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

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

Fusion

Distinct well defined boundaries

Motivation: Why I use the individual-based approach?

NIMBioS Investigative Workshop Individual Based Ecology of Microbes: Observation and Modeling June 8 – 10, 2011

Components• solids: - cells (AOB, NOB, HET) and EPS• solutes: COD, O2, NH4

+, NO2- , NO3

-

Processes for solids• transfer - attachment of single cells

- attachment of other flocs

0.57 0.59 0.61 mg/L

Day 0 0.2

0.6

1

1.4

2

a

b c

0.57 0.59 0.61 mg/L

Day 0 0.2

0.6

1

1.4

2

a

b c

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.

NIMBioS Investigative Workshop Individual Based Ecology of Microbes: Observation and Modeling June 8 – 10, 2011

(Ofiteru et al., ESCAPE 21)

0 0.5 1 1.5 2 2.5 3 3.5 40

0.01

0.02

0.03

0.04

Time, dayR

eact

or c

once

ntra

tion,

kg/

m3

SNH4

NO2

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 detachmentNIMBioS Investigative Workshop Individual Based Ecology of Microbes: Observation and Modeling June 8 –

10, 2011

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

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