Smartphone-powered efficient water disinfection at the point of use

Abstract

Clean water free of bacteria is a precious resource in areas where no centralized water facilities are available. Conventional chlorine disinfection is limited by chemical transportation, storage, and the production of carcinogenic by-products. Here, a smartphone-powered disinfection system is developed for point-of-use (POU) bacterial inactivation. The integrated system uses the smartphone battery as a power source, and a customized on-the-go (OTG) hardware connected to the phone to realize the desired electrical output. Through a downloadable mobile application, the electrical output, either constant current (20–1000 µA) or voltage (0.7–2.1 V), can be configured easily through a user-friendly graphical interface on the screen. The disinfection device, a coaxial-electrode copper ionization cell (CECIC), inactivates bacteria by low levels of electrochemically generated copper with low energy consumption. The strategy of constant current control is applied in this study to solve the problem of uncontrollable copper release by previous constant voltage control. With the current control, a high inactivation efficiency of E. coli (~6 logs) is achieved with a low level of effluent Cu (~200 µg L−1) in the water samples within a range of salt concentration (0.2–1 mmol L−1). The smartphone-based power workstation provides a versatile and accurate electrical output with a simple graphical user interface. The disinfection device is robust, highly efficient, and does not require complex equipment. As smartphones are pervasive in modern life, the smartphone-powered CECIC system could provide an alternative decentralized water disinfection approach like rural areas and outdoor activities.

A Global Agenda for Household Water Security: Measurement, Monitoring, and Management

“…Recent research shows that water insecurity is very much a global phenomenonand one that has been seriously neglected in the Global North (Meehan, Jepson, et al 2020;Meehan, Jurjevich, et al 2020). This indicates a strong need for more precise tracking of who (and where) water insecurity is experienced across development gradients; new approaches for monitoring the efficacy of water interventions; and more effective management of complex, mobile, and multiple water infrastructures to achieve water security (Pooi and Ng 2018;Patil et al 2020;Yang et al 2020;Zhou et al 2020).…”

Decoupling locally enhanced electric field treatment (LEEFT) intensity and copper release by applying asymmetric electric pulses for water disinfection

“…Exposure of bacteria to a strong electric field results in an elevated transmembrane potential, which may cause direct bacteria inactivation or increase the permeability of the cell membrane, facilitating easier entry of chemical disinfectants into the cell ( Kotnik et al., 1997 , 2015 , 2019 ). In our previous studies, a coaxial-electrode copper ionization cell (CECIC) was rationally designed to combine copper disinfection and LEEFT ( Zhou et al., 2019 , 2020b ). In this LEEFT-Cu system, the copper concentration near the center electrode is much higher than that observed in the effluent because the copper ions are electrochemically released from the center electrode, creating a concentration gradient of copper.…”

“…Attributed to these synergistic effects of copper and LEEFT, superior bacteria inactivation performance (∼6-log removal) was achieved with a low voltage of ∼1.5 V and effluent copper concentrations less than 0.5 mg/L. ( Zhou et al., 2019 , 2020b ). However, in these studies, direct-current (DC) voltages were applied, which coupled the LEEFT intensity with copper release.…”

“…However, this coupling effect becomes a problem when the CECIC treats water with higher conductivities that are similar to more practical conditions: with higher conductivity, the system resistance decreases, which increases the current and Cu release; to maintain the designated low Cu release, a lower voltage should be applied, resulting in weaker electric field strength for LEEFT and thus lower antimicrobial efficiency. Therefore, the dilemma between low voltage required to limit Cu release and high voltage for effective electroporation needs to be resolved ( Zhou et al., 2020b ). For practical applications, it is important to have the capability of tuning the electric field strength while maintaining copper release at a low level.…”

Smartphone imaging spectrometer for egg/meat freshness monitoring

“…Therefore, the OTG port can meet the 5 V and 120 mA power supply requirements that are used by the complementary metal-oxide semiconductor (CMOS) power. 31–35 Traditional visible-near-infrared spectrometers are relatively expensive and cumbersome. Although a small spectrometer has been developed, spectral detection can only be performed in laboratories with halogen lamps, which limits the use of traditional spectrometers.…”