A fluorescence-based method for the visualization of enzymatic activity inside green wall wastewater treatment system.

Wastewater reuse is a central topic for the sustainable use of water resources. Nature-based solutions are a set of treatment technologies that employ biological processes in a porous medium to treat wastewater, in addition to the traditional physical and chemical treatments. The aim of this study is to optimise a non-invasive methodology that allows for a deeper comprehension of the microbial activities within a porous medium. The method has been specifically developed to be adapted to modular green walls designed to treat domestic light greywater directly on site. The present step of the study looks for the best camera settings, light intensity, position, materials in order to build a calibration curve that will be used in the second part of the project to quantify pore concentration and eventually enzymatic activities. This study will help to better understand bacterial processes into the porous medium in terms of spatial distribution and reaction rates, in order to enhance the design of nature-based solutions. It could be also used to study the interaction between bacteria and roots in constructed wetland and green walls.