Acciona Agua develops biological sludge pretreatment to increase biogas production at WWTPs

Acciona Agua is coordinating a project entitled Development of a Biological Pretreatment for Improving the Energy Efficiency and Sustainability of the Anaerobic Digestion Process. The project is co-funded by the EEA Grants programme and the Spanish Centre for the Development of Industrial Technology (CDTI) and is being carried out during 2014-2015.

The project has given rise to the development of a patented low cost anaerobic digestion pretreatment that allows the kinetics to be accelerated and the performance of the process to be enhanced in terms of biogas generation and sludge volume reduction. The system is characterised by a small footprint and simplicity of design and operation, which facilitates its implementation in both operational and newly built plants.

The project comprises three main activities: the development of the biological pretreatment and associated processes at laboratory scale, subsequent upscaling to a pilot plant and validation of the final applications of the new treatment prior to the anaerobic digestion of the sludge.

The pretreatment is based on selective enrichment of hydrolytic bacteria through the optimisation of parameters that are conducive to the growth of this group of microorganisms. This approach avails of the inherent biological capacities of the system, rather than relying on external energy inputs. Moreover, the volume of the system is smaller, thus considerably reducing energy requirements and operating costs. In general terms, the result is a pretreatment that enhances the energy balance and achieves a very positive outcome in terms of costs and energy efficiency.

Furthermore, this pretreatment reduces residual sludge production compared to traditional anaerobic digestion processes, thereby affording significant savings directly associated with residual sludge management.

Acciona Agua has a fully dedicated R&D&i centre in Barcelona with a team of 30 highly qualified professionals devoted to research and development that focuses on the study of new desalination, treatment and reuse processes and technologies.