Stage 01
Intake & Screening
Raw water is drawn from river, lake or reservoir through coarse bar screens that remove large debris — leaves, fish, plastics. A pump house lifts water into the treatment flow.
Bar screens: 10–50mm
Flow rate: 200 m³/h
Submersible pumps
Stage 02
Chemical Dosing
Coagulants (aluminium sulphate or ferric chloride) and pH-correction chemicals (lime) are precisely dosed into the water stream to destabilise suspended particles.
Alum: 10–50 mg/L
pH target: 6.5–7.5
Lime dosing
Stage 03
Flocculation
Slow paddle mixers gently agitate the water, encouraging destabilised particles to collide and form larger aggregates called "floc" that are heavy enough to settle.
Paddle speed: 1–5 RPM
Retention: 20–40 min
Floc size: 1–5 mm
Stage 04
Sedimentation
Water flows slowly through large clarifiers. Heavy floc particles sink to the bottom as sludge, which is collected by scrapers and removed. Clear water overflows at the top.
Retention: 2–4 hours
Surface rate: 1 m/h
Sludge removal
Stage 05
Rapid Sand Filtration
Clarified water passes down through layers of sand and gravel, removing remaining fine particles, microorganisms, and residual floc. Filters are backwashed periodically.
Sand depth: 0.6–1.2 m
Flow: 5–15 m/h
Backwash: every 24h
Stage 06
Chlorination & UV
Filtered water is disinfected by chlorine gas or sodium hypochlorite dosing, plus UV radiation that destroys DNA of resistant pathogens including Cryptosporidium and Giardia.
Cl₂: 0.5–2 mg/L
UV: 40 mJ/cm²
Contact: 30 min
Stage 07
Reservoir & Distribution
Clean drinking water is stored in covered service reservoirs before entering the distribution network of pipes, pumping stations and towers that deliver it to homes and businesses.
Storage: 12–24h supply
Pressure: 2–8 bar
Residual Cl₂: 0.2 mg/L