REVIEW

Jour. Functional Water Vol.7(1), pp.1-13, 2012

Electrolyzed Oxidizing Water Generation Methods
Brian WATERS1, Marcio AMAZONAS2, and Yen-Con HUNG1
1

Department of Food Science and Technology, The University of Georgia,
2General Manager, AMZ Resulting, USA.
2011.9.1

Received

Electrolyzed oxidizing (EO) water, also known as

Ultimately, the concentration and ratio of the species ofDenkaisui in Japan, or electro-chemically activated water

free chlorine, combined chlorine and chloride ion are(ECA or ECAW), is a solution generated by passing adependent on method of generation, and pH of EO water.

dilute salt solution (NaCl and KCl are commonly used)

In its pure form, chlorine (Cl2) is a poisonous

through an electrolytic cell.

The anode side of anyellow-greengas.

However,chlorine

exhibits

aelectrolytic cell, from which acidic EO water is obtained,

pH-dependent chemistry.

produces various chlorine compounds and ions such as

solution that chlorine is dissolved in will play a dominanthypochlorous acid (HOCl), hypochlorite ion (OCl-) androle in what compound chlorine will assume.

chlorine gas (Cl2), which are all collectively known as3 to 7, HOCl is the dominant chlorine species. HOCl is afree chlorine.

strong oxidant (ORP > 900 mV), and is the preferred free

HOCl is the main antimicrobial agent

present in EO water.

EO water generally has a low pH

In other words, the pH of theFrom pH

chlorine species for disinfection. HOCl is generated by(2.3 – 2.7) and a high oxidation – reduction potential

the hydrolysis of dissolved Cl2, as demonstrated in the(ORP) (> 1000 mV).

following equation:

On the cathode side of the electrolytic cell, a diluteCl2 + H2Osolution of NaOH is generated, and this is sometimes

HOCl + Cl- + H+(1)referred to as electrolyzed reducing (ER) water. Unlike

Due to the high molar concentration of water in

EO water, the principal use of ER water is not in the

aqueous solutions, this reaction proceeds via 1st order

reduction of microbial numbers. Instead, ER water iskinetics (k1 = 22.3s-1) 4). Disregarding the effects of all

mainly used as a degreaser and cleanser1). Additionally,other factors (i.e. product concentrations, temperature,

work has been done on the health benefits of ER water incatalysts), the concentration of Cl2 is the most important

terms of cancer prevention, wound care, skin care andfactor in determining forward reaction rate in equation 1.

also as drinking water for improving digestion and cow

Below pH 3, Cl2 becomes increasingly dominant.

milk production2). Chemically, ER water is characterized

One major cause of free chlorine loss from water at low

as having a high pH (10-11.5) and a low ORP (-800 topH (< 4) is due to off-gassing of Cl2. The solubility of3)-900 mV) .

chlorine gas at 20ºC is about 7g/l pure water, and it isreasonable to assume that this solubility can be altered bytemperature changes and changes in partial pressure overProperties of EO water
EO water is primarily a solution consisting of HOCl,

the surface of the liquid (as Henry's Law states). At-OCl , and dissolved Cl2, that when in contact withlow pHs, the reverse reaction of equation 1 predominates,organic materials, variable amounts of organic chlorides,

and it is a 3rd order reaction (k-1 = 4.3 x 104 M-2s-1) 4).

such as trihalomethanes (THMs), chloramines andAs evident, this reaction proceeds at a much greater ratehaloacetic acids (HAAs), all often referred to as boundthan(or combined) chlorine, are formed.

The sum total of ofHowever, it is important to understand that since thisHOCl, OCl-, Cl2, and chloramines is known as the total

reaction relies on the availability of free protons andchlorine concentration of an EO water solution.

hypochlorous acid, a low pH is necessary to shift thetheforward

reaction

describedYen-Con Hung: The University of Georgia, 1109 Experiment St., Griffin, GA. 30223, USA. yhung@uga.edu

previously.