Idaho Administrative Code
Title IDAPA 58 - Environmental Quality, Department of
Rule 58.01.08 - IDAHO RULES FOR PUBLIC DRINKING WATER SYSTEMS
Section 58.01.08.518 - FACILITY AND DESIGN STANDARDS: ADDITIONAL DESIGN CRITERIA FOR SURFACE WATER TREATMENT

Universal Citation: ID Admin Code 58.01.08.518

Current through August 31, 2023

Performance criteria for surface water treatment facilities are specified in National Primary Drinking Water Regulations, as set forth in Sections 300, 301, and 310 of these rules. Surface water treatment systems must comply with applicable general design requirements in Section 503. In addition, the following design requirements apply specifically to surface water treatment facilities: (3-24-22)

01. Engineering Design Requirements. The system shall ensure that filtration and disinfection facilities for surface water or ground water directly influenced by surface water sources are designed, constructed and operated in accordance with all applicable engineering practices designated by the Department. The design of the water treatment plant must consider the worst raw water quality conditions that are likely to occur during the life of the facility. (3-24-22)

02. Removal of Pathogens. Filtration facilities (excluding disinfection) shall be designed, constructed and operated to achieve at least two (2) log removal of Giardia lamblia cysts, two (2) log removal of Cryptosporidium oocysts, and one (1) log removal of viruses, except as allowed under Subsection 518.09.b. (3-24-22)

03. Disinfection. Disinfection facilities shall be designed, constructed and operated so as to achieve at least point five zero (0.50) log inactivation of Giardia lamblia cysts; and (3-24-22)

a. Two (2) log inactivation of viruses if using conventional and slow sand filtration technology; or (3-24-22)

b. Three (3) log inactivation of viruses if using direct and diatomaceous earth filtration technology; or (3-24-22)

c. Four (4) log inactivation of viruses if using alternate filtration technology. (3-24-22)

d. Four (4) log inactivation of viruses if filtration treatment is not used. (3-24-22)

04. Enhanced Disinfection. Higher levels of disinfection than specified under Subsection 518.03 may be required by the Department in order to provide adequate protection against Giardia lamblia and viruses. (3-24-22)

05. Filter to Waste. For plants constructed after December 31, 1992, each filter unit must be capable of filter to waste. For plants constructed prior to December 31, 1992, each filter unit must be capable of filter to waste unless the system demonstrates through continuous turbidity monitoring or other means acceptable to the Department that water quality is not adversely affected following filter backwashing, cleaning or media replacement. (3-24-22)

06. Continuous Turbidity Monitoring. For conventional, direct, membrane, and diatomaceous earth filtration technology, equipment must be provided to continuously measure the turbidity of each filter unit. (3-24-22)

07. Continuous Monitoring of Disinfectant. Equipment must be provided and operated for continuous measurement of disinfectant residual prior to entry to the distribution system, unless the system serves fewer than three thousand three hundred (3,300) people. (3-24-22)

08. Continuous Operation Required. Diatomaceous earth filtration facilities shall include an alternate power source with automatic startup and alarm, or be designed in a manner to ensure continuous operation. (3-24-22)

09. Acceptable Technology. The purveyor shall select a filtration technology acceptable to the Department. (3-24-22)

a. Conventional, direct, membrane, slow sand, diatomaceous earth, and membrane filtration technologies are generally acceptable to the Department on a case-by-case basis. (3-24-22)

b. Alternate filtration technologies may be acceptable if the purveyor demonstrates all of the following to the satisfaction of the Department: (3-24-22)
i. That the filtration technology: (3-24-22)
(1) Is certified and listed by the National Sanitation Foundation (NSF) under Standard 53, Drinking Water Treatment Units - Health Effects, as achieving the NSF criteria for cyst reduction; or (3-24-22)

(2) Removes at least ninety-nine percent (99%) (two (2) logs) of Cryptosporidium oocysts or surrogate particles and removes or inactivates at least ninety-nine percent (99%) (two (2) logs) of Giardia lamblia cysts or Giardia lamblia cyst surrogate particles in a challenge study acceptable to the Department. (3-24-22)

ii. Based on field studies or other means acceptable to the Department, it must be demonstrated that the filtration technology has the following capabilities: (3-24-22)
(1) In combination with disinfection treatment, consistently achieves at least ninety-nine percent (99%) (two (2) logs) removal of Cryptosporidium oocysts or surrogate particles and at least ninety-nine and nine tenths percent (99.9%) (three (3) logs) removal or inactivation of Giardia lamblia cysts and ninety-nine and ninety-nine hundredths percent (99.99%) (four (4) logs) removal or inactivation of viruses; and (3-24-22)

(2) Meets the turbidity performance requirements of 40 CFR 141.73 (b). (3-24-22)

10. Pilot Studies. The system shall conduct pilot studies in accordance with the following requirements and in accordance with Subsection 501.19 for all proposed filtration facilities and structural modifications to existing filtration facilities, unless the Department modifies the requirements in writing: (3-24-22)

a. The system shall obtain the Department's approval of the pilot study plan before the pilot filter is constructed and before the pilot study is undertaken. (3-24-22)

b. The design and operation of the pilot study shall be overseen by an Idaho licensed professional engineer. (3-24-22)

c. The system's pilot study plan shall identify at a minimum: (3-24-22)
i. The objectives of the pilot study; (3-24-22)

ii. Pilot filter design; (3-24-22)

iii. Water quality and operational parameters to monitor; (3-24-22)

iv. Amount of data to collect; and (3-24-22)

v. Qualifications of the pilot plant operator. (3-24-22)

d. The system shall ensure that the pilot study is: (3-24-22)
i. Conducted to simulate conditions of the proposed full-scale design; (3-24-22)

ii. Conducted for at least twelve (12) consecutive months or for a shorter period upon approval by the Department; (3-24-22)

iii. Conducted to evaluate the reliability of the treatment system to achieve applicable water quality treatment criteria specified for filtration systems in 40 CFR 141.72 and 40 CFR 141.73; and (3-24-22)

iv. Designed and operated in accordance with good engineering practices documented in references acceptable to the Department. (3-24-22)

11. Redundant Disinfection. Surface water systems constructed after July 1, 1985, are required to install redundant disinfection components or maintain a backup unit on site as required to maintain constant application of disinfectant whenever water is being delivered to the distribution system. (3-24-22)

Disclaimer: These regulations may not be the most recent version. Idaho may have more current or accurate information. We make no warranties or guarantees about the accuracy, completeness, or adequacy of the information contained on this site or the information linked to on the state site. Please check official sources.
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