Treatment and Fate of Chlorate, Bromate and Perchlorate in Drinking Water over Time
Perchlorate levels are not yet regulated, and have not been regulated in the past, in spite of the fact that contamination has been known to cause issues since the late 1990s-early 200s. These types of contamination are found in especially high concentrates “near weapons and rocket fuel manufacturing facilities, disposal sites, research facilities, and military bases”. In spite of the lack of regulation, the issue has not been ignored; the EPA did request additional commentary on approaches regarding the regulatory determination of perchlorate in 2009.
This information would serve to provide the necessary information to the EPA, providing them with the information necessary in order to initiate a regulatory determination regarding whether or not the health effects of perchlorate are severe enough to warrant the start of the rulemaking process, and whether or not the levels of perchlorate are high enough, or widespread enough, in order to be able to warrant such a measure.
The information that the EPA was looking for at that time would not be dissimilar from the information that will be presented in the final report regarding this particular study, providing information regarding how the particulates form, why the particulates form, the side effects associated with these contaminants, and the projected costs associated with the treatment of water in order to remove these particulates. In 2011, in regards to their request for commentary, the EPA made its regulatory determination on perchlorate. The decision at this time was that the levels of perchlorate present within the water met the criteria outlined by the Safe Water Drinking Act (SWDA) requiring that the contaminant be regulated. As a result of this regulatory determination, the next step in the process was to determine the specific levels at which perchlorate would be required to remain under in order for the drinking water, and subsequently the water treatment plants that this water originates from, to meet the national primary drinking water regulation, setting the maximum allowable levels. Next, the NPDR (National Primary Drinking water Regulation) would need to be created, and following its creation it would then need to be approved and passed into law. In 2009 the EPA published a health advisory warning of health risks for exposure to perchlorate in amounts greater than 15 ppb; though this health advisory was not something that was enforceable, it was designed to assist local and state agencies in being able to protect the public health during the interim regulatory process.
The new regulation of perchlorate, being proposed under the Safe Water Drinking Act, was presented in February 2013, working to put in place distinct required levels that may not be exceeded in drinking water, with necessary risk assessment and cleanup methods being required should those levels be reached or exceeded. These set levels will work to regulate the treatment of drinking water in order to decrease the level of contaminants present. This will be done in order to be able to work to ensure that the adverse health effects discussed previously do not occur widespread throughout the population levels, making what is now considered to be potable drinking water into actually potable drinking water, with contaminants removed or present only in safe levels.
Given that the Department of Defense is in large part responsible for the release of perchlorate contamination in certain areas, they have allocated resources to be able to work to address the problem, and as of 2008 they had “spent more than $114 million on research activities regarding perchlorate treatment technologies, detection methods, toxicity studies, and substitutes;” this does not count the additional funding that they have spent on cleanup of these materials. The Department of Defense was not required to take these steps, but opted to do so in light of the research undertaken into the adverse health effects of these contaminants, which says something for the severity of the threat that these contaminants may pose towards humans. In 2006, the Department of Defense, in response to their research, and out of concern for the contaminants, set their own policy, before the EPA completed their regulatory research, using 24 parts per billion as their measure to become concerned about the perchlorate levels in the area, and if this is exceeded, they must complete a “site-specific risk assessment;...if the assessment indicates that the perchlorate could result in adverse health effects, then the site must be prioritized for risk management”. This self-regulation works to ensure the safety of individuals whose work takes them to those sites while also working to decrease the risk of the contaminants seeping into the groundwater, further contaminating water supplies.
The treatment costs required in order to meet the levels of perchlorate mandated by the National Primary Drinking Water Regulation have been estimated, based upon the maximum possible contaminant levels that could be utilized in the regulation in order to be able to estimate national cost implications regarding the setting of a federal mandate on contaminant levels. Russell, et al. (2009) undertook such a study, and at the most stringent potential maximum contamination levels, national compliance costs were estimated to fall between $76 million and $140 million per year, including a 3% discounted rate in those figures; in comparison, arsenic compliance cost $280 million per year, showing that while the numbers are exorbitant for the common individual, they are not as expensive in terms of contaminant cleanup as other contaminants have been. The issue with the numbers presented by this particular study is that it only covers the national public water supply compliance costs, it does not factor in the costs that would be incurred by individual privatized water treatment compliance if perchlorate was federally regulated.
A similar study was done by Malcolm Pirnie, Inc. in 2008 in order to determine the total annuitized costs associated with regulatory levels for perchlorate at the national level; these numbers were also designed to only cover the national public water supply compliance costs. Based on a 20 year life of service, and including the same 3% discount as Russell, et al., at the most stringent potential maximum contamination levels, the cost for national compliance was estimated to be $140 million per year, which is still less than the arsenic compliance cost. Russell, et al.’s study, was done the year following Malcolm Pirnie, Inc.’s study, and the total determined by the second study was far less, most likely due to shifting costs for certain products and services as a result of increased market time for those products and services. As with any product or service, the longer that it is on the market, the greater the drop in price, and no doubt this played a factor in the calculations of the study undertaken by Russell, et al. Through a review of the numbers in both studies, it is possible to see that the estimate of $140 million per year is not that far off, in spite of the fact that the first study uses this number as its baseline, while the second study works off of this number as its high end for total potential costs. These numbers allow for a more realistic determination of the total anticipated national costs, given the two different studies provide different numbers, leaving a high likelihood that the associated costs will be somewhere close to the $140 million dollar per year mark, but may be lower, given lower equipment and manufacturing costs of the items used in cleanup.
Perchlorate may be “removed from drinking water sources using” different advanced treatment techniques including, but not limited. The aforementioned treatment options have the side benefit of removing nitrates from the water, though they do create other challenges in return. One example of the challenges that this treatment option presents may be seen with both regenerable ion exchange and reverse osmosis. These both produce waste brine which must be disposed of in a certain manner, one that is quite costly at the current time given the fact that biological treatments have not yet been approved for use within the United States. Biological treatments are low cost, and when they are approved, they are also able to be used to treat waste brine should the other treatment methods discussed still be in use, as opposed to the shift over to simply using biological treatments, which would be lower in cost and would not need to be used as a secondary treatment. Alternatively, both treatment methods may be used in order to be able to retrieve the maximum amount of potable water from the treatments, and the dual filtering would work to guarantee lower levels of contaminants present within the water supply. At the present time, single-pass ion exchange is one of the most common treatment methods used, given its low cost and simple methodology, estimated to cost only $0.33 for every 1,000 gallons of treated water.
There have been several new methods developed in recent years in order to remove perchlorate by anion exchange via the use of resins and engineering processes. These resins “preferentially replace perchlorate, but leave behind bicarbonate, sulfate, silicate, and other native background anions”. These types of commercial anion exchange systems are accepted widely by utilities and regulatory agencies, and because they are widely accepted and familiar to these entities, they are likely to be the first choice to go to for use in the treatment of perchlorate, though there are some implementation issues to be overcome. As a result, in order to minimize the levels of chlorate and other transition metal ions in drinking water, some water treatment plants have demanded higher quality bleach, filtered in order to reduce the concentration of transition metal ions and reduce the inert sediments present within the chemical compound, thereby reducing the coating found on both pumps and piping in the treatment plants and decreasing the amount of accumulated “heavy metal sludge” present on the bottoms of the tanks.
It is not just higher quality bleaches that are being manufactured; one company, Powell Fabrications, has produced a new form of bleach known as HSLS Bleach, or high strength low salt bleach. This particular type of bleach has been shown to have 1.7 times longer shelf/storage stability even at temperatures higher than what is recommended for traditional bleach storage, resulting in lower concentrations of chlorate and perchlorate being formed within the bleach, and the rate at which chlorate and perchlorate form within the HSLS bleach is much slower than that of traditional bleach providing not only higher quality products with less contaminants, but giving the product a longer shelf life. In addition, the HSLS bleach contains 64% less salt than traditional bleach, as a result of a salt recovery system used in the production of this product, a recovery system patented by Powell Fabrications; by utilizing HSLS bleach, treatment plants and utilities will be able to prepare for the federal regulations going into place for both chlorate and perchlorate. The HSLS technology allows for the production of a higher strength of bleach, up to 30% from the standard 13% of traditional bleaches, which may go up to 16.5% at the most, thus not only saving on shipping costs, but making it more beneficial for the companies who will be using these chemicals at the same time, given that this product may be shipped in concentrate and diluted later when received at the site in order to not only make it easier for the companies, decrease their costs, and decrease the space necessary for storage, but also reduce the formation of perchlorate, bromate, and chlorate even further. Finally, this particular product is not only safer than chlorine gas, but it is also easier to handle, further simplifying the jobs of the utilities and treatment plants, while decreasing the job hazards at the same time.
Another alternative method being used in order to treat water and remove perchlorate is the use of reverse osmosis and nano-filtration. The reverse osmosis units work to remove the contaminants by passing the water through a semi-permeable membrane which blocks the passage of perchlorate, but allows water to pass through. Reverse osmosis units will typically contain a pre-filter used to remove solids from the water and extend the life of the membrane, an activated carbon filter that is used to remove odors, chlorine, and taste from the water, the semi-permeable membrane which allows pressurized water to flow through, the tank holding the treated water, and a drain for the wastewater that is produced by this treatment process.
There are issues with this particular treatment as well, given that the filters are unable to be selective in the salts that are removed from the water, resulting in demineralization of the water once cleaned; in addition, reverse osmosis units typically only recover between 20 and 30 percent of water treated with the remainder being sent to a water treatment facility with the rest of the wastewater. The upside to this is that membrane based filtration systems, and point of use devices would be considered to be practical for usage in businesses, homes, or for users who are well isolated from cities or who are using a well for their water source, allowing the concentrate removed from the filters to simply be discarded as wastewater back into the city’s water supply; that which remains is potable water, perfectly safe for drinking and cooking.
Over the past three decades, a new and effective approach to drinking water treatment has immerged that has significantly improved the quality of drinking water that is available to the United States population. This new approach includes the use of chlorine, which is extensively used to disinfect, control water taste and odor, and address oxidation of iron and manganese. Furthermore, chlorine has been adopted as an effective means of controlling microbiological growth in the distribution systems for drinking water. For much of the 20th century, little regulatory control was placed over the quality and treatment of American drinking water and it was not until the passage of the Safe Drinking Water Act of 1974 and its associated amendments, that American drinking water became well regulated and controlled, ensuring consistent quality and safety. Part of the provisions of the Safe Drinking Water Act of 1974 involved a mandate that required utilities throughout the United States make changes to the way water is disinfected in order to meet the more stringent regulations outlined in the Act, thus ensuring the elimination of microbial contamination and disinfection byproducts and guaranteeing the quality and safety of American drinking water.
The changes to water treatment brought about by the passing of the Safe Drinking Water Act of 1974 included the pursuit of alternative water treatment approaches to chlorine. These alternatives have been known to include ozone and chlorine dioxide for primary disinfection and the use of chloramines for secondary disinfection. During the years that followed the passing of the Act, the increased and widespread use of chlorine worked to effectively provide a means of disinfecting drinking water for human consumption. While chlorine was first used for the disinfection of drinking water in 1908, it was not a common practice until the 1970s, the use of which is estimated to have increased overall population life expectancy by 50% since the start of its steady use.