Ariz. Admin. Code § R18-9-F834 - Total Organic Carbon Management

A. An AWPRA shall select, achieve, and maintain an up-to-date TOC limit in the advanced treated water using one of the two approaches described in subsections (B) and (C) below.

1. Upon AWTF operation, an AWPRA may switch between the two approaches each calendar year.

2. The TOC management annual approach shall be reported as part of the annual report pursuant to R18-9-E831.

B. Standard Approach or Limit.

1. An AWTF shall not exceed 2 mg/L of TOC in the advanced treated water.

2. The AWPRA shall monitor TOC using continuous online analyzers in the advanced treated water.

C. Site-Specific Approach or Limit. An AWPRA shall perform the two procedures described in subsections (C)(1) and (2) below. The site-specific TOC limit shall be the lower of the two preliminary TOC values obtained from these procedures.

1. Trace Organics Removal Procedure. The AWPRA shall submit a plan to characterize the TOC of all original drinking water sources that feed the collection system(s) that are used by the AWTF as a treated wastewater source. This plan shall be submitted for approval by the Department as part of the Pilot Study Plan pursuant to R18-9-C815(B)(3) and (D) and again in the permit application as part of the R18-9-C816(A)(2)(d) submittals.

a. Original Drinking Water TOC Characterization requires, but is not limited to, the following:

i. Use of Departmentally approved TOC sampling locations,

ii. Sampling for a minimum of one year,

iii. Sampling at weekly intervals,

iv. Calculation of the TOC at the 50th percentile (median), 75th percentile, and 95th percentile,

v. Establishment of a TOC alert level at the 75th percentile, and

vi. Establishment of the TOC action level at 1.5 * 95th percentile.

b. Upon the characterization of TOC in the original drinking water and approval from the Department, an AWPRA shall monitor for TOC in the advanced treated water using continuous online analyzers.

c. For the purposes of this subsection, the preliminary TOC value in mg/L for the Trace Organics Removal Procedure is the action level established in subsection (C)(1)(a)(vi) above.

2. Disinfection Byproducts Precursor Reduction Procedure.

a. Method 5710 C: "Simulated Distribution System Trihalomethanes (SDS - THM)"

i. The AWPRA shall apply 5710 C Method "Simulated Distribution System Trihalomethanes (SDS - THM)" to the advanced treated water in order to determine the total trihalomethane (THM) concentration.

ii. Testing and sampling shall be conducted monthly for one year.

iii. The AWPRA shall simultaneously sample for TOC in mg/L in the advanced treated water monthly for one year.

iv. If the average THM concentration is below the corresponding MCL for THM pursuant to R18-9-E825, the average TOC value from subsection (C)(2)(a)(iii) is the Method 5710C TOC value for the purposes of comparison in subsection (C)(2)(d) below.

v. If the average THM concentration is at or above the corresponding THM MCL pursuant to R18-9-E825, the AWPRA may not use the average TOC value from subsection (C)(2)(a)(iii) as the Method 5710C TOC value. The AWPRA may adjust components of their operation and repeat the steps in subsection (C)(2)(a) until an average THM concentration in the advanced treated water is below the corresponding THM MCL pursuant to R18-9-E825.

b. The AWPRA shall submit the following information on the conditions at the time Method 5710 C from subsection (C)(2)(a) above was conducted to the Department as part of the Pilot Study Report pursuant to R18-9-C815(D) and again in the permit application as part of the R18-9-C816(A)(2)(d) submittals:

i. Temperature,

ii. pH,

iii. Disinfectant dose,

iv. Residual and reaction time within the distribution system, and

v. Other standard conditions as described in Section 5710 B "Trihalomethane Formation Potential (THMFP)".

c. CCL5 - Disinfectant Byproducts Sampling Method.

i. The AWPRA shall sample for the following disinfection byproducts in the advanced treated water, Formaldehyde (CAS No. 50-00-0) and N-Nitrosodimethylamine (NDMA) (CAS No. 65-75-9), which are the only disinfection byproducts that exist in both EPA's "Contaminant Candidate List 5 - Exhibit 1b - Unregulated DBPs in the DBP Group on CCL 5" and EPA's "2018 Edition of the Drinking Water Standards and Health Advisories Tables".

ii. Sampling shall be conducted monthly for one year.

iii. The AWPRA shall simultaneously sample for TOC in mg/L in the advanced treated water monthly for one year.

iv. If the average sampling result for any one DBP is below the corresponding health advisory in EPA's "2018 Edition of the Drinking Water Standards and Health Advisories Tables", the average TOC value from subsection (C)(2)(c)(iii) is the CCL5 DBP TOC value for the purposes of comparison in subsection (C)(2)(d) below.

v. If the average sampling result for any one DBP is at or above the corresponding health advisory in EPA's "2018 Edition of the Drinking Water Standards and Health Advisories Tables", the AWPRA may not use the average TOC value from subsection (C)(2)(c)(iii) as the CCL5 DBP TOC value. The AWPRA may adjust components of their operation and repeat the steps in subsection (C)(2)(c) until the average sampling results from any one DBP is below the corresponding health advisory in EPA's "2018 Edition of the Drinking Water Standards and Health Advisories Tables".

d. The lower of the two resultant TOC values in mg/L derived from the methods described in subsections (C)(2)(a) and (C)(2)(c) above is the preliminary TOC value for the Disinfection Byproducts Precursor Reduction Procedure.

3. AWPRA's Site-Specific TOC Approach or Limit. The lower of the two preliminary TOC values in mg/L derived from the two procedures in (C)(1) and (2) above is the AWPRA's site-specific TOC limit.

4. Once a site-specific TOC approach or limit is ascertained, an AWPRA shall establish a TOC action level and alert level based on that approach or limit, using the lower of the two values derived from subsections (C)(1) and (2). Upon the exceedance of a TOC action level, the AWPRA shall conduct one of the following two actions within 72 hours of becoming aware of the exceedance:

a. Stop conveying advanced treated water, investigate, identify, and correct the issue; or

b. Correct the issue with confirmation that advanced treated water TOC does not exceed the action level, and identify the issue.

5. Frequency of Site-Specific Procedures. AWPRA's re-selecting the site-specific TOC approach to begin a new calendar year shall repeat the two procedures in subsections (C)(1) and (2) in order to reestablish an up-to-date TOC action level and TOC alert level.

Notes

Ariz. Admin. Code § R18-9-F834

New Section made by final rulemaking at 31 A.A.R. 1070, effective 3/4/2025.