Comparison between OCl−-Injection and In Situ Electrochlorination in the Formation of Chlorate and Perchlorate in Seawater

Abstract

To prevent biofouling from occurring in the cooling systems of coastal power plants, chlorine is often added to the cooling water. In this study, we have evaluated the fate of the total residual oxidants and the formation of inorganic chlorination byproducts including ClO3− and ClO4− during in situ electrochlorination with seawater. Then, the results were compared with those during direct OCl−-injection to seawater. The in situ electrochlorination method based on Ti/RuO2 electrodes produced much less ClO3−, while a similar level of total residual oxidants could be achieved with a reaction time of 5 min. Moreover, no ClO4− was observed, while the direct OCl−-injection system could still result in the production of ClO4−. The less or no production of ClO3− or ClO4− by the electrochlorination of seawater was mainly attributed to two reasons. First, during the electrolysis, the less amount of OCl− is available for ClO3− formation. Secondly, the formation of ClO3− or ClO4− is affected by the electrode material. In other words, if the electrode material is carefully chosen, the production of harmful reaction byproducts can be prevented or minimized. In short, based on the results from our study, electrochlorination technology proves to be a marine environmentally friendly method for controlling biofouling in the pipes of the cooling system in a coastal power plant.

Drinking Water Electrochlorination in a Single-Pass Biomimetic Flow Cell with Zero Salt Dosing

“…69 Studies suggest that the decomposition of hypochlorite follows a second-order reaction, so that the formation of chlorate and perchlorate are increased by higher concentrations of hypochlorite. 70,71 It has also been proposed that the chloride concentration in the solution has an effect on chlorate formation. 72 In this study, the maximum applied current density was 129.4 versus 1500 A•m −2 , one order of magnitude lower than the currents reported in the first mentioned study.…”

The competitive effect of Electro-chlorination over chlorination for controlling disinfection by-product formation in phenol and aniline enriched groundwater

“…Pillai and Gupta (2016) also attained more than 99% phenol removal efficiency using NaCl as an electrolyte at all pH ranges. It clearly suggests lesser by-product formation in the EC process than that of conventional chlorination methods, making it an environmentally friendly and sustainable technology (Yi et al, 2019). The in-situ production of hypochlorite due to electrolysis of NaCl may initially result in the formation of p-chlorophenol, which will assist in a higher degradation rate of phenol, as its degradation rate is much higher than phenol (Sathish and Vishwanath 2005).…”

“…Positively charged ions, on the other hand, such as hydrogen, calcium, magnesium, sodium, and potassium ions, gain electrons at the cathode and form hydroxide and hydrogen gas (Ashokan and Subrmaniyan 2009;Yi et al, 2019).…”

Application of Computational Fluid Dynamics in Chlorine-Dynamics Modeling of In-Situ Chlorination Systems for Cooling Systems

“…Since electrochemically generated chlorine would have higher density than water (>1.2 kg L −1 ), two different density flows were applied to simulate flows of seawater with and without chlorine; the water containing chlorine flows on the surface of electrodes. The chemical reactions between chlorine and oxidant-demanding matters in seawater were modeled using Equations ( 1)-( 5) and (9). The other simulation parameters and physical model structures are described in detail in Section S2 of the Supplementary Materials.…”

“…Chlorination is generally conducted by directly injecting chlorine into pipes or by electrochemically producing chlorine using seawater in water-intake pipes. The latter is called in-situ electro-chlorination, and a few of its advantages include the reduced production of harmful byproducts and the elimination of chlorine storage needs [9]. Furthermore, if electrodes are prepared with an optimized shape and installed at appropriate intervals near the inner surface of water-intake pipes, in-situ electro-chlorination can be controlled to maintain a relatively high concentration of chlorine specifically near the pipe wall, where biofouling occurs.…”