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Flocculator Setup
The experimental setup, including equipment, chemicals, and computer software, remained nearly identical to what has been used in past semesters. The main features of the flocculator setup include one 11 gallon bucket containing an alum concentration of 1.5 g/L (originally at 3g/L, but was diluted because flow rates were too low) and another 11 gallon bucket containing a kaolin clay-water mixture of 750 NTU, or roughly 2.02 g/L of clay per liter of water. The alum stock bucket was connected to a Masterflex L/S peristaltic pump manufactured by Cole-Parmer Instrument Company by a size 13 flexible rubber tube, whereas the clay stock bucket was connected to a peristaltic pump by a size 14 flexible rubber tube. Raw water from a temperature controlled constant head tank connects to a peristaltic pump with two pump heads by two size 17 flexible rubber tubes. All three pump rates are controlled independently based on the experiment and controlled by the computer program Process Controller. The clay solution and raw water streams are joined and the two mix before entering the influent turbidimeter. One MicroTol 2 Turbidimeter manufactured by HF Scientific, Inc. is connected to the tube leading into and one out of the tube flocculator. The alum solution connects with the rest of the influent solution after the influent turbidimeter, as alum should not be figured into the influent turbidimeter reading, as it is added for the purpose of cleaning the water. A short length of tubing coiled with a 3 inch diameter and a tubing size of a ¼ inch inner diameter - smaller than the flocculator tubing - is placed in between the influent turbidimeter and the start of the tube flocculator, acting as a rapid mix unit. After rapid mix, the solution flows through a clear plastic tube of 6mm inner diameter of varying length (depending on the specifications of a particular experimental run) wrapped around a large, hollow plastic cylinder. This part is the tube flocculator, where particles will have a chance to react with the alum to form flocs. After flocculation, the flocs will flow through the effluent turbidimeter, which consists of a long, clear plastic tube placed through the center of the turbidimeter sensor in order to allow better flow of flocculated material through the sensor and to facilitate clarification once the flow is stopped. The effluent turbidimeter also provides visual confirmation that flocs have formed and settle out at differing rates depending on the size of the floc.
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Regular maintenance and cleaning of the apparatus was critical in ensuring accurate data collection. The regular cleaning of the influent turbidimeter vial and the effluent turbidimeter settling column were of particular importance, because impurities and residues collected on the walls of these two instruments interfere with the turbidimeter's ability to accurately determine the turbidity of the water. Before each run, the turbidimeters are powered down and the vial and column are carefully removed for cleaning. After powering down the instruments, all water must be drained out of the chambers and the instrument must be kept dry. For the influent turbidimeter, the glass vial can be removed from the head cap by twisting, but the influent and effluent tubes must be pinched shut to stop the flow of water in and out of the glass vial. For the effluent turbidimeter, the tube leading out of the bottom of the settling column must be disconnected and the manual valve connected to the top of the column must be manually opened to drain the water inside the column. Once all the water is drained, the metal connectors connected to the top and bottom of the column must be removed before the glass column can be pulled out from the top. Once carefully removed from the turbidimeter, a soft foam brush should be used to dislodge and remove all the residue and contaminants on the inner wall of the column. When clean, insert the column from the top down and secure all connectors tightly and reconnect all tubes to prevent leakage. Once the apparatus is reconnected, run the state that cleans the effluent turbidimeter with the manual valve open to remove all the air from the system. Once all of the air has been removed, the apparatus is ready to be used again.
Determining an Effective Alum Dose
Addition of Humic Acid
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