WPI — BC / AB / SK / MB

Class I Water Treatment
Formula Sheet

CT values, chlorine dosage, flow rate, turbidity, chemical dosing, sedimentation, and pumping — aligned with WPI Need-to-Know Criteria.

🦠 CT Values & Disinfection

6 formulas
CT Value
CT = C × T
Units: mg·min/L
▾
CT Required vs. CT Achieved
CT_achieved ≥ CT_required
▾
Log Inactivation
Log inactivation = log₁₀(N₀ / N)
▾
Baffling Factor (BF)
T₁₀ = BF × HRT
▾
Chlorine Demand
Cl₂ Demand = Cl₂ Applied − Cl₂ Residual
Units: mg/L
▾
Breakpoint Chlorination
Breakpoint dose ≈ 7.6 × NH₃-N concentration
Units: mg/L Cl₂
▾

📋 WPI Class I Quick Reference

Turbidity target
≤ 0.3 NTU (95% of samples)
Free Cl₂ residual
0.2–4.0 mg/L at entry
Giardia inactivation
3-log (99.9%)
Virus inactivation
4-log (99.99%)
Fluoride target
0.7 mg/L (Health Canada)
pH range (drinking water)
7.0–8.5
Alum optimal pH
6.5–7.5
Rapid mix G value
300–1,000 s⁻¹
Flocculation G value
10–100 s⁻¹
Typical SOR
20–40 m/d
Rapid sand filter rate
5–15 m/h
Backwash rate
30–60 m/h