Title: Section 5-1.63 - Enhanced coagulation performance requirements

5-1.63 Enhanced coagulation performance requirements. Systems must achieve the percent reduction of TOC specified in subdivision (a) of this section (Step 1) between the source water and the combined filter effluent, unless the State approves a system's request for alternate minimum TOC removal (Step 2) requirements, which are provided in subdivision (d) of this section.

(a) Required (Step 1) TOC reductions, which are provided in the following table, are based upon specified source water TOC and alkalinity levels:

(b) Systems that must comply with the requirements contained in subdivision (a) of this section must calculate compliance using the method provided in either paragraph (1) of this subdivision or the applicable provisions of paragraph (2) of this subdivision.

(1) Systems must calculate compliance quarterly, beginning after the system has collected 12 months of data, by determining an annual average using the following method:

(i) Determine actual monthly TOC percent removal, equal to: (1 – (treated water TOC/source water TOC)) X 100.

(ii) Determine the required monthly TOC percent removal from either subdivision (a) or (d) of this section.

(iii) Divide the value in subparagraph (i) of this paragraph by the value in subparagraph (ii) of this paragraph.

(iv) Add together the results of subparagraph (iii) of this paragraph for the last 12 months and divide by 12.

(v) If the value calculated in subparagraph (iv) of this paragraph is less than 1.00, the system is not in compliance with the TOC percent removal requirements.

(2) Systems may use the provisions in subparagraphs (i) through (iii) of this paragraph instead of the calculations in paragraph (1) of this subdivision to determine compliance with TOC percent removal requirements.

(i) In any month that the system's treated or source water TOC level is less than or equal to 2.0 mg/L, the system may assign a monthly value of 1.00 (instead of the value calculated in paragraph (1) of this subdivision) when calculating compliance under the provisions of subdivision (a) of this section.

(ii) In any month that the system's source water SUVA, prior to any treatment, is less than or equal to 2.0 L/mg-m, the system may assign a monthly value of 1.00 (instead of the value calculated in paragraph (1) of this subdivision) when calculating compliance under the provisions of subdivision (a) of this section.

(iii) In any month that the system's finished water SUVA is less than or equal to 2.0 L/mg-m, the system may assign a monthly value of 1.00 (instead of the value calculated in paragraph (1) of this subdivision) when calculating compliance under the provisions of subdivision (a) of this section.

(c) Systems that cannot achieve the (Step 1) TOC removals required by subdivision (a) of this section due to water quality parameters or operational constraints must apply to the State, within three months of failure to achieve the TOC removals required by (Step 1), for approval of alternate minimum TOC removal (Step 2) requirements, described in subdivision (d) of this section. Until the State approves the alternate minimum TOC removal (Step 2) requirements, the system must meet the (Step 1) TOC removals contained in subdivision (a) of this section.

(d) Alternate minimum TOC removal (Step 2) requirements. Applications made to the State by enhanced coagulation systems for approval of alternate minimum TOC removal (Step 2) requirements must include, as a minimum, results of bench- or pilot-scale testing conducted using the methodology prescribed in paragraph (1) of this subdivision to determine the alternate enhanced coagulation level. Applications for alternate minimum TOC (Step 2) requirements must be approved by the State before they can replace the previous (Step 1) TOC removal requirements. The alternate TOC removal is determined by the method described in paragraphs (1) through (5) of this subdivision.

(1) The alternate minimum TOC removal is the percentage of TOC removed at the point where an incremental addition of 10 mg/L of alum, or equivalent amount of iron coagulant (ferric salt), results in a TOC removal of ≤0.3 mg/L. This TOC removal percentage is then defined as the minimum TOC removal required for the system. Once approved by the State, this minimum TOC removal requirement supersedes the minimum TOC (Step 1) removal required by the table in subdivision (a) of this section. This requirement will be effective until such time as the State approves a new value based on the results of a new bench- and pilot-scale test. Failure to achieve State-set alternative minimum TOC removal levels is a violation.

(2) 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 iron coagulant, 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:

(3) 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.

(4) The system may operate at any coagulant dose or pH necessary (consistent with the State Sanitary Code) to achieve the minimum TOC percent removal approved under paragraph (1) of this section.

(5) 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 for a waiver of enhanced coagulation requirements.