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The initial rapid mix system proposed for the Agalteca plant was much different than the system designed this semester. As can be seen in Figure 2, water from the entrance tank flows into a pipe that carries it into the flocculation tank.
Figure 2. Initial Rapid Mix system design and integration into the plant. As indicated, the Rapid Mix Orifice in this design is completely submerged and accessed through the flocculation tank.
Rapid mix is achieved in this system when the water flows through an orifice at the end of the pipe leading into the flocculation tank, allowing small-scale mixing of the aluminum sulfate with the raw water to occur before reaching the flocculation tank. One of the main problems with this system is the location of the rapid mix orifice; it is submerged in the bottom of the flocculation tank, making it very difficult to reach or remove. Flow to the plant would have to be stopped and the flocculation tank drained at least partially to remove and clean this orifice if it ever clogged or needed to be replaced or exchanged. Another problem with this design is that the exit tube taking water from the entrance tank to the flocculation tank is flush with the side wall of the entrance tank and is located quite deep in the tank. Thus, for flow to the plant to be stopped, the entrance tank would have to be emptied completely.
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