Who am I? PhD, Chemical Engineering Department, University Politehnica of Bucharest

1. Who am I? • PhD, Chemical Engineering Department, University Politehnica of Bucharest • Two years postdoctoral stage in a Marie Curie Excellence Grant (ECOSERV) at Newcastle University • In 2009 returned to University Politehnica of Bucharest as lecturer. • Research domains: • - Biochemical reactors - mathematical modeling, complex sensitivity analysis of animal cell bioreactors- Optimization of bioprocesses implying animal (hybridoma) cells • - Control oriented modeling of TCA cycle of E. coli • - Neutral theory assembly of the bacterial community • Activated sludge floc modeling NIMBioS Investigative Workshop Individual Based Ecology of Microbes: Observation and Modeling June 8 – 10, 2011

2. Example of a project Activated sludge floc modeling: structure formation and scale up Understanding/simulating floc formation and functioning is the first step in trying to control the activated sludge process at its core. It can be argued that such detailed understanding is not necessary for the successful operation of a treatment plant. However, if we want to be able to understand and predict the true limits of the biological treatment process, we need good reliable and detailed models to complement experimentation and practice at larger scales. NIMBioS Investigative Workshop Individual Based Ecology of Microbes: Observation and Modeling June 8 – 10, 2011

3. Motivation: Why I use the individual-based approach? Fusion Distinct well defined boundaries NIMBioS Investigative Workshop Individual Based Ecology of Microbes: Observation and Modeling June 8 – 10, 2011

4. Components • solids: - cells (AOB, NOB, HET) andEPS • solutes: COD, O2, NH4+, NO2- , NO3- • Processes for solids • transfer - attachment of single cells • - attachment of other flocs

5. Example of simulated floc development. Left: microbial colonies in the floc after 3.6 days (AOB - blue, NOB - red, HET - green, EPS – grey, background – nitrite concentration in bioreactor) Arrows: (a) nitrite accumulation – high density of AOB colonies; (b) nitrite consumption – NOB colonies; (c) concentration boundary layer. Right: different stages of floc development. (Ofiteru et al., ESCAPE 21) NIMBioS Investigative Workshop Individual Based Ecology of Microbes: Observation and Modeling June 8 – 10, 2011

6. Substrate concentrations in the reactor reaching a quasi-steady state after 3.5 days. Variation in the number of flocs in the reactor due to attachment and detachment NIMBioS Investigative Workshop Individual Based Ecology of Microbes: Observation and Modeling June 8 – 10, 2011

7. what QUESTIONS am I interested in? Q1) Interactions within populations (e.g. quorum sensing, social behavior) Q6) Spatial heterogeneity and structure (e.g. biofilms, flocs) what TECHNOLOGY do I use? T2) Individual-based modeling         T2c) Up-scaling        T2g) Model calibration, validation, evaluation NIMBioS Investigative Workshop Individual Based Ecology of Microbes: Observation and Modeling June 8 – 10, 2011

8. Challenges: What prevents me from use the individual-based approach? • The data about attachment/detachment frequency in relationship with the bioreactor’s time scale • How to take into account the solid debris of the dead cells – now, we consider them as small spheres • Opportunities: What (else) the individual-based approach could be used for? • Linking this with neutral model • Building a more realistic two/three time scale e-bioreactor for biological wastewater treatment NIMBioS Investigative Workshop Individual Based Ecology of Microbes: Observation and Modeling June 8 – 10, 2011