Mar 15, 2026
PFAS in Drinking Water: What's Happening, What Works, and What's Coming
Current EPA MCLs, California requirements, and the treatment technologies that actually remove PFAS.
Read the noteA working operator's notebook.
I'm Jason Wiltsey, a California T-5 drinking water treatment operator. I keep two kinds of notes here: free study help for the T-5 exam, and the things I'm learning and building along the way.
Written by one operator. Sources cited. Views are my own and don't represent my employer.
Who's writing
Jason Wiltsey
T-5 Water Treatment Operator, California. T-5 certified (2026). Nine years in water treatment. I also design high-performance HMI displays, the grey-screen kind. About me
Study for the T-5
Free study guides for the California T-5 exam. I built them while I was preparing for it, and I passed in 2026. Each guide covers one rule the exam tests, from the Surface Water Treatment Rule to the Title 22 chapters, and the study pack bundles all the quick-reference cards into one PDF.
Federal rule
Surface Water Treatment Rule
The most heavily tested rule on the T-5 exam. Filtration, disinfection CT, log removal, and turbidity.
Read the guideFederal ruleRevised Total Coliform Rule
The E. coli MCL, total coliform treatment technique triggers, and Level 1 and Level 2 assessments.
Read the guideFederal ruleStage 1 DBPR
TTHM and HAA5 MCLs, maximum residual disinfectant levels, and the balance between disinfection and byproducts.
Read the guidePDFT-5 Regulatory Study Pack
All the quick-reference cards in one PDF.
Download the PDFWhat I'm still figuring out
The things I'm trying to learn, the things that keep my attention, and the things I'm building. Some of it is treatment technology, like PFAS and membranes. Some of it is software. I cite my sources, and if I haven't run a process myself, I say so.
Notes
Mar 19, 2026
Activated Carbon for PFAS Removal: GAC Selection, Design & Performance Guide
Carbon selection, EBCT design, bed life, and breakthrough planning for PFAS removal.
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Apr 1, 2026
Ion Exchange for PFAS Removal: How IX Works and When to Use It
How ion exchange removes PFAS, when to choose IX over GAC, and what pre-treatment the resins demand.
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Mar 22, 2026
Membrane Filtration Explained: MF vs UF vs NF vs RO
Pore sizes, rejection rates, and costs compared across the four membrane classes.
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Mar 24, 2026
Digital Twin Software for Water Treatment (2026)
What digital twins actually are, where utilities are using them, and what an operator should do with that.
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Mar 24, 2026
AI in Water Treatment: Where Utilities Actually Stand and How to Get Started
What real utilities are doing with AI today, and a practical way to start.
Read the noteProjects
Drinking Water Treatment Corpus
An open knowledge base for drinking water treatment that you can check, not just read. Every regulatory quote is verified against its source on a schedule, and the plain-English notes beside it carry a named, credentialed reviewer. When a rule changes, the affected pages flip to review on their own. The design is written up as open RFCs, and the first pages, on the disinfection byproduct rules, are in progress.
View on GitHubRekindle
AI assistants forget everything between sessions. Rekindle is a small open-source tool that gives them a way to pick up where they left off: who they're working with, what was decided, and what they might be missing. It runs locally on SQLite, with no API keys.
View on GitHubLong-form guides
Membrane Filtration
MF, UF, NF, and RO: process, applications, maintenance, and performance.
Open guideOzone Disinfection
Ozone chemistry, advanced oxidation, system design, and operational guidance.
Open guideBiologically Activated Carbon
BAC theory, system configuration, performance, and operation.
Open guideDocument library
Reference documents
Regulations, technical papers, and plant references, searchable on this site.
Open the libraryWrite to me.
If you're studying for the T-5, or you spot something I got wrong, I'd like to hear from you.