System and process design of the locally enhanced electric field treatment (LEEFT) for water disinfection
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Disinfection is a water treatment process designed to inactivate waterborne pathogens and enhance overall public health. Conventional disinfection methods suffer from the formation of carcinogenic by-products, microbial regrowth, and/or high energy consumption. Locally enhanced electric field treatment (LEEFT) has been developed as a physical water disinfection method with the advantages of low energy consumption, wide spectrum effectivity, and the absence of by-product-forming chemical additives. This dissertation focuses on the system and process design of LEEFT to investigate its feasibility in real-world water disinfection systems. In terms of the system design, a coaxial-electrode LEEFT device is designed with both micro-scale and macro-scale electric field enhancement approaches applied. Efficient inactivation (>6-log) of multiple strains of bacteria is achieved with 1 V applied voltage. Such tubular configuration potentially enables LEEFT devices to be adopted in current water distribution systems as segments of the pipelines. Subsequently, two combined disinfection processes, including LEEFT-O3 and LEEFT/Cu, are developed. In the LEEFT-O3 process, an enhanced inactivation of ozonation by the LEEFT is observed and explained by the increased sublethal bacterial population after LEEFT. The application of LEEFT as a pretreatment process is beneficial to reduce the ozone dosage and disinfection by-product formation with a broad inactivation spectrum. The combined disinfection LEEFT and copper ions (LEEFT/Cu) is studied in a LEEFT system with only macro-scale electric field enhancement. When a voltage is applied, the electric field is generated, and copper ions are electrochemically released from the center electrode. Assisted by the electric field treatment, the LEEFT/Cu system achieves an efficient disinfection with much lower copper dosage. Lastly, energy sources suitable for LEEFT disinfection are developed. A water turbine electromagnetic generator directly is used to extract mechanical energy from the flowing water and convert the mechanical energy to electric energy to power LEEFT disinfection. By adopting this system, the LEEFT disinfection does not relies on the grid electricity. An integrated system, TriboPump, is developed for point-of-use water disinfection. With a manual powered triboelectric nanogenerator, the TriboPump pumps and disinfects the water by a LEEFT device with no need of additional complicated circuits and external energy sources. A smartphone-based energy workstation is also developed to power LEEFT disinfection. The integrated system uses the smartphone battery as a power source, and a customized on-the-go hardware connected to the phone to realize the desired electrical output. As smartphones are pervasive in modern life, the integrated system provides an alternative decentralized water disinfection approach like rural areas and outdoor activities. The results presented in this dissertation broaden the applications of LEEFT in different scenarios and scales of water disinfection.