Coagulation and Flocculation Essay Example for Free

clotting and Flocculation Essay1.0 IntroductionIn this lab, we atomic number 18 conducting two experiments on natural show up water. The first experiment is to conduct jar tests to estimate an optimum pane of iron salt to recede suspended solids. The seconds experiment is to observe the rate of floc formation nad sedimentation.2.0 BackgroundCoagulation and FlocculationCoagulation and flocculation are important part in water and wastewater treatment. Coagulation is the destabilization of particulate question by physical or chemical processes. Flocculation is the formation of larger particles that will settle out of the solution. They are usually the first form of treatment of water and wastewater to remove suspended matter or color.Jar tests are used as a control test for plant operations. Aluminum or iron salts can be used to for coagulation of particles and to form flocs that can settle out. Coagulation and flocculation tests set up the optimum dosages to remove turbidit y and color, along with secondary effects such as adjusting pH. Jar tests likewise provide information on the amount of energy needed to provide the coagulation and flocculation treatments, as swell as settleability of the flocs, and clarity of the water. They can also be used to study basic processes, for instance, kinetics of reactions and removal of constituents.3.0 ProcedureDetermination of Optimum Coagulant DosageTo determine the optimum coagulation dosage, a serial publication of jar tests were conducted. First, 400 mL of clay and sodium bicarbonate amended DI water was measured and poured into a 500 mL Erlenmeyer flask using a graduated cylinder. The initial pH of that sample was past measured and recorded. The predetermined dose of coagulator was poured into a 100mL graduated cylinder and DI water was added to reach a total solution volume of 100 mL. A stir bar was added to the Erlenmeyer flask along with the coagulator dose. The flask was then placed on a magnetic stir plate was rapidly tangled for one minute.After a minute of rapid mixing, the fastness was reduced to low and the solution underwent subdued mixing for ten transactions. The flask was then removed from the magnetic plate and was allowed to settle. Samples were extracted from the top of the flask later on five, ten, and fifteen minutes had elapsed using a 10 mL sampling syringe. Special safekeeping was taken to not disturb the sediment while sampling. The sample was transferred from the syringe to a vile, shaken, and placed in a Turbidimeter to determine the turbidity.The turbidity was recorded and the vile was emptied and rinsed between each sample. After fifteen minutes had elapsed and the last turbidity reading had been recorded, the pH of the sample was measured and recorded. The sample was then dumped into a specified waste container, the flask was rinsed with tap water and DI water, and the entire experiment was repeated using a new specified coagulant dose.4.0 Results and DiscussionAfter plotting turbidity against dosage from our results, we found that the optimum dosage of coagulant to be 1000 mg/L Fe2O3 as shown in Figure 1. Also, longer subsidence times produced lower levels of turbidity, with 15 minutes being most successful. Optimum pH for a coagulant is determined empirically from laboratory testing by keeping dosage constant and testing a pH range for optimal coagulation. Generally after adding Fe2O3, final pH decreased. Although we did not perform this in the lab, our samples had best success with a pH around 6.5 as seen in Table 1.Mixing speed is also important in coagulation and flocculation. Initially flash mixing is used, where high mixing speeds broadcast the coagulant stock-stillly throughout the container. Later, slower mixing speeds are used to promote particle collisions, which conduce to larger floc formations. The lab is performed this way because higher speeds will help disperse the coagulant only when will break up the floc s that form. By reducing the speed to slow after one minute, it allows for an even dispersion but also the formation of flocs.