Linear Chemical Dose Controller (LCDC/LFOM)| Excerpt |
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The linear Chemical Dose Controller (LCDC) is a critical piece of the AguaClara technology which couples the plant flow rate with the flow rate of the coagulant or disinfectant stock solution. The result is a semi-automated system in which the plant operator only needs to set a dose for the chemical and it will be administered automatically as the plant flow rate varies. |
The system has evolved steadily with major advances every year. The ability to accurately and predictably control the alum and chlorine dosages without electricity sets AguaClara apart from other water treatment technologies. Fall 2016: This semester the CDC team redesigned the CHTs so that all four tanks are connected to each other, and so that the calibration columns are attached to the CHT module. Additionally, the team recreated and modified the modular CDC system designed in past semesters to address the goals of being fully chemical resistant, compact, and simple in operation and maintenance. The new CHT will be demonstrated and eventually implemented in Honduras. The chemical dose controller consists of four total stock tanks, two calibration columns, and four constant head tanks. There are two stock tanks for chlorine and two stock tanks for polyaluminum chloride. If one tank for a particular chemical runs out, the second stock tank serves as a backup. The two chlorine stock tanks have individual outlet tubing but this tubing joins together into one tube. At this point, there is a diverted pipe that leads an upright rigid clear PVC pipe which serves as our calibration column. There is one calibration column each for chlorine and for polyaluminum chloride. The calibration columns serve to measure the dosage of the chemicals being added to the treated water. The calibration columns function by first closing the valve to the CHT and then opening the valve to the calibration column from the stock tank. The plant operator allows the calibration column to fill, closes the valve to the stock tank, then opens the valve to the CHT. The operator then measures how much much time it takes for a predetermined amount of chemical to drop and based off this, determines the dosing rate. The design of the second and final iteration for the semester maintained the same basic structure as the first iteration of Fall 2016, save for the alterations in plumbing orientation. In the second iteration, the tanks were extended in the direction of the float valves, so that the plumbing can be vertically oriented in the back of the CHT and attached to the wall as opposed to being horizontally oriented through the back of the CHT.  Image AddedSpring 2013: The Spring 2013 team fabricated two new chemical dose controllers - one for use in Honduras and another for use in India. The team also made improvements to the Fall 2012 design. Improvements included application of a powder coat finish instead of anodizing the lever arm to improve chemical resistance, design and fabrication of a chemical- resistant PVC manifold system that can allow the chemical flow through each tube to be shut off if necessary, and creating a constant head tank that can be more easily adjusted during calibration and can accommodate larger flows. An entrance tank improvement to prevent excessive movement of the float at some plants in Honduras, which can introduce error in dosing rates, was also designed. A clear, concise Google SketchUp 3-D drawing of the latest LCDC system was created, which can be used in training exercises and to fabricate new chemical dose controllers in the future. The Spring 2013 team created a laboratory setup of the LCDC system and through experiments determined that the system was within ten percent error of the predicted MathCAD output. Finally, the team also presented options for manufacture of the lever arm in the US or locally in the host country. Retrofitting existing plants in Honduras was determined to not be a priority at this time.
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