New Standards to Impact the Use of Hypochlorite for Drinking Water

Changes to NSF/ANSI Standard 60 may impact the use of sodium hypochlorite in drinking water systems. New rules are being considered for the contaminates bromate, perchlorate and chlorate, all of which can be traced to sodium hypochlorite.

US drinking water systems are concerned about disinfection products that might contaminate the water either from contaminants that are in the chemicals used in the treatment or develop in the treatment process. Many of these contaminants have been identified by researchers and regulators and are regulated under the NSF/ANSI Standard 60. Changes to Standard 60 are always under consideration and new changes that can impact the disinfection process are anticipated to be effective in the year 2013.

Standard 60 covers the chemicals used in the treatment of water, including the disinfection chemicals, in general, and sodium hypochlorite and chlorine, in particular. Although there may be other changes to Standard 60, those effecting bleach are of importance to the industry. The changes relate to sodium hypochlorite and the contaminants in hypochlorite. These contaminants are bromate, perchlorate and chlorate.

Bromate

Bromate is a potent human carcinogen.. It can come from two separate sources in drinking water. The first is in the hypochlorite manufacturing process itself. Sodium hypochlorite is generally produced for bulk use by the reaction of chlorine gas with sodium hydroxide or can be produced on-site by the electrolysis of brine (salt) solutions. The compounds used in bulk production (chlorine gas and sodium hydroxide) can contain bromine (chlorine gas) or bromide (sodium hydroxide).

The bromine in the chlorine gas and bromide in sodium hydroxide are converted to bromate at the pH level of the sodium hypochlorite solution produced by the reaction. The addition of this hypochlorite to water in the disinfection process adds bromate to the finished water. Brine is used to feed on-site generation which also produces hypochlorite with bromate contamination.

Bromide ions can be present in the raw water supply, surface or ground water. When water containing bromide ions is exposed to disinfection using the ozonation process, the reaction of bromide with ozone will produce bromate ions. Most water system, however do not contain sufficient levels of bromide ions to make this a serious problem.

Perchlorate

Perchlorate affects the ability of the thyroid gland to take up iodine. This would affect the functions of the thyroid gland and its performance in the body. Perchlorate is a product of sodium hypochlorite decomposition. The longer hypochlorite is kept by the utility before use, the more likely the significant increase in perchlorate.

Chlorate Source

Chlorate can affect the health of certain population groups such as senior citizens, children, etc. Chlorate is included in the contaminant candidate list and will probably be included in the unregulated contaminant mandatory rule. Chlorate is formed when sodium hypochlorite decomposes in a bleach solution. Thermal decomposition of bleach is the primary source of chlorate.

Regulatory Considerations

The following are the current or proposed regulatory actions or regulations for each of the three contaminants or byproducts mentioned above:

1. Bromate – The maximum level of bromine allowed in sodium hypochlorite is expected to be reduced by January 2013 to around a level of 39 ppm. Currently, 69 ppm of bromate is the Maximum Contaminant Level (MCL) allowed in sodium hypochlorite.

2. Perchlorate – Several states have established regulatory limits for perchlorate in drinking water. Standard 60 is expected to have a perchlorate limit established by January 2013. The EPA has an advisory of 15 ppb of chlorate per liter of water but there is no deferral regulation for perchlorate in drinking water at this time. California has a maximum level of 6 ppb and in Massachusetts the maximum allowable is 2 ppb for perchlorate. New Jersey has a proposed MCL of 5 ppb.

3. Chlorate – Limits are being considered for addition to Standard 60 with a target date of January 2013. No current Federal regulations have been issues for chlorate. Currently Canada has guidelines established for drinking water for a MAC of 1 ppm.

The selection of a primary and secondary disinfectant is governed by both the requirements for pathogen inactivation and the production of disinfection byproducts. The choice between ozone and other agents such a hypochlorite with respect to bromate formation will depend on source water bromide levels. In areas where bromide levels are low and disinfection requirements are high, ozone will likely be the choice of more drinking water treatment facilities

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Marines to Recycle Wastewater in San Diego for Landscape Irrigation

The Marine Corps Recruit Depot in San diego is pioneering a type of on-site wastewater recycling system. It will divert 10,000 gallons of sewage at the base each day, treat it to state standards and pump it through irrigation lines to the roots of landscape plants. If all works according to plan, passers-by won’t notice anything except verdant vegetation, and the technology will be deployed at military bases nationwide.

It will process wastewater from barracks and it’s expected to start working in January. The effluent will need to meet health and safety codes for a year before it’s used for irrigation around a memorial for drill instructors.

The idea for the process goes back at least to the 1970s, when a few designers started mimicking natural processes to provide electricity and clean water. Wetlands served as inspiration for removing pollutants from water, and engineers constructed various wetland-based systems that have been deployed across the country. The whole process takes place underground until the effluent is clean enough for irrigation and industrial processes where health codes permit.

Depending on the type of reuse, the water can be treated by ozone, ultraviolet, or chlorine to kill any pathogens that remain.

Numerous reuse schemes are popping up around the country as water shortages and green initiatives create a demand for these processes. Ozone and UV often play a prominent role where the water can come in contact with humans.

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Monteray Bay Aquarium Uses Ozone and UV to Treat Water Returned to Bay

Monterey Bay Aquarium is one of the largest wastewater dischargers of water into the protected Pacific Grove area of the bay. The State Water Resources Control Board exempted the aquarium from a state ban on dumping wastewater into a marine protected zone.

The aquarium continuously takes in about 1,400 gallons of seawater a minute and discharges a like amount. Part of the reason for the exemption is none of the waste seawater samples exhibited toxicity effects. In addition, the facility takes steps to treat the water prior to discharge. The aquarium routes all seawater exposed to birds and mammals through ultraviolet (UV) sterilization. This process gets rid of bacteria and other microbes. Other discharged water, particularly water that has been in contact with exotic species, is run through ozone treatment in order to kill any larvae or eggs that could potentially reach the bay. And water treated with chemicals or pharmaceuticals is isolated and not released back into the bay.

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Drinking Water Plants in the Atlanta Metro Area Moving Away from Chlorine Gas

Cobb County-Marietta Water Authority replaced 24 1,500-pound tanks of chlorine gas two years ago with an electrolytic bleach system at its James E. Quarles Water Trement Plant. A similar conversion is under way as part of the $103 million renovation of the authority’s other water purification facility, the Hugh A. Wyckoff Water Treatment Plant in Acworth.

Chlorine gas, which is used to disinfect water, is a terrorist risk, according to the Department of Homeland Security, because an attack on the plants could cause the release of the gas that can cause severe health problem when people are exposed to the chemical. Water treatment plants that used to be in rural areas are now in the middle of suburban developments intensifying the risk.

Other plants across metro Atlanta have converted to new systems that include treating the water with ozone or UV. These systems can serve as the primary drinking water disinfecting system with bleach used as the secondary disinfectant.

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Cottonwood, Az Plans to Reclaim Wastewater for Drinking Water Using Advanced Oxidation

Cottonwood, AZ is planning on using reclaimed wastewater as a drinking water source sometime in the next15 or 20 years. The city plans to build an $8 million, wastewater treatment plant capable of removing many trace synthetic compounds via advanced oxidation using ozone and hydrogen peroxide. The focus is on pharmaceuticals which have recently become an emerging issue in drinking water systems.

The process calls for the raw sewage flows into a large screen to remove major solids, then into a tank where bacteria eat more solids, then into what’s called a “clarifier” where more solids separate from the water, and then into an oxygen-free zone that further removes solids. The wastewater next gets filtered through sand. This is followed by advanced oxidation process (AOP) using ozone and peroxide. After AOP, the wastewater will be sent to membrane filtration and finally ultraviolet treatment.

Construction is planned to start in about a year.

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