Page History

Linear Chemical Dose Controller (LCDC/LFOM)

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 2012: The main challenges of the Fall 2012 team were to create, refine, and test a prototype of the lever arm assembly based on a design created during the Summer of 2012. The LCDC system was scaled up to a plant flow rate of 44 L/s and is currently ready for deployment in Winter 2013 for use in the Piedras Amarillas plant located in the town of Las Vegas, Honduras. The Fall 2012 team made the following changes to the Summer 2012 design: devised a drop tube connection design to reduce leakage, added cross bracing to the lever arm assembly to reduce bending of the lever arms, and devised a new calibration device to enable fine-tuned adjustments. In order to create an aesthetically pleasing design, the team had the lever arm anodized, added a modified weight, and had a label, scale and logo mechanically engraved on the lever arm. Finally, the LCDC system was tested for linearity with respect to the influent plant flow rate and percent dosage. Percent error for the percentage dose analysis and entrance tank height changes were highest at low chemical flows, which may be due to surface tension effects.

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.

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