Microbial ecology in industrial activated sludge process: linking functional diversity to system performance

Activated sludge process is the most common biological process applied worldwide to treat municipal and industrial wastewaters. The main two challenges of activated sludge process are an efficient removal of nitrogen and phosphorus compounds, and an effective control of bulking and foaming, which are the are the main two disturbances affecting the process. One thing these two challenges have in common, is that they both have microbial components, which not long ago were seeing as a black box with questions around, such as: who is there? What are they doing? Is there any connection between stability and populations dynamics? And the most important of all, how to control the process? To answer these questions, different methods have been developed over time for the detection of the identity and function of activated sludge microorganism. The evolution of these methods from simple microscopy of cultivated bacteria, to the application of molecular techniques on environmental samples without the need of previous cultivation have gave the opportunity to better understand the microbial interactions occurring in complex systems such as an industrial system. In this research, special attention is given to communities’ interactions at species level (within species of the same community), community level (within communities i.e. mutualistic and competition) and ecosystem level (between communities and the ecosystem). The aim of this work is to have a better understanding of microbial diversity and interactions in industrial activated sludge processes and to investigate the influence of diversity level on system performance. For this, different molecular tools targeting 16S rRNA sequences are applied. High throughput sequencing using a new amplicon duo method and fluorescence in situ hybridization (FISH) using new design oligoprobes will be applied to identify and characterize functional bacteria. Then, real-time polymerase chain reaction (real-time PCR) using new design primers will be carried out to track changes on the composition of these bacteria over time. In addition, specific growth promotors of bacteria will be determined and assessed to establish the conditions of a stable performance.