1. 1 Lake water (raw) Flocculation Flash mix Gentle mix Quiescent condition Sedimentation Precipitation Coagulant

2. Coagulation Flocculation/Sedimentation 2

3. Coagulation Flocculation 3

4. Jar Test 4 Objective: To determine the best coagulant and optimum coagulant dose Reference: ASTM D2035 - 08 Standard Practice for Coagulation-Flocculation Jar Test of Water

5. Jar Test - Procedure 1.Place 2000 mL of raw water in each 2 L nominal size beaker and set them on the jar tester. 2.To simulate flash mixing, begin by initiating mixing for all six beakers at 100 rpm. Then, add a predetermined amount of coagulant solution to each beaker as quickly as possible. Note that if a coagulant aid is added, it should be added separately 3.To simulate tapered flocculation, mix as follows: 7.5 min at a mixing speed of 70 rpm 7.5 min at a mixing speed of 40 rpm 7.5 min at mixing speed of 25 rpm 4.Settle for 20 min and analyze the supernatant 5

6. Advantage of 2-L Square Jars  Better mixing  Mixing curve available  Plexglas®: Better insulating properties  More water for testing – 2 liters  Standard Sampling location (10 cm) used to set settling velocity  Do not use glass beaker due to poor insulation and inability of simulating mixing conditions in the field 6

7. Velocity Gradient vs. Mixing Speed 100010010 100 1000 Velocity Gradient, G, s Rotational Speed of Paddle, rpm 10°C < t  32°C (µ = 1.29 × 10 -3 N·sec/m 2 ) 1°C  t  10°C (µ = 2.57 × 10 -3 N·sec/m 2 ) A p : 1.857 × 10 -3 C D : 1.8 : 1.058 × 10 -3  : 1001.7 V 7

8. Jar Test - Measurements 1.Time: Record the minimum time required to form “pinpoint” floc during flocculation step. 2.Size: At the end of the flocculation step, record the size of the majority floc: 3.Water quality: Measure temp., turbidity, and pH 4.Filtrability: Filter 70 mL of the supernatant through Whatman No. 1 or similar filter paper (1~2 µm pore size) and record the time required to filter 50 mL of the sample. Measure the turbidity of the filtrate. 0.3 0.5 0.75 1.0 1.5 2.25 3.0 4.5 mm A B C D E F G Size Settleable floc 8

9. Jar Test - Optimization 1.Optimization of Coagulant: Alum or ferric chloride with cationic polymers as a coagulant aid 2.Proper Dosage: (1) a wide range of dosages: 2.5, 5, 10, 20, 40, and 80 mg/L of coagulant; (2) a refinement Optimization of Coagulant Aid: The suggested dosages are 0.25, 0.5, 1.2, and 4 mg/L Example Dosage Alum (mg/L)6122061220 + polymer (mg/L)0.250.250.250.50.50.5 9

10. Coagulation - A Multidimensional View 10

11. Coagulation - Data Fitting Jar Test TOC Result 3-D Plot 11

12. Coagulation - Fitting Data Contour plot Best way of determining the optimum condition 12

13. Alum Contour Mapping Turbidity DOC 1.8 2.0 2.1 2.2 2.3 1.9 0.50.6 0.7 0.8 0.9 1.0 1.1 Experimental condition Optimum pH 5.9 & Alum 41 mg/L Optimum pH 5.82 & Alum 47 mg/L Select optimum condition based on the goal of water treatment 13

14. Floc Settling Velocity Measurement Procedure: 1.After the completion of flocculation, collect 10-20 mL samples at 1, 2, 4, 8, and 16 minutes by pipetting or siphoning from a fixed depth of 10 cm from the original water level and measure turbidity. The fixed depth represents settling velocities of 10, 5, 2.5, 1.25, and 0.63 cm/min, respectively. 2.Plot the turbidity of the settled water samples at the designated times divided by velocities and the corresponding settling velocity in the log- probability scale. 14

15. Two-Liter Jar for Bench-Scale Testing Jar test reference: http://www.phippsbird.com/instruct.htmlhttp://www.phippsbird.com/instruct.html 15

16. Example Plot 1 10 0. 5 2 0. 5 0. 5 0. 3 5 % Turbidity remaining Initial turbidity = 500 NTU 100 NTU 10 NTU 1 10 0. 5 0. 3 25 Settling velocity, ft/sec 2 108 215 360 720 1800 2880 Overflow rate, gpd/ft 2 16

17. 17 Flocculation tank in a water treatment plant

18. Gravity Settlement Conventional/traditional Sedimentation tank Flocculation tank 18