Inactivation of Bacteria in Seawater by Low-Amperage Electric Current

Abstract

Seawater used in mariculture has been suspected of being a potential source of infection. In this study, the lethal effects of low-amperage electric treatment on microorganisms were examined in natural seawater and in seawater inoculated with Vibrio parahaemolyticus. In both cases, bacteria including V. parahaemolyticus in seawater were completely eliminated in 100 ms by a 0.5-A, 12-V direct current. Electron microscopic investigation of the electrically treated bacteria revealed substantial structural damage at the cellular level. In conclusion, our results indicate that low-amperage electric treatment is effective for rapid inactivation of microorganisms in seawater.The prevalence and distribution of bacteria such as Vibrio species in aquatic environments are of great public health concern because Vibrio spp. are pathogenic for both humans and animals (18). Recent outbreaks of Vibrio parahaemolyticus in the United States have been associated with eating behavior such as the consumption of raw or undercooked seafood, including fish and shellfish (1, 4, 9). Hence, seawater used for the cultivation and washing of fish and shellfish is another potential source of infection. However, conventional techniques of water sterilization are typically unsuitable for seawater. Antibiotics, for example, have come to be commonly used to prevent diseases due to seafood in fishery and culture, but chemical disinfectants may be toxic, deteriorate with an abnormal smell, and cause increased resistance to antibiotics (8). Heat sterilization is not suitable for large-scale treatment and culturing of fish (12). Ozone and UV light are efficient and produce harmless derivatives but are more costly (3,5,19). Recently, the use of pulsed electric fields, which are nonthermal and nonchemical, has been researched for sterilization of water (13,16,21,22). However, the industrial plant required for such treatment represents a major investment for manufacturers because of the limited application of high-voltage electric fields. We also have studied an electric sterilization method for seawater that is based on low-amperage direct-current transfer between bacterial cells and electrodes rather than on the generation of toxic substrates such as H 2 O 2 (10). In contrast to a pulsed electric field, the method described here uses a lowintensity electric current and is therefore potentially much simpler and cheaper to implement. In the present study, the sterilizing effect of low-amperage electric treatment for various times was studied with natural seawater and seawater inoculated with V. parahaemolyticus. Because V. parahaemolyticus is known to cause gastrointestinal illness in humans, it seemed to be suitable as our experimental model.The natural seawater used in this study was collected in the seashore of In-cheon in Korea. V. parahaemolyticus (ATCC 17802; Shirasu food-poisoning isolate) was grown in nutrient broth (Difco Laboratories, Detroit, Mich.) containing 3% (wt/ vol) NaCl at 37°C. At the end of the exponential growth phase, the cells we...

Application of Advanced Oxidation Methods for Water Disinfection

“…O sistema eletroquímico de tratamento de águas poderia ser utilizado para a desinfecção da água do mar utilizada frequentemente em aquicultura onde os peixes estão propensos a doenças bacterianas e agentes patogênicos como Vibrio anguillarum e V. parahaemolyticus que foram completamente desativados em alguns experimentos de ensaio. 41,42 Além disso, quando foram aplicados 0,33 A de corrente, a fração de bactérias sobreviventes de B. subtilis, E. coli, S. aureus e Pseudomonas aeruginosa foi reduzida para 1% depois de 1h de tratamento eletroquímico. 43 A bactéria Legionella, que se acreditava ser uma fonte de doença em torres de resfriamento e sistemas de água quente, diminuiu em quantidade de 3,4×10 2 para 1,7 CFU por cada 100 mL a 1,0 kV; ao passo que quando aplicado 1,5 kV não foram detectados resíduos dessa bactéria.…”

Studies on the electrochemical disinfection of water containing Escherichia coli using a Dimensionally Stable Anode

“…Also, most of the works are in batch mode, taking to fouling on electrodes surface. There are some other methods related to electrolysis or electrical current effects such as disinfection using metal ions generated by electrolytic processes (Khaydarov et al, 2004), electric inactivation of bacteria in sea water and saline wastewater (Park et al, 2003;Li et al, 2002) and electrolytic generation of biocides (Zinkevich et al, 2000). Oxide-coated electrodes are used in many studies of electrochemical treatment of water containing organic pollutants and are known as Dimensionally Stable Anodes (DSA).…”

Inactivation of Vibrio parahaemolyticus in Effluent Seawater by Alternating-Current Treatment

“…Consequently, the effluent speed of 850 ml/min was converted to the approximate duration of 350 ms in accordance with the 5-ml quantity of the previous static seawater experiment. Although treatment for 350 ms was sufficient to completely inactivate V. parahaemolyticus in seawater under static conditions (13), the effectiveness of the comparable sterilizing action under the effluent condition was not certain. In addition, the continuative electrolysis of seawater under the effluent conditions produces an excessive concentration of Cl 2 due to the approximately 19,000-ppm concentration of Cl Ϫ in natural seawater (2).…”

“…Thus, seawater used in mariculture requires a sterile process to prevent the propagation of bacteria. As an alternative to conventional techniques of water sterilization, such as antibiotics (8), heat sterilization (10), ozone (15), UV light (3), and pulsed electric field (14), low-amperage electric treatment of bacteria in seawater was developed in a previous study (13). The method as proposed above was potentially much simpler and cheaper than any other methods for disinfection of seawater.…”

“…In passing through the space between the pipe and rod, the seawater containing V. parahaemolyticus flowed at the speed of 850 ml/min while being treated with a certain electric current. In the experiments involving static conditions, an electrolysis vessel used in previous study (13) was also employed. In this case, each experiment was applied to a stationary quantity of 5 ml of seawater.…”