Electrochemical Microsensors for In Situ Monitoring of Chemical Compounds in Engineered and Natural Aquatic Systems

The adaption of needle-type electrochemical microsensor (or microelectrode) techniques to environmental science and engineering systems has transformed how we understand mass transport in biotic and abiotic processes. Their small tip diameter (5-20μm) makes them a unique experimental tool for direct measurements of analytes with high spatial and temporal resolutions, providing a quantitative analysis of flux, diffusion, and reaction rate at a microscale that cannot be obtained using conventional analytical tools. However, their applications have been primarily limited to understanding mass transport dynamics and kinetics in biofilms. With the advancement of sensor fabrication and utilization techniques, their potential applications can surpass conventional biofilm processes. In this dissertation, microsensors were utilized to elucidate mass transport and chemical reactions in multidisciplinary research areas including biological nutrient uptake, oily wastewater treatment, photocatalytic disinfection, and plant disease management, which have not yet explored using this emerging technology. The main objective of this work was to develop novel microsensors and use them for better understanding various natural and engineered aquatic systems. These include; 1) investigating localized photo-aeration and algal-bacterial symbiotic interaction in an advanced algal-bacterial biofilm process for nutrient removal from wastewater, 2) characterizing oil-in-water emulsions for better understanding bilge water emulsion stability, 3) evaluating sun-light driven photocatalytic reactions using a novel MoS2 nanofilm for water disinfection and microcystins-LR removal, 4) developing a zinc ion-selective microsensor and applying them for monitoring the transport of zinc in citrus trees, and 5) integrating heavy metal detection using anodic stripping voltammetry (ASV) in a microelectrode platform for plant applications. Overall, microsensors capable of measuring pH, oxidation-potential reduction (ORP), dissolved oxygen (DO), ammonia (NH3), hydrogen peroxide (H2O2), and zinc (Zn2+) were developed and applied to the systems described above to significantly contribute to a better understanding of interfacial transport mechanisms in various natural and engineered systems

Use of Microalgae for Advanced Wastewater Treatment and Sustainable Bioenergy Generation

Given that sustainable energy production and advanced wastewater treatment for producing clean water are two major challenges faced by modern society, microalgae make a desirable treatment alternative by providing a renewable biomass feedstock for biofuel production, while treating wastewater as a growth medium. Microalgae have been known to be resilient to the toxic contaminants of highly concentrated organic wastewater (e.g., organic nitrogen, phosphorus, and salinity) and are excellent at sorbing heavy metals and emerging contaminants. Economic and environmental advantages associated with massive algae culturing in wastewater constitute a driving force to promote its utilization as a feedstock for biofuels. However, there are still many challenges to be resolved which have impeded the development of algal biofuel technology at a commercial scale. This review provides an overview of an integrated approach using microalgae for wastewater treatment, CO2 utilization, and biofuel production. The main goal of this article is to promote research in algae technologies by outlining critical needs along the integrated process train, including cultivation, harvesting, and biofuel production. Various aspects associated with design challenges of microalgae production are described and current developments in algae cultivation and pretreatment of algal biomass for biofuel production are also discussed. Furthermore, synergistic coupling of the use of microalgae for advanced wastewater treatment and biofuel production is highlighted in a sustainability context using life cycle analysis.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/140370/1/ees.2016.0132.pd

Serum short chain fatty acids mediate hippocampal BDNF and correlate with decreasing neuroinflammation following high pectin fiber diet in mice

IntroductionDietary components, such as prebiotic fiber, are known to impact brain chemistry via the gut-brain axis. In particular, short chain fatty acids (SCFAs) generated from excessive soluble fiber consumption are thought to impact neuroimmune signaling and brain function through increased production of neurotropic factors. Given reports that high dietary fiber intake is associated with increased mental health and improved quality of life scores, we set out to identify whether changes in SCFA levels as a result of a high soluble fiber diet mediate hippocampal neuroinflammation and brain derived neurotrophic factor (BDNF) in mice.MethodsAdult male and female C57BL/6 mice were fed a 1-month high pectin fiber or cellulose-based control diet. Following 1 month of excessive pectin consumption, serum SCFAs were measured using gas chromatography–mass spectrometry (GC-MS) and hippocampal cytokines and BDNF were assessed via multiplex magnetic bead immunoassay.ResultsPectin-based fiber diet increased circulating acetic acid in both sexes, with no effect on propionic or butyric acid. In the hippocampus, a high fiber diet decreased TNFa, IL-1ß, IL-6, and IFNγ and increased BDNF levels. Furthermore, increased SCFA levels were inversely correlated with neuroinflammation in the hippocampus, with acetic acid revealed as a strong mediator of increased BDNF production.ConclusionCollectively, these findings highlight the beneficial effects of fiber-induced molecular changes in a brain region known to influence mood- and cognition-related behaviors. Dietary composition should be considered when developing mental health management plans for men and women with an emphasis on increasing soluble fiber intake

Dishwashing Water Recycling System and Related Water Quality Standards for Military Use

As the demand for reliable and safe water supplies increases, both water quality and available quantity are being challenged by population growth and climate change. Greywater reuse is becoming a common practice worldwide; however, in remote locations of limited water supply, such as those encountered in military installations, it is desirable to expand its classification to include dishwashing water to maximize the conservation of fresh water. Given that no standards for dishwashing greywater reuse by the military are currently available, the current study determined a specific set of water quality standards for dishwater recycling systems for U.S military field operations. A tentative water reuse standard for dishwashing water was developed based on federal and state regulations and guidelines for non-potable water, and the developed standard was cross-evaluated by monitoring water quality data from a full-scale dishwashing water recycling system using an innovative electrocoagulation and ultrafiltration process. A quantitative microbial risk assessment (QMRA) was also performed based on exposure scenarios derived from literature data. As a result, a specific set of dishwashing water reuse standards for field analysis (simple, but accurate) was finalized as follows: turbidity (\u3c 1 NTU), E. coli (\u3c 50 cfu mL-1), and pH (6–9). UV254 was recommended as a surrogate for organic contaminants (e.g., BOD5), but requires further calibration steps for validation. The developed specific water standard is the first for dishwashing water reuse and will be expected to ensure that water quality is safe for field operations, but not so stringent that design complexity, cost, and operational and maintenance requirements will not be feasible for field use. In addition the parameters can be monitored using simple equipment in a field setting with only modest training requirements and real-time or rapid sample turn-around. This standard may prove useful in future development of civilian guidelines

A Novel Approach For In Situ Monitoring Of Zn\u3csup\u3e2+\u3c/sup\u3e In Citrus Plants Using Two-Step Square-Wave Anodic Stripping Voltammetry

This study presents in situ detection of Zn2+ using a novel two-step square-wave anodic stripping voltammetry (SWASV)-based needle-type microsensor for citrus plant applications. A double-barrel bismuth/platinum (Bi/Pt) microelectrode was fabricated with a solid metal tip (∼110 μm), which was durable enough to penetrate the thick skin of the citrus leaves and sensitive enough to detect ppb changes in Zn2+ concentration using SWASV. The microelectrode tip size was also determined to reduce mass transport limitation and improve limit of detection. Overall, the developed Bi/Pt microelectrode successfully measured Zn2+ concentrations within the vascular bundle of citrus plants

An Innovative Symbiotic Microalgae-Ifas Process For Nutrient Removal And Photo-Oxygenation: Multiscale Investigations Using Microelectrodes And Next-Generation Molecular Tools

A combination treatment of wastewater, utilizing the interaction of algae and bacteria, can offer lower energy consumption using photosynthetic aeration while also providing algal biomass for biofuel production. Here we demonstrate a successful algal-bacterial biofilm can assist in photoaeration for nitrification and algal driven direct denitrification without the need for additional carbon sources or mechanical aeration. Nutrient removal stabilized after 36 days with ammonia removal reaching 100% and 57% for the Microalgae Integrated Fixed Film Activated Sludge (MAIFAS) and suspended reactors, respectively, while MAIFAS and suspended reactors removed 51 and 49% of the phosphorous, respectively. Furthermore, the algae bacteria consortia showed excellent settling with an sludge volume index (SVI) ranging from 74 to 111 and less than 1 mg/L Chl. α in the effluent. Overall this research shows the feasibility of a microalgae-based IFAS wastewater treatment process for reducing energy cost for aeration while meeting stringent effluent standards

An Innovative Symbiotic Microalgae-IFAS Process for Nutrient Removal and Photo-oxygenation: Multiscale Investigations Using Microelectrodes and Next-generation Molecular Tools

A combination treatment of wastewater, utilizing the interaction of algae and bacteria, can offer lower energy consumption using photosynthetic aeration while also providing algal biomass for biofuel production. Here we demonstrate a successful algal-bacterial biofilm can assist in photoaeration for nitrification and algal driven direct denitrification without the need for additional carbon sources or mechanical aeration. Nutrient removal stabilized after 36 days with ammonia removal reaching 100% and 57% for the Microalgae Integrated Fixed Film Activated Sludge (MAIFAS) and suspended reactors, respectively, while MAIFAS and suspended reactors removed 51 and 49% of the phosphorous, respectively. Furthermore, the algae bacteria consortia showed excellent settling with an sludge volume index (SVI) ranging from 74 to 111 and less than 1 mg/L Chl. α in the effluent. Overall this research shows the feasibility of a microalgae-based IFAS wastewater treatment process for reducing energy cost for aeration while meeting stringent effluent standards

In Situ Characterization Of Oil-In-Water Emulsions Stabilized By Surfactant And Salt Using Microsensors

Chemically stabilized emulsions are difficult to break because of micelle stability. Many physical and chemical processes have been used for emulsion breaking/separation; however, most operational parameters are based on empirical data and bulk analysis. A multiscale understanding of emulsions is required before these processes can advance further. This study utilized needle-type microsensors and confocal laser scanning microscopy (CLSM) for characterizing simulated bilge water emulsions with different types of surfactants (Triton X-100 and sodium dodecyl sulfate [SDS]) under various NaCl concentrations at microscale. Using microsensors, a diffusion process was clearly visualized across the oil/water interface which appears to be related to emulsion formation kinetics and mass transfer. While emulsion stability decreased with NaCl concentrations, SDS (anionic surfactant) is more likely to form emulsion as salinity increases, requiring more salinity to coalesce SDS emulsions than Triton X-100 (nonionic surfactant) emulsions. Triton X-100 emulsions showed the potential to exhibit particle stabilized emulsions with NaCl concentration below 10-2.5 M. The research demonstrated that the use of nonionic surfactant allows better oil-in-water separation than anionic surfactant. Significant pH changes of emulsions from unknown additives have implications when operating pH-sensitive emulsion breaking/separation processes (e.g., electrocoagulation)