LIFE SEACAN has demonstrated the flexibility and robustness of biofilm technologies with two case studies, one based on promoting the development of aerobic granules in a SBR and the other one combining suspended and fixed growth in an innovative hybrid bioreactor

Biofilms are complex and coherent structure of cells spontaneously formed as large and dense granules or growing attached to a surface, which can be static or mobile. The implementation of biofilm-based systems increases the retention of biomass within the bioreactor, resulting in an improved volumetric conversion and easier separation from treated water.
Organic matter and oxygen diffussion along the biofilm structure promotes different environmental conditions and concentration profiles, allowing a more diverse bacteria consortium able to accomplish with different treatment pathways, i.e. nitrification and denitrification. The existence of a growth rate gradient stratifies the biofilm, promoting the inner development of slower-growing organisms well-protected from external shear forces and less likely to be lost due to detachment and/or wash-out. Therefore, there are different types of biofilm systems depending on several design aspects and process variables.

Case Study 1: Aerobic Granular BioReactor

Industrial references using aerobic granules can be found in several countries, but none of these are focused on removing the pollutants present in the effluents generated in fish processing industries. Previous lab-scale studies about the stability of an aerobic granular reactors fed with wastewater from the seafood industry showed stable performance treating organic loading rates up to 4.4 kg COD/m3·d with removal efficiencies of 90% in terms of nitrogen and organic matter with lower biomass production (reduction of 54% in comparison to conventional systems). Based on those previous experiences, a demo-scale Aerobic Granular BioReactor has been designed and built as SBR to promote the development of aerobic granules and to carry out a complete optimisation of the process variables.

Case Study 2: Hybrid Biofilm Reactor

The use of biomass grown on carrier materials have been widely used for anaerobic treatment of different highly loaded wastewaters. However, the number of references using hybrid aerobic biofilms to treat industrial wastewater is scarce, and negligible in the case of fish canning industries. In case study 2, an aerobic process has been developed in a packed bed reactor where biofilm has grown attached to carriers, integrating an additional stage where suspended and fixed biomass coexisted. This innovative configuration has provided high flexibility treating variable organic loads and excellent performance in terms of nutrient removal.