prevent the resurgence of Escherichia coli in digested sludge cake.
In this context, the three techniques inverted phase fermentation, digestion intensification and competitive exclusion were tested.
3. Development of added value derivative from sludge:
An organo-mineral-fertiliser (OMF) was developed as replacement for common fertilisers in crop production. The new process for producing the OMF made use of combined heat & power (CHP) and other sources of waste heat to produce granules with a guaranteed nutrient content. The agronomic performance of this OMF proved to be equivalent to other fertilisers. (read dedicated article: Fertilisers from wastewater sludge)
4. Improvement of energy efficiency of waste water and sludge treatment:
As water and wastewater treatment processes are highly energy intensive, END-O-SLUDG developed a strategic planning approach. It consisted of an integrated series of tools and methods to carry out the comparison of a number of scenarios and options for managing sludge throughout Europe.
Why did it work?
END-O-SLUDG performed a holistic approach with regard to sludge and wastewater treatment management systems, thereby considering the whole wastewater sludge treatment value chain. This approach was demonstrated in a 25-year management plan regarding sludge management in the region of Asturias (Spain). On the short term, it was estimated that anaerobic digestion should be integrated for instance. On the long-term, further technologies developed in END-O-SLUDG were identified to be integrated as well.
Several technologies developed during END-O-SLUDG were tested at prototype scale and/or demonstrated. However, several technical and commercial risks have still to be removed. The technology readiness level is therefore estimated to be 7 on the TRL scale.