From Source to Tap
Every glass of safe drinking water passes through a multi-stage treatment process refined over more than a century. Raw water from rivers, lakes, or reservoirs typically contains suspended sediment, dissolved organics, bacteria, viruses, and parasites. The treatment train — coagulation, flocculation, sedimentation, filtration, and disinfection — progressively removes these contaminants to meet strict safety standards. This simulation lets you design each stage and see how turbidity and pathogens are reduced through the process.
Coagulation and Flocculation
Coagulation is the critical first step: adding chemicals (typically aluminum sulfate or ferric chloride) destabilizes colloidal particles so they can clump together. Rapid mixing disperses the coagulant; then gentle flocculation allows particles to aggregate into larger flocs that settle under gravity. The optimal coagulant dose depends on raw water turbidity, pH, temperature, and organic content — too little leaves particles dispersed, too much wastes chemicals and can increase aluminum in finished water.
Filtration
After sedimentation removes large flocs, water passes through granular media filters — typically sand, anthracite, or dual-media beds. Filtration captures remaining flocs and particles through straining, adhesion, and sedimentation within pore spaces. Filter rate is critical: too fast and particles break through; too slow and the plant cannot meet demand. Well-operated rapid sand filters reduce turbidity below 0.3 NTU and contribute 0.5–2 log pathogen removal.
Disinfection
The final barrier against waterborne disease is chemical or physical disinfection. Chlorination remains the most common method, providing both primary disinfection and a residual that protects water in the distribution system. The CT concept (concentration × contact time) quantifies disinfection effectiveness. However, chlorine reacting with organic matter forms disinfection byproducts, driving interest in alternative methods like UV irradiation and ozonation, which leave no residual but produce fewer harmful byproducts.