Applications

Primary Chlorination Treatment

The use of chlorine gas to disinfect water has prevented disease and saved millions of lives in developed countries over the past century.  Before cities began routinely treating drinking water with chlorine (starting with Jersey City in 1908), cholera, typhoid fever, dysentery and hepatitis A killed millions of people annually. Drinking water chlorination and filtration have helped to virtually eliminate these diseases across the world. Chlorination is regarded as a reliable, cost-effective method for disinfecting water for drinking purposes. It is principally used on large-scale sophisticated drinking water treatment plants as a primary treatment.

Meeting the goal of clean, safe drinking water requires a multi-step approach that includes: protecting source water from contamination, appropriately treating raw water, and helping ensure safe distribution of treated water to consumers’ taps. During the treatment process, chlorine is added to drinking water as elemental chlorine (chlorine gas), sodium hypochlorite solution or dry calcium hypochlorite. When applied to water, each of these forms “free chlorine,” which destroys pathogenic (disease-causing) organisms.

In addition, only chlorine-based disinfectants can provide a “residual” level to prevent microbial re-growth in treated water. The U.S. Environmental Protection Agency (EPA) requires water systems to maintain disinfection residuals all the way to consumers’ taps.

While protecting against microbial contamination is the top priority, water systems must also control disinfection by-products (DBPs), chemical compounds formed unintentionally when chlorine and other disinfectants react with natural organic matter in water. In the early 1970s, US Environmental Protection Agency scientists first determined that drinking water chlorination could form a group of by-products known as trihalomethanes (THMs), including chloroform. The EPA set the first regulatory limits for THMs in 1979. Recent EPA and WHO regulations have further limited THMs and other DBPs in drinking water.

Secondary ECA Treatment

ECA technology is ideal in providing secondary protection to Municipality and Water Authority’s potable water supplies after traditional primary treatment by chlorination.  The advantages include:

• ECA generators are scalable so can treat everything from a house or block of flats to a district water supply
• Will provide enhanced residual protection from secondary treatment to point-of-use with additional water quality benefits
• Will destroy all bacteria, viruses, protozoan cysts, spoors, fungi and algae in the water delivery system including pipes, tanks and cisterns
• Effective at low doses
• No hazardous chemicals to transport, store or use so completely safe for Health & Safety compliance
• Destroys biofilm in pipelines and therefore eliminates the environment in which bacteria thrive
• Does not form toxic chloramines or trihalomethanes
• Does not form toxic bromates and bromorganic by-products in the presence of sunlight and chlorine
• Can destroy phenols and remove foreign flavours and odours
• Can remove heavy metals such as iron, manganese and magnesium by rapid oxidation
• Will degrade some pesticides and contaminants
• Removes turbidity
• Easy to install and operate in remote areas and where expertise in water chemistry is lacking
• Ideal for treating waters containing specific contaminants such as polluted ground and well waters

ECA technology provides a very biocidal effective, cheap and safe secondary disinfectant solution that can be deployed across a wide variety of public and private water sources to enhance the quality, purity and safety of potable water.

Research into the Use of ECA Technology for Water Disinfection in Municipality Supplies

Scientific research has demonstrated that Electrolyzed ECA Water (generated from NaCl solution) has a higher oxidation potential when compared to conventional pre-chlorination (using sodium hypochlorite). This is shown to be due to the majority of the free available chlorine (FAOx) existing as un-dissociated molecular Cl2 (oxidation potential 1.39 V) arising from the low pH and high chloride concentrations in Electrolyzed Water, whereas in sodium hypochlorite solutions the FAOx is present mainly as OCl- (oxidation potential 0.9 V). . The reaction of un-dissociated molecular Cl2 tends to decrease the pH which favours the HOCL formation whereas the sodium hypochlorite solutions increase the pH with the formation of hydroxyl ions (OH-) by formation of sodium hydroxide.

No ozone, hydrogen peroxide or chlorine dioxide were detected in Electrolyzed Water. Some of these species may be present during electrochemical activation but degrade rapidly, possibly contributing decomposition products such as OH radicals and chlorates and chlorites to the oxidation potential of Electrolyzed Water.

With regard to synthetic organics, the Electrolyzed Water was shown to be capable of higher removal efficiencies for some pesticides (e.g. atrazine) and PAHs (e.g fluorene and napthaline) when compared to pre-chlorination using hypochlorite. Other compounds such as isoproturon, benzo(a)pyrene, anthracene showed no enhanced degradation when dosed with electrochemically activated solutions as their carboxy acid bonds are readily broken down by OCl-. Recalcitrant synthetic organics such (e.g. atrazine, fluorene, napthaline) require a higher oxidation potential for breakdown of their ring structure and were thus only oxidised when treated with Electrolyzed Water. The oxidation ability of the Electrolyzed Water was hindered in hard waters because of the reducing effect of OH- ions converting Cl2 to OCl- and the
scavenging effect of bicarbonate ions on species such as OH radicals.

Pre-oxidation of natural organic matter (NOM) with Electrolyzed Water was found to aid subsequent coagulation processes when used at dosing levels that enhance biopolymer formation. However if used in excessive quantities the Electrolyzed Water was found to hinder coagulation due to the breaking up of the organic molecules into very small fragments which prevent bipolymer formation. It was concluded that the optimum pre-oxidant dose depends on the composition of the organic matrix in the aquatic system together with factors such as hardness and pH. For hard waters containing high initial concentrations of NOM dosing with Electrolyzed Water produced higher coagulation removal efficiencies than pre-treatment with hypochlorite solution.

The main by-products of atrazine oxidation (DIA and DEA) were not observed in Electrolyzed Water dosed samples, although they were identified in atrazine dosed with hypochlorite, suggesting there may be fewer problems associated with breakdown products when electrochemically activated solutions are used.

THM formation in waters containing natural organics was studied and it was found that in waters containing algae and humic substances 50% less chloroform was formed when dosed with Electrolyzed Water compared to similar waters dosed with hypochlorite. This is because OCl- is the active reagent for THM formation, and this represents less than 12% of the FAOx in Neutral Electrolyzed Water, as 88% of FAOx was found to be in the form of HOCL.

The work has used a series of matrix jar tests to study how the highly oxidative ionic species in the electrochemically activated solutions break down complex organic molecules such as insecticides and pesticides (atrazine and isoproturon), polyaromatic hydrocarbons (e.g. napthalene, fluorene, anthracene, chrysene, benzo(a)pyrene). Results obtained to date suggest destruction of these compounds is very effective and the solutions are also found to be useful in dealing with algal species such as anabaena flos-aquae, and asterionella formosa. The work is also investigating the breakdown products of these chemicals after they have been treated. It has been found that when treating humic or algal waters THM formation is reduced by 50-60% when compared with conventional pre-chlorination techniques.

The relative disinfecting capabilities of NEW, which are significantly greater than that of chlorine alone, is believed to be caused by synergism of the oxidants working together; synergy between oxidants has been demonstrated by other researchers and is now being actively investigated in the water treatment research community.

NEW is able to maintain a more stable chlorine residual with less fluctuation. Typically the residual will last longer in comparison to chlorine gas or hypochlorite. The user also sees a reduction in oxidant demand of about 33%, which signifies that the NEW has about 1.4 times more oxidizing power than chlorine.