Chlorine Contact Tank and DBP Reduction Measures Showing Effectiveness
On September 8, 2017, the Steelton Borough Authority placed its chlorine contact tank into operation after a nearly year-long project. The tank coupled with DBP reduction measures that have already been put into place are actively reducing disinfection byproducts as expected.
Customers should expect public notices in the future due to test results from earlier in the year (before the tank was operational) factoring into the yearly running average. However, we anticipate that once the higher results from earlier this year are no longer factored into the running average, public notices will stop. We also anticipate the tank and DBP measures to effectively reduce DBPs to below the MCL going forward.
Recent tests that were conducted after the chlorine contact tank went into operation show that it is already effectively reducing DBP levels—in most instances below the maximum contaminant level. The Authority is anticipating DBP levels from now on to consistently remain below the levels used for compliance barring extraordinary circumstances.
The current public notice stems from a high running annual average for DBPs that can be heavily attributed to the high levels recorded before the contact tank was operational and other DBP reduction measures were enacted at the plant.
The table below shows the most recent test results both before and after the tank was operational.
Except for one HAA5 sampling at Site 700, which was marginally above the MCL, all test results post contact tank are well below the MCL at all testing sites and exhibit a trend of consistent reduction.
|8/8/2017 – Pre-Tank
|9/14/2017 – Post Tank
*TTHM MCL = 0.080
**HAA5 MCL =0.060
The Steelton Borough Authority will continue to make supplemental improvements that continue to reduce DBPs and is encouraged by the trends seen above.
We thank residents for their patience as we made the necessary capital improvements to reduce DBPs. The contact tank is now operational and going forward we anticipate DBP levels to be well below the MCL.
Below we have defined the technical terms associated with fully understanding this notice and answers to frequently asked questions:
Chlorine Contact Tank: A 260,000-gallon contact tank that will allow for the chlorination of water post-filtration thus reducing the occurrence of disinfection byproducts.
Disinfection Byproducts (DBP): Chemicals found in drinking water when disinfectants such as chlorine react with naturally-occurring materials to form byproducts. Disinfectants, like chlorine, are used to kill microbes that can cause disease (e.g. gastrointestinal illness). Long-term exposures to consistently high levels of some disinfection byproducts have been associated with an increased risk of cancer.
Haloacetic Acids (HAA5) and Trihalomethanes (TTHMs): Disinfection byproducts that may, when consistently consumed in large quantities over a long period of time, slightly increase the risk for certain health impacts.
Locational Running Annual Average (LRAA): The average of the four most recent quarterly samples collected at specific sample sites. Each quarter, the LRAA is recalculated for purposes of determining compliance and the need for a public notice.
Maximum Contaminant Level (MCL): The maximum level of DBPs in parts per million that can exist in drinking water and remain compliant with EPA standards.
Source Water: Raw water that is drawn from the Susquehanna River and treated at the Steelton Water Treatment Plant. After treatment, the water is distributed through a network of water lines to Steelton residents.
Testing Locations: Two locations chosen in consultation with DEP that historically have the highest levels of DBPs. Test sites most likely represent the worst-case reading for the system at any given time.
Turbidity: The cloudiness of raw source water. Turbidity is indicative of the amount of matter in source water and is higher when the Susquehanna River is more turbulent (i.e. during rain storms and high river levels). High turbidity many times indicates more organic matter thus higher DBPs.
Why am I receiving another drinking water violation notice?
The enclosed non-emergency notice is required due to the LRAA for Haloacetic Acids (HAA5) and Trihalomethanes (TTHMs) being higher than the maximum contaminant level at one testing site (Site 701). Both TTHMs and HAA5s tested below the MCL at both sites this quarter. However, higher results from before the contact tank was operational led to our average remaining above the maximum, hence this notice.
Are HAA5 and TTHM violations unique to Steelton’s water system?
No. Many water systems in the country are dealing with TTHM and HAA5 violations due to more stringent EPA standards, changes in testing/reporting requirements, and aging water treatment infrastructure. Complying with these standards requires older water systems like Steelton’s to make long-term capital improvements. Steelton just completed its Chlorine Contact Tank Project and placed the tank in operation. We are already seeing significant reductions in DBPs since placing the tank in service.
Why do disinfection byproducts like HAA5s and TTHMs occur in our water?
Virtually all water systems have disinfection byproducts of some level due to the fact that chlorine remains the most widely used chemical for water disinfection in the world. According to the Center for Disease Control, “Chlorine revolutionized water purification, reduced the incidence of waterborne diseases across the western world,” and “chlorination and/or filtration of drinking water has been hailed as the major public health achievement of the 20th century.” It is necessary to chlorinate water to eliminate bacteria that causes immediate emergency health risks. No such emergency health risks are occurring due to Steelton’s continued treatment of water.
While chlorination kills harmful pathogens in water (the primary concern of water treatment facilities), the process of chlorine interacting with organic material in water creates what are known as disinfection byproducts, primarily Trihalomethanes and Haloacetic Acids.
The most recent Filter Plant Performance Evaluation study by DEP found that operational standards and procedures at the plant are satisfactory and significantly improved. The only remaining course to address the DBP issue is to upgrade water plant infrastructure. This is being accomplished by the construction of the Chlorine Contact Tank and the addition of other equipment at the water plant.
It is recognized that the removal of immediate pathogenic threats in water through chlorination takes first priority. Higher levels of disinfection byproducts are considered a Tier II non-acute violation (like the one enclosed). A lack of chlorination and the resulting microbial pathogens that would be present in water, represent a Tier I emergency violation.
Am I required to buy bottled water?
No. DEP and EPA clearly state that you do not need to change your source of water.
What if I have concerns about long term health risks associated with HAA5s and TTHMs?
Please consult your physician if you have any concerns about health risks associated with HAA5s and TTHMs.
What is the Water Authority doing to reduce/eliminate DBPs?
On September 8, 2017, the Chlorine Contact Tank was officially placed into operation. The tank, in conjunction with new DBP monitoring equipment and changes to treatment strategies, has already led to a reduction in DBPs below the maximum level. We will continue to work diligently to ensure levels remain below the MCL.
If you have any additional questions about disinfection byproducts or what we are doing, and have done, to ensure your drinking water is safe, please feel free to contact me at 717-939-9842 or Mark Handley at 717-939-0425 Ext. 5110. Douglas E. Brown, Borough Manager and Authority Secretary.