About Practical Notes Lab
Practical Notes Lab is a collection of free, practical calculators and reference tools for water and wastewater treatment. It is built for the people who do the day-to-day math of the industry: treatment plant operators, process engineers, consultants, and students learning the field.
The mission is simple: make everyday engineering calculations fast, transparent, and reliable, and keep the core tools free for everyone. Every calculator shows its formula and units so you can see exactly what it is doing — no black boxes.
Who runs this site
This site is run by Benjamin, who holds a Ph.D. in Environmental Science and Engineering and works in the water/environment field, with a background in drinking water and wastewater practice.
The tools on this site grew out of that daily practice: the same calculations consultants and operators run again and again, packaged so anyone can use them without a spreadsheet.
What the site offers
- Process calculators — SRT/MCRT, F/M ratio, SVI, detention time, BOD/COD removal, oxygen demand, and more.
- Hydraulics calculators — Hazen-Williams and Manning equations for pipe and channel flow.
- Unit converters — concentration, hardness, flow, pressure, volume, mass loading, and temperature.
- Drinking Water Compliance Center — a side-by-side reference of 40 CFR Part 141 standards, the DoD OEBGD, and DoD/Navy PFAS policy — plus custom comparison against state, FGS, or client standards, with the strictest value marked, sources cited, and last-verified dates shown.
A note on scope
These tools are practical aids for study, field checks, and preliminary work — they are not a substitute for engineering design, regulatory review, or professional judgment. Where it matters, verify results against current regulations and applicable standards. See the Terms & Disclaimer for details.