OverviewThe Chemical Dose Controller 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.  Image Removed
Figure 1: General Schematic of Chemical Dose Controller
The Non-Linear CDC makes it possible for an operator to set the chemical dose without referring to any tables. This could be a significant advantage. The disadvantage is that this design is more complex and thus we will need to work this carefully to ensure that the CDC technology is sustainable. Current Research TeamChallenges - Our goals are 1)To become familiar with the current apparatus, design parameters and constraints. 2) To design a Nonlinear Chemical Dose Controller that can be scaled up or down depending on an input plant flow rate. Also, we would like to improve the design so that it will incorporate the different chemicals used in the plant in addition to alum such as chlorine.3)To create appropriate databases for the materials used (i.e.: float valves, frame, tubing). Additionally, we will be further investigating frame and component materials that are compatible with the chemicals and can be found locally.
Past Research TeamsAcademic Year 2009/2010 Nonlinear Chemical Doser - Redesigning a chemical doser with a precise nonlinear chemical dose response to changes in plant flow while also minimizing aeration in an attempt in prevent surface foams.
Summer 2009 Research: Surface Foam Formation - Trying to model the surface foam formation that takes place at the end of rapid mix in current plants and come up with a retrofit design that will minimize air entrainment.
Linear Chemical Dose Controller - The linear dose controller uses major losses to adjust chemical doses to the plant as raw water flow rates change.
Nonlinear Chemical Dose Controller Fall08-Summer09 - Major losses cannot be used to adjust chemical flow rates when flow in the dosing tube is turbulent. Therefore, a chemical doser with a precise nonlinear chemical dose response to changes in plant flow is being designed.
Rapid Mix Chamber Design Program - The design of the entrance tank for high flow rate plants such as Gracias.
Summer 2010 CDC Research - Validate the Nonlinear Chemical Doser by measuring both precision and accuracy to determine the best manufacturing techniques, document surface tension issues and to determine if material selection plays a role in accuracy or precision.
- Investigation of various materials and determine the most appropriate components to use.
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 Added
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