Turbidity lab 7
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The document describes a jar test experiment to determine the optimal coagulant dosage for treating turbid water. Jar tests simulate the coagulation/flocculation process in water treatment plants. In this experiment, different dosages of aluminum sulfate were added to water samples, which were then rapidly and slowly mixed to form and combine floc. Turbidity measurements after settling showed an optimal dosage between 6-8 ml of aluminum sulfate coagulant reduced turbidity the most. The jar test process and results help operators adjust treatment chemicals to changing source water quality.
Turbidity lab 7
- 1. Jordan University of Science and Technology Faculty of Engineering Civil Engineering Department CE 453 “Environmental lab” “Jar Testing of Coagulation-Flocculation Process” Experiment (7) Student Name: Anas Mohammad Maghayreh. Student ID: 20120023117. Section #:1 Submission Date: 5/8/2015. Submitted to: Dr. Hani Abu Qdais
- 2. Abstract: Jar testing is a pilot-scale test of the treatment chemicals used in a particular water plant. It simulates the coagulation/flocculation process in a water treatment plant and helps operators determine if they are using the right amount of treatment chemicals, and, thus, improves the plant’s performance. Introduction: Turbidity is the technical term referring to the cloudiness of a solution and it is a qualitative characteristic which is imparted by solid particles obstructing the transmittance of light through a water sample. Turbidity often indicates the presence of dispersed and suspended solids like clay, organic matter, silt, algae and other microorganisms. The jar test is a method of measuring the effect of coagulation, flocculation, and sedimentation on turbidity. Although the procedure is not outlined in Standard Methods, it is used in most water treatment plants to find the best coagulant dosages under varying conditions. Coagulation/flocculation is the process of binding small particles in the water together into larger, heavier clumps which settle out relatively quickly. The larger particles are known as floc. Properly formed floc will settle out of water quickly in the sedimentation basin, removing the majority of the water's turbidity. In many plants, changing water characteristics require the operator to adjust coagulant dosages at intervals to achieve optimal coagulation. Different dosages of coagulants are tested using a jar test, which mimics the conditions found in the treatment plant. The first step of the jar test involves adding coagulant to the source water and mixing the water rapidly (as it would be mixed in the flash mix chamber) to completely dissolve the coagulant in the water. Then the water is mixed more slowly for a longer time period, mimicking the flocculation basin conditions and allowing the forming floc particles to cluster together. Finally, the mixer is stopped and the floc is allowed to settle out, as it would in the sedimentation basin. The type of source water will have a large impact on how often jar tests are performed. Plants which treat groundwater may have very little turbidity to remove are unlikely to be affected by weather-related changes in water conditions. As a result, groundwater plants may perform jar tests seldom, if at all, although they can have problems with removing the more difficult small suspended particles typically found in groundwater. Surface water plants, in contrast, tend to treat water with a high turbidity which is susceptible to sudden
- 3. changes in water quality. Operators at these plants will perform jar tests frequently, especially after rains, to adjust the coagulant dosage and deal with the changing source water turbidity. :Objective* To become familiar with fundamentals of jar testing used for the evaluating of coagulation and flocculation and determinations of velocity gradient vs. mixture rpm relationship ,optimal coagulant dosage , and optimal PH in coagulation –flocculation process. *Apparatus: 1. Jar testing mixing assembly. 2. Four 1 liter Pyrex beakers. 3. Aluminum sulfate (Alum) Solution. 4. Pipets. 5. Timer. 6. The pH meter. 7. Distilled water turbidity meter calibration. 8. Colorimeter device or any other available turbidity meter. Picture (1):NephelometricTurbidimeter Picture (2):Jar mixer
- 4. *Procedure: 1. test the timer and rpm meter attached to the mixer for smooth functioning 2. Record the temp. , pH , and turbidity of initial water 3. make the sol. (800ml )by adding (2,4,6,8 )ml from Al2(SO4)3 4. fill the baker and put it in its place such that the mixer rotating shafts remain approximately at the center of the beakers 5. Mixing the sol. at rpm meter is 170 rpm until 1 min. (flash mixing to distribute the coagulant homogenously in sol.) 6. mixing the sol. at rpm meter is 80rpm until 20 min ( gentle mixing ) 7. Close the motor and keep the sol. to precipitation the sol. 8. Measure the pH, temperature and recorded it. 9. Compare the turbidity of each baker after coagulation and flocculation process with that of initial water. 10.Find the optimum alum. we must added to the sample :Results and Calculations sample size: )PAU(turbidity: 460initial 8070605040300Concentration(mg/L) 786435186336460Turbidity (FTU) Discussion: Coagulation –flocculation process removes turbidity ,organics, inorganics, color, bacteria, pathogens, and testes of water .in the process. The coagulation step is usually proceeded by the flocculation and floc setting processes for the coagulation. Aluminum sulfate known as dry alum –are widely used coagulants, depending on water PH and alkalinity, the cat ionic part of the coagulant combines with the hydroxide complex of AL(OH)3 And Fe(OH)3 are precipitates which entrap each other .suspended solids ,and colloids from water body and form flocs in the subsequent process of flocculation .the grown flocs settle down by their own weight. Turbidity is linked to the look of water and therefore the public’s perception of water quality. Table (1): Turbidity and concentration DATA
- 5. In drinking water, the higher the turbidity level, the higher the risk that people may develop gastrointestinal diseases. In drinking water turbidity should equal zero. The greater the amount of total suspended solids (TSS) in the water, the murkier it appears and the higher the measured turbidity The major source of turbidity in the open water zone of most lakes is typically phytoplankton. The lower the NTU number the cleaner the water. Turbidity is usually measured using an optical instrument in a laboratory called a Nephelometric Turbidimeter. Conclusion Turbidity is proportional to the concentration of solution. Turbidity is proportional to the absorbency of solution. Colloidal particles causes turbidity because of their specific gravity is lower than specific gravity of the solution and because their negative charge. Releasing turbidity can by be coagulation and fluctuation process. Colloidal particles cause sun light regression which affect marine life. Turbidity can be indicate from the amount of light absorbency and transmitted. Temperature variation affects the coagulation-flocculation process. At higher temperature, some coagulants were found to be more effective in the removal of water turbidity. References: *Sanitary LAB. Manual (Experimental Water Quality Engineering) *The LAB Lecture note. Appendix: