New Directions for Chemical Engineering (2022) / Chapter Skim
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4 Sustainable Engineering Solutions for Environmental Systems
4 Sustainable Engineering Solutions for Environmental Systems
Pages 87-116
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From page 87... ...
After a discussion of the WEF nexus, scientific gaps in understanding of the fundamental properties of water, as well as the need for engineering solutions for water quality and supply, are reviewed. Opportunities for chemical engineers to both pioneer and contribute to multidisciplinary efforts to advance agricultural and food processing technologies are then described, followed by a discussion of the research needs for understanding and improving air quality.
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From page 88... ...
Fundamental insights from chemical engineering disciplines form the foundational knowledge necessary to understand and create solutions in the WEF nexus, which inherently spans multiple disciplines. Examples include the structure and dynamics of water, the nature and physics of aerosol particles, and the scaling of synthetic protein production.
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From page 89... ...
. In 2016, the United Nations estimated that 800 million people suffer from food insecurity, approximately 1.2 billion people lack access to electricity, and 800 million people lack access to safe drinking water (Scanlon et al., 2017)
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From page 90... ...
frames integrated solutions for the WEF nexus around six pillars: optimizing the freshwater efficiency of energy production, electricity gener ation, and end-use systems; optimizing the energy efficiency of water management, treatment, distribu tion, and end-use systems; enhancing the reliability and resilience of energy and water systems; increasing safe and productive use of nontraditional water sources; promoting responsible energy operations with respect to water quality, eco system, and seismic impacts; and exploiting productive synergies among water and energy systems. FIGURE 4-2 The water–energy–food nexus emphasizes the interconnectivity of these three major resources.
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From page 91... ...
Some key examples include the following: Reducing water demand (conservation) – reduction of food waste and development of technologies that reduce spoilage, and use of food waste to produce chemicals (e.g., bio-oils)
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From page 92... ...
and population groups that can accommodate the higher costs; - capturing stormwater; - developing advanced materials for removing chemical and biological contaminants from water (e.g., removing lead contamination from drinking water to address contamination scenarios such as those faced by residents of Flint, Michigan) ; and - treating municipal wastewater (D'Odorico et al., 2018)
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From page 93... ...
While chemical engineering's role in the energy sector is discussed in Chapter 3, the ties among food, water, air, the environment, and energy are apparent and are key to the future of both the discipline and society writ large. MOLECULAR SCIENCE AND ENGINEERING OF WATER SOLUTIONS Chemical engineers have a leading role in molecular science and engineering that requires a fundamental understanding of water structure, dynamics, and interactions, as well as in the development of new complex separation processes.
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From page 94... ...
FIGURE 4-4 Comparison of several conventional and membrane processes for water purification and the subsequent mechanisms of water transport through membranes based on solute size and molecular weight. NOTE: ED = electrodialysis; MF = microfiltration; NF = nanofiltration; NOM = natural organic matter; RO = reverse osmosis; UF = ultrafiltration.
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From page 95... ...
The science of coagulation and flocculation is well known and practiced in municipal water treatment plants, but the implementation of new coagulants or flocculates is often too costly. Nonetheless, there are substantial opportunities to develop new polymer or surfactant chemistries that can address these challenges and to leverage the principles of self-assembly to treat these waste streams.
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From page 96... ...
The low concentrations of trace elements make removal challenging, especially in waters containing high salinity or highly complex organic matrices. A wide variety of conventional separations have been employed (e.g., chemical precipitation, coagulation-flocculation, flotation, solvent extraction, ion exchange, adsorption, membrane processes, filtration, reverse osmosis, and electrochemical techniques)
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From page 97... ...
Lead contamination of drinking water resulting from dissolution of lead solder, fixtures, and piping is another concern requiring innovative solutions, including consideration of point-of-use treatment technologies. Maintenance of lead scales within distribution systems is the typical control mechanism for ensuring water quality; however, changes in water quality can dramatically affect lead release and compromise drinking
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From page 98... ...
Removal of microplastics from water and other media presents opportunities for chemical engineers. Removal methods include physical sorption and filtration, biological removal and ingestion, and chemical treatments (Iyare et al., 2020; Padervand et al., 2020)
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From page 99... ...
. Various types of vibrational spectroscopy, as well as elastic and inelastic neutron scattering, have gradually been refined to provide detailed insights into the structure and dynamic processes in bulk water and at interfaces, particularly when coupled with selective deuteration, at time scales ranging from fractions of a picosecond to tens of nanoseconds.
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From page 100... ...
. Over the past 30 years, the issue of water polymorphism in pure water and aqueous solutions has gradually been fleshed out (Bachler et al., 2019; Debenedetti, 2003; Gallo et al., 2016; Handle et al., 2017)
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From page 101... ...
This last issue is of particular significance to electrochemistry and, more generally, to chemical reactions at interfaces, and presents exciting opportunities for chemical engineering. It is also important for the interpretation and design of adsorption processes at aqueous interfaces.
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From page 102... ...
Recent approaches involving various combinations of advanced sampling concepts from statistical mechanics, quantum mechanical calculations of intermolecular interactions, and emerging concepts from machine learning offer considerable promise for reducing the description of water and aqueous solutions and their interfaces to a tractable problem. As chemical engineers strive to conceive and design chemical processes involving aqueous interfaces, it will be important for such predictive models to be developed and brought to bear on the design and optimization of modern water-based technologies.
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From page 103... ...
Research on technologies for water transport through protein pores, such as ion pumps or aquaporins, has been used in the design of the high-flux systems mentioned above or selective pores for ion transport. Fundamental theoretical and computational research has paved the way for the design of intriguing separation or energy-generation processes, including recent discoveries about the transport of aqueous ionic solutions through Janus nanopores -- designer pores consisting of adjacent sections with different diameters and surface charges -- that could potentially become important sources of energy from simple salinity gradients (Yang et al., 2018; Zhang et al., 2017; Zhu et al., 2018)
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From page 104... ...
. As a result of continued population growth and anthropogenic climate change, humankind will need to rethink and reinvent agricultural and food production practices toward more sustainable land and resource use (Tilman et al., 2011)
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From page 105... ...
. Since the emergence of metabolic engineering and synthetic biology, tools of modern molecular biology have become commonplace in chemical engineering.
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From page 106... ...
Examples include recent research wherein dairy cows were fed small amounts of seaweed, which reduced overall per-animal methane emissions (Roque et al., 2021)
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From page 107... ...
There are undoubtedly many others. The problem of food production is inherently global in nature, and systems-level thinking at multiple scales -- a hallmark of the chemical engineering profession -- will be critical to enable positive change toward a more sustainable agricultural system.
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From page 108... ...
As discussed in the section on feedstock flexibility in Chapter 6, the use of waste-based feedstocks for valuable products, especially for food production enabled by biological and catalytic transformations pioneered by the chemical engineering community, offers a clear path toward a more circular carbon and nitrogen economy that is more sustainable than today's agricultural practices, and chemical engineers will play a critical role in this much-needed transition. Food Engineering and Processing and Storage Supplying the world's population with food that is nutritious, affordable, and sustainable is a global challenge.
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From page 109... ...
chemical engineering community. Food Processing and Storage While producing food in better ways is critical to meeting global food needs, reducing food waste could also have an enormous impact.
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From page 110... ...
In higher-income countries, the sustainability of food production and packaging is a major concern that can be addressed through the use of nonfood containers to hold food during shipping or storage and edible coatings that can be applied to food to prolong shelf life. Chemical engineers are well suited to the challenging task of applying systems-level life-cycle assessment to the development of solutions in these areas.
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From page 111... ...
Other air pollutants include CO2 and other GHGs, which are discussed further in the context of energy (Chapter 3) and the circular economy (Chapter 6)
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From page 112... ...
. This class of pollutants has garnered considerable attention with respect to indoor air quality during the COVID-19 pandemic because of the ability of exhaled virus-laden aerosols to cause infection.
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From page 113... ...
The chemical engineering profession has made key contributions to improving air quality, including the development of catalytic converters for vehicles (Box 4-1) , cleaner-burning fuels, flue gas desulfurization and selective catalytic reduction systems for NOx conversion to nitrogen gas and water, wet flue gas scrubbing methods, and better coal gasification technologies (Haywood, 2016)
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From page 114... ...
This achievement represents the result of a combination of novel materials and core chemical engineering concepts, made to work through the systems-based approach that characterizes chemical engineering as a discipline.
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From page 115... ...
. Sensor technologies that would allow better monitoring, chemical characterization, and knowledge of the spatial distributions of aerosols would also help address air pollution.
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From page 116... ...
Specific opportunities for chemical engineers include precision agriculture, non–animal-based food and low-carbon-intensity food production, and reduction or elimination of food waste. Advanced agricultural practices designed to improve yield while reducing demand for both energy and water will require collaboration with other disciplines, as well as systems-level approaches such as life-cycle assessment.
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