Los Plancitos

Design Files containing current design

Overall Hydraulic Alternatives for Aguaclara plant at Los Plancitos
AutoCAD drawing with design changes
Design calculations to confirm component dimensions

Design Files created by the Design Tool

The freeboard was set to 35 cm so that the walls were drawn high enough on the sed tank. The walls on the rest of the plant will need to be trimmed to match the height of the sed tank walls.
AguaClara Design Tool data input
Excel sheet with design values
Draft AutoCAD drawing (this is not to be used for construction)

Design decisions

The water treatment plant at Los Plancitos (site map) is being designed for Aguas de Santa Rosa to serve the villages of El Rodeo, El Derrumbo, and Los Plancitos. The plant is to have a design flow rate of 10 L/s. The water for the plant comes from the Río Higuito and is pumped to Los Plancitos.

Figure 1: The Río Higuito close to the raw water intake.

Figure 2: The 75 L/s pump that transfers water from Río Higuito to a high pressure pump station next to the river.

The water is pumped using a series of high lift pumps from the Río Higuito up to Los Plancitos.

Figure 3: Two of the 3 high pressure pumps in the first pump station that lifts water up to Los Plancitos.

The effluent from the AguaClara plant will be pumped through 5 pressurized rapid sand filters.

Figure 4: The proposed site for the AguaClara plant. The site already contains the 150 cubic meter storage tank and rapid sand filters that will be used after the AguaClara plant.

Figure 5: Two prefilters and 2 of the 5 rapid sand filters. We propose that they no longer use the prefilters and instead send the water from the AguaClara plant directly to the 5 rapid sand fitlers.

This design is being created using the current design tool version (The version number of the MathCAD files used to create this design is 1893). This version is Cuatro Comunidades technology that uses inlet manifolds in the triangles that form the valley in the sedimentation tank. The inlet design will be modified manually in AutoCAD to create a design that uses a pipe for the inlet manifold.

The hydraulic design for this facility will be modified from the conventional AguaClara design to have the flow controlled by the pump that is sending water to the filters. The conventional AguaClara design uses a valve at the inlet to the entrance tank as the flow control. If we used that same design for Los Plancitos it would be difficult to operate because it would be necessary to match the flow into the plant to the pump flow rate and as head loss through the filters changed and the pump flow rate changed it would be necessary for the operator to continually regulate the AguaClara plant flow. To avoid this operational difficulty the hydraulics of this plant will be changed from upstream flow control to downstream flow control. The flow through the plant will be completely controlled by the effluent pump. The flow rate into the entrance tank will not be controlled. Instead, the water level in the entrance tank will be controlled. There are two options for this control.

1. A sharp crested weir will be used to control the water level and excess water will be wasted (a bad choice given the high cost of pumping this water), returned to the 150 cubic meter storage tank, or somehow added to the transmission line that takes water to the water treatment plant for Santa Rosa de Copan.
2. A float valve will be used to control the water level in the entrance tank. This would be the easiest option to implement. A disadvantage may be the wear on the float valve due to the high sediment load in the raw water. This will also need to be a large float valve and thus it will be a relatively expensive item.
   The plant will be designed with the plant walls all having the same height as the entrance tank. Thus when the effluent pump turns off the water level in the plant will all rise to the water level in the entrance tank and as the water levels in the plant increase the flow through the plant will decrease and finally stop.