New approach to sewage sludge treatment

Sewage sludge (also termed wastewater sludge) is the main by-product of the treatment of wastewater. However, disposal of sewage sludge can be up to 60 % of the total operating cost of a wastewater treatment plant (WWTP) by consuming enormous quantities of energy.

The MFC4SLUDGE project is working with European SMEs to develop a suitable commercial alternative to existing wastewater sludge treatments. The consortium is taking an innovative approach to ensure environmental impacts are minimised and that no additional energy demands will be placed upon current WWTPs.

Project partners' sustainable solution takes the form of a microbial fuel cell (MFC) coupled to hydrolytic-acidogenic anaerobic digestion (HA-AD). Researchers are employing these complementary technologies to achieve an energy system capable of reducing organic compounds in wastewater by more than 90 % and produce energy at the same time.

Development of MFCs is concentrating on improving the system's efficiency and cost effectiveness. This will be achieved through the design of control strategies in order to reach optimal performance as well as through the development of new cell configuration and cathodes. A lab-scale HA-AD digester has also been designed and built and initial tests conducted to determine operational ranges.

The effluent from partial anaerobic digestion of WWTP sludge was studied with regard to volatile fatty acids production. Results indicate that the effluent from partial anaerobic digestion is suitable for bioelectricity production in MFCs. Mathematical models have also been developed for the HA-AD, MFC and coupled processes.

MFC4SLUDGE will reduce the environmental impact of sewage sludge by reducing its volume and providing a source of energy, thus valorising such waste. It will also help improve the competitiveness of participating SMEs by providing them with valuable know-how and increased employment opportunities.