ANC CONTROL

FUTURE CHALLENGES

INTRODUCTION

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):

For the current experiment, the Fall '09 ANC Control team changed the variables and made runs to compare the behavior. However there was not enough time and there is just one trial for every variables combination. It is suggested to run more trials conserving the design but changing the variables. In this way it is possible to confirm the theory and scale up to the design for the actual water treatment plant in Honduras.

The first experiment required is finding the optimal upflow velocity. It is required to sieve the lime and use fine particles, with the sieve diameter is possible to calculate the lime particles size. The lime has to be dissolved in enough water before go into the apparatus. Start with low upflow velocities and figure out visually is all lime is in suspension through the apparatus. In addition, take the pH measures and compare the pH duration (at 12 units). Is necessary to leave the lime settle down or to replace it before making a new experiment with different upflow velocities.

The experiment has to be carried out at least two times with each upflow velocity. After finding it, include the last variable (lime composition). It is not required to use the same brand that the Fall '09 ANC Control team used. It would be great to find the composition of commercial lime in Honduras. The combination of variables suggested is:

• 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.