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Biodegradation of isothiazolone biocide (Kathon WT) and treatment efficiency in a laboratory-scale rotating biological contactor
Special Abstracts / Journal of Biotechnology 150S (2010) S1–S576
using Fenton reaction enabled to break down the nitro aromatic compounds in RW, the chemically-treated RW (T-RW) still contained a high concentration of total nitrogen (TN) components and remained severe toxicity. Here, we attempted to reduce the remaining TN in T-RW by microbial activities of the two types of waste activated sludge: 1: industrial sludge (IS) and 2: sewage sludge (SS). The TN degradation by IS was successful by adding an appropriate carbon source although the biomass of IS increased 5 to 10%. On the other hand, SS has no TN-reducing ability for T-RW; however, the acclimation of SS to T-RW for 6 weeks achieved the same level of TN-reducing ability as IS. The number of viable culturable cells in the acclimated SS (acSS) remarkably increased 1000-fold compared to that in SS. To understand the mechanism of TN reduction in T-RW, the gene expression of nirK, a denitrification-related gene was analyzed by RT real-time PCR against the three samples (IS, SS, and acSS). The results showed that the nirK gene expression in acSS was 3.2-fold higher than that in IS; as corroborating evidence, acSS showed a 2-fold higher nitrogen gas production than IS. Taken together, our results implied that the TN reduction by acSS and IS was due to the two different systems, denitrification activity and nitrogen assimilation. doi:10.1016/j.jbiotec.2010.09.063 [P-E.42] Biodegradation of isothiazolone biocide (Kathon WT) and treatment efficiency in a laboratory-scale rotating biological contactor L. Laopaiboon ∗ , P. Laopaiboon Khon Kaen University, Thailand Keywords: biodegradation; biofilm; isothiazolones; RBC; wastewater treatment; acclimatization Isothiazolone compounds (5-chloro-2-methyl-4-isothiazoline3-one and 2-methyl-4-isothiazoline-3-one) are biocides which achieve their biocidal activity by reaction with thiol-containing enzymes. They are used widely as antimicrobial agents in a variety of applications Collier et al., 1990. The aim of this research was to investigate the effects of operating conditions, hydraulic retention time (HRT) and the presence of other carbon sources (i.e. lab-lemco broth) in synthetic wastewater Laopaiboon et al., 2002 containing 7 ppm (active ingredients) isothiazolones (Kathon WT, a commercial name) on the treatment efficiency and biodegradation of the biocide in a laboratory-scale rotating biological contactor (RBC). Mature, 3-week-old, biofilms were established on the RBC before they were acclimatized in 7 ppm isothiazolones at a hydraulic loading rate of 0.18 m3 m-2 d-1 and HRT of 0.60 h (Run 1). Seven experimental runs were performed under various operating conditions as follows: organic loading rate (OLR) of lab-lemco broth, 0-46 g COD m-2 d-1 and HRT, 0.6-3.0 h. The results showed that COD removal was significantly decreased in the presence of the biocide at all operating conditions. The biofilms could be acclimatized to 7 ppm isothiazolones and the biodegradation by the acclimatized biofilms could be carried out via cometabolism using lab-lemco broth as a primary or growth substrate. After a period of acclimatization, the degree of isothiazolone degradation increased with increasing the OLR of the growth substrate and/or the HRT. The acclimatized biofilms degraded 23-30% and 74% of 7 ppm isothiazolones at the HRTs of 0.6 and 3 h, respectively at the OLR (of lab-lemco broth) of 23 g COD m-2 d-1 . When the OLR of the growth substrate was doubled, the biocide degradation increased to 50% at the HRT of 0.6 h. Introducing synthetic wastewater containing 7 ppm isothiazolones to the RBC under different operating condi-
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tions did not cause adverse effects on ATP content or viability of bacterial cells in the biofilms as long as the growth substrate was present in the wastewater. References Collier, P.J., Ramsey, A., Waigh, R.D., Douglas, K.T., Austin, P., Gilbert, P., 1990. Chemical reactivity of some isothiazolone biocides. J Appl Bacteriol 69, 578–584. Laopaiboon, L., Hall, S.J., Smith, R.N., 2002. The effect of a quaternary ammonium biocide on the performance and characteristics of laboratory-scale rotating biological contactors. J Appl Microbiol 93, 1051–1058.
doi:10.1016/j.jbiotec.2010.09.064 [P-E.43] Sliding mode control of an anaerobic upflow fixed bed bioreactor Hamed Osouli Tabrizi 1,3,∗ , Gassem Amoabediny 2,3 , Behzad Moshiri 1 , Aras Adhami 1 , Mahdi Pesaran Haji Abbas 3 , Emad Imenipour 3 1 Control and Intelligent Processing Center of Excellence, School of Electrical and Computer Engineering, The University of Tehran, Iran, Islamic Republic of 2 Department of Chemical Engineering – Biotechnology Group, The University of Tehran, Iran, Islamic Republic of 3 Research Center for New Technologies in Life Science Engineering, The University of Tehran, Iran, Islamic Republic of Keywords: Bioreactor; Sliding Mode Control; Parametric Uncertainty; Output Regulation
In this paper sliding mode control is employed to regulate the output of an upflow fixed bed bioreactor which is applicable for any kind of industrial waste water treatment. The growth rate and condition of living organisms are not well known. Therefore parametric uncertainty is inevitable in any bioreactor model. Even though in some previous papers model parameters for growth rate are considered known parameters, they follow an inherent uncertainty. In this paper, in addition to these uncertainties a four state model is considered. This model is the most comprehensive model available for this kind of bioreactor. The major contribution is the first use of a robust control method for dealing with parametric uncertainties and disturbance rejection for the so called bioreactor model. The model is first introduced by F. Angulo et.al Angulo et al., 2007 and the authors used feedback linearization method to regulate the output. Since feedback linearization method is not robust toward uncertainties a robust control method is needed to make sure that the output always follows a reference which is set to below the environmental restrictions. For this reason sliding mode control via integral control is applied to the model. Assuming an arbitrary scenario for growth rate parameter change of both living organisms and disturbance value change in a period of 250 days the proposed control method is simulated using MATLAB. Simulation results showed that this control approach can make the output follow the desired value in the presence of parametric uncertainties and disturbances. Figure (1) shows the output tracking the desired value and compares sliding mode control via feedback linearization. Similar results is obtained for all of the 4 state parameters.
using Fenton reaction enabled to break down the nitro aromatic compounds in RW, the chemically-treated RW (T-RW) still contained a high concentration of total nitrogen (TN) components and remained severe toxicity. Here, we attempted to reduce the remaining TN in T-RW by microbial activities of the two types of waste activated sludge: 1: industrial sludge (IS) and 2: sewage sludge (SS). The TN degradation by IS was successful by adding an appropriate carbon source although the biomass of IS increased 5 to 10%. On the other hand, SS has no TN-reducing ability for T-RW; however, the acclimation of SS to T-RW for 6 weeks achieved the same level of TN-reducing ability as IS. The number of viable culturable cells in the acclimated SS (acSS) remarkably increased 1000-fold compared to that in SS. To understand the mechanism of TN reduction in T-RW, the gene expression of nirK, a denitrification-related gene was analyzed by RT real-time PCR against the three samples (IS, SS, and acSS). The results showed that the nirK gene expression in acSS was 3.2-fold higher than that in IS; as corroborating evidence, acSS showed a 2-fold higher nitrogen gas production than IS. Taken together, our results implied that the TN reduction by acSS and IS was due to the two different systems, denitrification activity and nitrogen assimilation. doi:10.1016/j.jbiotec.2010.09.063 [P-E.42] Biodegradation of isothiazolone biocide (Kathon WT) and treatment efficiency in a laboratory-scale rotating biological contactor L. Laopaiboon ∗ , P. Laopaiboon Khon Kaen University, Thailand Keywords: biodegradation; biofilm; isothiazolones; RBC; wastewater treatment; acclimatization Isothiazolone compounds (5-chloro-2-methyl-4-isothiazoline3-one and 2-methyl-4-isothiazoline-3-one) are biocides which achieve their biocidal activity by reaction with thiol-containing enzymes. They are used widely as antimicrobial agents in a variety of applications Collier et al., 1990. The aim of this research was to investigate the effects of operating conditions, hydraulic retention time (HRT) and the presence of other carbon sources (i.e. lab-lemco broth) in synthetic wastewater Laopaiboon et al., 2002 containing 7 ppm (active ingredients) isothiazolones (Kathon WT, a commercial name) on the treatment efficiency and biodegradation of the biocide in a laboratory-scale rotating biological contactor (RBC). Mature, 3-week-old, biofilms were established on the RBC before they were acclimatized in 7 ppm isothiazolones at a hydraulic loading rate of 0.18 m3 m-2 d-1 and HRT of 0.60 h (Run 1). Seven experimental runs were performed under various operating conditions as follows: organic loading rate (OLR) of lab-lemco broth, 0-46 g COD m-2 d-1 and HRT, 0.6-3.0 h. The results showed that COD removal was significantly decreased in the presence of the biocide at all operating conditions. The biofilms could be acclimatized to 7 ppm isothiazolones and the biodegradation by the acclimatized biofilms could be carried out via cometabolism using lab-lemco broth as a primary or growth substrate. After a period of acclimatization, the degree of isothiazolone degradation increased with increasing the OLR of the growth substrate and/or the HRT. The acclimatized biofilms degraded 23-30% and 74% of 7 ppm isothiazolones at the HRTs of 0.6 and 3 h, respectively at the OLR (of lab-lemco broth) of 23 g COD m-2 d-1 . When the OLR of the growth substrate was doubled, the biocide degradation increased to 50% at the HRT of 0.6 h. Introducing synthetic wastewater containing 7 ppm isothiazolones to the RBC under different operating condi-
S227
tions did not cause adverse effects on ATP content or viability of bacterial cells in the biofilms as long as the growth substrate was present in the wastewater. References Collier, P.J., Ramsey, A., Waigh, R.D., Douglas, K.T., Austin, P., Gilbert, P., 1990. Chemical reactivity of some isothiazolone biocides. J Appl Bacteriol 69, 578–584. Laopaiboon, L., Hall, S.J., Smith, R.N., 2002. The effect of a quaternary ammonium biocide on the performance and characteristics of laboratory-scale rotating biological contactors. J Appl Microbiol 93, 1051–1058.
doi:10.1016/j.jbiotec.2010.09.064 [P-E.43] Sliding mode control of an anaerobic upflow fixed bed bioreactor Hamed Osouli Tabrizi 1,3,∗ , Gassem Amoabediny 2,3 , Behzad Moshiri 1 , Aras Adhami 1 , Mahdi Pesaran Haji Abbas 3 , Emad Imenipour 3 1 Control and Intelligent Processing Center of Excellence, School of Electrical and Computer Engineering, The University of Tehran, Iran, Islamic Republic of 2 Department of Chemical Engineering – Biotechnology Group, The University of Tehran, Iran, Islamic Republic of 3 Research Center for New Technologies in Life Science Engineering, The University of Tehran, Iran, Islamic Republic of Keywords: Bioreactor; Sliding Mode Control; Parametric Uncertainty; Output Regulation
In this paper sliding mode control is employed to regulate the output of an upflow fixed bed bioreactor which is applicable for any kind of industrial waste water treatment. The growth rate and condition of living organisms are not well known. Therefore parametric uncertainty is inevitable in any bioreactor model. Even though in some previous papers model parameters for growth rate are considered known parameters, they follow an inherent uncertainty. In this paper, in addition to these uncertainties a four state model is considered. This model is the most comprehensive model available for this kind of bioreactor. The major contribution is the first use of a robust control method for dealing with parametric uncertainties and disturbance rejection for the so called bioreactor model. The model is first introduced by F. Angulo et.al Angulo et al., 2007 and the authors used feedback linearization method to regulate the output. Since feedback linearization method is not robust toward uncertainties a robust control method is needed to make sure that the output always follows a reference which is set to below the environmental restrictions. For this reason sliding mode control via integral control is applied to the model. Assuming an arbitrary scenario for growth rate parameter change of both living organisms and disturbance value change in a period of 250 days the proposed control method is simulated using MATLAB. Simulation results showed that this control approach can make the output follow the desired value in the presence of parametric uncertainties and disturbances. Figure (1) shows the output tracking the desired value and compares sliding mode control via feedback linearization. Similar results is obtained for all of the 4 state parameters.