Section 179-16-008 - TREATMENT TECHNIQUE FOR CONTROL OF DISINFECTION BYPRODUCT (DBP) PRECURSORS008.01 Applicability 16-008.01A Public water systems using surface water or ground water under the direct influence of surface water using conventional filtration treatment must operate with enhanced coagulation or enhanced softening to achieve the TOC percent removal levels specified in 179 NAC 16-008.02 unless the system meets at least one of the alternative compliance criteria listed in 179 NAC 16-008.01B or 16-008.01C. 16.008.01B Alternative Compliance Criteria for Enhanced Coagulation and Enhanced Softening Systems: Public water systems using surface water or ground water under the direct influence of surface water using conventional filtration treatment may use the alternative compliance criteria in 179 NAC 16-008.01B items 1 through 6 to comply with this section in lieu of complying with 179 NAC 16-008.02. Systems must still comply with monitoring requirements in 179 NAC 16-005.04. 1. The system's source water TOC level, measured according to 179 NAC 16-004.04 item 3, is less than 2.0 mg/L, calculated quarterly as a running annual average.2. The system's treated water TOC level, measured according to 179 NAC 16-004.04 item 3, is less than 2.0 mg/L, calculated quarterly as a running annual average.3. The system's source water TOC level, measured according to 179 NAC 16-004.04 item 3, is less than 4.0 mg/L, calculated quarterly as a running annual average; the source water alkalinity, measured according to 179 NAC 16-004.04 item 1, is greater than 60 mg/L (as CaCO3), calculated quarterly as a running annual average; and either the TTHM and HAA5 running annual averages are no greater than 0.040 mg/L and 0.030 mg/L, respectively; or prior to the effective date for compliance in 179 NAC 16-001.01, the system has made a clear and irrevocable financial commitment not later than the effective date for compliance in 179 NAC 16-001.01 to use of technologies that will limit the levels of TTHMs and HAA5 to no more than 0.040 mg/L and 0.030 mg/L, respectively. Systems must submit evidence of a clear and irrevocable financial commitment, in addition to a schedule containing milestones and periodic progress reports for installation and operation of appropriate technologies, to the Department for approval not later than the effective date for compliance in 179 NAC 16-001.01. These technologies must be installed and operating not later than June 30, 2005. Failure to install and operate these technologies by the date in the approved schedule will constitute a violation of these regulations.4. The TTHM and HAA5 running annual averages are no greater than 0.040 mg/L and 0.030 mg/L, respectively, and the system uses only chlorine for primary disinfection and maintenance of a residual in the distribution system. 5. The system's source water SUVA, prior to any treatment and measured monthly according to 179 NAC 16-004.04 item 4 is less than or equal to 2.0 L/mg-m, calculated quarterly as a running annual average.6. The system's finished water SUVA, measured monthly according to 179 NAC 16-004.04 item 4 is less than or equal to 2.0 L/mg-m, calculated quarterly as a running annual average.16.008.01C Additional Alternative Compliance Criteria for Softening Systems: Systems practicing enhanced softening that cannot achieve the TOC removals required by 179 NAC 16-008.02B may use the alternative compliance criteria in 179 NAC 16-008.01C items 1 and 2 in lieu of complying with 179 NAC 16-008.02. Systems must still comply with the monitoring requirements in 179 NAC 16-005.04. 1. Softening that results in lowering the treated water alkalinity to less than 60 mg/L (as CaCO3), measured monthly according to 179 NAC 16-004.04 item 1 and calculated quarterly as a running annual average.2. Softening that results in removing at least 10 mg/L of magnesium hardness (as CaCO3), measured monthly according to 179 NAC 16-004.04 item 6 and calculated quarterly as an annual running average.008.02 Enhanced Coagulation and Enhanced Softening Performance Requirements 16-008.02A Systems must achieve the percent reduction of TOC specified in 179 NAC 16-008.02B between the source water and the combined filter effluent, unless the Department approves a system's request for alternate minimum TOC removal (Step 2) requirements under 179 NAC 16-008.02C.16-008.02B Required Step 1 TOC reductions, indicated in the following table, are based upon specified source water parameters measured in accordance with 179 NAC 16-004.04. Systems practicing softening are required to meet the Step 1 TOC reductions in the far-right column (Source water alkalinity >120 mg/L) for the specified source water TOC: STEP 1 REQUIRED REMOVAL OF TOC BY ENHANCED COAGULATION AND ENHANCED SOFTENING FOR PUBLIC WATER SYSTEMS USING SURFACE WATER OR GROUND WATER UNDER THE DIRECT INFLUENCE OF SURFACE WATER USING CONVENTIONAL TREATMENT1,2
Source-Water TOC, Mg/L | Source-Water Alkalinity, Mg/L as CaCO3 (in Percentages) |
0-60 | > 60-120 | >1203 |
> 2.0- 4.0 | 35.0 | 25.0 | 15.0 |
> 4.0- 8.0 | 45.0 | 35.0 | 25.0 |
> 8.0 | 50.0 | 40.0 | 30.0 |
1 Systems meeting at least one of the conditions in 179 NAC 16-008.01B, items 1 to 6, are not required to operate with enhanced coagulation.
2 Softening systems meeting one of the alternative compliance criteria in 179 NAC 16-008.01C are not required to operate with enhanced softening.
3 Systems practicing softening must meet the TOC removal requirements in this column.
16-008.02C Public water systems using surface water or ground water under the direct influence of surface water as a source and having conventional treatment systems that cannot achieve the Step 1 TOC removals required by 179 NAC 16-008.02B due to water quality parameters or operational constraints must apply to the Department, within three months of failure to achieve the TOC removals required by 179 NAC 16-008.02B, for approval of alternative minimum TOC (Step 2) removal requirements submitted by the system. If the Department approves the alternative minimum TOC removal (Step 2) requirements, the Department may make those requirements retroactive for the purposes of determining compliance. Until the Department approves the alternate minimum TOC removal (Step 2) requirements, the system must meet the Step 1 TOC removals contained in 179 NAC 16-008.02B.16-008.02D Alternate Minimum TOC Removal (Step 2) Requirements: Applications made to the Department by enhanced coagulation systems for approval of alternative minimum TOC removal (Step 2) requirements under 179 NAC 16-008.02C must include, at a minimum, results of bench- or pilot-scale testing conducted under 179 NAC 16-008.02D1. The submitted bench- or pilot-scale testing must be used to determine the alternate enhanced coagulation level. 16-008.02D1 Alternate enhanced coagulation level is defined as coagulation at a coagulant dose and pH as determined by the method described in 179 NAC 16-008.02D1 through 16-008.02D5 such that an incremental addition of 10 mg/L of alum (or equivalent amount of ferric salt) results in a TOC removal of <= 0.3 mg/L. The percent removal of TOC at this point on the "TOC removal versus coagulant dose" curve is then defined as the minimum TOC removal required for the system. Once approved by the Department, this minimum requirement supersedes the minimum TOC removal required by the table in 179 NAC 16-008.02B. This requirement will be effective until such time as the Department approves a new value based on the results of a new bench- and pilot-scale test. Failure to achieve Department-set alternative minimum TOC removal levels is a violation of these regulations.16-008.02D2 Bench- or pilot-scale testing of enhanced coagulation must be conducted by using representative water samples and adding 10 mg/L increments of alum (or equivalent amounts of ferric salt) until the pH is reduced to a level less than or equal to the enhanced coagulation Step 2 target pH shown in the following table: ENHANCED COAGULATION STEP 2 TARGET pH
Alkalinity (mg/L as CaCO3) | Target pH |
0-60 | 5.5 |
> 60-120 | 6.3 |
> 120-240 | 7.0 |
>240 | 7.5 |
16-008.02D3 For waters with alkalinities of less than 60 mg/L for which addition of small amounts of alum or equivalent addition of iron coagulant drives the pH below 5.5 before significant TOC removal occurs, the system must add necessary chemicals to maintain the pH between 5.3 and 5.7 in samples until the TOC removal of 0.3 mg/L per 10 mg/L alum added (or equivalent addition of iron coagulant) is reached.16-008.02D4 The system may operate at any coagulant dose or pH necessary to achieve the minimum TOC percent removal approved under 179 NAC 16-008.02C.16-008.02D5 If the TOC removal is consistently less than 0.3 mg/L of TOC per 10 mg/L of incremental alum dose at all dosages of alum (or equivalent addition of iron coagulant), the water is deemed to contain TOC not amenable to enhanced coagulation. The system may then apply to the Department for a waiver of enhanced coagulation requirements.008.03 Compliance Calculations 16-008.03A Public water systems using surface water or ground water under the direct influence of surface water other than those identified in 179 NAC 16-008.01B or 16-008.01C must comply with requirements contained in 179 NAC 16-008.02B or 16-008.02C. Systems must calculate compliance quarterly, beginning after the system has collected 12 months of data, by determining an annual average using the following method: 1. Determine actual monthly TOC percent removal, equal to: [1 - (treated water TOC/source water TOC)] X 100.2. Determine the required monthly TOC percent removal (from either the table in 179 NAC 16-008.02B or from 179 NAC 16-008.02C).3. Divide the value in 179 NAC 16-008.03A item 1 by the value in by 179 NAC 16-008.03A item 2.4. Add together the results of 179 NAC 16-008.03A item 3 for the last 12 months and divide by 12.5. If the value calculated in 179 NAC 16-008.03A, item 4 is less than 1.00, the system is not in compliance with the TOC percent removal requirements.16-008.03B Systems may use the provisions in 179 NAC 16-008.03B items 1 through 5 in lieu of the calculations in 179 NAC 16-008.03A items 1 through 5 to determine compliance with TOC percent removal requirements. 1. In any month that the system's treated or source water TOC level, measured according to 179 NAC 16-004.04 item 3 is less than 2.0 mg/L, the system may assign a monthly value of 1.0 (in lieu of the value calculated in 179 NAC 16-008.03A item 3) when calculating compliance under the provisions of 179 NAC 16-008.03A.2. In any month that a system practicing softening removes at least 10 mg/L of magnesium hardness (as CaCO3), the system may assign a monthly value of 1.0 (in lieu of the value calculated in 179 NAC 16-008.03A item 3) when calculating compliance under the provisions of 179 NAC 16-008.03A.3. In any month that the system's source water SUVA, prior to any treatment and measured according to 179 NAC 16-004.04 item 4 is <= 2.0 L/mg-m, the system may assign a monthly value of 1.0 (in lieu of the value calculated in 179 NAC 16-008.03A item 3) when calculating compliance under the provisions of 179 NAC 16-008.03A.4. In any month that the system's finished water SUVA, measured according to 179 NAC 16-004.04 item 4 is <= 2.0 L/mg-m, the system may assign a monthly value of 1.0 (in lieu of the value calculated in 179 NAC 16-008.03A item 3) when calculating compliance under the provisions of 179 NAC 16-008.03A.5. In any month that a system practicing enhanced softening lowers alkalinity below 60 mg/L (as CaCO3), the system may assign a monthly value of 1.0 (in lieu of the value calculated in 179 NAC 16-008.03A item 3) when calculating compliance under the provisions of 179 NAC 16-008.03A.16-008.03C Public water systems using surface water or ground water under the direct influence of surface water using conventional treatment may also comply with the requirements of this section by meeting the criteria in 179 NAC 16-008.01B or 16-008.01C.008.04 Treatment Technique Requirements for DBP Precursors The Department identifies the following as treatment techniques to control the level of disinfection byproduct precursors in drinking water treatment and distribution systems: For public water systems using surface water or ground water under the direct influence of surface water using conventional treatment, enhanced coagulation or enhanced softening.
179 Neb. Admin. Code, ch. 16, § 008