KNS 3621 Civil Engineering Laboratory 6 Faculty of Engineering Universiti Malaysia Sarawak ________________________________________________________________________TITLE: W5- Coagulation & Flocculation THEORY: Coagulation and flocculation using jar testing is a method of creating a complete water treatment process. Some solid portion in water surface cannot settle by itself thus coagulant is needed in the test to make it removed by the process of coagulation followed by flocculation and then sedimentation. In the process, small particles bind together in the water into larger and heavier compact mass which settle out relatively quickly. The larger particles are known as flocs. The floc will settle down from water surface quickly in the beaker in order to remove the majority of turbidity of water (Mountain Empire Community College, 2000). Turbidity is an opaque and cloudy appearance of water caused by small particles suspended therein. Water with slight or no turbidity is clear and vice versa. The maximum allowable level of turbidity in water is 0.5 NTU and the recommended level is about 0.1 NTU (Nephelometric Turbidity Units) (Mountain Empire Community College, 2000). Figure 1: Turbid wastewater sample in lab W5 Floc can be defined as the end product of a well-regulated coagulation or flocculation process in water which the majority of the turbidity has been 1 period of reaction and energy supplied from the stirrer device. then settle out in the sedimentation basin. n. 2000). It includes the adjustment of amount of treatment chemicals which added to samples of water in the beaker.1 to 3 mm. development and settlement of floc can be watched by eyesight in the full-scale treatment plant (Coagulation and Flocculation. 2 . A series of tests perform to compare the effects of different amounts of flocculation agents at different pH values to determine the right size of flocs (based on appendix C of KNS 3621 Lab Manual) for particular water in the beaker. Figure 2: Floc formed of sample of lab W5 Many factors affecting the results of the test such as coagulant dose which is alum. However.).d. floc which is too small also may not settle too (Mountain Empire Community College. the pH.KNS 3621 Civil Engineering Laboratory 6 Faculty of Engineering Universiti Malaysia Sarawak ________________________________________________________________________ collected and formed into floc. The best floc size is 0. The right size of floc depends upon the system’s filter dimensions and other considerations. Larger floc may does not settle and is easy to breakup in the flocculation basin. The sample stirred in order to produce the formation. The chemistry of coagulation and flocculation is first and foremost based on electricity. the behavior of negative and positively charged particles due to their attraction and repulsion. 3 . 2000). the mixer is stopped and the floc is allowed to settle out. The flocculation will take place. It is a process of gentle mixing to bring the fine particles which formed by coagulation into contact with each other therefore form floc (Mountain Empire Community College. Different dosages of coagulants are tested using a jar test. which removes solid particles in the treatment plant or water sample.vccs. as it would in the sedimentation beaker. Finally.htm) During coagulation. Then the water is mixed more slowly for a longer time period. i. constituting an imitation of the flocculation basin conditions and allowing the forming floc particles to cluster together.KNS 3621 Civil Engineering Laboratory 6 Faculty of Engineering Universiti Malaysia Sarawak ________________________________________________________________________ INTRODUCTION: Coagulation and flocculation can be done for treatment plant.me. like charges repel each other while opposite charges attract each other. Figure 3: Steps of coagulation and flocculation processes (Source: http://water.e. the coagulant neutralized the electrical charges of the particles in the water to allow the particles to come closer to each other and lastly form large clumps. It is a step by step process which involves the adding of coagulant to the water sample and mixing the water to completely dissolve the coagulant in the water.edu/courses/env110/lesson4. the particles no longer repel each other. hence they will neutralize the turbidity particles to prevent those particles from repelling each other. When there are enough particles joined together.htm) 4 .edu/courses/env110/lesson4_2. As a result. If the zeta potential is large.me. Also. In addition. 2000). Then. After that. which is a measurement of the magnitude of electrical charge surrounding the colloidal particles. then more coagulants will be needed (Mountain Empire Community College. 2000). van der Waal’s force is taking place to attract the particles which without or lack of charges weakly together in nature.vccs. coagulants tend to be positively charged so that they are attracted to the negative particles in the water.KNS 3621 Civil Engineering Laboratory 6 Faculty of Engineering Universiti Malaysia Sarawak ________________________________________________________________________ As all knows. Figure 4: Attraction of positive and negative charges Figure 5: Floc formed (Source: http://water. most particles dissolved in water have a negative charge so they tend to repel each other. the combination of positive and negative charge results in neutral charge or can be said as lack of charge. the amount of coagulant which should be added to the water will depend on the zeta potential. due to most coagulant will neutralize the negative charges on the particles. they form floc and will settle out of the water (Mountain Empire Community College. Consequently. especially with coagulants. OBJECTIVE: To determine the optimum dose of coagulant using jar test method with adding different dosage of alum solution to six samples of beaker from A to F. coagulation and flocculation is beneficial in other ways. One of the easiest things an operator can do for optimization of the plant is jar testing. 2000). Another important reason to perform jar testing is to save money. This may not hurt the quality of water. in contrast. Operators at these plants will perform jar tests frequently. How often the jar tests are performing depends on the type of source water. tend to treat water with a high turbidity which is susceptible to sudden changes in water quality. Jar test may perform to remove small suspended particles typically found in groundwater. but it can cost a lot of money. and jar testing is a must when looking at best available technologies (Zane Satterfield. to adjust the coagulant dosage and deal with the changing source water turbidity (Mountain Empire Community College.KNS 3621 Civil Engineering Laboratory 6 Faculty of Engineering Universiti Malaysia Sarawak ________________________________________________________________________ Moreover. 2000). 2005). this test is probably the most useful laboratory test too. In addition to remove turbidity from the water. One of the common problems in water treatment is overfeeding or overdosing. 5 . especially after rains. Surface water plants. The process removes many bacteria which are suspended in the water and can be used to remove color from the water (Mountain Empire Community College. 3) Then. 6 .KNS 3621 Civil Engineering Laboratory 6 Faculty of Engineering Universiti Malaysia Sarawak ________________________________________________________________________ APPARATUS: a) Jar tester apparatus b) Burette c) Beakers d) Pipette e) Analytical balance f) Magnetic stirrer g) PH meter h) Turbidimeter i) j) Distilled water Alum stock solutions k) Sulfuric acid l) Natrium hydroxide PROCEDURE: 1) Alum stock solution was prepared by dissolving 2. 2) Each of 6 one liter beakers was marked as A to F.5 g aluminium sulphate (Al(SO4)3) into 1000 ml of distilled water.0 ppm when added to 500 ml of water sample. Each 1. 4) The initial pH and turbidity of the water sample was measured by using pH meter and turbidimeter.0 ml of this solution is equal to 5. each beakers was filled with 500 ml of wastewater sample that provided by assistant. 7) pH of each beaker was checked and either H2SO4 or NaOH was titrated slowly to each beaker so that the pH was fixed to 6.05. This is to ensure the dispersion of the coagulant throughout the sample.5±0.KNS 3621 Civil Engineering Laboratory 6 Faculty of Engineering Universiti Malaysia Sarawak ________________________________________________________________________ Figure 6: pH meter Figure 7: Turbidimeter 5) Each beaker was put on a magnetic stirrer and alum solution was added according to the dosage below: Beaker Dosage (ppm) Volume (ml) A 0 0 B 50 10 C 75 15 D 100 20 E 125 25 F 150 30 6) Two different burettes were filled in with sulfuric acid (H2SO4) and natrium hydroxide (NaOH) respectively for pH correction purpose. 7 . Figure 8: Titration to adjust pH value 8) The beakers were placed in the jar tester and the stirrers all were started on a fast speed of 100 rpm for 1 minute. Figure 9: Jar tester 10) The size and appearance of the floc formed were noted by referring Appendix C. Figure 10: Settle of floc 12) pH and turbidity of the supernatant (the clear liquid above the solids) of each beaker was determined.KNS 3621 Civil Engineering Laboratory 6 Faculty of Engineering Universiti Malaysia Sarawak ________________________________________________________________________ 9) The stirrer speed was reduced to 60 rpm to allow flocculation to take place. Figure 11: Taking upper layer of clear water sample 13) Graph of turbidity versus coagulant dosage was plotted. 11) The stirring was stop after 10 minutes and the floc was allowed to settle for 30 minutes. 8 . 20 6.80 6.98 D 2 E 125 25 7.97 D 3 D 100 20 6.24 6.90 : 21 NTU Table 1: Parameters of Wastewater sample tested Beaker Parameter A Alum dosage (ppm) Alum volume (ml) Initial Ph Adjusted Ph Final Ph Floc size Turbidity (NTU) 0 0 6.70 6.57 A 13 B 50 10 6.05 E 1 F 150 30 7.20 E 9 C 75 15 7.97 D 1 Turbidity versus Alum Dosage 14 12 Turbidity (NTU) 10 8 6 4 2 0 0 25 50 75 Alum Dosage (ppm) 100 125 150 Figure 12: Graph of Turbidity vs.94 6. Alum Dosage 9 .49 3.52 3.53 4.52 4.46 6.KNS 3621 Civil Engineering Laboratory 6 Faculty of Engineering Universiti Malaysia Sarawak ________________________________________________________________________ RESULT: Water sample pH Water sample turbidity : 6.47 5.54 3. the nature of the complexes formed may be controlled by the pH of the system. Besides that. will hydrolyze rapidly forming a series of metal hydrolysis species. aluminium chlorohydrate. Since 1. For instance. For example of Beaker B: Alum dosage (ppm) / 5 = 50/5 = 10 ml The same calculation was continued for other beakers.0 ppm. and polyaluminium chloride with organic polymers while iron coagulants are ferric chloride sulphate.0 ml = 5. polyaluminium silicate chloride. The aluminium coagulants are aluminium sulphate. The 10 . Al and Fe. ferric chloride sulphate. polyaluminium sulphate chloride. sodium aluminate. aluminium chloride. when metal coagulants are added to water.e.KNS 3621 Civil Engineering Laboratory 6 Faculty of Engineering Universiti Malaysia Sarawak ________________________________________________________________________ Calculation: To convert dosage of alum from the unit of ppm into ml. polyferric sulphate and ferric salts with organic polymers. the metal ions. Also. Aluminum and iron coagulants can be effectively used as they are able to form multi-charged polynuclear complexes with better adsorption characteristics. i. polyaluminium chloride. DISCUSSIONS: 1) What are other chemical or material that can be used as coagulant replacing alum? Alum can be replaced by aluminium coagulants and iron coagulants. there are some other chemicals can used as coagulants such as hydrated lime and magnesium carbonate. the value of turbidity is the highest. And if the added dose of alum is more than 150 ppm. Turbidity versus Alum Dosage 14 12 10 8 6 4 2 0 0 25 50 75 100 125 150 Alum Dosage (ppm) Turbidity (NTU) Figure 12: Graph of Turbidity vs. Therefore. If the added dose of alum is lesser than 125 ppm. and the coagulant dosage determine which hydrolysis species is effective for wastewater treatment (IWA Water Wiki. 2) What are the optimum doses of alum for this experiment? From the graph of Turbidity against coagulant dosage. when no dose of alum is added into beaker A. the graph line has shown it curves downward and the lowest point of curve is where the water is the most clean by adding 130 ppm dosage of alum solution into the sample.KNS 3621 Civil Engineering Laboratory 6 Faculty of Engineering Universiti Malaysia Sarawak ________________________________________________________________________ efficiency of rapid mixing. 3) Comment on your result. the value of turbidity will increase. n.d. Alum Dosage From the plotted graph of Turbidity against coagulant dosage. 11 . the optimum dose of alum for this experiment is 130 ppm which means the water is the cleanest at the point. the pH. 1 NTU of value of turbidity at the points of 125 ppm and 150 ppm is showing the optimum dose of alum is in the range of them.). the value of turbidity also will increase. The pH also must be adjusted to in the range 6. Degree of agitation is also an important factor in coagulation and flocculation. it will settle quickly when the sample is left undisturbed.5 mm as no alum added in to form floc. temperature. there is living organism which is small shrimp in 3 beakers that disturbing the floc which already settled at bottom of beaker. D and F have similar size of floc which is 1.5±0. There are several factors that need to be considered in coagulation and flocculation process such as turbidity. The obtained result is inaccurate as the graph is not perfect curve. If the speed is too slow. Samples in beaker C. 2007). Coagulant serves its purpose to form floc from dirt in water sample and make floc size become larger.25 mm. then “short-circuiting” may occur or 12 .3-0. Therefore. If the speed of the stirring process is too fast. Thus. cationic and anionic composition and concentration. The original sample is not shaken well before pour into beakers. adjusted pH for each beaker has to be consistent so that the result is comparable. As the floc is formed. rate of chemical reaction in the sample increases and the coagulation becomes more effective.0-1.5mm while samples in beaker B and E also have similar size of floc which is1. duration and degree of agitation during coagulation and flocculation.5-2. pH. Water temperature can affect rate of chemical reaction when the sample is added in with alum. 2000).05 so that the reaction of alum and water sample can be at optimum potential. dosage and nature of the coagulant (cvcamp. 4) Discuss other factors that need to be considered in coagulation and flocculation processes. suspended solids. certain beaker has more turbidity compared to others. tougher and denser along the time. Besides that. the floc particles will be “sheared” or broken apart causing an increase in turbidity (Mountain Empire Community College.KNS 3621 Civil Engineering Laboratory 6 Faculty of Engineering Universiti Malaysia Sarawak ________________________________________________________________________ Comparing floc size among 6 beakers. Higher the water temperature. sample in beaker A has smallest size which is 0. Lower the water temperature will lower down the rate of chemical reaction as the reaction has less energy to take place. alkalinity in water is also an important factor in coagulation process.5 parts alkalinity added in water for proper coagulation (Mountain Empire Community College. formation of flocs is in better structure and stable at low pH too. zeta potential of particles in water also affects the effective of coagulation and flocculation process. probably mixing becomes improper as coagulant is not fully mixed with water. low pH in between 4. Proper mixing and detention times are very important (Mountain Empire Community College. If detention time is too long. 2000). At optimum speed. coagulant fully spreads in the water and flocs are formed by coagulant and its size gets larger slowly until suspended solid in water fully forms into flocs. The higher the charge will be causing stronger repulsion between the turbidity particles and less effective in the coagulation process. 13 . for the water with color. Moreover. an effective coagulation would be perfect in reducing the zeta potential charge to almost zero. Zeta potential is the charge at the margin of the colloidal turbidity particle and the water surrounding the particles (Mountain Empire Community College. it causes the processes taken too long time and is ineffective. carbonates. water pH is also needed to be considered. Besides. Normally. Besides that. 2000). Moreover. Alkalinity could be found naturally or has to be added in alkaline chemical such as hydroxides. Higher coagulant dose would be needed for higher zeta potential in water. Alkalinity is necessary to be present in water to provide anions such as (OH) for forming insoluble compounds to separate them out from dissolved in water. 2000). On the other hand. If detention time is too short. removal or reduction of zeta potential is necessary to increase effectiveness of coagulation. Usually the ratio would be 1 part alum to 0. or bicarbonates. Effectiveness of a coagulant is relatively pH sensitive. It causes not all of solid in water form into flocs. time plays important role in the processes as well.4-6 will be better condition for coagulating with alum.KNS 3621 Civil Engineering Laboratory 6 Faculty of Engineering Universiti Malaysia Sarawak ________________________________________________________________________ flocculation process will be shortened incompletely. Besides. Thus. From obtained result. 2. 3. 4. The size of all 6 beakers should be made sure that is same in dimension. the optimum dose of alum coagulant for the sample is 130 ppm or 26 ml where it results in lowest turbidity in water. All beakers must be made sure that are not shaken to avoid inaccuracy or disturbance in taking readings of final pH and final turbidity of sample 14 . Sulphuric acid must be made sure that is titrating slowly into each beaker to get the pH in the range 6. pH and other factors.5±0. 5. After flocculation process is done. 6. The turbidimeter must be made sure that is washed with distilled water before use to avoid disturbance in reading. The pH meter is needed to clean with distilled water before and after test the pH of each sample.KNS 3621 Civil Engineering Laboratory 6 Faculty of Engineering Universiti Malaysia Sarawak ________________________________________________________________________ CONCLUSIONS: The optimum dose used is depending on the type of sources water as it varies in turbidity. RECOMMENDATION: 1. the magnetic stirrer must be taken out gently and carefully so that to reduce disturbance to floc formed and settled in the beaker.05. All the apparatus especially beakers are needed to be washed with distilled water to make sure that no solid stuck on apparatus which would affect the result. Jar test.pdf cvcamp (2007.vccs.htm 15 . Retrieved 12 February 2011 from http://water.ce.edu/courses/env110/Lesson4_print. Water Treatment .). Lesson 4: Coagulation and flocculation.edu/1112/notes/water_treatment/water_treatment_p art_2_coagulation.vccs.me. Coagulation and Flocculation in Water and Wastewater Treatment: The coagulants. Retrieved 12 February 2011 from http://water. January 1). Retrieved 12 February 2011.KNS 3621 Civil Engineering Laboratory 6 Faculty of Engineering Universiti Malaysia Sarawak ________________________________________________________________________ REFERENCES: Coagulation and Flocculation (n. Mountain Empire Community College (2000).htm Mountain Empire Community College (2000). Department of Civil Engineering. Retrieved 13 February 2011 from http://www.htm Mountain Empire Community College (2000).vccs. Lesson 4: Coagulation and flocculation: Part 2: Chemistry.me. Retrieved February 13.me.). Lesson 4: Coagulation and flocculation.edu/courses/ENV115/coagulation.pdf IWA Water Wiki (n.memphis. Lab experiment: Jar test.Coagulation.htm Mountain Empire Community College (2000). from Water Treatment: http://www.iwawaterwiki.d.edu/courses/env110/lesson4_2.me.vccs.nl/fileadmin/ocw/courses/DrinkingWaterTreatment1/res00 080/embedded/!436f6167756c6174696f6e20616e6420666c6f6363756c617 4696f6e202d206a61722074657374. from http://ocw. Retrieved 12 February 2011 from http://water. 2011. UNIMAS.org/xwiki/bin/view/Articles/CoagulationandFlocc ulationinWaterandWastewaterTreatment KNS 3621 Lab Manual (2011).edu/courses/env110/lesson4.d.tudelft. Retrieved 12 February 2011 from http://water. Jar testing. E.nesc. Retrieved 12 February 2011. 5(1). (2005).KNS 3621 Civil Engineering Laboratory 6 Faculty of Engineering Universiti Malaysia Sarawak ________________________________________________________________________ Zane Satterfield. The National Environmental Services Center. from http://www.wvu.pdf 16 .edu/ndwc/articles/ot/SP05/TB_jartest. P.