Integration of multiscale models for industrial biological systems modeling and optimization
Outline
1. Processes and systems involved in industrial biological systems
2. Integration of subsystems into an overall industrial biological systems and optimization (Xin
Gao’s part)
a. Integration of biological and physical chemical processes
b. Models of key subsystems and model integration
c. Challenge and opportunities for enhanced model capabilities by integrating process
models from lower level
3. Modeling at community (reactor) level and interaction with cell and plant level
a. Mass transfer and cell growth
b. Signal induction and cell communications
c. Challenge and opportunities by considering interactions with next levels
4. Modeling at cell level and interactions with gene and community levels
a. Modeling cell growth
b. Interactions between productivity, cell growth and substrate utilization
c. Internal mass transport affecting cell growth
d. Challenge and opportunities by considering interactions with next levels
5. Modeling at molecule level and interaction with cell level activities
a. Flux modeling
b. Interactions between flux and mass transport within a cell
c. Interaction between flux and external mass transfer
d. Flux regulation and its impact to internal and external environment
e. Challenge and opportunities
2. Integration of subsystems into an overall industrial biological systems and optimization
a. Integration of biological, physical and chemical processes
b. Models of key subsystems and model integration
c. Challenge and opportunities for enhanced model capabilities by integrating process
models from lower level
Integration of biological and physical chemical processes are most broadly applied to degraded (usually
oxidative) of organic contaminants in water. So let’s take this as the example. Beneficial effects of such
combination of chemical and biological two-step treatments suggest potential advantages for water
treatment via process integration rather than single technology processing: 1.) recalcitrant compounds;
2.) biodegradable wastes with small amounts of recalcitrant compounds; 3.) inhibitory compounds; and
4.) intermediate dead-end products. [1]
Recent developments (1996–2003) [1] on the integration of chemical and biological processes for the
degradation and treatment of problematic pollutants in wastewater were conducted on the integration
of chemical and biological processes with different objectives, such as modeling the degradation in
chemical and biological reactors, observing the effects of combination on total removal and comparing
with individual processes, comparing the effects of different advanced oxidation processes (AOPs) on
the biodegradation of a certain compound, and investigating the effects of different parameters on the
combination of processes. The compounds used were mostly difficult to degrade by biological processes
alone and needed post or pretreatment by AOPs. In most cases there was just one chemical reactor
followed by biological reactor or vice versa in series. However, there is one case in which the chemical
and biological reactors are parallel, [2] three cases in which there are more than two stages for the
treatment, [3, 4 and 5] and four cases in which there is a biological pretreatment followed by a chemical
oxidation treatment step, which is followed by further biological treatment. [6, 7, 8 and 9] In such
processes, the first biological step removes the biodegradable organics and the chemical reactor
increases the biodegradability of residual organics for the second biological step. [10]
In spite of the fact that AOPs are capable to produce high quality effluent in most cases, the important
drawback of these processes is their high capital and operating costs such as chemicals, electricity, and
sludge disposal. However, in order to avoid the high operation costs for complete oxidation, only partial
oxidation is desired. It has been shown that a photochemical pretreatment step may enhance the
biodegradability of wastewater containing recalcitrant or inhibitory compounds, if and only if, the
intermediates produced are biodegradable and are more soluble and less toxic than the parent
compounds. It has been frequently shown that the pre-oxidation by AOPs improves the biodegradability
of non or poorly biodegradable organic compounds and this effect could be due to the change in their
molecular structure. However, little is known about the exact mechanisms during the oxidation. The
possible changes after oxidation and their effects on biodegradability could be due to the decrease of
aromacity and destruction of high molecular structure, which leads to the formation of functional
groups such as hydroxyl, carboxyl, and aldehyde. [8] The effect on biodegradability of these chemical
changes is significant on the enzyme activity. It can also be concluded that the destruction of toxic
substances has positive effect on enzyme activity, whereas the formation of toxic metabolites had a
negative effect on the inhibition of biochemical processes. Moreover, destruction of organic nitrification
inhibitors causes an improvement in nitrification processes. [8]
As a general treatment strategy, four types of treatment for a chemical compound are possible. [6]
(i) In some cases only biological treatment alone is sufficient to enhance the effluent quality.
(ii) In the presence of some refractory or toxic compounds in wastewater, chemical
pretreatment is required.
(iii) In case biological treatment is not sufficient for biodegradable compounds, chemical posttreatment is also necessary.
(iv) In some rare cases, combination of chemical and biological treatment in multi-stages is
necessary.
A general strategy that can be used to develop a combined advanced oxidation and biological processes
for the treatment of a certain wastewater, which might contain non-biodegradable or toxic organics, is
as follows:
As a first step to avoid utilization of high cost due to AOPs, it must be confirmed that whether the
wastewater contains recalcitrant or toxic organics. If the wastewater is biodegradable, conventional
biological reactors are used to treat the waste. If it is confirmed that wastewater contains recalcitrant or
toxic organics, it would be pretreated by AOPs to modify the structure of pollutants by transforming
them into less toxic and easily biodegradable intermediates, which are degraded in the subsequent
biological reactor in a shorter time. This method can also prove to be less expensive in comparison to
the AOPs alone and less time consuming compared to the biological process. Moreover, if the effluent
from the final biological reactor has met the requirements, it will leave the treatment plant; otherwise it
has to go through the previous cycle.
The ultimate treatment goal, whether specific pollutant removal or reduction of a global parameter
must be known so that appropriate and complementary processes can be utilized. More work is needed
concerning the degradation kinetics within the combined process, from initial attack of the primary
compound through dynamics of intermediates and on to total mineralization. [1]
The design key for such two-step systems lies in choosing processes that complement each other and
lead to a synergistic effect. Predicting this performance outcome requires knowledge of the physical,
chemical and biological properties of the major reaction intermediates and their susceptibility to
degradation by each process. Also, economic, physical and technological limitations of the individual
processes should be recognized for design of more effective and economical integrated processes. [1]
References:
1. Jon P. Scott, David F. Ollis. Integration of chemical and biological oxidation processes for water
treatment: Review and recommendations. Environmental Progress. Volume 14, Issue 2, pages 88–
103, May 1995.
2. Lee, H.W.; Chen, G.; Yue, P.L. Integration of chemical and biological treatments for textile industry
wastewater. Water Sci. Technol. 2001, 44 (5), 75–83.
3. Helble, A.; Schlayer, W.; Liechti, P.; Jenny, R.; Mobius, C. Advanced effluent treatment in the pulp
and paper industry with a combined process of ozonation and fixed bed biofilm reactors. Water Sci.
Technol. 1999, 40 (11–12), 343–350.
4. Karrer, N.J.; Ryhiner, G.; Heinzle, E. Applicability test for combined biological-chemical treatment of
wastewater containing biorefractory compounds. Water Res. 1997, 31 (5), 1013–1020.
5. Fahmi; Nishijima, W.; Okada, M. Improvement of DOC removal by multistage AOP-biological
treatment. Chemosphere 2003, 50 (8), 1043–1048.
6. Bertanza, G.; Collivignarelli, C.; Pedrazzani, R. The role of chemical oxidation in combined chemicalphysical and biological processes. Water Sci. Technol. 2001, 44 (5), 109–116.
7. Ito, K.; Jian, W.; Nishijima, W.; Baes, A.U.; Shoto, E.; Okada, M. Comparison of ozonation and AOPs
combined with biodegradation for removal of THM precursors in treated sewage effluents. Water
Sci. Technol. 1998, 38 (7), 179–186.
8. Jochimsen, J.; Jekel, M. Partial oxidation effects during the combined oxidative and biological
treatment of separated streams of tannery wastewater. Water Sci. Technol. 1997, 35 (4), 337–345.
9. Mobius, C.H.; Cordes-Tolle, M. Enhanced biodegradability by oxidative and radiative wastewater
treatment. Water Sci. Technol. 1997, 35 (2–3), 245–250.
10. Gelareh Bankian Tabrizi & Mehrab Mehrvar. Integration of Advanced Oxidation Technologies and
Biological Processes: Recent Developments, Trends, and Advances. Journal of Environmental Science
and Health, Part A: Toxic/Hazardous Substances and Environmental Engineering. Volume 39, Issue
11-12, 2004. pages 3029-3081