---
kind: "section"
citation: "40 C.F.R. § 141.712"
title: "40"
number: "141.712"
heading: "Unfiltered system Cryptosporidium treatment requirements."
url: "https://uscodex.org/cfr/40/141.712"
---

# §141.712. Unfiltered system Cryptosporidium treatment requirements.

- (a) **Determination of mean Cryptosporidium level.**
  - (1) Following completion of the initial source water monitoring required under [§ 141.701(a)](/cfr/40/141.701.md?p=a), unfiltered systems must calculate the arithmetic mean of all Cryptosporidium sample concentrations reported under [§ 141.701(a)](/cfr/40/141.701.md?p=a). Systems must report this value to the State for approval no later than 6 months after the month the system is required to complete initial source water monitoring based on the schedule in [§ 141.701(c)](/cfr/40/141.701.md?p=c).
  - (2) Following completion of the second round of source water monitoring required under [§ 141.701(b)](/cfr/40/141.701.md?p=b), unfiltered systems must calculate the arithmetic mean of all Cryptosporidium sample concentrations reported under [§ 141.701(b)](/cfr/40/141.701.md?p=b). Systems must report this value to the State for approval no later than 6 months after the month the system is required to complete the second round of source water monitoring based on the schedule in [§ 141.701(c)](/cfr/40/141.701.md?p=c).
  - (3) If the monthly Cryptosporidium sampling frequency varies, systems must first calculate a monthly average for each month of monitoring. Systems must then use these monthly average concentrations, rather than individual sample concentrations, in the calculation of the mean Cryptosporidium level in paragraphs [(a)(1)](#a-1) or [(2)](#a-2) of this section.
  - (4) The report to the State of the mean Cryptosporidium levels calculated under paragraphs [(a)(1)](#a-1) and [(2)](#a-2) of this section must include a summary of the source water monitoring data used for the calculation.
  - (5) Failure to comply with the conditions of [paragraph (a)](#a) of this section is a violation of the treatment technique requirement.
- (b) **Cryptosporidium inactivation requirements.** Unfiltered systems must provide the level of inactivation for Cryptosporidium specified in this paragraph, based on their mean Cryptosporidium levels as determined under [paragraph (a)](#a) of this section and according to the schedule in [§ 141.713](/cfr/40/141.713.md).
  - (1) Unfiltered systems with a mean Cryptosporidium level of 0.01 oocysts/L or less must provide at least 2-log Cryptosporidium inactivation.
  - (2) Unfiltered systems with a mean Cryptosporidium level of greater than 0.01 oocysts/L must provide at least 3-log Cryptosporidium inactivation.
- (c) **Inactivation treatment technology requirements.** Unfiltered systems must use chlorine dioxide, ozone, or UV as described in [§ 141.720](/cfr/40/141.720.md) to meet the Cryptosporidium inactivation requirements of this section.
  - (1) Systems that use chlorine dioxide or ozone and fail to achieve the Cryptosporidium inactivation required in [paragraph (b)](#b) of this section on more than one day in the calendar month are in violation of the treatment technique requirement.
  - (2) Systems that use UV light and fail to achieve the Cryptosporidium inactivation required in [paragraph (b)](#b) of this section by meeting the criteria in [§ 141.720(d)(3)(ii)](/cfr/40/141.720.md?p=d-3-ii) are in violation of the treatment technique requirement.
- (d) **Use of two disinfectants.** Unfiltered systems must meet the combined Cryptosporidium inactivation requirements of this section and Giardia lamblia and virus inactivation requirements of [§ 141.72(a)](/cfr/40/141.72.md?p=a) using a minimum of two disinfectants, and each of two disinfectants must separately achieve the total inactivation required for either Cryptosporidium, Giardia lamblia, or viruses.

## Notes

### Source

Source: 71 FR 769, Jan. 5, 2006, unless otherwise noted.

### Authority

Authority: 42 U.S.C. 300f, 300g-1, 300g-2, 300g-3, 300g-4, 300g-5, 300g-6, 300j-4, 300j-9, and 300j-11.

### Source

Source: 40 FR 59570, Dec. 24, 1975, unless otherwise noted.