Laleh Yerushalmi | Concordia University (Canada) (original) (raw)

Papers by Laleh Yerushalmi

Water Practice & Technology, Dec 24, 2019

A full-cycle water remediation process has been developed by expanding the capacity of an existin... more A full-cycle water remediation process has been developed by expanding the capacity of an existing water treatment technology that uses combined ozonation and ultrafiltration membrane processes. The developed water reclamation process treated the effluent of a full-scale wastewater treatment plant in Canada that uses biological treatment processes to treat municipal wastewater, and reduced the colour, turbidity, suspended solids, iron and pathogen content of the effluent. The removal of hardness from the wastewater effluent was accomplished by the precipitation process. The use of lime (0.2 g/L) in the presence of NaOH operating at pH 11 showed the best results, reducing the water hardness by 89.1%. The advanced treatment capability of ozonation (8–10% w/w) and polyvinylidene fluoride (PVDF) hollow fiber ultrafiltration (UF) membrane produced a reliable source of water for municipal, industrial and agricultural use. The developed process offers important environmental benefits by reducing the diversion of water from sensitive ecosystems, decreasing wastewater discharge and preventing pollution.

BACKGROUND: The simultaneous removal of carbon, nitrogen and phosphorus under variable operating ... more BACKGROUND: The simultaneous removal of carbon, nitrogen and phosphorus under variable operating conditions during the start-up period of a new multi-environment hybrid wastewater treatment technology called BioCAST is reported in this paper. The presence of both suspended-growth and immobilized microorganisms, as well as the continuous circulation of mixed liquor between the three zones of aerobic, microaerophilic and anoxic, supported high removal efficiencies of organic and inorganic contaminants. RESULTS: The removal efficiencies of carbon, nitrogen and phosphorus reached 99.3%, 98.0% and 92.3%, respectively, under varying organic loading rates in the range 0.4-3.0 kg m-3 d-1 , and nitrogen and phosphorus loading rates of 0.03-0.14 kg m-3 d-1 and 0.008-0.028 kg m-3 d-1 , respectively. Phosphorus removal increased steadily with the increase of nitrogen loading rate, producing a final effluent concentration of 2.9 mg L-1. Low sludge generation was obtained along with a low biomass yield of 11.5%. CONCLUSIONS: The start-up period of the BioCAST system demonstrated its potential for simultaneous removal of organic material, as well as nitrogen and phosphorus. Phosphorus removal demonstrated a strong dependence on nitrogen loading rate. Moreover, theoretical analysis of the liquid flow and energy balances in different zones of the treatment system showed that the pressure difference across the air diffuser is the governing force for the flow of liquid towards the aerobic zone and the controlling factor for the continuous circulation of mixed liquor among various zones.

Applied Microbiology and Biotechnology, Mar 1, 1987

SummaryA modified strain of Clostridium acetobutylicum and the fermentation medium conditions for... more SummaryA modified strain of Clostridium acetobutylicum and the fermentation medium conditions for good growth of the culture and normal production of solvents are described. The pretreatment of the culture with butyric-acid-enriched medium increased the final solvent yield on sugar and lowered the residual butyric acid accumulation. In a complex medium, relatively high concentrations of yeast extract (7.5 g/l) and ammonium sulphate (3 g/l to 6 g/l) were required for normal solvent synthesis. The nitrogen requirements for cellular growth and solvent production were distinctively different. Production of solvents and growth of the culture were dependent on the concentration of para-aminobenzoic acid and relatively independent of the variations of the initial pH of the medium in the range of 4.6 to 6.3. Solvent production was obtained with initial glucose concentrations of 20.5 g/l to 70 g/l, resulting in a maximum solvent concentration of 22 g/l and a maximum yield on glucose of 32.7%.

Water Quality Research Journal of Canada, Nov 1, 1999

The effects of several pretreatment techniques, including dilution, fungal pretreatment and addit... more The effects of several pretreatment techniques, including dilution, fungal pretreatment and addition of hydrogen peroxide on the enhancement of anaerobic biodegradability of spent liquor (SL) of the oxygen delignification process of recycled fibers, were evaluated. A 14% COD removal efficiency and a 37% acidification were obtained by the untreated effluent, indicating its low degree of biodegradability. After pretreatment, the efficiency of COD removal and the overall yield of methane production were increased by 24% to 246% and by 26% to 396%, respectively, compared to the untreated liquor. The acidification of spent liquor also increased to more than 70% following the pretreatment. Kinetics analysis of methane production and COD removal implied the production of inhibitory metabolites during the anaerobic biodegradation. The optimal dilution factor for the spent liquor sample under study, to reduce toxi-city while maximizing the specific rates of COD removal and methane production, was predicted to be less than five times.

Journal of Chemical Technology & Biotechnology, Apr 24, 2007

The optimum operating temperatures for the maximum production of ethanol and the maximum utilizat... more The optimum operating temperatures for the maximum production of ethanol and the maximum utilization of substrate in batch fermentations of a waste sulphite liquor (WSL) as well as a synthetic medium using Saccharomyces cerevisiae were determined. The fastest consumption of substrate resulting in the shortest fermentation times of 13 h and 45 h was achieved at 35°C and 30°C for the synthetic medium and the WSL, respectively. The concentrations of ethanol in the two media were also maximum under these conditions: 11.6g dm−3 and 9.4 g dm−3 for the synthetic medium and the WSL, respectively. The productivities of biomass and ethanol increased with the increase of temperature and reached maximum values of 0.89 g dm−3 h−1 and 0.21 g dm−3 h−1 in the synthetic medium and the WSL, respectively. The inhibiting agents in the waste sulphite liquor affected the metabolic rates of microbial activities and prolonged the overall fermentation time while decreasing the productivities of biomass and ethanol. From analysis of the fermentation kinetics a mathematical model based on the Monod model was developed to describe the cellular growth and ethanol production. The model included inhibition terms for ethanol and the inhibiting agents in the waste liquor. The temperature dependence of the model parameters followed the Arrhenius law for temperatures between 15°C and 35°C. The activation energies (E) and the frequency constants (A) of these parameters were also determined.

Applied Microbiology and Biotechnology, Apr 27, 1998

Aerobic biodegradation of gasoline and its constituents, benzene, toluene and ethylbenzene were s... more Aerobic biodegradation of gasoline and its constituents, benzene, toluene and ethylbenzene were studied by an enrichment from soil indigenous microbial population. The enrichment culture completely degraded 16.1±660 mg/l gasoline in 2.5±16 days respectively, without accumulation of any by-products. The kinetics of gasoline as well as benzene, toluene and ethylbenzene biodegradation was investigated with initial gasoline concentrations of 16.1±62.6 mg/l. The maximum speci®c rates of biodegradation of benzene, toluene and ethylbenzene were 0.12, 0.38 and 0.19 mg mg biomass A1 day A1 respectively. When benzene and toluene were used as sole substrate, the maximum speci®c rates of their biodegradation were 62.9 and 16.4 times greater than the corresponding values for a mixture (gasoline). The microbial culture was able to mineralize up to 200 mg/l pure toluene and benzene. Maximum mineralization eciencies of benzene and toluene were 76.7 5.1% and 76.8 1.3% respectively. Self-inhibition and competitive inhibition patterns were observed during the biodegradation of benzene and toluene alone and in the mixture respectively. The observed kinetics was modeled according to Andrews' inhibition model.

Bioresource Technology Reports, Dec 1, 2020

Abstract This study reports the recovery of single-stage partial nitrification (PN)/anammox biore... more Abstract This study reports the recovery of single-stage partial nitrification (PN)/anammox bioreactor treating nitrite-free and ammonium-rich synthetic wastewater affected by a high concentration of lactose (2000 mg/l). The lactose shock led to the collapse of the PN/anammox process in

Water Science and Technology, Feb 1, 2013

Simultaneous removal of carbon, nitrogen and phosphorus was examined along with reduced generatio... more Simultaneous removal of carbon, nitrogen and phosphorus was examined along with reduced generation of biological sludge during the treatment of synthetic wastewater and hog waste by the BioCAST technology. This new multi-environment wastewater treatment technology contains both suspended and immobilized microorganisms, and benefits from the presence of aerobic, microaerophilic, anoxic and anaerobic conditions for the biological treatment of wastewater. The influent concentrations during the treatment of synthetic wastewater were 1,300-4,000 mg chemical oxygen demand (COD)/L, 42-115 mg total nitrogen (TN)/L, and 19-40 mg total phosphorus (TP)/L. The removal efficiencies reached 98.9, 98.3 and 94.1%, respectively, for carbon, TN and TP during 225 days of operation. The removal efficiencies of carbon and nitrogen showed a minimal dependence on the nitrogen-to-phosphorus (N/P) ratio, while the phosphorus removal efficiency showed a remarkable dependence on this parameter, increasing from 45 to 94.1% upon the increase of N/P ratio from 3 to 4.5. The increase of TN loading rate had a minimal impact on COD removal rate which remained around 1.7 kg/m 3 d, while it contributed to increased TP removal efficiency. The treatment of hog waste with influent COD, TN and TP concentrations of 960-2,400, 143-235 and 25-57 mg/L, respectively, produced removal efficiencies up to 89.2, 69.2 and 47.6% for the three contaminants, despite the inhibitory effects of this waste towards biological activity. The treatment system produced low biomass yields with average values of 3.7 and 8.2% during the treatment of synthetic wastewater and hog waste, respectively.

Biotechnology and Bioengineering, Sep 1, 1986

The pronounced differences in performance of a strain of Clostridium acetobutylicum ATCC 824 were... more The pronounced differences in performance of a strain of Clostridium acetobutylicum ATCC 824 were analyzed by the method of systems analysis. The mechanism for cellular transport of substrate (glucose), solvents, and acids was studied and mathematically formulated. The systems analysis approach in the treatment of data from culture experiments pointed out the cell membrane malfunction indicated by its altered permeability and reflected in the altered number of active sugar transport sites. Experimental results obtained from the study of the cell uptake of 3-0-methyl glucose (0.7mM) by the "normal culture" and the "retarded culture" confirmed the theoretical predictions regarding a slower transport in the retarded culture. The initial uptake rate and the accumulation coefficient of the sugar in the normal culture were 15.0 and 4.1 times higher, respectively, than those for the retarded culture. Adjustment of the culture pH resulted in further increases in these parameters by factors of 3.0 and 3.5, respectively.

Applied Microbiology and Biotechnology, Jun 1, 1985

... of this compound. Decreased acetone production could be attributed to the inhibition of aceti... more ... of this compound. Decreased acetone production could be attributed to the inhibition of acetic acid formation which is a metabolic precursor for ace-tone synthesis in the sugar-metabolizing system. Although high H2 concentrations ...

Biotechnology and Bioengineering, Feb 1, 1986

A mathematical model for the batch culture of Clostridium acetobutylicum was formulated using exp... more A mathematical model for the batch culture of Clostridium acetobutylicum was formulated using experimental data for anaerobic solvent production. The model summarizes biochemical as well as physiological aspects of growth and metabolite synthesis by the production strain. The key fermentation rates are expressed and evaluated with regard to substrate consumption and butanol end‐product inhibitory effects. Parametric sensitivity analysis of the batch process model was carried out, indicating the importance of the key process parameters.

Springer eBooks, Sep 24, 2013

Retail gasoline outlets contribute to the emission of volatile organic compounds (VOCs). Accordin... more Retail gasoline outlets contribute to the emission of volatile organic compounds (VOCs). According to the United States Environmental Protection Agency (US EPA), the concentrations of the common constituents of gasoline such as benzene (a carcinogen), toluene, ethylbenzene, and xylene within 200 m of gas stations are found to be higher than ambient background levels. Many retail gasoline outlets are located in close proximity to populated commercial and residential neighbourhoods. In the light of the above, this paper presents estimates from the survey of industrial processes (SIP), a pilot survey conducted by the Canadian Government, for the overall evaporative emissions from retail gasoline outlets across Canada. The survey suggests that approximately 58 million litres of liquid gasoline is being evaporated each year into the ambient air from the 11,200 retail gasoline outlets across Canada. Such an emission rate is equivalent to the evaporation of the contents of three fully loaded gasoline delivery trucks on each and every day of the year. This silent emission contaminates the ambient air of urban populated neighbourhoods and subsequently the indoor air of buildings that are located in such neighbourhoods. To that end, this paper attempts to raise the awareness of building engineers regarding the locations of gasoline outlets within the vicinity of buildings and the potential short-circuiting of gasoline vapours from the ambient air to the indoor microenvironment.

Biotechnology and Bioengineering, Jun 11, 2002

A special microbial consortium adapted to degrade petroleum hydrocarbons at limited availability ... more A special microbial consortium adapted to degrade petroleum hydrocarbons at limited availability of oxygen, transformed benzene, a highly toxic and carcinogenic contaminant of groundwater and soil, at low initial dissolved oxygen (DO) concentrations of 0.05±2 mg/L. The employed initial concentrations of dissolved oxygen were considerably lower than the previously reported values. Under these conditions, the overall transformation of benzene ranged from 34% 1.7% to 100%, considerably higher than the theoretical predictions for complete mineralization of benzene based on the requirement of 3.08 mg oxygen/mg benzene. Unlike biotransformation that proceeded at the lowest examined DO concentration of 0.05 mg/L, the mineralization of benzene, de®ned by its conversion to CO 2 and water, required a minimum DO concentration of 0.2 mg/L. The mineralization of benzene under microaerophilic conditions (DO < 2 mg/L), ranged from 0.83% 0.06% to 89% 1.3%, which was less than the theoretical predictions at any given initial DO concentration. The regulatory effects of dissolved oxygen concentration or its partial pressure on the activities of enzymes catalyzing the biotransformation of aromatic hydrocarbons was postulated to account for the reduced mineralization of benzene. The ratio between the transformed benzene and the consumed oxygen increased with the decrease of initial DO concentration, reaching a value of 2.8, considerably higher than the theoretical value of 0.33 obtained for a complete aerobic oxidation of benzene. Phenol was the major and the most stable intermediate metabolite during the biotransformation of benzene at low concentrations of DO. While benzene transformation stopped after the depletion of oxygen in the experimental system, phenol continued to accumulate under strictly anaerobic conditions, indicating its formation from an alternative carbon source, possibly biomass. ã 2002 Government of Canada. Exclusive worldwide publication rights in this article have been transferred to Wiley Periodicals, Inc. Biotechnol Bioeng 79: 347±355, 2002.

Journal of Chemical Technology & Biotechnology, Apr 24, 2007

A specially developed temperature control system on a laboratory scale fermenter enabled continuo... more A specially developed temperature control system on a laboratory scale fermenter enabled continuous measurement of the rate of heat production during undisturbed growth of microbial cultures. Apart from being correlated with oxygen uptake rate, the heat of fermentation was established as an additional indicator of metabolic activity. The ‘aerobic respiration’ energetic activity of Candida utilis, Candida lipolytica and Saccharomyces cerevisiae on different carbon substrates was investigated with cultures of the latter species being also studied under the ‘aerobic fermentation’ conditions induced by glucose catabolite repression.

Biotechnology and Bioengineering, Sep 1, 1985

The specific rates of anaerobic solvent production by Clostridium acetobutylicum increased with i... more The specific rates of anaerobic solvent production by Clostridium acetobutylicum increased with increasing fermentor impeller speed from 190 to 340 rpm (NRe = 3.93 × 104). The maximum values were 5.54, 3.85, and 0.8 mmol/h · g cell for butanol, acetone, and ethanol, respectively. Corresponding rates for respective gases produced were 11.60 and 15.88 mmol/h · g cell for H2 and CO2. Further increases in agitation speed resulted in generally decreasing specific production rates to the point of inactive fermentation at 560 rpm. A competition observed between the cellular subsystems for butanol + butyric acid and biomass biosynthesis was evaluated through expressing the energetic yield coefficients. An imbalance between the production and outflux of the former metabolites is apparently further enhanced by a mechanical damage of the cells at high shear rates. A correlation was developed between the production of gases and solvents pointing at both H2‐to‐solvent as well as CO2‐to‐solvent ratios following the same pattern, peaking at 410 rpm.

Environmental Science and Pollution Research, Jul 2, 2019

This paper presents the treatment of a nitrite-limited wastewater by partial nitrification/anammo... more This paper presents the treatment of a nitrite-limited wastewater by partial nitrification/anammox process under different dissolved oxygen (DO) concentrations of < 1.2 mg/L, < 0.5 mg/L, and 0 mg/L, and at temperatures of 35 to 27°C in a pilot-scale single-stage hybrid bioreactor (BioCAST). The effect of operational parameters on microbial community structure and composition has also been investigated during the 1-year experimental period. Ammonium removal efficiencies of 73 ± 19% at 35-32°C and 87 ± 9% at 29-27°C were obtained from a synthetic nitrite-limited wastewater with ammonium concentration of 350-500 mg/L (175-250 g m −3 d −1). The adaptation of bacteria to a lower temperature (27°C) and lower free ammonia concentrations at 27°C was showed to be key factors leading to the optimal nitrite production by aerobic ammonium-oxidizing bacteria (AOB). No nitrite accumulation was observed due to the effective distribution and transfer of nitrite produced by the AOB in the aerobic zone to the microaerophilic/anoxic zones. The fast enrichment of Candidatus species in the suspended biomass in the anoxic zone at temperatures of 35-30°C and in the attached biofilm in the microaerophilic zone (DO < 0.5 mg/L) at 29-27°C suggests that the growth media (e.g., suspended biomass vs attached biofilm) had a minor effect on the diversity of microbial community in this bioreactor. This study supports the effective treatment of nitrite-limited wastewater with ammonium concentrations of < 500 mg/L by partial nitrification/anammox process at 35-27°C in a single-stage hybrid bioreactor by adjusting the DO concentration to < 0.5 mg/L and by providing longer retention times for aerobic (AOB) and anammox bacteria in the biofilm, which resulted in the long-term suppression of nitrite-oxidizing bacteria (NOB).

Canadian Journal of Chemical Engineering, Aug 1, 1986

A mathematical model of the batch acetone-butanol fermentation has been proposed which reflects t... more A mathematical model of the batch acetone-butanol fermentation has been proposed which reflects the process kinetics and biochemistry. The degree of importance of the key kinetic parameters has been established by a parametric sensitivity analysis. The basic model was further extended by incorporating additional culture physiological parameters such as the number of active mass transport sites and the permeability of the cellular membrane as well as the intracellular and extracellular conditions. The model assisted in studying the role of the cellular membrane in the control of the culture performance and solvent biosynthesis. The theoretical predictions were confirmed by experimental results.

Water Practice & Technology, Dec 24, 2019

A full-cycle water remediation process has been developed by expanding the capacity of an existin... more A full-cycle water remediation process has been developed by expanding the capacity of an existing water treatment technology that uses combined ozonation and ultrafiltration membrane processes. The developed water reclamation process treated the effluent of a full-scale wastewater treatment plant in Canada that uses biological treatment processes to treat municipal wastewater, and reduced the colour, turbidity, suspended solids, iron and pathogen content of the effluent. The removal of hardness from the wastewater effluent was accomplished by the precipitation process. The use of lime (0.2 g/L) in the presence of NaOH operating at pH 11 showed the best results, reducing the water hardness by 89.1%. The advanced treatment capability of ozonation (8–10% w/w) and polyvinylidene fluoride (PVDF) hollow fiber ultrafiltration (UF) membrane produced a reliable source of water for municipal, industrial and agricultural use. The developed process offers important environmental benefits by reducing the diversion of water from sensitive ecosystems, decreasing wastewater discharge and preventing pollution.

BACKGROUND: The simultaneous removal of carbon, nitrogen and phosphorus under variable operating ... more BACKGROUND: The simultaneous removal of carbon, nitrogen and phosphorus under variable operating conditions during the start-up period of a new multi-environment hybrid wastewater treatment technology called BioCAST is reported in this paper. The presence of both suspended-growth and immobilized microorganisms, as well as the continuous circulation of mixed liquor between the three zones of aerobic, microaerophilic and anoxic, supported high removal efficiencies of organic and inorganic contaminants. RESULTS: The removal efficiencies of carbon, nitrogen and phosphorus reached 99.3%, 98.0% and 92.3%, respectively, under varying organic loading rates in the range 0.4-3.0 kg m-3 d-1 , and nitrogen and phosphorus loading rates of 0.03-0.14 kg m-3 d-1 and 0.008-0.028 kg m-3 d-1 , respectively. Phosphorus removal increased steadily with the increase of nitrogen loading rate, producing a final effluent concentration of 2.9 mg L-1. Low sludge generation was obtained along with a low biomass yield of 11.5%. CONCLUSIONS: The start-up period of the BioCAST system demonstrated its potential for simultaneous removal of organic material, as well as nitrogen and phosphorus. Phosphorus removal demonstrated a strong dependence on nitrogen loading rate. Moreover, theoretical analysis of the liquid flow and energy balances in different zones of the treatment system showed that the pressure difference across the air diffuser is the governing force for the flow of liquid towards the aerobic zone and the controlling factor for the continuous circulation of mixed liquor among various zones.

Applied Microbiology and Biotechnology, Mar 1, 1987

SummaryA modified strain of Clostridium acetobutylicum and the fermentation medium conditions for... more SummaryA modified strain of Clostridium acetobutylicum and the fermentation medium conditions for good growth of the culture and normal production of solvents are described. The pretreatment of the culture with butyric-acid-enriched medium increased the final solvent yield on sugar and lowered the residual butyric acid accumulation. In a complex medium, relatively high concentrations of yeast extract (7.5 g/l) and ammonium sulphate (3 g/l to 6 g/l) were required for normal solvent synthesis. The nitrogen requirements for cellular growth and solvent production were distinctively different. Production of solvents and growth of the culture were dependent on the concentration of para-aminobenzoic acid and relatively independent of the variations of the initial pH of the medium in the range of 4.6 to 6.3. Solvent production was obtained with initial glucose concentrations of 20.5 g/l to 70 g/l, resulting in a maximum solvent concentration of 22 g/l and a maximum yield on glucose of 32.7%.

Water Quality Research Journal of Canada, Nov 1, 1999

The effects of several pretreatment techniques, including dilution, fungal pretreatment and addit... more The effects of several pretreatment techniques, including dilution, fungal pretreatment and addition of hydrogen peroxide on the enhancement of anaerobic biodegradability of spent liquor (SL) of the oxygen delignification process of recycled fibers, were evaluated. A 14% COD removal efficiency and a 37% acidification were obtained by the untreated effluent, indicating its low degree of biodegradability. After pretreatment, the efficiency of COD removal and the overall yield of methane production were increased by 24% to 246% and by 26% to 396%, respectively, compared to the untreated liquor. The acidification of spent liquor also increased to more than 70% following the pretreatment. Kinetics analysis of methane production and COD removal implied the production of inhibitory metabolites during the anaerobic biodegradation. The optimal dilution factor for the spent liquor sample under study, to reduce toxi-city while maximizing the specific rates of COD removal and methane production, was predicted to be less than five times.

Journal of Chemical Technology & Biotechnology, Apr 24, 2007

The optimum operating temperatures for the maximum production of ethanol and the maximum utilizat... more The optimum operating temperatures for the maximum production of ethanol and the maximum utilization of substrate in batch fermentations of a waste sulphite liquor (WSL) as well as a synthetic medium using Saccharomyces cerevisiae were determined. The fastest consumption of substrate resulting in the shortest fermentation times of 13 h and 45 h was achieved at 35°C and 30°C for the synthetic medium and the WSL, respectively. The concentrations of ethanol in the two media were also maximum under these conditions: 11.6g dm−3 and 9.4 g dm−3 for the synthetic medium and the WSL, respectively. The productivities of biomass and ethanol increased with the increase of temperature and reached maximum values of 0.89 g dm−3 h−1 and 0.21 g dm−3 h−1 in the synthetic medium and the WSL, respectively. The inhibiting agents in the waste sulphite liquor affected the metabolic rates of microbial activities and prolonged the overall fermentation time while decreasing the productivities of biomass and ethanol. From analysis of the fermentation kinetics a mathematical model based on the Monod model was developed to describe the cellular growth and ethanol production. The model included inhibition terms for ethanol and the inhibiting agents in the waste liquor. The temperature dependence of the model parameters followed the Arrhenius law for temperatures between 15°C and 35°C. The activation energies (E) and the frequency constants (A) of these parameters were also determined.

Applied Microbiology and Biotechnology, Apr 27, 1998

Aerobic biodegradation of gasoline and its constituents, benzene, toluene and ethylbenzene were s... more Aerobic biodegradation of gasoline and its constituents, benzene, toluene and ethylbenzene were studied by an enrichment from soil indigenous microbial population. The enrichment culture completely degraded 16.1±660 mg/l gasoline in 2.5±16 days respectively, without accumulation of any by-products. The kinetics of gasoline as well as benzene, toluene and ethylbenzene biodegradation was investigated with initial gasoline concentrations of 16.1±62.6 mg/l. The maximum speci®c rates of biodegradation of benzene, toluene and ethylbenzene were 0.12, 0.38 and 0.19 mg mg biomass A1 day A1 respectively. When benzene and toluene were used as sole substrate, the maximum speci®c rates of their biodegradation were 62.9 and 16.4 times greater than the corresponding values for a mixture (gasoline). The microbial culture was able to mineralize up to 200 mg/l pure toluene and benzene. Maximum mineralization eciencies of benzene and toluene were 76.7 5.1% and 76.8 1.3% respectively. Self-inhibition and competitive inhibition patterns were observed during the biodegradation of benzene and toluene alone and in the mixture respectively. The observed kinetics was modeled according to Andrews' inhibition model.

Bioresource Technology Reports, Dec 1, 2020

Abstract This study reports the recovery of single-stage partial nitrification (PN)/anammox biore... more Abstract This study reports the recovery of single-stage partial nitrification (PN)/anammox bioreactor treating nitrite-free and ammonium-rich synthetic wastewater affected by a high concentration of lactose (2000 mg/l). The lactose shock led to the collapse of the PN/anammox process in

Water Science and Technology, Feb 1, 2013

Simultaneous removal of carbon, nitrogen and phosphorus was examined along with reduced generatio... more Simultaneous removal of carbon, nitrogen and phosphorus was examined along with reduced generation of biological sludge during the treatment of synthetic wastewater and hog waste by the BioCAST technology. This new multi-environment wastewater treatment technology contains both suspended and immobilized microorganisms, and benefits from the presence of aerobic, microaerophilic, anoxic and anaerobic conditions for the biological treatment of wastewater. The influent concentrations during the treatment of synthetic wastewater were 1,300-4,000 mg chemical oxygen demand (COD)/L, 42-115 mg total nitrogen (TN)/L, and 19-40 mg total phosphorus (TP)/L. The removal efficiencies reached 98.9, 98.3 and 94.1%, respectively, for carbon, TN and TP during 225 days of operation. The removal efficiencies of carbon and nitrogen showed a minimal dependence on the nitrogen-to-phosphorus (N/P) ratio, while the phosphorus removal efficiency showed a remarkable dependence on this parameter, increasing from 45 to 94.1% upon the increase of N/P ratio from 3 to 4.5. The increase of TN loading rate had a minimal impact on COD removal rate which remained around 1.7 kg/m 3 d, while it contributed to increased TP removal efficiency. The treatment of hog waste with influent COD, TN and TP concentrations of 960-2,400, 143-235 and 25-57 mg/L, respectively, produced removal efficiencies up to 89.2, 69.2 and 47.6% for the three contaminants, despite the inhibitory effects of this waste towards biological activity. The treatment system produced low biomass yields with average values of 3.7 and 8.2% during the treatment of synthetic wastewater and hog waste, respectively.

Biotechnology and Bioengineering, Sep 1, 1986

The pronounced differences in performance of a strain of Clostridium acetobutylicum ATCC 824 were... more The pronounced differences in performance of a strain of Clostridium acetobutylicum ATCC 824 were analyzed by the method of systems analysis. The mechanism for cellular transport of substrate (glucose), solvents, and acids was studied and mathematically formulated. The systems analysis approach in the treatment of data from culture experiments pointed out the cell membrane malfunction indicated by its altered permeability and reflected in the altered number of active sugar transport sites. Experimental results obtained from the study of the cell uptake of 3-0-methyl glucose (0.7mM) by the "normal culture" and the "retarded culture" confirmed the theoretical predictions regarding a slower transport in the retarded culture. The initial uptake rate and the accumulation coefficient of the sugar in the normal culture were 15.0 and 4.1 times higher, respectively, than those for the retarded culture. Adjustment of the culture pH resulted in further increases in these parameters by factors of 3.0 and 3.5, respectively.

Applied Microbiology and Biotechnology, Jun 1, 1985

... of this compound. Decreased acetone production could be attributed to the inhibition of aceti... more ... of this compound. Decreased acetone production could be attributed to the inhibition of acetic acid formation which is a metabolic precursor for ace-tone synthesis in the sugar-metabolizing system. Although high H2 concentrations ...

Biotechnology and Bioengineering, Feb 1, 1986

A mathematical model for the batch culture of Clostridium acetobutylicum was formulated using exp... more A mathematical model for the batch culture of Clostridium acetobutylicum was formulated using experimental data for anaerobic solvent production. The model summarizes biochemical as well as physiological aspects of growth and metabolite synthesis by the production strain. The key fermentation rates are expressed and evaluated with regard to substrate consumption and butanol end‐product inhibitory effects. Parametric sensitivity analysis of the batch process model was carried out, indicating the importance of the key process parameters.

Springer eBooks, Sep 24, 2013

Retail gasoline outlets contribute to the emission of volatile organic compounds (VOCs). Accordin... more Retail gasoline outlets contribute to the emission of volatile organic compounds (VOCs). According to the United States Environmental Protection Agency (US EPA), the concentrations of the common constituents of gasoline such as benzene (a carcinogen), toluene, ethylbenzene, and xylene within 200 m of gas stations are found to be higher than ambient background levels. Many retail gasoline outlets are located in close proximity to populated commercial and residential neighbourhoods. In the light of the above, this paper presents estimates from the survey of industrial processes (SIP), a pilot survey conducted by the Canadian Government, for the overall evaporative emissions from retail gasoline outlets across Canada. The survey suggests that approximately 58 million litres of liquid gasoline is being evaporated each year into the ambient air from the 11,200 retail gasoline outlets across Canada. Such an emission rate is equivalent to the evaporation of the contents of three fully loaded gasoline delivery trucks on each and every day of the year. This silent emission contaminates the ambient air of urban populated neighbourhoods and subsequently the indoor air of buildings that are located in such neighbourhoods. To that end, this paper attempts to raise the awareness of building engineers regarding the locations of gasoline outlets within the vicinity of buildings and the potential short-circuiting of gasoline vapours from the ambient air to the indoor microenvironment.

Biotechnology and Bioengineering, Jun 11, 2002

A special microbial consortium adapted to degrade petroleum hydrocarbons at limited availability ... more A special microbial consortium adapted to degrade petroleum hydrocarbons at limited availability of oxygen, transformed benzene, a highly toxic and carcinogenic contaminant of groundwater and soil, at low initial dissolved oxygen (DO) concentrations of 0.05±2 mg/L. The employed initial concentrations of dissolved oxygen were considerably lower than the previously reported values. Under these conditions, the overall transformation of benzene ranged from 34% 1.7% to 100%, considerably higher than the theoretical predictions for complete mineralization of benzene based on the requirement of 3.08 mg oxygen/mg benzene. Unlike biotransformation that proceeded at the lowest examined DO concentration of 0.05 mg/L, the mineralization of benzene, de®ned by its conversion to CO 2 and water, required a minimum DO concentration of 0.2 mg/L. The mineralization of benzene under microaerophilic conditions (DO < 2 mg/L), ranged from 0.83% 0.06% to 89% 1.3%, which was less than the theoretical predictions at any given initial DO concentration. The regulatory effects of dissolved oxygen concentration or its partial pressure on the activities of enzymes catalyzing the biotransformation of aromatic hydrocarbons was postulated to account for the reduced mineralization of benzene. The ratio between the transformed benzene and the consumed oxygen increased with the decrease of initial DO concentration, reaching a value of 2.8, considerably higher than the theoretical value of 0.33 obtained for a complete aerobic oxidation of benzene. Phenol was the major and the most stable intermediate metabolite during the biotransformation of benzene at low concentrations of DO. While benzene transformation stopped after the depletion of oxygen in the experimental system, phenol continued to accumulate under strictly anaerobic conditions, indicating its formation from an alternative carbon source, possibly biomass. ã 2002 Government of Canada. Exclusive worldwide publication rights in this article have been transferred to Wiley Periodicals, Inc. Biotechnol Bioeng 79: 347±355, 2002.

Journal of Chemical Technology & Biotechnology, Apr 24, 2007

A specially developed temperature control system on a laboratory scale fermenter enabled continuo... more A specially developed temperature control system on a laboratory scale fermenter enabled continuous measurement of the rate of heat production during undisturbed growth of microbial cultures. Apart from being correlated with oxygen uptake rate, the heat of fermentation was established as an additional indicator of metabolic activity. The ‘aerobic respiration’ energetic activity of Candida utilis, Candida lipolytica and Saccharomyces cerevisiae on different carbon substrates was investigated with cultures of the latter species being also studied under the ‘aerobic fermentation’ conditions induced by glucose catabolite repression.

Biotechnology and Bioengineering, Sep 1, 1985

The specific rates of anaerobic solvent production by Clostridium acetobutylicum increased with i... more The specific rates of anaerobic solvent production by Clostridium acetobutylicum increased with increasing fermentor impeller speed from 190 to 340 rpm (NRe = 3.93 × 104). The maximum values were 5.54, 3.85, and 0.8 mmol/h · g cell for butanol, acetone, and ethanol, respectively. Corresponding rates for respective gases produced were 11.60 and 15.88 mmol/h · g cell for H2 and CO2. Further increases in agitation speed resulted in generally decreasing specific production rates to the point of inactive fermentation at 560 rpm. A competition observed between the cellular subsystems for butanol + butyric acid and biomass biosynthesis was evaluated through expressing the energetic yield coefficients. An imbalance between the production and outflux of the former metabolites is apparently further enhanced by a mechanical damage of the cells at high shear rates. A correlation was developed between the production of gases and solvents pointing at both H2‐to‐solvent as well as CO2‐to‐solvent ratios following the same pattern, peaking at 410 rpm.

Environmental Science and Pollution Research, Jul 2, 2019

This paper presents the treatment of a nitrite-limited wastewater by partial nitrification/anammo... more This paper presents the treatment of a nitrite-limited wastewater by partial nitrification/anammox process under different dissolved oxygen (DO) concentrations of < 1.2 mg/L, < 0.5 mg/L, and 0 mg/L, and at temperatures of 35 to 27°C in a pilot-scale single-stage hybrid bioreactor (BioCAST). The effect of operational parameters on microbial community structure and composition has also been investigated during the 1-year experimental period. Ammonium removal efficiencies of 73 ± 19% at 35-32°C and 87 ± 9% at 29-27°C were obtained from a synthetic nitrite-limited wastewater with ammonium concentration of 350-500 mg/L (175-250 g m −3 d −1). The adaptation of bacteria to a lower temperature (27°C) and lower free ammonia concentrations at 27°C was showed to be key factors leading to the optimal nitrite production by aerobic ammonium-oxidizing bacteria (AOB). No nitrite accumulation was observed due to the effective distribution and transfer of nitrite produced by the AOB in the aerobic zone to the microaerophilic/anoxic zones. The fast enrichment of Candidatus species in the suspended biomass in the anoxic zone at temperatures of 35-30°C and in the attached biofilm in the microaerophilic zone (DO < 0.5 mg/L) at 29-27°C suggests that the growth media (e.g., suspended biomass vs attached biofilm) had a minor effect on the diversity of microbial community in this bioreactor. This study supports the effective treatment of nitrite-limited wastewater with ammonium concentrations of < 500 mg/L by partial nitrification/anammox process at 35-27°C in a single-stage hybrid bioreactor by adjusting the DO concentration to < 0.5 mg/L and by providing longer retention times for aerobic (AOB) and anammox bacteria in the biofilm, which resulted in the long-term suppression of nitrite-oxidizing bacteria (NOB).

Canadian Journal of Chemical Engineering, Aug 1, 1986

A mathematical model of the batch acetone-butanol fermentation has been proposed which reflects t... more A mathematical model of the batch acetone-butanol fermentation has been proposed which reflects the process kinetics and biochemistry. The degree of importance of the key kinetic parameters has been established by a parametric sensitivity analysis. The basic model was further extended by incorporating additional culture physiological parameters such as the number of active mass transport sites and the permeability of the cellular membrane as well as the intracellular and extracellular conditions. The model assisted in studying the role of the cellular membrane in the control of the culture performance and solvent biosynthesis. The theoretical predictions were confirmed by experimental results.