Membrane biofouling is a common occurrence in water treatment plants that utilize reverse osmosis (RO). As bacteria and biofilm material build up on the membrane surface, it becomes more difficult for clean water to permeate through the membrane, and more pressure is required to produce the same amount of water. When pressures become critically high, membranes must be cleaned. This process is expensive in terms of chemical cost, labor, and downtime. Even after membranes have been cleaned, they can re-foul quickly if the cleaning did not effectively remove the biofilm. The water treatment plant in Dunedin, FL, which uses RO for treating groundwater, has experienced membrane biofouling since it began operation in 1992. Without the means to systematically evaluate a multitude of cleaning strategies on the bench scale, cleaning optimization must be conducted on the production skid level, which restricts the evaluation of alternative protocols. This problem is typical for many RO plants. The objectives of this project are: (1) using a multi-level and systematic approach, develop cleaning strategies for biofouled membranes that will lead to improved cleaning and decreased operational costs; (2) develop other cleaning strategies that will add to the scientific knowledge base; (3) quantify the effects of improved protocols; and (4) determine the policy implications of developed protocols in terms of cost suitability to Dunedin and elsewhere in Florida. This project consists of three phases, with phases progressively more similar to the water production environment. In the first phase, a series of bench tests were performed in the laboratory. Fouled membrane swatches were soaked and agitated in different cleaning solutions for different lengths of time, at different temperatures and pH. Protein and carbohydrate assays were then performed on both the cleaning solution and the membrane swatch to determine which conditions yield most complete removal of protein and carbohydrate from the membrane surface. Results indicate that carbohydrate removal does not appear to depend strongly on pH or temperature. Protein removal increases with increasing pH and is slightly greater at higher temperatures. The second phase of testing employed a 4"x6" stainless steel flat-sheet module in which cleanings were performed under different conditions to document corresponding changes in water flux and salt rejection. Operational parameters were based on pertinent literature and optimization results from Phase 1. Results indicate that water flux increases in response to cleaning at increasing pHs and increasing temperatures with best performances occuring after 30 minutes of cleaning. Salt rejection appears to decrease with pH. The most effective cleaning protocols, determined through trials in Phases 1 and 2, were put to the test again in Phase 3 where cleanings were performed on a specially constructed single-element cleaning system (for 8.5" x 40" elements), designed to clean a membrane element in isolation. This phase also served as final verification of new cleaning protocols before implementation on the production scale. Results from this phase were inconclusive due to mechanical problems. A multi-level, systematic cleaning evaluation leads to better understanding of the dependence of biofilm material removal and membrane performance on critical factors such as temperature, pH, time of cleaning, and chemical dose, which results in improved cleaning protocols and ultimately cost savings to RO water utilities such as Dunedin.

<p>There are over 30 million Foley urinary catheters used annually, and the greatest problem with Foley catheters is catheter-associated urinary tract infections (CAUTIs). CAUTIs are the number one cause of hospital-acquired infections and make up to 40% of nosocomial infections. Biofilms on urinary catheters are critical to the progression of symptomatic CAUTIs, but are difficult to treat due to the protective effect of the biofilm matrix against antibiotics. The anti-fouling catheter technology proposed and demonstrated herein uses a mechanical, non-antibiotic approach to physically remove biofilms and thereby provide an appealing option for potentially stopping the progression of symptomatic infections. Additionally, because the anti-fouling technology is mechanical, it can circumvent the persistent failings of chemical and biological approaches that have failed to address catheter-associated urinary tract infections for the last 50+ years since Foley catheters were introduced. </p><p>We designed and optimized urinary catheter prototypes capable of on-demand removal of biofilms from the previously-inaccessible main drainage lumen of catheters. The concept uses pressure-actuated chambers in elastomer constructs to generate regio-selective strain and thereby remove biofilms. We first grew mature Proteus mirabilis crystalline biofilms on flat silicone elastomer substrates, and showed that application of strain to the substrate debonded the biofilm, and that increasing the strain rate increased biofilm detachment. A quantitative relationship between the applied strain rate and biofilm debonding was found through an analysis of the biofilm segment length and the calculated driving force for debonding. We then constructed proof-of-concept prototypes of sections of anti-fouling catheter shafts using silicone and 3D printed reverse molding in methods akin to those used for soft robotics. The proof-of-concept prototypes demonstrated release of mature P. mirabilis crystalline biofilms from their strained surfaces, and prompted our development of more advanced multi-lumen prototypes. The multi-lumen prototypes were designed and optimized using successive rounds of finite element modeling to adjust the number and postion of intra-wall inflation lumens. We then constructed prototypes based on the optimized design with clinically relevant dimensions and showed they were able to generate greater than 30% strain on the majority of the luminal surface, and along their full length. Those catheter prototypes were able to on-demand, and repeatedly, remove greater than 80% of a mixed community biofilm of P. mirabilis and E. coli. In summary, this study shows (1) strain in the elastomeric substrate actively debonds crystalline biofilms in vitro (2) modeling based on characterization of biofilm properties and understanding of substrate strain informs and facilitates prototype catheter design (3) urinary catheter prototypes utilizing inflation-induced substrate strain are capable of on-demand and repeatedly removing biofilms in vitro.</p> / Dissertation

Carbon based materials, including porous carbons and carbon layer composites, are finding increased usage in latest environmental and energy related research. Among porous carbon materials, hierarchical porous carbons with multi-modal porosity are proving out to be an effective solution for applications where the traditional activated carbons fail. Thus, there has been a lot of recent interest in developing low-cost, facile, easy to scale-up, synthesis techniques for producing such multi-modal porous carbons. This dissertation offers two novel synthesis techniques: (i) ice templating integrated with hard templating, and (ii) salt templating coupled with hard templating, for producing such hierarchically porous carbons. The techniques offer tight control and tunability of porosity (macro- meso- and microscale) in terms of both size and extent. The synthesized multi-modal porous carbons are shown to be an effective solution for three important environment related applications – (i) Carbon dioxide capture using amine supported hierarchical porous carbons, (ii) Reduction in irreversible fouling of membranes used for wastewater reuse through a deposition of a layer of hierarchical porous carbons on the membrane surface, (iii) Electrode materials for electrosorptive applications. Finally, because of their tunability, the synthesized multi-modal porous carbons serve as excellent model systems for understanding the effect of different types of porosity on the performance of porous carbons for these applications. Also, recently, there has been a lot of interest in developing protective layer coatings for preventing photo-corrosion of semiconductor structures (in particular Cu2O) used for photoelectrochemical water splitting. Most of the developed protective strategies to date involve the use of metals or co-catalyst in the protective layer. Thus there is a big need for developing low-cost, facile and easy to scale protective coating strategies. Based on the expertise gained in synthesizing porous carbon materials, and owing to our group’s interest in developing suitable photoelectrode materials, this dissertation also proposes a novel carbon-Cu2O composite comprising of a carbon layer coated Cu2O nanowire array structure as a high performance and stable photoelectrode material for photoelectrochemical water splitting.

Stringent water quality regulations and general aesthetic issues have urged drinking water industry to apply advanced water treatment technologies that can meet multiple treatment objectives. Removal of significant amount of natural organic matter (NOM), including colour causing organics, to meet stringent disinfection by product (DBP) regulations from source water with low alkalinity and low turbidity is very challenging with conventional water treatment processes. Membrane filtration processes are effective in removing significant amount of NOM thus minimizing the formation of carcinogenic DBPs. However, fouling of membrane is a major problem affecting system performance. Improved pretreatment of feed water helps reduce or eliminate membrane fouling. This study characterized source water, examined fouling in nanofiltration (NF) membranes and explored various pretreatment options to reduce NF fouling. Resin fractionation was performed to characterize NOM and to identify the major fractions responsible for DBP formation in natural source water of the Tatamagouche water treatment plant (WTP) in Nova Scotia. The source water primarily comprised of hydrophilic neutrals (HIN) and hydrophobic acid (HOA) compounds, with the latter being a major contributor to the DBP formation. Fouling behaviour of the NF membranes was examined at bench- and full-scale levels to understand the impact of source water quality on membrane fouling in the Tatamagouche and Collins Park WTPs. Bench- and full-scale results revealed higher fouling in the Collins Park WTP which together supported ongoing membrane cleaning practices in the plant. Surface enhanced Raman spectroscopy (SERS), demonstrated here as a novel technique, suggested that carbohydrates and proteins are the main foulants in the source water. Bench-scale experiments conducted to evaluate the performance of ozone (O3), ultraviolet (UV), hydrogen peroxide plus ozone (H2O2/O3), H2O2 plus UV (H2O2/UV) and O3 plus UV (O3/UV) for reducing NOM and DBP precursors suggested that the O3/UV AOP offers the optimum reduction of NOM. Integrating AOP pretreatments with NF membrane resulted in an improved permeate flux but not permeate quality of the NF membrane.

The use of staged scouring aeration to reduce energy for membrane fouling was studied using one pilot-scale submerged membrane bioreactor to treat municipal wastewater. The experiments were conducted by varying each of permeate fluxes, scouring air scouring intensities and sequence during both permeation and relaxation periods while keeping other factors same. The critical and recoverable fluxes were measured by the stepwise flux method. Mixed liquor, permeate and filtrate was characterized by analysing COD, cTOC, SMP contents, etc. The recorded transmembrane pressure data were used to calculate the fouling resistance after relaxation and fouling rate of each cycle. The results showed that when operated at relatively high permeate flux rate, membrane fouling could be effectively controlled by using relatively lower air scouring intensity and/or less infrequent aeration sequence during the permeation combined subsequently with more vigorous and frequent air scouring during the relaxation. At lower permeate flux rate with good permeability sludge, membrane fouling was effectively controlled by relatively low air scouring intensity and/or relatively infrequent aeration sequence during both permeation and relaxation periods. For each sludge condition, an optimal combination of cyclic air scouring intensity and sequence existed which could minimize the aeration energy consumption while maintaining effective fouling control. The frequency of aeration sequence plays a more dominant role than the air scouring intensity during the permeation in aeration optimization. / GE Water & Process Technologies Natural Sciences and Engineering Research Council of Canada

Wastewater contains many valuable constituents, including phosphorus, nitrogen and more energy than what is required to treat it. This, combined with increasingly more stringent effluent requirements and the desire for water reuse, creates a demand for a system capable of both nutrient and energy recovery. The main objective was to develop a new wastewater treatment process configuration capable of maximizing energy recovery while enhancing biological phosphorus removal. Three pilot membrane bioreactors were operated at SRTs ranging from 2 days to 8 days to evaluate membrane fouling, treatment performance, sludge production and sludge settleability. The results showed high organics removal and near complete nitrification at all SRTs. Membrane fouling was highest at lower SRTs. The collected data were then used to calibrate a series of model configurations. The best configuration consisted of two sludge systems in series, with a short SRT anaerobic-aerobic first stage and an extended SRT pre-anoxic second stage. / Canadian Water Network

Despite emerging water shortages, most water is only used once, and often with low efficiency. However, with appropriate treatment, water can be re–used to reduce the demand on freshwater sources. The Department of Water Affairs, South Africa, promotes industries to reduce discharges into water resources in order to sustain an overall good water quality of all water systems. All of this ultimately leads to industries striving towards zero effluent discharge. Primary Column Bottoms (PCBs) is a wastewater stream derived from the Fischer–Tropsch Gas to Liquid process and consists mainly of organic acids, but no nitrogen or phosphorous, which by implication excludes possible biodegradation. In the operation of cooling towers in industrial processes, cooling water quality has a direct impact on the cooling performance of the system, where nutrient levels may affect fouling, scaling and corrosion observed in the cooling towers. Fouling, scaling and corrosion affect the operating efficiency of cooling water systems and may necessitate the addition of chemical agents to control these phenomena. This has a financial and labour time impact on the operation of these systems. In this study a mini cooling tower test rig was operated with a synthetic PCB effluent as cooling water and various cycles of concentration, pH and linear flow velocities (LFVs). A constant delta temperature of 10 °C was maintained. Cycles of concentration (COC) evaluated included 2, 4 and 6 cycles of concentration and linear flow velocities evaluated was 0.6 m/s, 0.9 m/s and 1.2 m/s. Fouling, scaling and corrosion rates were determined using corrosion coupons and heat exchanger tubes for mild steel and stainless steel. Besides the evaluation of the various operational parameters for fouling, scaling and corrosion, the possibility for chemical oxygen demand (COD) removal by operating the cooling tower as a bioreactor was also evaluated. To this end nutrient correction was applied to the reactor to allow for a CNP ratio of 100:10:1. With regard to fouling, scaling and corrosion, mild steel was more affected by fouling, scaling and corrosion compared to stainless steel where almost no fouling, scaling and corrosion was observed. Overall increased linear flow velocities resulted in higher fouling and scaling rates, whereas lower linear flow velocities resulted in decreased corrosion rates. In terms of cycles of concentration, increased COC resulted in higher fouling, scaling and corrosion rates. Despite the high nutrient removal levels, the accompanying fouling, scaling and corrosion was still below the particular industry’s guidelines. Besides physical–chemical evaluation of the towers under the various operational conditions, culture–dependent and culture–independent methods were also employed. Concerning culture–dependent approaches the study demonstrated that aerobic and anaerobic organisms are present in both the planktonic and sessile phase of the cooling tower reactors. Heterotrophic aerobes were found to be the most abundant under all the operating conditions. Sulphate reducing bacteria were more abundant in the sessile phase of the cooling towers, and the presence of high sulphate levels in the experiments could be indicative of the sulphate reducing bacteria actively participating in the microbial community. Lower than expected corrosion levels, however, suggest that a combination of the organisms in the biofilm rather than sulphate reducing bacteria alone, contributed to the corrosion rates observed. Culture–independent methods, specifically phospholipid fatty acid analysis supported the results from the culture–dependent methods. Furthermore results demonstrated that linear flow velocity had a greater effect on the community structure than cycles of concentration. Finally molecular methods, specifically denaturing gradient gel electrophoresis, found that increasing cycles of concentration resulted in increased microbial community diversity, while increasing linear flow velocity resulted in decreased microbial community diversity. Regarding COD removal, nutrient correction of the synthetic PCB effluent achieved 89.35 % COD removal at 2 COC and 1.2 m/s LFV, while 80.85 % COD removal was achieved at 4 COC at 1.2 m/s LFV. From these results it was recommended that the operation of the cooling tower should be at 4 COC and 1.2 m/s, which despite slightly lower % COD removal, were characterised by fouling, scaling and corrosion rates well within guidelines. / Thesis (M. Environmental Science)--North-West University, Potchefstroom Campus, 2012.

Despite emerging water shortages, most water is only used once, and often with low efficiency. However, with appropriate treatment, water can be re–used to reduce the demand on freshwater sources. The Department of Water Affairs, South Africa, promotes industries to reduce discharges into water resources in order to sustain an overall good water quality of all water systems. All of this ultimately leads to industries striving towards zero effluent discharge. Primary Column Bottoms (PCBs) is a wastewater stream derived from the Fischer–Tropsch Gas to Liquid process and consists mainly of organic acids, but no nitrogen or phosphorous, which by implication excludes possible biodegradation. In the operation of cooling towers in industrial processes, cooling water quality has a direct impact on the cooling performance of the system, where nutrient levels may affect fouling, scaling and corrosion observed in the cooling towers. Fouling, scaling and corrosion affect the operating efficiency of cooling water systems and may necessitate the addition of chemical agents to control these phenomena. This has a financial and labour time impact on the operation of these systems. In this study a mini cooling tower test rig was operated with a synthetic PCB effluent as cooling water and various cycles of concentration, pH and linear flow velocities (LFVs). A constant delta temperature of 10 °C was maintained. Cycles of concentration (COC) evaluated included 2, 4 and 6 cycles of concentration and linear flow velocities evaluated was 0.6 m/s, 0.9 m/s and 1.2 m/s. Fouling, scaling and corrosion rates were determined using corrosion coupons and heat exchanger tubes for mild steel and stainless steel. Besides the evaluation of the various operational parameters for fouling, scaling and corrosion, the possibility for chemical oxygen demand (COD) removal by operating the cooling tower as a bioreactor was also evaluated. To this end nutrient correction was applied to the reactor to allow for a CNP ratio of 100:10:1. With regard to fouling, scaling and corrosion, mild steel was more affected by fouling, scaling and corrosion compared to stainless steel where almost no fouling, scaling and corrosion was observed. Overall increased linear flow velocities resulted in higher fouling and scaling rates, whereas lower linear flow velocities resulted in decreased corrosion rates. In terms of cycles of concentration, increased COC resulted in higher fouling, scaling and corrosion rates. Despite the high nutrient removal levels, the accompanying fouling, scaling and corrosion was still below the particular industry’s guidelines. Besides physical–chemical evaluation of the towers under the various operational conditions, culture–dependent and culture–independent methods were also employed. Concerning culture–dependent approaches the study demonstrated that aerobic and anaerobic organisms are present in both the planktonic and sessile phase of the cooling tower reactors. Heterotrophic aerobes were found to be the most abundant under all the operating conditions. Sulphate reducing bacteria were more abundant in the sessile phase of the cooling towers, and the presence of high sulphate levels in the experiments could be indicative of the sulphate reducing bacteria actively participating in the microbial community. Lower than expected corrosion levels, however, suggest that a combination of the organisms in the biofilm rather than sulphate reducing bacteria alone, contributed to the corrosion rates observed. Culture–independent methods, specifically phospholipid fatty acid analysis supported the results from the culture–dependent methods. Furthermore results demonstrated that linear flow velocity had a greater effect on the community structure than cycles of concentration. Finally molecular methods, specifically denaturing gradient gel electrophoresis, found that increasing cycles of concentration resulted in increased microbial community diversity, while increasing linear flow velocity resulted in decreased microbial community diversity. Regarding COD removal, nutrient correction of the synthetic PCB effluent achieved 89.35 % COD removal at 2 COC and 1.2 m/s LFV, while 80.85 % COD removal was achieved at 4 COC at 1.2 m/s LFV. From these results it was recommended that the operation of the cooling tower should be at 4 COC and 1.2 m/s, which despite slightly lower % COD removal, were characterised by fouling, scaling and corrosion rates well within guidelines. / Thesis (M. Environmental Science)--North-West University, Potchefstroom Campus, 2012.

This research examined the influence of organic loading rate (OLR) and biosolids type on the performance of fermentative H2-producing membrane bioreactors (HPMBRs) with respect to H2 production and membrane fouling. Five OLRs ranging from 4.0 to 30 g COD L-1 d-1 were examined in a lab-scale HPMBR. The system performance with both suspended and granulated biosolids was also investigated. The H2 yield from the suspended biosolids HPMBR was not significantly influenced by OLR at OLRs ≤ 13 g COD L-1 d-1, appeared to be maximized at an OLR of 22 g COD L-1 d-1, and then decreased as the OLR was increased further. An optimum OLR that maximizes H2 yield may be near the OLR that causes reactor overload with respect to substrate utilization. Under the same operating conditions, the H2 yield from a suspended HPMBR was significantly higher than that from a granulated HPMBR. A higher H2 consumption rate and a higher concentration of bound extracellular polymeric substances from the granulated HPMBR may contribute 5–48% and 25–67% of the H2 production difference between the two systems, respectively. The experimental results accompanied with microscopic examination of fouled membrane surfaces indicated that biosolids deposition and colloidal adhesion were the two dominant membrane fouling mechanisms in the HPMBRs. Membrane fouling was characterized by two distinct stages: an initial stage with a relatively higher fouling rate and a second stage with a lower fouling rate. Membrane fouling rates and resistances were influenced by the properties of biosolids and colloids in the mixed liquor. The fouling rates increased with increased biomass concentration, but decreased as colloids became more negatively charged. The irreversible and irremovable fouling resistance increased with increased concentration of colloids, while the removable fouling resistance had no relationship with biomass concentration. Biosolids granulation may benefit membrane performance due to a lower colloidal concentration produced. The single cake filtration model was proper to simulate membrane performance in the initial fouling stage. Both cake filtration and combined cake-standard models provided good fits for the second fouling stage, whereas future study is required to improve model predictability for membrane fouling in this stage.

This research examined the influence of organic loading rate (OLR) and biosolids type on the performance of fermentative H2-producing membrane bioreactors (HPMBRs) with respect to H2 production and membrane fouling. Five OLRs ranging from 4.0 to 30 g COD L-1 d-1 were examined in a lab-scale HPMBR. The system performance with both suspended and granulated biosolids was also investigated. The H2 yield from the suspended biosolids HPMBR was not significantly influenced by OLR at OLRs ≤ 13 g COD L-1 d-1, appeared to be maximized at an OLR of 22 g COD L-1 d-1, and then decreased as the OLR was increased further. An optimum OLR that maximizes H2 yield may be near the OLR that causes reactor overload with respect to substrate utilization. Under the same operating conditions, the H2 yield from a suspended HPMBR was significantly higher than that from a granulated HPMBR. A higher H2 consumption rate and a higher concentration of bound extracellular polymeric substances from the granulated HPMBR may contribute 5–48% and 25–67% of the H2 production difference between the two systems, respectively. The experimental results accompanied with microscopic examination of fouled membrane surfaces indicated that biosolids deposition and colloidal adhesion were the two dominant membrane fouling mechanisms in the HPMBRs. Membrane fouling was characterized by two distinct stages: an initial stage with a relatively higher fouling rate and a second stage with a lower fouling rate. Membrane fouling rates and resistances were influenced by the properties of biosolids and colloids in the mixed liquor. The fouling rates increased with increased biomass concentration, but decreased as colloids became more negatively charged. The irreversible and irremovable fouling resistance increased with increased concentration of colloids, while the removable fouling resistance had no relationship with biomass concentration. Biosolids granulation may benefit membrane performance due to a lower colloidal concentration produced. The single cake filtration model was proper to simulate membrane performance in the initial fouling stage. Both cake filtration and combined cake-standard models provided good fits for the second fouling stage, whereas future study is required to improve model predictability for membrane fouling in this stage.