GSFA

High-rate VFA production from industrial waste using the granular sludge process

The GFSA project was awarded March 2013, within the STW Partnershipprogram: “Partnership Paques – The VFA Platform”. The project grants two PhD candidates, one at Sanitary Engineering and one at Environmental Biotechnology (AS) at the TU Delft.

Partial pre-acidification of organic substrates in industrial wastewater as pretreatment step for anaerobic digestion typically is conducted in large mixed tanks. Primary aim of this pretreatment step is equilibration of the wastewater composition and concentration. Partial pre-acidification in a side process has a positive impact on subsequent methanation of the organic acids produced.

For alternative processes for VFA processing, like polyhydroxyalkanoate (PHA) production, direct recovery of VFA, or reductive carbon chain length elongation, the VFA production step needs to fulfill other objectives. (i) the extent of substrate acidification needs to be maximized, (ii) the VFA composition should be controlled, (iii) production of methane containing biogas should be avoided, (iv) biomass concentrations in the bioreactor effluent should be minimized, and (v) compact bioreactors will need to be developed in order minimize the footprint and investment costs.

This project aims for development of the Granular Sludge process for volatile Fatty Acid production (GSFA) that can achieve these objectives. Granular sludge technology is successfully applied for both aerobic and anaerobic wastewater treatment, but the application potential for pre-acidification of wastewater is a largely unexplored research topic. The project aims for elucidating typical process engineering related aspects of the process like the impact of the solid retention time, and operational variables like the temperature and the pH. Experiments will be conducted with model substrates, mixtures of substrates, and industrial wastewaters like those encountered in agroindustry. The project will need to clarify the fermentation product spectrum and corresponding microbial community structure as a function of the operational variables. Specific objectives in this area are the formation of unwanted side products like molecular hydrogen and methane, and the possibility to direct the process towards lactate, propionate or butyrate that are preferred products in subsequent VFA processing step. Experiments will be combined with thermodynamics based quantitative computational process models that will be capable of identifying key regulators in the process and will describe the development in time of the process and the microbial community structure. In particular the identification of the environmental drivers of the different fermentation profiles possible is a major challenge in the field of microbial ecology and related process development.

Consortium:

Paques
Delft University of Technology (Sanitary Engineering (CiTG) and Environmental Biotechnology (AS)), STW (Partnershipprogram: “Partnership Paques – The VFA Platform”)

Project Coordinator:

Dr.ir. Merle de Kreuk
m.k.dekreuk@tudelft.nl

Period:
2013 - 2017