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Disinfection Requirements Rule

The Disinfection Requirements Rule (DRR) was published in the PA Bulletin on April 28, 2018. The amendments are intended to protect public health through a multiple barrier approach designed to guard against microbial contamination by ensuring the adequacy of treatment designed to inactivate microbial pathogens and the integrity of drinking water distribution systems.

Safe drinking water is vital to maintaining healthy and sustainable communities. Proactively avoiding incidents such as waterborne disease outbreaks can prevent loss of life, reduce the incidents of illness and reduce health care costs. Proper investment in public water system infrastructure and operations helps ensure a continuous supply of safe drinking water, enables communities to plan and build future capacity for economic growth, and ensures their long-term sustainability.

The significant requirements of the DRR fall into two categories: provisions that are effective immediately and provisions that have delayed implementation dates.

Here is the final rule:

Training and Resources

DRR classroom training has concluded, but the following resources are available:

DRR Provisions Effective Upon Publication

  • Reporting Distribution System Residual Data: All water systems that are reporting distribution system disinfectant residual data will need to begin reporting individual residual measurements instead of the number of measurements and the average result value. The SDWA–Summary format used to report distribution system disinfectant residual measurements is eliminated and water suppliers will no longer be required to calculate the distribution system disinfectant residual monthly average value. Instead, beginning with the May 2018 disinfectant residual data (that is reported by June 10, 2018), report all individual distribution system disinfectant residual measurements using the SDWA–1 format. Please refer to the reporting instructions document:
  • Note that the requirements to report daily ENTRY POINT Chlorine residuals on the SDWA–1 for has not changed. Entry point disinfectant residuals are reported using Sample Type 'E,' and distribution system disinfectant residuals are reported using Sample Type 'D.'
  • Minimum Entry Point Disinfectant Residual: Water systems using filtered surface water (SW) or groundwater under the direct influence of SW (GUDI) sources must maintain a minimum disinfectant residual at the entry point (EP) of at least 0.20 mg/L. The previous minimum residual was 0.2 mg/L. The minimum residual for water systems with 4-log disinfection of groundwater (GW) sources has not changed.
  • Calculating & Reporting Log Inactivation: Water systems using filtered SW or GUDI sources must calculate the Giardia log (%) inactivation at least once/day during the hour of expected peak flow. If the Giardia log inactivation is less than 1.0 log (90%), the Giardia log inactivation should continue to be calculated every 4 hours until the Giardia log inactivation is at least 1.0.
    • The Giardia log inactivation calculation components are not reported to DEP with the log inactivation value (except for the EP chlorine residuals as noted above), but this information needs to be made available to DEP upon request. Therefore, accurate records need to be maintained for the following parameters: chlorine residual, pH, flow (gpm), tank volume (gal) and baffling factor, and temperature (°C).
    • If a disinfectant other than free chlorine is used to achieve some portion of the minimum Giardia log inactivation, the log inactivation value for viruses will also need to be calculated at the same time using the same data.
    • Log inactivation will also need to be calculated whenever the EP disinfectant residual falls below 0.20 mg/L and continue to be calculated every 4 hours until the residual is > 0.20 mg/L.
    • The log inactivation values will need to be reported monthly, beginning with the May 2018 compliance period (that is the May 2018 CT values will need to be reported by June 10, 2018).
    • Instructions and tools for calculating and reporting log inactivation values:
  • Bottled, Vended, Retail and Bulk (BVRB) water systems that are purchasing water from another public water system that provides filtration of surface water (SW) or Groundwater Under Direct Influence (GUDI) sources. Starting in July, 2018, BVRB systems using SW/GUDI sources or purchasing water from SW/GUDI sources will also need to comply with the federal and state Surface Water Treatment Rule treatment technique requirement that mandates a minimum distribution system disinfectant residual (0.20 ppm chlorine or 0.1 ppm ozone). Compliance with the SWTR treatment technique is based on disinfectant residual measurements conducted at the same time coliform samples are collected. If the disinfectant residual is below the minimum level, the sample location (EP) is in compliance if the Heterotrophic Plate Count (HPC), from the same or equivalent sample, is less than 500 colonies per mL. Therefore, any BVRB system in this category (including permit-by-rule) that removes residual chlorine will need to begin collecting HPC samples at the same time as the weekly (or monthly) coliform samples. These requirements do NOT apply to entry points that are using ONLY groundwater or purchasing water from groundwater sources.
    • Any BVRB entry point that is using purchased SW/GUDI sources and that uses a chemical disinfectant at that entry point, should begin measuring the disinfectant residual at that entry point at the time coliform samples are collected. Bottlers will need to conduct measurements at least once/week at a time that is representative of the water being produced. If the residual measurement is below the required minimum value, the coliform compliance sample(s) should also be tested for HPC.
    • Any BVRB water system (including permit-by-rule) that removes residual chlorine prior to the entry point will need to begin collecting HPC samples at the same time as the weekly (or monthly) coliform samples.
    • Bottled water systems and retail water facilities using ozone as a final disinfectant are still required to maintain an ozone residual of 0.1 to 0.4 ppm in the bottle immediately after filling.
    • For bottled water systems that measure a disinfectant residual at the time of filling and then ship the bottle to the laboratory for microbiological analysis, note:
      • Sample and analysis dates for residual disinfectant should be the date the sample was collected and analyzed at the time of fill.
      • Sample and analysis dates for microbiological parameters should correspond to the date the bottle was opened by the lab and analyzed.
    • Please refer to the reporting instructions document:
  • Water Systems Using Chlorine Dioxide. New analytical method codes (that correspond to specific EPA-approved analytical methods) have been established for reporting chlorine dioxide and chlorite results. Please refer to the reporting instructions document.

DRR Provisions With Delayed Implementation

  • Sample Siting Plan: All community water systems, any nontransient noncommunity water system with chemical disinfection and any transient noncommunity water system with filtration of SW or GUDI sources or 4-log disinfection of GW sources must develop and submit a DRR sample siting plan by October 29, 2018. The plan must include representative locations (including dead ends, storage facilities, interconnections, areas of high water age, areas with previous RTCR detects, and mixing zones) and a sample collection schedule. The plan may be combined with the RTCR sampling plan if all content elements are included.
  • The Department has created a template that systems may use to develop the DRR sample siting plan:
  • Distribution System Minimum Residual: All community water systems, any nontransient noncommunity water system with chemical disinfection and any transient noncommunity water system with filtration of SW or GUID sources or 4-log disinfection of GW sources must maintain a minimum disinfectant residual concentration in the distribution system of at least 0.2 mg/L (unless a higher number has been specified in a permit) beginning April 29, 2019.
    • Disinfectant residual measurements must continue to be collected at representative locations at the same time and location(s) as coliform samples.
    • Disinfectant residual measurements must also be conducted at least once/week. Water systems that do not collect at least 1 coliform sample each week will need to conduct additional disinfectant residual measurements each week that a coliform sample is not collected.
    • Any location that has a disinfectant residual less than 0.2 mg/L in a month must also be sampled the following month. The Heterotrophic Plate Count alternative compliance criteria is eliminated.
  • Nitrification Control Plan: Any community or nontransient noncommuity water system using chloramines or purchasing water treated with chloramines must develop and implement a nitrification control plan by April 29, 2019. Then plan must conform to industry standards (such as AWWA's M56 Manual on Nitrification) and contain a system-specific monitoring plan and a response plan with expected water quality ranges and action levels. The plan must be updated as necessary, retained on site and made available to DEP upon request.

Method 334.0 For Disinfectant Residual Measurements

  • Pennsylvania's SDW regulations require that sampling and analysis for compliance monitoring are conducted in accordance with analytical techniques approved by the US EPA. Method 334.0 was published in 2009 by the US EPA and specifies the quality control practices for measuring chlorine disinfectant residuals for compliance purposes to ensure that these measurements are accurate.
  • Water systems conducting compliance measurements for free or total chlorine residual need to ensure both the analyst(s) and equipment used are compliant with Method 334.0 quality control practices. Please refer to the Fact Sheet and the Method 334.0 webpage for additional information.

History And Background

The proposed DRR rulemaking was originally included in the Proposed Revised Total Coliform Rule (RTCR). However, on April 21, 2015, the Environmental Quality Board (EQB) approved the proposed RTCR with modifications. The modifications included splitting out the non-RTCR provisions for additional stakeholder input. On April 30, 2015, the Small Water Systems Technical Assistance Center (TAC) Board voted to recommend that the regulation be split further, with the non-RTCR rulemaking to focus solely on the disinfection requirements and the minor corrections needed to obtain or maintain primacy. Additional TAC meetings were held on May 18, May 26, June 16, and June 30, 2015.

For more information about the TAC meetings, please visit TAC's website.

Two additional meetings were held with large water systems on June 29, and July 16, 2015, to gather additional comments. As a result of these additional meetings, several revisions were made during the pre-draft rulemaking process.

The Proposed Disinfection Requirements Rule was published in the PA Bulletin on February 20, 2016. During the public comment period, three public hearings were held and 3 additional stakeholder meetings were convened.

Additional Stakeholder Meetings

The draft-final DRR language presented to TAC on July 13, 2017; TAC provided recommendations on Aug 24, 2017. Several changes were made to the draft-final DRR in response to public comments and TAC's recommendations. The final DRR rulemaking was approved by the EQB on December 12, 2017. The rulemaking documents can be found on the EQB website under the 2017 Meetings tab.