40 CFR § 141.711 - Filtered system additional treatment requirements.
---
identifier: "/us/cfr/t40/s141.711"
source: "ecfr"
legal_status: "authoritative_unofficial"
title: "40 CFR § 141.711 - Filtered system additional treatment requirements."
title_number: 40
title_name: "Protection of Environment"
section_number: "141.711"
section_name: "Filtered system additional treatment requirements."
chapter_name: "ENVIRONMENTAL PROTECTION AGENCY"
subchapter_number: "D"
subchapter_name: "WATER PROGRAMS"
part_number: "141"
part_name: "NATIONAL PRIMARY DRINKING WATER REGULATIONS"
positive_law: false
currency: "2026-04-05"
last_updated: "2026-04-05"
format_version: "1.1.0"
generator: "[email protected]"
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."
regulatory_source: "40 FR 59570, Dec. 24, 1975, unless otherwise noted."
cfr_part: "141"
---
# 141.711 Filtered system additional treatment requirements.
(a) Filtered systems must provide the level of additional treatment for *Cryptosporidium* specified in this paragraph based on their bin classification as determined under § 141.710 and according to the schedule in § 141.713.
| | | | | |
| --- | --- | --- | --- | --- |
| Bin 1 | No additional treatment | No additional treatment | No additional treatment | No additional treatment. |
| Bin 2 | 1-log treatment | 1.5-log treatment | 1-log treatment | () |
| Bin 3 | 2-log treatment | 2.5-log treatment | 2-log treatment | () |
| Bin 4 | 2.5-log treatment | 3-log treatment | 2.5-log treatment | () |
| As determined by the State such that the total removal and inactivation is at least 4.0-log. | | | | |
| As determined by the State such that the total removal and inactivation is at least 5.0-log. | | | | |
| As determined by the State such that the total removal and inactivation is at least 5.5-log. | | | | |
(b)(1) Filtered systems must use one or more of the treatment and management options listed in § 141.715, termed the microbial toolbox, to comply with the additional *Cryptosporidium* treatment required in paragraph (a) of this section.
(2) Systems classified in Bin 3 and Bin 4 must achieve at least 1-log of the additional *Cryptosporidium* treatment required under paragraph (a) of this section using either one or a combination of the following: bag filters, bank filtration, cartridge filters, chlorine dioxide, membranes, ozone, or UV, as described in §§ 141.716 through 141.720.
(c) Failure by a system in any month to achieve treatment credit by meeting criteria in §§ 141.716 through 141.720 for microbial toolbox options that is at least equal to the level of treatment required in paragraph (a) of this section is a violation of the treatment technique requirement.
(d) If the State determines during a sanitary survey or an equivalent source water assessment that after a system completed the monitoring conducted under § 141.701(a) or § 141.701(b), significant changes occurred in the system's watershed that could lead to increased contamination of the source water by *Cryptosporidium,* the system must take actions specified by the State to address the contamination. These actions may include additional source water monitoring and/or implementing microbial toolbox options listed in § 141.715.