Journal of Environmental Science and Health, Part A, 2006
This paper explores the merit of the oxygen uptake rate (OUR) profile obtained by means of respir... more This paper explores the merit of the oxygen uptake rate (OUR) profile obtained by means of respirometry as the basic mechanistic instrument for evaluating activated sludge inhibition. Experimental OUR data are generated using the synthetic peptone-based substrate and inhibition is tested with 60 mg/L hexavalent chromium and 33 mg/L nickel additions, corresponding to EC50 levels determined using the standard ISO 8192 procedure. Experimental results are evaluated by model calibration using ASM1 modified for dual hydrolysis and ASM3 modified for simultaneous growth. Model evaluations indicate that inhibition affects not only growth, but also other significant microbial mechanisms such as substrate storage and hydrolysis, leading to conclude that the proposed approach will enable to visualize the overall impact of the inhibitory compound on every stage of substrate biodegradation, through inspection and evaluation of the entire OUR profile.
Ozonation applied prior to biological processes, has proved to be a very effective chemical treat... more Ozonation applied prior to biological processes, has proved to be a very effective chemical treatment step mostly for colour removal when soluble dyes are used in textile finishing operations. Its impact on biological treatability however has not been fully evaluated yet. This study evaluates the effect of ozonation on the quality of wastewater from a textile mill involving bleaching and reactive dyeing of cotton and synthetic knit fabric. The effect of ozonation on COD fractionation and kinetic coefficients defining major biological processes is emphasised. The results indicate that the extent of ozone applied greatly affects the remaining organic carbon composition in the wastewater. The relative magnitude of different COD fractions varies as a function of the ozone dose. Ozonation does not however exert a measurable impact on the rate of major biological processes.
Synthetically prepared wastewater originating from the H-acid (4-Amino-5-hydroxy-2,7-naphthalene ... more Synthetically prepared wastewater originating from the H-acid (4-Amino-5-hydroxy-2,7-naphthalene disulfonic acid) manufacturing process was subjected to respirometric analysis for evaluating the level of achievable biodegradation in the presence of this commercially important azo dye precursor. For this purpose, H-acid was mixed with synthetic substrate having the same characteristics as sewage at a concentration and composition being typical for H-acid manufacturing wastewater. Experimental results indicated that H-acid was not biodegradable under activated sludge treatment conditions even after prolonged acclimation periods. The results were also confirmed by model evaluation of oxygen uptake rate profiles. H-acid also did not inhibit the biodegradation of synthetic sewage but accumulated as soluble inert COD in the treated wastewater.
The study presents a conceptual approach for the identification of the inhibition mechanisms of b... more The study presents a conceptual approach for the identification of the inhibition mechanisms of biodegradable inhibitors. Synthetic sewage was selected as the model degradable substrate to simulate domestic wastewaters. LAS, known to be a biodegradable but inhibitory compound, was selected as a model substrate for the determination of the inhibition mechanisms. Biodegradation of synthetic sewage and LAS were monitored through oxygen uptake rate (OUR) tests conducted to observe the dynamic response of the system when fed with synthetic sewage and synthetic sewage-LAS mixtures. The approach uses respirometry to calibrate the kinetic and stoichiometric coefficients of the proposed biochemical model. Model simulation results confirmed that presence of LAS has inhibitory effects on the biodegradation mechanisms of synthetic sewage. LAS imposed non-competitive inhibition on the hydrolysis process with an inhibition coefficient of 500 mg COD/L and effected heterotrophic growth through a competitive inhibition mechanism with an inhibition coefficient of 150 mg COD/L.
Xenobiotic compounds are widely used in several industries; hence they frequently appear in indus... more Xenobiotic compounds are widely used in several industries; hence they frequently appear in industrial wastewaters. It is a well-known fact that even the discharge of conventionally treated wastewater may have adverse effects on the receiving water environment. Turkey, a developing EU applicant country, has many industrial sectors producing large amounts of xenobiotic-containing wastewaters. The problem is only enlarged by the lack of monitoring of these substances due to the deficiencies associated with their analysis and detection. Thus, studies in Turkey are based on the use of some collective parameters as a substitute for the xenobiotic itself. Biological, physicochemical, and integrated treatment technologies have been investigated for the removal and/or minimization of the possible adverse effects of xenobiotics in industrial wastewaters. In this respect, this paper provides an overview of the studies conducted on xenobiotic-containing wastewaters from specific industries in Turkey. Although the studies add invaluable information to the scientific background on the subject, new research on the exact biochemical mechanisms of xenobiotic biodegradation will further extend our understanding for improving treatment.
... Gülseda DİZDAROĞLU RİŞVANOĞLU*, Özlem KARAHAN, Emine UBAY ÇOKGÖR, Mark CM Van LOOSDRECHT, Der... more ... Gülseda DİZDAROĞLU RİŞVANOĞLU*, Özlem KARAHAN, Emine UBAY ÇOKGÖR, Mark CM Van LOOSDRECHT, Derin ORHON ... Depolama ürünlerinin sentezi tüm hücre sentezinden daha basit olduğundan, daha az fizyolojik adaptasyon gerektirmekte ve bundan dolayı ...
Foreword xiii 2.2.4.1 VSS as a biomass parameter 2.2.4.2 VSS and BOD 5 as biomass and substrate p... more Foreword xiii 2.2.4.1 VSS as a biomass parameter 2.2.4.2 VSS and BOD 5 as biomass and substrate parameters 2.3 PROCESS STOICHIOMETRY 2.3.1 System defined with biomass COD and substrate COD 2.3.2 System defined with biomass VSS and substrate COD 2.3.3 System defined with biomass VSS and substrate BOD 5 2.4 REFERENCES 3 MODELLING OF ORGANIC CARBON REMOVAL 3.1 PRINCIPLES OF MODELLING vi Industrial Wastewater Treatment by Activated Sludge viii Industrial Wastewater Treatment by Activated Sludge 7.3.1.3 Inert particulate COD of influent origin 7.3.1.4 Total biomass in the reactor 7.
This paper provides an overview of common problems encountered when using oxygen uptake rate (OUR... more This paper provides an overview of common problems encountered when using oxygen uptake rate (OUR) measurements for the assessment of wastewater characteristics and process kinetics. Emphasis is placed upon pitfalls that would lead to significant errors. It covers model dependency of the OUR measurements and the need to select appropriate models; interpretation of OUR perturbations as a way to identify new model components and processes; the need for simultaneous observation of relevant model components and multicomponent modelling for appropriate evaluation of OUR measurements; parameter identifiability problems and the effect of active biomass concentration and the endogenous decay rate on model simulation and calibration. Relevant experimental OUR data from previous studies are presented to illustrate and underline common scientific pitfalls.
ÐThis study mainly investigated the conceptual and experimental aspects related to the assessment... more ÐThis study mainly investigated the conceptual and experimental aspects related to the assessment of the particulate inert COD in tannery, domestic and synthetic wastewaters. The assumption of a constant f EX coecient de®ning the residual fraction of endogenous biomass was not justi®ed. Experimental proof was provided for the eect of residual microbial products generation, both soluble and particulate, on the assessment of inert COD fractions of dierent wastewaters. The results enabled the description of a uni®ed procedure for the experimental assessment of inert COD fractions of wastewaters, as well as residual microbial products.
This study investigated the fate of 2,6-dihydroxybenzoic acid in a mixed microbial culture acclim... more This study investigated the fate of 2,6-dihydroxybenzoic acid in a mixed microbial culture acclimated to peptone under aerobic conditions. A laboratory-scale sequencing batch reactor receiving a pulse feeding of peptone at the start of each daily cycle was used for this purpose. Experimental evaluations interpreted changes induced by continuous benzoic acid additions on the oxygen uptake rate profiles associated with peptone biodegradation. At first exposure, 2,6-dihydroxybenzoic acid reduced the activity of the mixed culture and impaired peptone biodegradation. Around one-third of peptone removed could be utilized for microbial metabolism. With continuous feeding the mixture culture became acclimated and simultaneously removed peptone and 2,6-dihydroxybenzoic acid. After 30 days, oxygen uptake rate tests performed separately on peptone, 2,6-dihydroxybenzoic acid and the substrate mixture supported the existence of a dual biomass restructured with the selective growth of another group of microorganisms capable of utilizing 2,6-dihydroxybenzoic acid as an organic carbon source.
The study presents a conceptual approach for the identification of the inhibition mechanisms of b... more The study presents a conceptual approach for the identification of the inhibition mechanisms of biodegradable inhibitors. Synthetic sewage was selected as the model degradable substrate to simulate domestic wastewaters. LAS, known to be a biodegradable but inhibitory compound, was selected as a model substrate for the determination of the inhibition mechanisms. Biodegradation of synthetic sewage and LAS were monitored through oxygen uptake rate (OUR) tests conducted to observe the dynamic response of the system when fed with synthetic sewage and synthetic sewage-LAS mixtures. The approach uses respirometry to calibrate the kinetic and stoichiometric coefficients of the proposed biochemical model. Model simulation results confirmed that presence of LAS has inhibitory effects on the biodegradation mechanisms of synthetic sewage. LAS imposed non-competitive inhibition on the hydrolysis process with an inhibition coefficient of 500 mg COD/L and effected heterotrophic growth through a competitive inhibition mechanism with an inhibition coefficient of 150 mg COD/L.
The study presented an evaluation of the effect of culture history (sludge age) on the growth kin... more The study presented an evaluation of the effect of culture history (sludge age) on the growth kinetics of a mixed culture grown under aerobic conditions. It involved an experimental setup where a lab-scale sequencing batch reactor was operated at steady-state at two different sludge ages (h X) of 2 and 10 days. The system sustained a mixed culture fed with a synthetic substrate mainly consisting of peptone. The initial concentration of substrate COD was selected around 500 mg COD/L. Polyhydroxyalkanoate (PHA) storage occurred to a limited extent, around 30 mg COD/L for h X = 10 days and 15 mg COD/L for h X = 2 days. Evaluation of the experimental data based on calibration of two different models provided consistent and reliable evidence for a variable Monod kinetics where the maximum specific growth rate, was assessed as 6.1/day for h X = 2 days and 4.1/day for h X = 10 days. A similar variability was also applicable for the hydrolysis and storage kinetics. The rate of storage was significantly lower than the levels reported in the literature, exhibiting the ability of the microorganisms to regulate their metabolic mechanisms for adjusting the rate of microbial growth and storage competing for the same substrate. This adjustment evidently resulted in case-specific, variable kinetics both for microbial growth and substrate storage.
ABSTRACT The oxygen uptake rate, (OUR), may be regarded as one of the most significant modeling t... more ABSTRACT The oxygen uptake rate, (OUR), may be regarded as one of the most significant modeling tools for the understanding and interpretation of behavior of complex microbial cultures sustained under aerobic conditions. The wastewaters investigated in this study were obtained from a tannery and a chemical plant producing asetilsalisilikat, (ASS). The scope of the study, involved aside from conventional characterization, an assessment of significant kinetic and stoichiometric coefficients for chemical plant and tannery wastewaters and their mixtures, by using respirometric measurements. Results have shown that the addition of pharmaceutical effluents having a biodegradable character on tannery wastewaters would not therefore cause any negative effect on the biodegradability of tannery wastewaters.
Water science and technology : a journal of the International Association on Water Pollution Research, 2001
Wastewater recovery and reuse in industries requires all the basic steps of quality management. I... more Wastewater recovery and reuse in industries requires all the basic steps of quality management. It should involve a comprehensive in plant survey of processes with wastewater generation, identification of recoverable streams, and treatment requirements for reuse. It should equally undertake evaluation of wastewater quality remaining after segregation of the recovered portion, with specific emphasis on technological implications of appropriate treatment and compliance with effluent limitations. In this study, all these factors were experimentally assessed and evaluated for a knit fabric processing textile plant.
Journal of Environmental Science and Health, Part A, 2006
This paper explores the merit of the oxygen uptake rate (OUR) profile obtained by means of respir... more This paper explores the merit of the oxygen uptake rate (OUR) profile obtained by means of respirometry as the basic mechanistic instrument for evaluating activated sludge inhibition. Experimental OUR data are generated using the synthetic peptonebased substrate and inhibition is tested with 60 mg/L hexavalent chromium and 33 mg/L nickel additions, corresponding to EC 50 levels determined using the standard ISO 8192 procedure. Experimental results are evaluated by model calibration using ASM1 modified for dual hydrolysis and ASM3 modified for simultaneous growth. Model evaluations indicate that inhibition affects not only growth, but also other significant microbial mechanisms such as substrate storage and hydrolysis, leading to conclude that the proposed approach will enable to visualize the overall impact of the inhibitory compound on every stage of substrate biodegradation, through inspection and evaluation of the entire OUR profile.
This study evaluates the effect biochemical storage on the denitrification potential (N(DP)) of a... more This study evaluates the effect biochemical storage on the denitrification potential (N(DP)) of acetate. The fate of bacterial storage is evaluated in a sequencing batch reactor system operated in a sequence of anoxic/aerobic phases, fed with acetate as a pulse and continuously under anoxic conditions. N(DP) is defined based on system stoichiometry both for direct growth and storage on acetate. Experimental results do not support conceptual calculations based on system stoichiometry, yielding a higher denitrification potential, N(DP), for continuous feeding than the N(DP) obtained with pulse feeding, due to partial utilisation of the stored PHB within the anoxic phase. The nitrate, acetate and poly-beta-hydroxybutyrate (PHB) profiles obtained in the experimental studies were used in model calibrations for two different feeding patterns. Results of model simulations confirm the experimental results and evaluate the effects imposed on the denitrification potential by sludge age and the anoxic volume ratio.
Journal of Environmental Science and Health, Part A, 2006
This paper explores the merit of the oxygen uptake rate (OUR) profile obtained by means of respir... more This paper explores the merit of the oxygen uptake rate (OUR) profile obtained by means of respirometry as the basic mechanistic instrument for evaluating activated sludge inhibition. Experimental OUR data are generated using the synthetic peptone-based substrate and inhibition is tested with 60 mg/L hexavalent chromium and 33 mg/L nickel additions, corresponding to EC50 levels determined using the standard ISO 8192 procedure. Experimental results are evaluated by model calibration using ASM1 modified for dual hydrolysis and ASM3 modified for simultaneous growth. Model evaluations indicate that inhibition affects not only growth, but also other significant microbial mechanisms such as substrate storage and hydrolysis, leading to conclude that the proposed approach will enable to visualize the overall impact of the inhibitory compound on every stage of substrate biodegradation, through inspection and evaluation of the entire OUR profile.
Ozonation applied prior to biological processes, has proved to be a very effective chemical treat... more Ozonation applied prior to biological processes, has proved to be a very effective chemical treatment step mostly for colour removal when soluble dyes are used in textile finishing operations. Its impact on biological treatability however has not been fully evaluated yet. This study evaluates the effect of ozonation on the quality of wastewater from a textile mill involving bleaching and reactive dyeing of cotton and synthetic knit fabric. The effect of ozonation on COD fractionation and kinetic coefficients defining major biological processes is emphasised. The results indicate that the extent of ozone applied greatly affects the remaining organic carbon composition in the wastewater. The relative magnitude of different COD fractions varies as a function of the ozone dose. Ozonation does not however exert a measurable impact on the rate of major biological processes.
Synthetically prepared wastewater originating from the H-acid (4-Amino-5-hydroxy-2,7-naphthalene ... more Synthetically prepared wastewater originating from the H-acid (4-Amino-5-hydroxy-2,7-naphthalene disulfonic acid) manufacturing process was subjected to respirometric analysis for evaluating the level of achievable biodegradation in the presence of this commercially important azo dye precursor. For this purpose, H-acid was mixed with synthetic substrate having the same characteristics as sewage at a concentration and composition being typical for H-acid manufacturing wastewater. Experimental results indicated that H-acid was not biodegradable under activated sludge treatment conditions even after prolonged acclimation periods. The results were also confirmed by model evaluation of oxygen uptake rate profiles. H-acid also did not inhibit the biodegradation of synthetic sewage but accumulated as soluble inert COD in the treated wastewater.
The study presents a conceptual approach for the identification of the inhibition mechanisms of b... more The study presents a conceptual approach for the identification of the inhibition mechanisms of biodegradable inhibitors. Synthetic sewage was selected as the model degradable substrate to simulate domestic wastewaters. LAS, known to be a biodegradable but inhibitory compound, was selected as a model substrate for the determination of the inhibition mechanisms. Biodegradation of synthetic sewage and LAS were monitored through oxygen uptake rate (OUR) tests conducted to observe the dynamic response of the system when fed with synthetic sewage and synthetic sewage-LAS mixtures. The approach uses respirometry to calibrate the kinetic and stoichiometric coefficients of the proposed biochemical model. Model simulation results confirmed that presence of LAS has inhibitory effects on the biodegradation mechanisms of synthetic sewage. LAS imposed non-competitive inhibition on the hydrolysis process with an inhibition coefficient of 500 mg COD/L and effected heterotrophic growth through a competitive inhibition mechanism with an inhibition coefficient of 150 mg COD/L.
Xenobiotic compounds are widely used in several industries; hence they frequently appear in indus... more Xenobiotic compounds are widely used in several industries; hence they frequently appear in industrial wastewaters. It is a well-known fact that even the discharge of conventionally treated wastewater may have adverse effects on the receiving water environment. Turkey, a developing EU applicant country, has many industrial sectors producing large amounts of xenobiotic-containing wastewaters. The problem is only enlarged by the lack of monitoring of these substances due to the deficiencies associated with their analysis and detection. Thus, studies in Turkey are based on the use of some collective parameters as a substitute for the xenobiotic itself. Biological, physicochemical, and integrated treatment technologies have been investigated for the removal and/or minimization of the possible adverse effects of xenobiotics in industrial wastewaters. In this respect, this paper provides an overview of the studies conducted on xenobiotic-containing wastewaters from specific industries in Turkey. Although the studies add invaluable information to the scientific background on the subject, new research on the exact biochemical mechanisms of xenobiotic biodegradation will further extend our understanding for improving treatment.
... Gülseda DİZDAROĞLU RİŞVANOĞLU*, Özlem KARAHAN, Emine UBAY ÇOKGÖR, Mark CM Van LOOSDRECHT, Der... more ... Gülseda DİZDAROĞLU RİŞVANOĞLU*, Özlem KARAHAN, Emine UBAY ÇOKGÖR, Mark CM Van LOOSDRECHT, Derin ORHON ... Depolama ürünlerinin sentezi tüm hücre sentezinden daha basit olduğundan, daha az fizyolojik adaptasyon gerektirmekte ve bundan dolayı ...
Foreword xiii 2.2.4.1 VSS as a biomass parameter 2.2.4.2 VSS and BOD 5 as biomass and substrate p... more Foreword xiii 2.2.4.1 VSS as a biomass parameter 2.2.4.2 VSS and BOD 5 as biomass and substrate parameters 2.3 PROCESS STOICHIOMETRY 2.3.1 System defined with biomass COD and substrate COD 2.3.2 System defined with biomass VSS and substrate COD 2.3.3 System defined with biomass VSS and substrate BOD 5 2.4 REFERENCES 3 MODELLING OF ORGANIC CARBON REMOVAL 3.1 PRINCIPLES OF MODELLING vi Industrial Wastewater Treatment by Activated Sludge viii Industrial Wastewater Treatment by Activated Sludge 7.3.1.3 Inert particulate COD of influent origin 7.3.1.4 Total biomass in the reactor 7.
This paper provides an overview of common problems encountered when using oxygen uptake rate (OUR... more This paper provides an overview of common problems encountered when using oxygen uptake rate (OUR) measurements for the assessment of wastewater characteristics and process kinetics. Emphasis is placed upon pitfalls that would lead to significant errors. It covers model dependency of the OUR measurements and the need to select appropriate models; interpretation of OUR perturbations as a way to identify new model components and processes; the need for simultaneous observation of relevant model components and multicomponent modelling for appropriate evaluation of OUR measurements; parameter identifiability problems and the effect of active biomass concentration and the endogenous decay rate on model simulation and calibration. Relevant experimental OUR data from previous studies are presented to illustrate and underline common scientific pitfalls.
ÐThis study mainly investigated the conceptual and experimental aspects related to the assessment... more ÐThis study mainly investigated the conceptual and experimental aspects related to the assessment of the particulate inert COD in tannery, domestic and synthetic wastewaters. The assumption of a constant f EX coecient de®ning the residual fraction of endogenous biomass was not justi®ed. Experimental proof was provided for the eect of residual microbial products generation, both soluble and particulate, on the assessment of inert COD fractions of dierent wastewaters. The results enabled the description of a uni®ed procedure for the experimental assessment of inert COD fractions of wastewaters, as well as residual microbial products.
This study investigated the fate of 2,6-dihydroxybenzoic acid in a mixed microbial culture acclim... more This study investigated the fate of 2,6-dihydroxybenzoic acid in a mixed microbial culture acclimated to peptone under aerobic conditions. A laboratory-scale sequencing batch reactor receiving a pulse feeding of peptone at the start of each daily cycle was used for this purpose. Experimental evaluations interpreted changes induced by continuous benzoic acid additions on the oxygen uptake rate profiles associated with peptone biodegradation. At first exposure, 2,6-dihydroxybenzoic acid reduced the activity of the mixed culture and impaired peptone biodegradation. Around one-third of peptone removed could be utilized for microbial metabolism. With continuous feeding the mixture culture became acclimated and simultaneously removed peptone and 2,6-dihydroxybenzoic acid. After 30 days, oxygen uptake rate tests performed separately on peptone, 2,6-dihydroxybenzoic acid and the substrate mixture supported the existence of a dual biomass restructured with the selective growth of another group of microorganisms capable of utilizing 2,6-dihydroxybenzoic acid as an organic carbon source.
The study presents a conceptual approach for the identification of the inhibition mechanisms of b... more The study presents a conceptual approach for the identification of the inhibition mechanisms of biodegradable inhibitors. Synthetic sewage was selected as the model degradable substrate to simulate domestic wastewaters. LAS, known to be a biodegradable but inhibitory compound, was selected as a model substrate for the determination of the inhibition mechanisms. Biodegradation of synthetic sewage and LAS were monitored through oxygen uptake rate (OUR) tests conducted to observe the dynamic response of the system when fed with synthetic sewage and synthetic sewage-LAS mixtures. The approach uses respirometry to calibrate the kinetic and stoichiometric coefficients of the proposed biochemical model. Model simulation results confirmed that presence of LAS has inhibitory effects on the biodegradation mechanisms of synthetic sewage. LAS imposed non-competitive inhibition on the hydrolysis process with an inhibition coefficient of 500 mg COD/L and effected heterotrophic growth through a competitive inhibition mechanism with an inhibition coefficient of 150 mg COD/L.
The study presented an evaluation of the effect of culture history (sludge age) on the growth kin... more The study presented an evaluation of the effect of culture history (sludge age) on the growth kinetics of a mixed culture grown under aerobic conditions. It involved an experimental setup where a lab-scale sequencing batch reactor was operated at steady-state at two different sludge ages (h X) of 2 and 10 days. The system sustained a mixed culture fed with a synthetic substrate mainly consisting of peptone. The initial concentration of substrate COD was selected around 500 mg COD/L. Polyhydroxyalkanoate (PHA) storage occurred to a limited extent, around 30 mg COD/L for h X = 10 days and 15 mg COD/L for h X = 2 days. Evaluation of the experimental data based on calibration of two different models provided consistent and reliable evidence for a variable Monod kinetics where the maximum specific growth rate, was assessed as 6.1/day for h X = 2 days and 4.1/day for h X = 10 days. A similar variability was also applicable for the hydrolysis and storage kinetics. The rate of storage was significantly lower than the levels reported in the literature, exhibiting the ability of the microorganisms to regulate their metabolic mechanisms for adjusting the rate of microbial growth and storage competing for the same substrate. This adjustment evidently resulted in case-specific, variable kinetics both for microbial growth and substrate storage.
ABSTRACT The oxygen uptake rate, (OUR), may be regarded as one of the most significant modeling t... more ABSTRACT The oxygen uptake rate, (OUR), may be regarded as one of the most significant modeling tools for the understanding and interpretation of behavior of complex microbial cultures sustained under aerobic conditions. The wastewaters investigated in this study were obtained from a tannery and a chemical plant producing asetilsalisilikat, (ASS). The scope of the study, involved aside from conventional characterization, an assessment of significant kinetic and stoichiometric coefficients for chemical plant and tannery wastewaters and their mixtures, by using respirometric measurements. Results have shown that the addition of pharmaceutical effluents having a biodegradable character on tannery wastewaters would not therefore cause any negative effect on the biodegradability of tannery wastewaters.
Water science and technology : a journal of the International Association on Water Pollution Research, 2001
Wastewater recovery and reuse in industries requires all the basic steps of quality management. I... more Wastewater recovery and reuse in industries requires all the basic steps of quality management. It should involve a comprehensive in plant survey of processes with wastewater generation, identification of recoverable streams, and treatment requirements for reuse. It should equally undertake evaluation of wastewater quality remaining after segregation of the recovered portion, with specific emphasis on technological implications of appropriate treatment and compliance with effluent limitations. In this study, all these factors were experimentally assessed and evaluated for a knit fabric processing textile plant.
Journal of Environmental Science and Health, Part A, 2006
This paper explores the merit of the oxygen uptake rate (OUR) profile obtained by means of respir... more This paper explores the merit of the oxygen uptake rate (OUR) profile obtained by means of respirometry as the basic mechanistic instrument for evaluating activated sludge inhibition. Experimental OUR data are generated using the synthetic peptonebased substrate and inhibition is tested with 60 mg/L hexavalent chromium and 33 mg/L nickel additions, corresponding to EC 50 levels determined using the standard ISO 8192 procedure. Experimental results are evaluated by model calibration using ASM1 modified for dual hydrolysis and ASM3 modified for simultaneous growth. Model evaluations indicate that inhibition affects not only growth, but also other significant microbial mechanisms such as substrate storage and hydrolysis, leading to conclude that the proposed approach will enable to visualize the overall impact of the inhibitory compound on every stage of substrate biodegradation, through inspection and evaluation of the entire OUR profile.
This study evaluates the effect biochemical storage on the denitrification potential (N(DP)) of a... more This study evaluates the effect biochemical storage on the denitrification potential (N(DP)) of acetate. The fate of bacterial storage is evaluated in a sequencing batch reactor system operated in a sequence of anoxic/aerobic phases, fed with acetate as a pulse and continuously under anoxic conditions. N(DP) is defined based on system stoichiometry both for direct growth and storage on acetate. Experimental results do not support conceptual calculations based on system stoichiometry, yielding a higher denitrification potential, N(DP), for continuous feeding than the N(DP) obtained with pulse feeding, due to partial utilisation of the stored PHB within the anoxic phase. The nitrate, acetate and poly-beta-hydroxybutyrate (PHB) profiles obtained in the experimental studies were used in model calibrations for two different feeding patterns. Results of model simulations confirm the experimental results and evaluate the effects imposed on the denitrification potential by sludge age and the anoxic volume ratio.
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