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The graphs show that as plant flow rate decreases, the effluent turbidity also decreases, until we reach 50 mlmL/min. At 25 mlmL/min, we found that the effluent turbidity is unstable but seems to be greater not lower than that of 50 ml/min. From this, we conclude that the optimal flow rate of this flocculator and sedimentation tank is approximately 50 ml/min. This is much lower than the 100 ml/min flow rate the plant was designed for. This is most likely due to slight inaccuracies in construction of the sedimentation tank that caused the flow rates in each of the lamellas to be different, resulting in a settling time that was lower than expected. Thus, when plant flow rate was decreased, resulting in a longer settling time, the flocs had a more reasonable amount of time to settle out, and effluent turbidity decreased.mL/min.

To test if To verify that the lamellas in the sedimentation tank experienced varied very non-uniform flow rates, we added red dye to the last column channel of the flocculator, and observed its progress through the plantsedimentation tank. We saw that the red dye proceeded mostly through the last 3 -4 lamellas of each side of the sedimentation tank, and that it moved the fastest through the last oneones. Also, upon further observation, we saw that at 100 mlmL/min, medium and small sized flocs were being carried up these channels in of the sedimentation tank and leaving the tank to the effluent water supplyturbidity meter.

Simply by observing the Demo Plant as experiments were being run, we saw we noted that the largest flocs were created at a flow rate of 50 mlmL/min. These results also show us that the G-theta in our plant is high enough at 50 mlthe degree of mixing provided by the flocculator is sufficient at 50 mL/min to create very large flocs. However, at 25 mlmL/min, the flocs were very small, showing that the G-theta was no longer large enough to create flocs.

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that the lower shear had reduced the degree of mixing so much that the increased residence time could not compensate for it.

Conclusion

From the data acquired and our direct observations, we conclude that the optimal flow rate of this flocculator and sedimentation tank is approximately 50 mL/min. This is much lower than the 100 mL/min design flow rate. This is most likely due to slight inaccuracies in construction of the sedimentation tank that caused the flow rates in each of the lamellas to be different, resulting in a settling time that was lower than expected. Thus, when plant flow rate was decreased, resulting in a longer settling time, the flocs had a more reasonable amount of time to settle out, and effluent turbidity decreased.