Statutes, codes, and regulations
Delaware Administrative Code
Title 16 - Health and SafetyDepartment of Health and Social ServicesDivision of Public HealthHealth Systems Protection (HSP)
Public Drinking Water Systems
Section 4462-17.0 - Interim Enhanced Surface Water Treatment Rule

16 Del. Admin. Code § 4462-17.0

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Current through Register Vol. 28, No. 7, January 1, 2025
Section 4462-17.0 - Interim Enhanced Surface Water Treatment Rule
17.1 The requirements of this section constitute national primary drinking water regulations. These regulations establish requirements for filtration and disinfection that are in addition to criteria under which filtration and disinfection are required by surface water or ground water under the direct influence of surface water systems. The requirements of this section are applicable to surface water or ground water under the direct influence of surface water systems serving at least 10,000 people, beginning December 17, 2001 unless otherwise specified in this section. The regulations in this section establish or extend treatment technique requirements in lieu of maximum contaminant levels for the following contaminants: Giardia lamblia, viruses, heterotrophic plate count bacteria, Legionella, Cryptosporidium, and turbidity. Each surface water or ground water under the direct influence of surface water system serving at least 10,000 people must provide treatment of its source water that complies with these treatment technique requirements and are in addition to those identified in subsection 16.2. The treatment technique requirements consist of installing and properly operating water treatment processes which reliably achieve:
17.1.1 At least 99 percent (2-log) removal of Cryptosporidium between a point where the raw water is not subject to recontamination by surface water runoff and a point downstream before or at the first customer for filtered systems, or Cryptosporidium control under the watershed control plan for unfiltered systems.
17.1.2 Compliance with the profiling and benchmark requirements under the provisions of subsection 17.5.
17.2 A public water system subject to the requirements of this section is considered to be in compliance with the requirements of subsection 17.1 if:
17.2.1 It meets the applicable filtration requirements in either subsections 16.4 or 17.9 and the disinfection requirements in subsections 16.3 and 17.5.
17.3 Systems are not permitted to begin construction of uncovered finished water storage facilities beginning February 16, 1999.
17.4 Surface water or ground water under the direct influence of surface water systems that did not conduct optional monitoring under subsection 17.5 because they served fewer than 10,000 people when such monitoring was required, but serve more than 10,000 people prior to January 1, 2005 must comply with subsections 16.1, 17.5, 17.6, 17.7 and 17.8. These systems must also consult with the Division to establish a disinfection benchmark. A system that decides to make a significant change to its disinfection practice, as described in subsections 17.5.3.1.1 through 17.5.3.1.4 must consult with the Division prior to making such change.
17.5 Disinfection Profiling and Benchmarking.
17.5.1 Determination of systems required to profile. A public water system subject to the requirements of this section must determine its TTHM annual average using the procedure in subsection 17.5.1.1 and its HAA5 annual average using the procedure in subsection 17.5.1.2. The annual average is the arithmetic average of the quarterly averages of four consecutive quarters of monitoring.
17.5.1.1 The TTHM annual average must be the annual average during the same period as is used for the HAA5 annual average.
17.5.1.1.1 Those systems that collected data under the provisions of 61 FR 24368, May 14, 1996 must use the results of the samples collected during the last four quarters of required monitoring under the Information Collection Rule.
17.5.1.1.2 Those systems that use "grandfathered" HAA5 occurrence data that meet the provisions of subsection 17.5.1.2.2 must use TTHM data collected at the same time under the provisions of 40 CFR 141.12 and 141.30 . Copies may be obtained from the Office of Drinking Water.
17.5.1.1.3 Those systems that use HAA5 occurrence data that meet the provisions of subsection 17.5.1.2.3.1 must use TTHM data collected at the same time under the provisions of 40 CFR 141.12 and 141.30 . Copies may be obtained from the Office of Drinking Water.
17.5.1.2 The HAA5 annual average must be the annual average during the same period as is used for the TTHM annual average.
17.5.1.2.1 Those systems that collected data under the provisions of 61 FR 24368, May 14, 1996 must use the results of the samples collected during the last four quarters of required monitoring under the Information Collection Rule.
17.5.1.2.2 Those systems that have collected four quarters of HAA5 occurrence data that meets the routine monitoring sample number and location requirements for TTHM in 40 CFR 141.12 and 141.30 and handling and analytical method requirements of the Information Collection Rule may use those data to determine whether the requirements of this section apply. Copies may be obtained from the Office of Drinking Water.
17.5.1.2.3 Those systems that have not collected four quarters of HAA5 occurrence data that meets the provisions of either subsections 17.5.1.2.1 or 17.5.1.2.2 by March 16, 1999 must either:
17.5.1.2.3.1 Conduct monitoring for HAA5 that meets the routine monitoring sample number and location requirements for TTHM in 40 CFR 141.12 and 141.30 and handling and analytical method requirements of 61 FR 24368, May 14, 1996. Copies may be obtained from the Office of Drinking Water, to determine the HAA5 annual average and whether the requirements of section 17.5.2 apply. This monitoring must be completed so that the applicability determination can be made no later than March 16, 2000, or
17.5.1.2.3.2 Comply with all other provisions of this section as if the HAA5 monitoring had been conducted and the results required compliance with subsection 17.5.2.
17.5.1.3 The system may request that the Division approve a more representative annual data set than the data set determined under subsections 17.5.1.1 or 17.5.1.2 for the purpose of determining applicability of the requirements of this section.
17.5.1.4 The Division may require that a system use a more representative annual data set than the data set determined under subsections 17.5.1.1 or 17.5.1.2 for the purpose of determining applicability of the requirements of this section.
17.5.1.5 The system must submit data to the Division on the schedule in subsections 17.5.1.5.1 through 17.5.1.5.5.
17.5.1.5.1 Those systems that collected TTHM and HAA5 data under the provisions of 61 FR 2436, May 14, 1996, as required by subsections 17.5.1.1.1 and 17.5.1.2.1, must submit the results of the samples collected during the last 12 months of required monitoring under 61 FR 2436, May 14, 1996 not later than December 16, 1999. Copies may be obtained from the Office of Drinking Water.
17.5.1.5.2 Those systems that have collected four consecutive quarters of HAA5 occurrence data that meets the routine monitoring sample number and location for TTHM in 40 CFR 141.12 and 141.30 and handling and analytical method requirements 61 FR 2436, May 14, 1996, copies may be obtained from the Office of Drinking Water, as allowed by subsections 17.5.1.1.2 and 17.5.1.2.2, must submit those data to the Division not later than April 16, 1999. Until the Division has approved the data, the system must conduct monitoring for HAA5 using the monitoring requirements specified under subsection 17.5.1.2.3
17.5.1.5.3 Those systems that conduct monitoring for HAA5 using the monitoring requirements specified by subsections 17.5.1.1.3 and 17.5.1.2.3.1, must submit TTHM and HAA5 data not later than March 16, 2000.
17.5.1.5.4 Those systems that elect to comply with all other provisions of this section as if the HAA5 monitoring had been conducted and the results required compliance with this section, as allowed under subsection 17.5.1.2.3.2, must notify the Division in writing of their election not later than December 16, 1999.
17.5.1.5.5 If the system elects to request that the Division approve a more representative annual data set than the data set determined under subsection 17.5.1.2.1, the system must submit this request in writing not later than December 16, 1999.
17.5.1.6 Any system having either a TTHM annual average >0.064 mg/L or an HAA5 annual average >0.048 mg/L during the period identified in subsections 17.5.1.1 and 17.5.1.2 must comply with subsection 17.5.2.
17.5.2 Disinfection profiling.
17.5.2.1 Any system that meets the criteria in subsection 17.5.1.6 must develop a disinfection profile of its disinfection practice for a period of up to three years.
17.5.2.2 The system must monitor daily for a period of 12 consecutive calendar months to determine the total logs of inactivation for each day of operation, based on the CT99.9 values in Tables 1.1-1.6, 2.1, and 3.1 of 40 CFR 141.74(b), as appropriate, through the entire treatment plant. This system must begin this monitoring not later than March 16, 2000. As a minimum, the system with a single point of disinfectant application prior to entrance to the distribution system must conduct the monitoring in subsections 17.5.2.2.1 through 17.5.2.2.4. A system with more than one point of disinfectant application must conduct the monitoring in subsections 17.5.2.2.1 through 17.5.2.2.4 for each disinfection segment. The system must monitor the parameters necessary to determine the total inactivation ratio, using analytical methods in 40 CFR 141.74(a), copies may be obtained from the Office of Drinking Water, as follows:
17.5.2.2.1 The temperature of the disinfected water must be measured once per day at each residual disinfectant concentration sampling point during peak hourly flow.
17.5.2.2.2 If the system uses chlorine, the pH of the disinfected water must be measured once per day at each chlorine residual disinfectant concentration sampling point during peak hourly flow.
17.5.2.2.3 The disinfectant contact time(s) ("T") must be determined for each day during peak hourly flow.
17.5.2.2.4 The residual disinfectant concentration(s) ("C") of the water before or at the first customer and prior to each additional point of disinfection must be measured each day during peak hourly flow.
17.5.2.3 In lieu of the monitoring conducted under the provisions of subsection 17.5.2.2 to develop the disinfection profile, the system may elect to meet the requirements of subsection 17.5.2.3.1. In addition to the monitoring conducted under the provisions of subsection 17.5.2.2 to develop the disinfection profile, the system may elect to meet the requirements of subsection 17.5.2.3.2.
17.5.2.3.1 A PWS that has three years of existing operational data may submit those data, a profile generated using those data, and a request that the Division approve use of those data in lieu of monitoring under the provisions of subsection 17.5.2.2 not later than March 16, 2000. The Division must determine whether these operational data are substantially equivalent to data collected under the provisions of subsection 17.5.2.2. These data must also be representative of Giardia lamblia inactivation through the entire treatment plant and not just of certain treatment segments. Until the Division approves this request, the system is required to conduct monitoring under the provisions of subsection 17.5.2.2.
17.5.2.3.2 In addition to the disinfection profile generated under subsection 17.5.2.2, a PWS that has existing operational data may use those data to develop a disinfection profile for additional years. Such systems may use these additional yearly disinfection profiles to develop a benchmark under the provisions of subsection 17.5.3. The Division must determine whether these operational data are substantially equivalent to data collected under the provisions of subsection 17.5.2.2. These data must also be representative of inactivation through the entire treatment plant and not just of certain treatment segments.
17.5.2.4 The system must calculate the total inactivation ratio as follows:
17.5.2.4.1 If the system uses only one point of disinfectant application, the system may determine the total inactivation ratio for the disinfection segment based on either of the methods in subsections 17.5.2.4.1.1 or 17.5.2.4.1.2.
17.5.2.4.1.1 Determine one inactivation ratio CTcalc/CT99.9 before or at the first customer during peak hourly flow.
17.5.2.4.1.2 Determine successive CTcalc/ CT99.9 values, representing sequential inactivation ratios, between the point of disinfectant application and a point before or at the first customer during peak hourly flow. Under this alternative, the system must calculate the total inactivation ratio by determining (CTcalc/CT99.9) for each sequence and then adding the (CTcalc/CT99.9) values together to determine ([SIGMA](CTcalc/ CT99.9)).
17.5.2.4.2 If the system uses more than one point of disinfectant application before the first customer, the system must determine the CT value of each disinfection segment immediately prior to the next point of disinfectant application, or for the final segment, before or at the first customer, during peak hourly flow. The (CTcalc/CT99.9) value of each segment and ([SIGMA](CTcalc/CT99.9)) must be calculated using the method in subsection 17.5.2.4.1.
17.5.2.4.3 The system must determine the total logs of inactivation by multiplying the value calculated in subsection 17.5.2.4.1 or 17.5.2.4.2 by 3.0.
17.5.2.5 A system that uses either chloramines or ozone for primary disinfection must also calculate the logs of inactivation for viruses using a method approved by the Division.
17.5.2.6 The system must retain disinfection profile data in graphic form, as a spreadsheet, or in some other format acceptable to the Division for review as part of sanitary surveys conducted by the Division.
17.5.3 Disinfection benchmarking.
17.5.3.1 Any system required to develop a disinfection profile under the provisions of subsections 17.5.1 and 17.5.2 and that decides to make a significant change to its disinfection practice must consult with the Division prior to making such change. Significant changes to disinfection practice are:
17.5.3.1.1 Changes to the point of disinfection;
17.5.3.1.2 Changes to the disinfectant(s) used in the treatment plant;
17.5.3.1.3 Changes to the disinfection process; and
17.5.3.1.4 Any other modification identified by the Division.
17.5.3.2 Any system that is modifying its disinfection practice must calculate its disinfection benchmark using the procedure specified in subsections 17.5.3.2.1 through 17.5.3.2.2.
17.5.3.2.1 For each year of profiling data collected and calculated under subsection 17.5.2, the system must determine the lowest average monthly Giardia lamblia inactivation in each year of profiling data. The system must determine the average Giardia lamblia inactivation for each calendar month for each year of profiling data by dividing the sum of daily Giardia lamblia of inactivation by the number of values calculated for that month.
17.5.3.2.2 The disinfection benchmark is the lowest monthly average value (for systems with one year of profiling data) or average of lowest monthly average values (for systems with more than one year of profiling data) of the monthly logs of Giardia lamblia inactivation in each year of profiling data.
17.5.3.2.3 A system that uses either chloramines or ozone for primary disinfection must also calculate the disinfection benchmark for viruses using a method approved by the Division.
17.5.3.2.4 The system must submit information in subsections 17.5.3.4.1 through 17.5.3.4.4 to the Division as part of its consultation process.
17.5.3.2.4.1 A description of the proposed change;
17.5.3.2.4.2 The disinfection profile for Giardia lamblia (and, if necessary, viruses) under subsection 17.5.2 and benchmark as required by subsection 17.5.3.2; and
17.5.3.2.4.3 An analysis of how the proposed change will affect the current levels of disinfection; and
17.5.3.2.4.4 Any additional information requested by the Division.
17.6 Filtration Interim Enhanced Surface Water Treatment Rule: A public water system subject to the requirements of this section must provide treatment consisting of both disinfection, as specified in subsection 16.3, and filtration treatment which complies with the requirements of subsections 17.6.1 or 17.6.2 or subsection 16.4 by December 17, 2001.
17.6.1 Conventional filtration treatment or direct filtration.
17.6.1.1 For systems using conventional filtration or direct filtration, the turbidity level of representative samples of a system's filtered water must be less than or equal to 0.3 NTU in at least 95 percent of the measurements taken each month, measured as specified in 40 CFR 141.74(a) and (c).
17.6.1.2 The turbidity level of representative samples of a system's filtered water must at no time exceed 1 NTU, measured as specified in 40 CFR 141.74(a) and (c).
17.6.1.3 A system that uses lime softening may acidify representative samples prior to analysis using a protocol approved by the Division.
17.6.2 Filtration technologies other than conventional filtration treatment, direct filtration, slow sand filtration, or diatomaceous earth filtration. A public water system may use a filtration technology not listed in subsection 17.6.1 or in 40 CFR 141.73(b) or (c) if it demonstrates to the Division, using pilot plant studies or other means, that the alternative filtration technology, in combination with disinfection treatment that meets the requirements of subsection 16.3, consistently achieves 99.9 percent removal and/or inactivation of Giardia lamblia cysts and 99.99 percent removal and/or inactivation of viruses, and 99 percent removal of Cryptosporidium oocysts, and the Division approves the use of the filtration technology. For each approval, the Division will set turbidity performance requirements that the system must meet at least 95 percent of the time and that the system may not exceed at any time at a level that consistently achieves 99.9 percent removal and/or inactivation of Giardia lamblia cysts, 99.99 percent removal and/or inactivation of viruses, and 99 percent removal of Cryptosporidium oocysts.
17.7 Filtration sampling requirements:
17.7.1 Monitoring requirements for systems using filtration treatment. In addition to monitoring required by 40 CFR 141.74, a public water system subject to the requirements of this section that provides conventional filtration treatment or direct filtration must conduct continuous monitoring of turbidity for each individual filter using an approved method in 40 CFR 141.74(a) and must calibrate turbidimeters using the procedure specified by the manufacturer. Systems must record the results of individual filter monitoring every 15 minutes.
17.7.2 If there is a failure in the continuous turbidity monitoring equipment, the system must conduct grab sampling every four hours in lieu of continuous monitoring, but for no more than five working days following the failure of the equipment.
17.8 Reporting and recordkeeping requirements: In addition to the reporting and recordkeeping requirements in 40 CFR 141.75, a public water system subject to the requirements of this section that provides conventional filtration treatment or direct filtration must report monthly to the Division the information specified in subsections 17.8.1 and 17.8.2 beginning December 17, 2001. In addition to the reporting and recordkeeping requirements in 40 CFR 141.75, a public water system subject to the requirements of this section that provides filtration approved under subsection 17.6.2 must report monthly to the Division the information specified in 17.8.1 beginning December 17, 2001. The reporting in subsection 17.8.1 is in lieu of the reporting specified in 40 CFR 141.75(b)(1).
17.8.1 Turbidity measurements as required by subsection 17.6 must be reported within 10 days after the end of each month the system serves water to the public. Information that must be reported includes:
17.8.1.1 The total number of filtered water turbidity measurements taken during the month.
17.8.1.2 The number and percentage of filtered water turbidity measurements taken during the month which are less than or equal to the turbidity limits specified in subsections 17.6.1 or 17.6.2.
17.8.1.3 The date and value of any turbidity measurements taken during the month which exceed 1 NTU for systems using conventional filtration treatment or direct filtration, or which exceed the maximum level set by the Division under subsection 17.6.2
17.8.2 Systems must maintain the results of individual filter monitoring taken under subsection 17.7 for at least three years. Systems must report that they have conducted individual filter turbidity monitoring under subsection 17.7 within 10 days after the end of each month the system serves water to the public. Systems must report individual filter turbidity measurement results taken under subsection 17.7 within 10 days after the end of each month the system serves water to the public only if measurements demonstrate one or more of the conditions in subsections 17.8.2.1 through 17.8.2.4. Systems that use lime softening may apply to the Division for alternative exceedance levels for the levels specified in subsections 17.8.2.1 through 17.8.2.4 if they can demonstrate that higher turbidity levels in individual filters are due to lime carryover only and not due to degraded filter performance.
17.8.2.1 For any individual filter that has a measured turbidity level of greater than 1.0 NTU in two consecutive measurements taken 15 minutes apart, the system must report the filter number, the turbidity measurement, and the date(s) on which the exceedance occurred. In addition, the system must either produce a filter profile for the filter within 7 days of the exceedance (if the system is not able to identify an obvious reason for the abnormal filter performance) and report that the profile has been produced or report the obvious reason for the exceedance.
17.8.2.2 For any individual filter that has a measured turbidity level of greater than 0.5 NTU in two consecutive measurements taken 15 minutes apart at the end of the first four hours of continuous filter operation after the filter has been backwashed or otherwise taken offline, the system must report the filter number, the turbidity, and the date(s) on which the exceedance occurred. In addition, the system must either produce a filter profile for the filter within 7 days of the exceedance (if the system is not able to identify an obvious reason for the abnormal filter performance) and report that the profile has been produced or report the obvious reason for the exceedance.
17.8.2.3 For any individual filter that has a measured turbidity level of greater than 1.0 NTU in two consecutive measurements taken 15 minutes apart at any time in each of three consecutive months, the system must report the filter number, the turbidity measurement, and the date(s) on which the exceedance occurred. In addition, the system must conduct a self-assessment of the filter within 14 days of the exceedance and report that the self-assessment was conducted. The self-assessment must consist of at least the following components: assessment of filter performance; development of a filter profile; identification and prioritization of factors limiting filter performance; assessment of the applicability of corrections; and preparation of a filter self-assessment report.
17.8.2.4 For any individual filter that has a measured turbidity level of greater than 2.0 NTU in two consecutive measurements taken 15 minutes apart at any time in each of two consecutive months, the system must report the filter number, the turbidity measurement, and the date(s) on which the exceedance occurred. In addition, the system must arrange for the conduct of a comprehensive performance evaluation (CPE), as defined in Section 2.0, by the Division or a third party approved by the Division no later than 30 days following the exceedance and have the evaluation completed and submitted to the Division no later than 90 days following the exceedance. In consultation with the Division, the water supplier must implement any follow-up recommendations that result, as part of the CPE.
17.8.3 Additional reporting requirements:
17.8.3.1 If at any time the turbidity exceeds 1 NTU in representative samples of filtered water in a system using conventional filtration treatment or direct filtration, the system must inform the Division as soon as possible, but no later than the end of the next business day.
17.8.3.2 If at any time the turbidity in representative samples of filtered water exceeds the maximum level set by the Division under subsection 17.9.2 for filtration technologies other than conventional filtration treatment, direct filtration, slow sand filtration, or diatomaceous earth filtration, the system must inform the Division as soon as possible, but no later than the end of the next business day.

16 Del. Admin. Code § 4462-17.0

24 DE Reg. 794(2/1/2021)
24 DE Reg. 904( 4/1/2021) (Errata)