5-Step Jar Test SOP to Optimize FeCl3 & PAC Coagulant Dosage | Lộc Thiên

• Standardized 5-step SOP: Sample & Stock Solution Preparation → Dosage & Paddle Setup → Rapid Mixing → Slow Mixing → Settling & Measurement.
• Precise determination of optimal pH range: FeCl3 performs best at pH 5.0–8.5, while PAC operates optimally at pH 6.0–8.0.
• Cost-effective ETP operation solution that thoroughly resolves issues of floc breakage or sludge floating in settling tanks.

1. The Role of Jar Test SOP in ETP Operation

In industrial wastewater treatment plant operation, dosing chemicals based on intuition or maintaining old dosage records when wastewater characteristics change (turbidity, COD, pH, flow rate) is the leading cause of budget waste and non-compliant effluent. The Jar Test (a coagulation-flocculation simulation using a multi-position stirrer) is an essential technical "compass."

Implementing the Jar Test SOP helps:

Optimize Chemical Costs (Cost-in-Use)

Identify the coagulation saturation point, avoiding overdosing that causes restabilization and re-turbidity of the water.

Reduce Sludge Volume

Optimal dosing creates dense, compact flocs, reducing sludge moisture content and the cost of hiring hazardous sludge treatment services.

Protect Process Equipment

Prevent pipeline corrosion or metering pump clogging caused by excess chemical scaling.

2. Technical Specifications Table for Standard Coagulants Used in Jar Test

Below are the standard technical specifications for the primary coagulants directly supplied by Lộc Thiên for Jar Test experiments:

3. Standard 5-Step Jar Test SOP for the Lab

1. Step 1: Prepare Wastewater Sample & Stock Solutions

   Collect a representative sample (approx. 10–20 liters) from the equalization tank inlet or reaction tank. Measure initial parameters: pH, turbidity (NTU), COD, TSS, temperature. Prepare a 1.0% stock solution of the coagulant (10g of pure chemical dissolved in 1000ml of distilled water). At this concentration, 1ml of stock solution added to a 1000ml sample corresponds to a dosage of 10 mg/L (ppm).

2. Step 2: Distribute Samples into Jar Test Beakers & Set Dosage Range

   Accurately pour 1000ml of wastewater into each of the 6 glass beakers on the Jar Test apparatus. Set the expected dosage range based on wastewater characteristics (e.g., Beaker 1 = 50 ppm, Beaker 2 = 100 ppm, Beaker 3 = 150 ppm, Beaker 4 = 200 ppm, Beaker 5 = 250 ppm, Beaker 6 = 300 ppm). If the sample pH is outside the working range, adjust it using NaOH 50% or Acid to the optimal range beforehand.

3. Step 3: Rapid Mixing Phase (Coagulation)

   Lower the paddles into the center of the beakers. Set the rapid mixing speed to 150 – 200 rpm (equivalent to G = 300 s⁻¹). Using a pipette, simultaneously add the calculated volume of coagulant stock solution (FeCl3 45% or PAC 30%) to all 6 beakers. Maintain rapid mixing for 60 – 90 seconds to ensure uniform chemical dispersion and neutralization of colloidal particle surface charges.

4. Step 4: Slow Mixing Phase (Flocculation)

   Reduce the mixing speed to 30 – 40 rpm (G = 40 s⁻¹) for a duration of 15 – 20 minutes. If needed, add 1–2 ppm of polymer flocculant (Anionic or Cationic) during the 2nd minute of slow mixing. Observe the formation and growth of flocs (micro-floc size, agglomeration rate).

5. Step 5: Settling Phase & Result Evaluation

   Raise the paddles and allow the beakers to settle undisturbed for 30 minutes. Observe the settling rate (cm/min), the color and clarity of the supernatant, and the volume of accumulated sludge at the bottom. Using a siphon, collect supernatant water from a depth of 2cm below the surface to re-measure: Turbidity (NTU), pH, residual COD, TSS.

4. How to Convert Lab Results to Actual Metering Pump Settings

Formula for converting the optimal lab dosage ($C_{lab}$ mg/L) to the actual chemical pump flow rate ($Q_{chemical}$ Liters/hour) for the ETP plant:

$$Q_{chemical} (L/h) = \frac{Q_{water} (m^3/h) \times C_{lab} (g/m^3)}{C_{stock} (\%) \times 10 \times \rho (kg/L)}$$

Practical Example: Wastewater flow rate $Q_{water} = 50\text{ m}^3\text{/h}$. Optimal Jar Test dosage $C_{lab} = 150\text{ mg/L}$ FeCl3. Using FeCl3 45% solution with specific gravity $\rho = 1.42\text{ kg/L}$.

$$Q_{FeCl3} = \frac{50 \times 150}{45 \times 10 \times 1.42} = \frac{7500}{639} \approx 11.73\text{ Liters/hour}$$

5. FAQ - Frequently Asked Questions about the Jar Test SOP

If your wastewater treatment plant is experiencing chemical dosing failures or needs cost optimization, refer to our article: When your chemical dosing system still fails — 8 operational pain points.