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The Fall '09 ANC Control team had worked on the development of a lime feeder for hydrated lime. Including constraints as non electricity use, low cost and replicable design; the team had founded some important parameters.
1. It is possible to assimilate the particles behavior in the lime feeder to the behavior of flocs into plate settlers of the sedimentation tank. A description of the theory is detailed in Experiment 3.
2. The main variables to consider in the lime feeder operation are the upflow velocity, the lime quality and the water composition.
3. The required lime needs to have very fine particles to avoid the apparatus clog caused by big lime chunks.
4. It is required a water with low presence of carbonate system, to facilitate the dissolution and pH change.
Despite this findings more research is required in order to confirm the theories and to find the explanation for some variables that are not enough clear yet.
FUTURE CHALLENGES
The following are proposed challenges for the next team:
1. Determine the optimal lime particles size and an easy way to reach it.
2. Determine the optima upflow velocity which will maintain the suspension bed for the required particle size.
3. Compare different chemical compositions or commercial lime, especially those available in Honduras, and evaluate the apparatus behavior with them.
PROPOSED EXPERIMENTS
To accomplish the future challenges the Fall '09 ANC Control team propose the following experiments:
1. Continue with the current design (Experiment 3):
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• A specific commercial lime composition + tap water.
• A specific commercial lime composition + distilled water.
Is suggested to change the apparatus and use tubes with big diameter, that will allow to increase the upflow velocity and to experiment with higher amount of lime, making easy for the water to flow in the vertical direction and avoiding the fast expulsion of lime.
2. Change of apparatus design:
Another option is to develop a complete new design. As suggestion, there is a lime feeder design described in the book "Surface Water Treatment for Communities in Developing Countries" by Schultz and Okun, 1992. According with the authors, this apparatus was used in water treatment in Brazil. The design doesn't involves electricity just hydraulic considerations.