Inactivation of Microcystis aeruginosa by Continuous Electrochemical Cycling Process in Tube Using Ti/RuO₂ Electrodes

Abstract

Algae in waters often bring about influence in drinking water supplies. In this study, an electrochemical tube employing titanium coated with RuO2 as anode was constructed for inactivation of cyanobacteria (often called bluegreen algae) Microcystis aeruginosa. Suspensions containing M. aeruginosa (2-4 x 10(9) L(-1)) were exposed to current densities ranging from 1 to 10 mA cm(-2) in a detention time of 52 min. The variations of cell density, chlorophyll-a, optical density, pH, and conductivity were examined during the treatment. After 3.5 min the population of M. aeruginosa dropped rapidly and was reduced from 3 x 10(9) to 0.6 x 10(9) L(-1) after 52 min at current densities from 5 to 10 mA cm(-2). The cell density and optical density of M. aeruginosa decreased proportionally to the current density and the detention time. Scanning electron microscopy investigation of algae revealed surface damage and apparent leakage of intracellular contents after electrochemical cycling process. Due to the damage of cells, the chlorophyll-a released from the cells was degraded by electrochemical oxidation. The removal rate of chlorophyll-a could reach 96% at the current density of 10 mA cm(-2). Electrochemical treatment caused minor variation of pH values and conductivity of the suspensions. After electrochemical cycling processes, the optical density at 680 nm of algal cell suspensions remained below 0.1 after 6 days, and it showed that cells had no potential to survive and grow. The results implicated that the inactivation of M. aeruginosa was successfully performed by the electrochemical treatment, and it made the algal cells lose ability to survive, demonstrating the potential of such an alternative process for efficient water purification.

Inactivation of Microcystis aeruginosa with Contact Glow Discharge Electrolysis

“…[14]. The samples were filtered through 0.45 lm cellulose acetate membrane under low vacuum, and the chlorophylls were extracted using 10 mL of ethanol, stored 24 h at 5°C.…”

“…Algae in waters often pose serious threat to the drinking safety. Many electrochemical techniques, such as low-frequency AC discharges, micro-gap discharge etc., have been studied for the inactivation of algae [11][12][13][14][15][16]. However, the inactivation of algae with CGDE has not been reported so far.…”

Electrochemical Alternatives for Drinking Water Disinfection

“…However, the short lifetime of COH and other ROS in solution makes only possible to underline their possible role in disinfection using direct current. Liang et al [30] utilized a tubular electrochemical cell with a Ti/RuO 2 anode (see Figure 1) for the batch treatment of an aqueous chloride solution (600 mL, ca. pH 7) containing a suspension of the alga Microcystis aeruginosa.…”

Optimization of Ti/SnO2–Sb2O5 anode preparation for electrochemical oxidation of organic contaminants in water and wastewater

“…Ozone and ultraviolet (uv) light are sometimes used as alternatives to chlorine, but these technologies are limited by high operation and maintenance costs [5]. As an alternative to these technologies, several electrochemical systems have recently been studied for water disinfection using electrodes composed of titanium [6], carbon cloth [7,8], graphite [9], titanium nitride [10], platinum [11], platinum coated with niobium [12], titanium coated with ruthenium oxide (RuO 2 ) [13][14][15][16], and boron-doped diamond [17,18]. Hydroxyl radical generated at the anode surface is likely the disinfecting agent in these systems [12,19,20].…”