Papers by Catherine Mulligan
Applied and Environmental Microbiology, Nov 1, 1989
A direct relationship between increased glutamine synthetase activity and enhanced biosurfactant ... more A direct relationship between increased glutamine synthetase activity and enhanced biosurfactant production was found in Pseudomonas aeruginosa grown in nitrate and Proteose Peptone media. A chloramphenicoltolerant strain showed a twofold increase in biosurfactant production and glutamine synthetase activity. Increased ammonium and glutamine concentrations repressed both phenomena.
Food Research International, 2004
Soy hydrolysate and the soy-fermented foods, natto and tempeh, were dephosphorylated, deglycosyla... more Soy hydrolysate and the soy-fermented foods, natto and tempeh, were dephosphorylated, deglycosylated and digested with a variety of endoproteases (pronase, trypsin, Glu C protease, plasma proteases and kidney membrane proteases) to generate oligopeptides. ...
Biomass and Bioenergy, 2011
Covering a concrete manure storage tank with an airtight floating membrane should induce anaerobi... more Covering a concrete manure storage tank with an airtight floating membrane should induce anaerobic digestion of the stored manure. If the microbial community in the manure can acclimate to the ambient conditions, then In-Storage Psychrophilic Anaerobic Digestion (ISPAD) could be used by Canadian livestock producers to produce methane and stabilize manure. The objective of this study was to determine whether the microbial community in swine manure can successfully acclimate to the psychrophilic operating conditions in ISPAD and develop robust anaerobic digestion. This was done in the laboratory by analyzing manure from a three-year old full-scale pilot ISPAD facility located in St. Francois Xavier, Quebec, Canada, along with fresh manure and manure from an uncovered storage tank. Biochemical methane production assays performed at the three temperatures were used to quantify the performance of the microbial community and its temperature dependence. The ISPAD microbial community produced methane, in terms of VS added, at rates of 44.6, 9.8 and 8.5 dm 3 kg À1 d À1 , at 35, 18 and 8 C, respectively. The ISPAD process reduced the organic matter content of the manure by 24% while releasing 63% of the potential methane in the manure, as opposed to the open storage tank where no measurable reduction in solids occurred, and only 15% of the potential methane was released. These results indicate that a robust, acclimated microbial community actively digests manure in the pilot ISPAD installation.
Water
Lake water has been impaired with nutrients due to the synergic action of human-made activities a... more Lake water has been impaired with nutrients due to the synergic action of human-made activities and climate change. This situation is increasing eutrophication around the globe faster than before, causing water degradation, loss of its uses, and water-associated economic and health effects. Following the Sustainable Development Goal 6, more precisely its target 6.6, nations are already behind schedule in protecting and restoring water-related ecosystems (i.e., rivers and lakes). As concerns with eutrophication are escalating, eutrophic water remediation practices are the keys for restoring those lake waters. Diverse methodologies have been investigated focusing on the nutrient that limit primary productivity (i.e., phosphorus), but few have been applied to in-lake eutrophic water remediation. Thus, the objective of this paper is to provide an overview and critical comments on approaches and practices for facing eutrophic lake water remediation. Information on the successful cases an...
International Journal of Molecular Sciences
Oil-contaminated soil is one of the most concerning problems due to its potential damage to human... more Oil-contaminated soil is one of the most concerning problems due to its potential damage to human, animals, and the environment. Nanoparticles have effectively been used to degrade oil pollution in soil in the lab and in the field for a long time. In recent years, surfactant foam and nanoparticles have shown high removal of oil pollutants from contaminated soil. This review provides an overview on the remediation of oil pollutants in soil using nanoparticles, surfactant foams, and nanoparticle-stabilized surfactant foams. In particular, the fate and transport of oil compounds in the soil, the interaction of nanoparticles and surfactant foam, the removal mechanisms of nanoparticles and various surfactant foams, the effect of some factors (e.g., soil characteristics and amount, nanoparticle properties, surfactant concentration) on remediation efficiency, and some advantages and disadvantages of these methods are evaluated. Different nanoparticles and surfactant foam can be effectively...
Materials
The estimation of optical density (OD) with viable cells is challenging for engineering purposes.... more The estimation of optical density (OD) with viable cells is challenging for engineering purposes. In this study, the OD conversion based on previous study was used. The inhibited and retarded behavior of the microbially induced carbonate precipitation (MICP) process was examined. The experimental results showed that high Ca2+ drastically influences the inhibited and retarded behavior on MICP processes. The analysis showed that the inhibition and retardation effects occurred when the Ca2+/OD loading rate exceeded 8.46 M. The critical value was equal to the proportional constant for obtaining carbonate precipitation rate (CPR) from OD. Due to this, the blending design of materials became possible, with no risk of inhibition. In conclusion, the inhibition and retardation of the MICP process are governed by the Ca2+ load and the linear standard line (LSL), which may be attributed to the capacity or tolerance of viable cells, i.e., CPR/OD = 8.46 M or Ca2+/OD = 8.46 M.
Molecules
The removal of NH4+, NO3−, and NH3− from wastewater can be difficult and expensive. Through physi... more The removal of NH4+, NO3−, and NH3− from wastewater can be difficult and expensive. Through physical, chemical, and biological processes, metals and nutrients can be extracted from wastewater. Very few scientific investigations have employed surfactants with high biodegradability, low toxicity, and suitability for ion removal from wastewater at different pH and salinity levels. This research employed a highly biodegradable biosurfactant generated from yeast (sophorolipid) through micellar-enhanced ultrafiltration (MEUF). MEUF improves nutrient removal efficiency and reduces costs by using less pressure than reverse osmosis (RO) and nanofiltration (NF). The biosurfactant can be recovered after the removal of nutrient- and ion-containing micelles from the filtration membrane. During the experiment, numerous variables, including temperature, pH, biosurfactant concentration, pollutant ions, etc., were evaluated. The highest amount of PO43− was eliminated at a pH of 6.0, which was report...
Water
Climate change and human actions will exacerbate eutrophication cases in inland waters. By extern... more Climate change and human actions will exacerbate eutrophication cases in inland waters. By external or internal inputs, there will be an increase in nutrient concentrations in those systems worldwide. Those nutrients will bring faster trophic changes to inland waters and possible health and recreational advisories. A novel approach using a floating filtration system, a silt curtain, and geotextiles (woven and non-woven) is under investigation. This method has been applied as an in-situ pilot experiment deployed at Lake Caron, a shallow eutrophic lake in Quebec, for two summers. Turbidity, total suspended solids (TSS), total phosphorus (TP), blue-green-algae-phycocyanin (BGA-PC) and chlorophyll-a showed statistically significant average removal efficiencies of 53%, 22%, 49%, 57% and 56%, respectively, in the first year and 17%, 36%, 18%, 34% and 32% in the second. Statistical correlations were found with TSS, turbidity and variables that could represent particles (TP, turbidity, chlo...
Membranes
A membrane-based technique for production of pressure-retarded osmosis (PRO) is salinity gradient... more A membrane-based technique for production of pressure-retarded osmosis (PRO) is salinity gradient energy. This sustainable energy is formed by combining salt and fresh waters. The membrane of the PRO process has a significant effect on controlling the salinity gradient energy or osmotic energy generation. Membrane fouling and operating conditions such as temperature have an extreme influence on the efficiency of the PRO processes because of their roles in salt and water transportation through the PRO membranes. In this study, the temperature impact on the power density and the fouling of two industrial semi-permeable membranes in the PRO system was investigated using river and synthetic sea water. Based on the findings, the power densities were 17.1 and 14.2 W/m2 at 5 °C for flat sheet and hollow fiber membranes, respectively. This is the first time that research indicates that power density at low temperature is feasible for generating electricity using PRO processes. These results...
Materials, 2022
The engineering practices for applying the microbial precipitation of carbonates require a design... more The engineering practices for applying the microbial precipitation of carbonates require a design of the blending biocement solution (BCS). The BCS is usually blended with concentrated strains NO-A10, reaction media, such as urea and CaCl2, and a solvent, i.e., water or seawater. To characterize the BCS, the unknown microbial characteristics, such as the cell viability, are complex factors. Therefore, the optical density (OD) was redefined as Rcv OD*, in which OD* was the tentative OD of the BCS used and Rcv was the conversion rate concerning the cell viability. To determine Rcv values, a standard precipitation curve based on the precipitation rate at 24 h was determined. It was found that the curve was expressed by λ1 OD+ λ2 OD2, in which λ1 and λ2 were 8.46 M and −17.633 M, respectively. With this, the Rcv and OD values of unknown BCS were estimated from the results of precipitation tests using arbitrary OD* values. By extending the testing time, the second order term of OD or OD*...
Environmental Science and Engineering, 2018
Nutrients enter into lakes through point and non-point sources are finally settled in bottom sedi... more Nutrients enter into lakes through point and non-point sources are finally settled in bottom sediments where they accumulate and eventually release back into the overlaying water. Sediment phosphorus release is one of the main reasons for eutrophication in many shallow lakes around the world. This present study examines sediment samples collected from Lake Johanne, a shallow, meso-eutrophic lake, and its neighboring wetland, to which the lake inlet is opened, for sediment phosphorus concentration and its speciation to understand the potential of sediment phosphorus to release into the lake water. Speciation of the sediment phosphorus was performed according to the SMT sequential extraction technique. The sequential extraction technique allowed extraction and quantification of different forms of phosphorus in the sediment as follows: (i) non apatite inorganic phosphorus (ii) apatite inorganic phosphorus, (iii) organic phosphorus and total phosphorus. The lake sediment and water quality were also monitored in terms of heavy metal concentrations.
Eutrophication has been identified as one of the leading risks to surface water quality especiall... more Eutrophication has been identified as one of the leading risks to surface water quality especially for lake water quality in Canada. The objective of the study is to evaluate the effectiveness of nonwoven geotextiles in reducing the nutrients and suspended solids to improve lake water quality. A small scale field experiment was conducted beside a lake by using nonwoven geotextiles as filter media. Custom-made geotextiles were used in different combinations to provide maximum efficiency in removing nutrients and suspended solids (SS) to achieve an acceptable level within a shorter period of time. For an initial turbidity ranging from 4 to 9 NTU, 2 layers of 110 μm pore size filters with 3 layers of 90 μm pore size showed the best result at the 7 day of filtration, whereas 2 layers of 110 μm pore size with 3 layers of 75 μm pore size geotextiles had been found to restore the water quality at the 3 day of filtration for an initial turbidity ranging from 9 to 14 NTU. The combination of ...
To deepen the water column near the docking area of a yacht club, the sediments need to be remove... more To deepen the water column near the docking area of a yacht club, the sediments need to be removed from a selected area to facilitate the passage of the larger yachts. Prior to dredging, the quality of the sediments needed to be determined. Sampling and analysis of a series of sediments in the proposed dredging area were performed. Two sets of samples were taken within the proposed dredging zone. The first set consisted of surface samples taken with a Birge Ekman sampler and the second set were core composite samples to reach sediments of approximately 46 cm in depth (the proposed dredging depth). Overall, the samples in the extreme regions will need to be handled with care due to contamination most likely from boat maintenance and from upstream industries. The sediments cannot be disposed of in open water. The region needs to be defined by further sampling. The middle region could potentially be disposed of in open water. In order for open water disposal to occur, samples would nee...
Japanese Geotechnical Society Special Publication, 2020
Various techniques can be considered for the remediation of contaminated sediments. The options c... more Various techniques can be considered for the remediation of contaminated sediments. The options can include capping, dredging, or physical, biological, and/or chemical treatments and natural recovery. Natural recovery could be beneficial over dredging due to a reduction in costs and lack of solid disposal requirements. Source control, however, is a major issue for sustainable remediation. In a case study, surface and core sediment samples were collected from a harbor on the north bank of the St. Lawrence River in the province of Quebec to assess heavy metal pollution and determine if natural recovery was occurring. Comparing the results of all analysis done for sediment for three different years (2015, 2017 and 2019) in the sampling area, it can be seen that some metals increased, some decreased and some of them showed nearly the same level of contamination. The results also indicated that during the sampling periods, copper, zinc and chromium were the main elements that exceeded the occasional effect level based on the Environment Canada sediment quality guidelines. Therefore, metal pollution has become a noticeable problem in this area and natural recovery was not achieved for several metals due to ongoing contamination and thus source control is critical.
Environmental Science and Pollution Research, 2021
Human exposure to metals on road dust might have potential health risks through touching, ingesti... more Human exposure to metals on road dust might have potential health risks through touching, ingesting, and inhaling. There were limited studies to link seasonal emission sources to health risks from metals on road dust. In this study, metals on road dust from different functional areas were seasonally monitored. The pollutant sources in study city varied slightly with the seasons, but the major pollutant source in the particular study site were significantly affected by the seasons. By combining the source apportionment model (PMF), line sources model and health risk models (HI: Hazard index and ILCR: Incremental Lifetime Carcinogenic risk), industrial and construction activity was identified as the crucial source of both the pollutants on road dust (29%-47%), and the HI for adults (27%-45%) and children (41%-50%) in different seasons. The traffic non-exhaust emission dominated in the carcinogenic risks for children in spring (45%) and summer (36%). Factors such as seasons, particle size, metal bioavailability, human exposure time, and exposure area were all taken into consideration to avoid overestimating or underestimating health risks. The carcinogenic risks for children (1.6 E-06) and adults (2.8 E-06) exposed to Cr both exceed the minimum threshold (10-6). Measured metals mainly posed hazard to human health through ingestion route. Pb and Mn, Fe and Mn were the main harmful elements that induced non-carcinogenic risks for adults and children, respectively. Effectively identifying the source-specific health risks in different seasons will help in the formulation of adaptive strategies to diminish the potential risks.
Applied and Environmental Microbiology, 1985
This study considered the possibility of using water expressed during the drying of fuel-grade pe... more This study considered the possibility of using water expressed during the drying of fuel-grade peat as a substrate for microbial growth. Highly humified peat pressed for 2.5 min at 1.96 MPa produced water with a chemical oxygen demand of 690 mg/liter. Several biological compounds could be produced by using the organic matter in expressed peat water as a substrate. These included polymers such as chitosan, contained in the cell wall of Rhizopus arrhizus , and two extracellular polysaccharides, xanthan gum and pullulan, produced by Xanthomonas campestris and Aureobasidium pullulans , respectively. A very effective surfactant was produced by Bacillus subtilis grown in the expressed water. Small additions of nutrients to the peat pressate were necessary to obtain substantial yields of products. The addition of peptone, yeast extract, and glucose improved production of the various compounds. Biological treatment improved the quality of the expressed water to the extent that in an industr...
Water Quality Research Journal, 2003
Biological treatment of wastewater has been employed successfully for many types of industries. A... more Biological treatment of wastewater has been employed successfully for many types of industries. Aerobic processes have been used extensively. Production of large amounts of sludge is the main problem and methods such as biofilters and membrane bioreactors are being developed to combat this phenomenon. Anaerobic waste treatment has undergone significant developments and is now reliable with low retention times. The UASB, the original high rate anaerobic reactor, is now becoming less popular than the EGSB reactor. New developments such as the Annamox process are highly promising for nitrogen removal. For metal removal, processes such as biosorption and biosurfactants combined with ultrafiltration membranes are under development. Biosurfactants have also shown promise as dispersing agents for oil spills. If space is available, wetlands can be used to reduce biological oxygen demand (BOD), total suspended solids (TSS), nutrients and heavy metals. These innovative processes are described...
Separation and Purification Technology, 2018
One of the main challenges for generating osmotic power by using PRO technology is the membrane f... more One of the main challenges for generating osmotic power by using PRO technology is the membrane fouling which reduces the permeate flux and consequently increases the cost and decreases the osmotic power generation. In this research, different feed waters with various qualities were used to investigate the effect of fouling on a commercial membrane in PRO mode in continuous conditions. Also, the fouling mechanisms were investigated in order to study the cleaning of the membrane in PRO mode in the future research. In addition, four classic fouling models such as complete blocking model (CBM), intermediate blocking model (IBM), standard blocking model (SBM) and cake filtration model (CFM) were used. Cake enhanced osmotic pressure as a new mechanism for osmotically driven membranes was studied as well. According to the results, the fouling rate when the draw solution was synthetic salt water followed the order of: untreated river water > multimedia sand filter > microfiltration > ultrafiltration effluents. The fouling rate in ultrafiltration and microfiltration effluents using sea water occurred faster compared to the results for untreated synthetic salt water. Complete fouling (permeate flux was negligible) 2 occurred after 580 hours using feed water from ultrafiltration unit. It was observed that cake filtration and cake enhanced osmotic pressure were the main fouling mechanisms that governed the membrane fouling. These models could describe the membrane fouling in PRO processes.
International Journal of Geomate, 2016
Preventing wastage of resources is an important priority for sustainability. Sludge from a wastew... more Preventing wastage of resources is an important priority for sustainability. Sludge from a wastewater treatment plant (WWTP) is such a resource that it often wasted. It is a source of nutrients and organic materials that can be used as a fertilizer. At a waste water treatment plant in Montreal, the sludge is currently incinerated and sent for disposal. Alternatives to the practice are thus desirable. Elevated concentrations of cadmium, copper, cobalt and selenium are found in the sludge and therefore a treatment process is required before use as a fertilizer according to the Province of Quebec regulations. Leaching was selected as there is potential for heavy metal removal. However, nutrient loss must be minimized to preserve its use as a fertilizer. To meet these goals, a new leaching agent (K2HPO4) was proposed, and investigated for heavy metal removal efficiency on the sludge. A correlation of heavy metal removal and preserved nutrient concentration with time and pH was found. Removal efficiencies of cadmium, copper, cobalt and selenium of 80%, 44%, 70% and 93%, respectively were determined. In addition, concentrations of nitrogen, phosphorus and potassium of 17%, 17% and 25%, respectively, resulted in the treated sludge. In conclusion, the use of dipotassium phosphate is an effective leaching method to remove heavy metals and simultaneously increase the primary macro nutrients at an acceptable cost.
Journal of Bioremediation & Biodegradation, 2015
This study investigated the role of natural oil-degrading bacteria in the weathered biodiesel (BD... more This study investigated the role of natural oil-degrading bacteria in the weathered biodiesel (BD), diesel (D) and light crude oil (L) in oil biodegradation in seawater with and without sophorolipid biosurfactant. Mixtures of artificial seawater and weathered oil with and without sophorolipid dispersant were incubated at 22 ± 1°C and 100 rpm for 28 days. Analysis of the remaining of total petroleum hydrocarbons showed degradation of 43 ± 0.7%, 45 ± 5.7% and 39 ± 4.6% of biodiesel, diesel and light crude oil, respectively, during the natural biodegradation and 44 ± 5%, 47.5 ± 3.9% and 44 ± 1% of biodiesel, diesel and light crude oil, respectively, with sophorolipid by the existing bacteria after 28 days. Characterization of bacteria isolated from the BD, D and L oil by 16S rRNA pyrosequencing showed that the Firmicutes was the dominant phylum in biodiesel (100%) and diesel (53%). The Actinobacteria was dominant in the diesel (47%) and the Proteobacteria (97%) and Actinobacteria (3%) were the two dominant phyla in the light crude oil. The hydrophobicity results showed that the bacteria consumed the hydrocarbons mainly by changing their cell surface structures in the natural biodegradation treatment and increase in the micellar dispersion of hydrocarbons in the biodegradation treatment with the sophorolipid. This study confirmed the significant contribution of natural bacteria in the weathered diesel, biodiesel and light crude oil in the biodegradation and the positive effect of sophorolipid on the biodegradation.
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Papers by Catherine Mulligan