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    The Vertical Flocculator Pilot Plant division of the Research and Development team has constructed and is working on testing a turbulent-flow hydraulic flocculator and rapid mix unit at the Cornell University Water Treatment Plant (CUWTP). A flow control module and sedimentation tank are also being added at adjacent parts that will work in conjunction with the main flocculator. Prior to the construction of the present tank, flocculation research was done on a small scale, laminar flow tube flocculator. In order to test flocculation under turbulent flow conditions the pilot plant hydraulic flocculator was built. It is a rectangular tank that is divided into three sections that are filled with vertical baffles similar to the baffles used in Ojojona, Honduras.
    The vertical baffles were spaced using equations written in a MathCAD program created to test for different velocity gradients, G and amount of mixing, Gtheta. An alternative baffles set-up was also created that has varying baffle spacings, where the baffles get farther and farther apart through the tank. The previous setup has a baffle spacing of 6.45 cm with 27 baffles per section. The new set- up is split into four sections with four separate baffle spacings. After preliminary testing, it was determined that the tapered spacing is more efficient and just as affective in a shorter residence time. Settling tubes were designed to measure flocculation performance at different locations in the tank. Through manipulation of the flocculator flow rate, it will be possible to manipulate G. The effects of changing the parameter Gtheta can be easily measured by varying the location of the sedimentation tubes. This setup will allow a systematic method to identify an optimal combination of the two parameters and verify their roles in efficient flocculation. Our goal for efficient turbidity removal is defined as NTU < 1. A sedimentation tank is also being constructed to work in conjunction with the flocculator and thus allow for testing of the entire aguaclara process. A flow control and measuring unit is also being added to the flocculator. The digital flow meter is currently in place will be used to test the accuracy of the flow control device that is in place in Honduras.

Keywords: turbulent-flow, hydraulic flocculator, rapid mix, vertical flocculator, Cornell Water Treatment Plant, velocity gradient, Gtheata, efficient flocculation, efficient turbidty removal, tapered flocculation flow control device, sedimentation tank.

    Since 2004, Cornell University's AguaClara team has worked in conjunction with Engineers for a Sustainable World (ESW), and Agua Para El Pueblo (APP)to design and build four water treatment plants in Honduras. In addition to providing clean water to the La 34 and Ojojona, a plant in Marcala is under construction and a design for a plant in Tamara is also being completed. The plant at Ojojona also functions as a pilot operation, demonstrating successes and potential problems for future plants.
    The R&D team focuses on optimizing flocculation technologies to make them more efficient and effective. Multiple sub-teams work on this task, each using a unique approach. The lab sub-team runs bench-scale experiments in the AguaClara lab, using a tube flocculator that operates in the laminar flow regime. In spring 2007, the Vertical Flow Pilot Plant sub-team worked with various Cornell University staff to design and build a larger-scale vertical flow flocculator at the Cornell University Water Treatment Plant (CUWTP), to facilitate to facilitate testing under turbulent flow conditions. The new flocculator more closely models Ojojona's existing configuration, hopefully allowing for more practical testing. This experiment will also allow verification and possible reduction of the large G¿ range (20,000 to 150,000) recommended for community-based flocculation. Flocculation effectiveness is influenced by a number of factors, including coagulant dosage, mixing value, influent turbidity and velocity gradient. The team hypothesizes that velocity gradient is the central variable for optimizing flocculation.
    After construction of the plant was completed at the end of the Spring 2007 semester, during the summer testing was done on the uniformly spaced baffles. Then in the Fall 2007 semester the uniform baffle spacing set-up was exchanged for a tapered baffle configuration. The Spring 2008 semester is going to be spent doing more extensive testing on the tapered set-up.
    Initially the main goal for this semester was to do research on this set-up to learn more about where flocs were breaking up in the flocculator. Research over the summer was focused on several areas of the interest with this test flocculator. First, we wanted to determine a floc formation and floc break-up profile through the flocculator. This would help us determine different aspects of the tank that were either helping or hindering flocculation. Secondly, there was a focus on determining the optimum alum dose based on raw water turbidity for ideal floc formation. This test was designed to help in the design of a better alum dosing algorithm. After the summer ended, the overall goals of the flocculator changed, attention shifted to the set-up and design of the flocculator itself.
    Experiments were leading to the conclusion that good floc formation would require an average velocity gradient that changed throughout the flocculator. Thus this semester's focus switched to the design and construction of a tapered baffle set-up. It was planned that this new set-up would be tested in the flocculator and performance compared to the previous baffle arrangement. The overriding goal is to determine which set-up is more effective at creating large flocs and doing so in the most efficient manner, and shortest residence time. Initial tests were designed to compare both baffle set-ups and determine which is more efficient.
    Research done on other sub-teams determined that the highest values of G were in the 180 degree bend and that the majority of flocculation was happening in these turns. The channels themselves seemed to be doing little to further flocculation. Thus the average velocity gradient that we were using for our calculations was not actually an accurate representation of the actual gradients that are occurring in the tank. Thus floc break could be occurring in the turn arounds because of a low estimate of the gradient. Our next step was to increase the G values in the channels to levels that were closer to those found in the turn arounds, essentially decreasing the variation in the gradient throughout the flocculator, and thus making the average gradient a more accurate representation of what was happening in the tank. A preliminary idea was to add some sort of obstacle structure to the channels to increase G. An initial design of interconnected PVC pipes that would be suspended in the channels between baffles creating higher shear levels and thus a higher velocity gradient.

There have been three major phases dealing with the pilot plant. The first phase was the initial design and construction of the tank and the uniformly spaced baffles. The second stage was the testing of the uniformly spaced baffles that resulted in some tank modification. Third stage was the construction of the tapered baffles configuration. The current stage is testing the tapered baffles set-up  and making additional tank changes based upon results.

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Testing of the uniform baffle configuration was done during the summer of 2007. 

The tapered baffles set-up that was the result of new research about velocity gradients in the tank was done during the Fall 2007 semester.

    Currently testing of the tapered flocculation baffle arrangement is underway. The first few weeks of the Spring 2008 semester were spent making a few additional tank modifications. When the tapered configuration was put in the baffles around the port holes were set farther apart and thus the port holes had to be enlarged to ensure flocs were not being broken up. Sludge that had settled to the bottom of the tank was removed and tank was cleaned before it was started for the semester. Additional sand was re-added to the bottom of the tank before the baffles were placed in. It was determined that a significant amount of flow is by-passing the system and flowing under the bottom panel, which is supporting the section dividers. It was noticed when the tank was filled that that the first and third sections were filling at all most the same rate. Before caulking was done additional sand was added to the bottom of the tank in the third section to try and see if significant enough head loss could be created in the tank to cause most of inflow to follow the correct flow path. The tank was drained, cleaned and dried of sand again so that caulk could be added to seal the gap.

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Enter your Results here.

Enter your Conclusions here.

Here is an example table. I refer to the table by creating an internal link (an anchor) that will take the viewer to the top of the table. For example here I am talking about the [#analog wiring standard] that we use in the AguaClara laboratory. Note that I position the floating table above the paragraph where it is first referenced so that it appears along the side of that paragraph. I haven't figured out an automatic way to set the width of the table. Currently I am doing it by trial and error. If someone figures out a better way, please edit this!

An [#output control box] designed and fabricated around the Basic Stamp® Microprocessors (Parallax 16 port BS2sx and 40 port BS2p BASIC Stamp® modules) is used for on/off control of up to six devices and for variable control of up to six peristaltic pumps.

The float macro keeps the graphic and the caption together and floats the figure on the page with text wrapping around it automatically. Because the top of the figure will align with the text that the float is above, I recommend insert the figure wrapped in the float macro immediately above the paragraph where the first reference to the figure occurs. This will place the figure along side the paragraph with the reference. Use anchors to refer to the figure just like you would use "Figure 11" refernces in a conventional manuscript. There is no way to implement auto numbering of the Figures so for now don't even bother to use numbers in the Figure. Instead, in the body of the report where you first reference the [#output control box] add an anchor link that connects to the Figure. Use heading 5 for table and figure captions. This makes it possible to generate a list of tables and figures. Note that there is no numbered Figure reference in the caption. Also note that the image is a hyperlink to the full size original image. If the image is from a different source file the hyperlink should be to the original source file such as a MathCAD or Excel sheet.

In this example I set the size of the float and the size of the image to 200px. The viewer can see the full image by clicking on it.

You can also use the [chart macro] to create a chart dynamically within the wiki.