Jar Test Procedure: Optimizing Coagulant and Flocculant Dosage

Equipment Needed

• 6-paddle jar test apparatus (gang stirrer)
• 6 × 1L or 2L square beakers
• Graduated cylinders, pipettes
• pH meter, turbidity meter
• Timer
• 0.1% PAM solution (dissolve 1g in 1L, stir 60 min)
• Coagulant stock solutions (1% PAC, 1% PFS)

Procedure

Phase 1: Coagulant Dose Optimization

1. Fill 6 beakers with 1L of raw wastewater
2. Record initial pH, turbidity, TSS, color
3. Add PAC at 6 different doses: 20, 40, 60, 80, 100, 120 ppm
4. Flash mix: 200 rpm for 1 minute
5. Slow mix: 40 rpm for 15 minutes
6. Settle: Turn off stirrers, settle 30 minutes
7. Sample from 2 cm below surface — measure turbidity, pH, color

Phase 2: pH Optimization

1. Use the optimal PAC dose from Phase 1
2. Fill 6 beakers, adjust pH to: 5.5, 6.0, 6.5, 7.0, 7.5, 8.0
3. Add PAC → flash mix → slow mix → settle → measure
4. The pH with lowest turbidity is optimal

Phase 3: Flocculant (PAM) Optimization

1. Use optimal PAC dose + optimal pH
2. Fill 6 beakers
3. Add PAC → flash mix 1 min
4. Add anionic PAM at: 0, 0.5, 1.0, 1.5, 2.0, 3.0 ppm
5. Slow mix 15 min → settle 30 min → measure

Data Recording Sheet

Beaker	Coagulant (ppm)	PAM (ppm)	pH	Turbidity (NTU)	Settling Rate	Floc Size	Notes
1	20	0
2	40	0
...	...	...

Common Mistakes

1. Using tap water to make PAM solution — use deionized water to avoid premature reaction
2. Adding PAM during flash mix — PAM should be added AFTER coagulation, during slow mix
3. Not waiting full 60 min for PAM dissolution — undissolved PAM gives poor results
4. Sampling too soon — wait full 30 min settling before sampling
5. Not testing pH effect — pH is often more important than dose