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In addition, in order to create a good turbine in the tank to prevent lime particle settling down, and the fact that it is not realistic for operator to do it manually, the team's proposal is to set a couple of propeller as shown in figure 2, the idea is to utilize the energy from influent flow to push the propeller in lime stocking tank. The way to dose the lime into the entrance tank is also shown in figure 2, by using with an appropriate orifice size it is expected to provide a relatively constant flow for 24 hours, but it still need furtehr study from the point that a small orifice would possibly cause clogging and the flow rate may change under the decreasing water level in stocking tank.     

*Case study*

To evaluate the new design, the team studied the feasibility to implement it in Cuatro Communidades plant. From figure 3, it can be seen that a flow ratio of 5*10^-3 between lime feeder flow over raw water could result a pH of 6.75, also notice that the lime feeder effluent flow has a pH of 12.6 under the scenario behind this model( see --), it is also known the plant flow of Cuatro Communidades is at 100 gpm. Based on these information, the required lime per day could be calculated, which is 2.5 kg/day. Under the assumption that the concentration in lime stocking tank is 5 gm/Liter, the required tank volume is then calculated to be 0.5 cubic meter. Because the lime in the tank is based on daily basis, so the flow rate through stocking tank into entrance tank could simply use the volume divided by 24 hours, which is 0.093 gpm.


Fig 1. Autocad drawing of new design with dimension description


Fig2. Propeller and Orifice position


Fig 3. ANC and pH as a funtion of flow ratio between lime feeder over raw water