Title 22 Chapter 17: Surface Water Treatment — Quick Reference

Minimum Log Removal/Inactivation Requirements

Filtration Credits (Title 22 §64653(b))

The remaining log removal beyond filtration credit must come from disinfection (CT).

Federal vs. California: Under federal rules (40 CFR 141.73), slow sand filtration receives 2-log virus credit, the same as conventional. California Title 22 §64653(b) does not adopt that distinction. It groups slow sand with direct and DE at 1-log virus. If you are studying for a California exam, know the California credits. If you are coming from another state, check whether your state adopted the federal credit or set its own.

Turbidity Performance Standards (Title 22 §64653, Table 64653)

Federal vs. California: The federal SWTR standard for DE filtration is 1.0 NTU at the 95th percentile, the same as slow sand. California adopted a more stringent DE standard of 0.5 NTU in Table 64653. The IESWTR and LT1ESWTR only tightened conventional and direct filtration (from 0.5 to 0.3 NTU). They did not change DE or slow sand standards at the federal level. California tightened DE independently.

Disinfection Requirements

• Entry to distribution: residual of 0.2 mg/L minimum. Cannot drop below 0.2 mg/L for more than 4 hours in any 24-hour period. No exemptions.
• Distribution system: detectable residual in 95% or more of samples each month. HPC of 500 CFU/mL or less counts as equivalent to a detectable residual.
• CT calculations must demonstrate required inactivation using EPA CT tables.

LT2ESWTR Bin Classification

Bins 3 and 4 require at least 1-log of additional treatment from bag filters, bank filtration, cartridge filters, ClO₂, membranes, ozone, or UV.

Filtration Avoidance Criteria (§64652.5)

Systems can avoid filtration only if ALL criteria are met: fecal coliform 20/100 mL or less (or TC 100/100 mL or less) in 90% or more of samples over 6 months, turbidity never exceeds 5 NTU, watershed control program maintained, annual on-site inspection, no waterborne disease outbreaks, E. coli MCL compliance in 11 of last 12 months, and all DBP requirements met. Fail any single criterion and filtration must be installed within 18 months.

What to Watch on the Exam

• Individual filter monitoring is required for systems serving 10,000 or more. Each filter must be continuously monitored, and any individual filter exceeding 1.0 NTU must be reported. A poorly performing filter cannot hide in blended effluent.
• The 0.2 mg/L entry point residual has no exemptions. That's a hard floor the exam tests directly.
• Conventional filtration gets 2.5-log Giardia credit, not 3-log. The remaining 0.5-log must come from disinfection CT. Direct, DE, and slow sand get 2-log, requiring 1-log from CT.
• California's DE turbidity standard (0.5 NTU) is more stringent than the federal standard (1.0 NTU). The exam may test whether you know the California number. Don't default to the federal value.
• Under Title 22, slow sand gets only 1-log virus credit, not the 2-log credit given under federal rules. This is a California-specific implementation that catches operators who studied federal materials.
• New plants must be designed to achieve 0.2 NTU average daily turbidity in combined filter effluent. That's a design goal, not the compliance standard.

Federal Rules Implemented

SWTR, IESWTR, LT1ESWTR, LT2ESWTR, and FBRR.