...
This set of experiments attempts to replicate the grain size research performed with the previous experimental setup. Additionally, the effectiveness of each of the components in the setup will be assessed with respect to theoretical expectations.
General Procedure
The procedure for this set of experiments is fairly similar with the exception of varying sand grain sizes. For the two experiments listed below, Sand 40 (0.49 mm - 0.57 mm) and Sand 30 (0.59 mm - 0.84 mm) were used for experiments one and two, respectively.
In Process Controller, configure the system so that the aerator air pressure is maintained at roughly 100 kPa. Fill the sand column with 60 cm of Sand 40 and adjust the flow rate on the pump forcing water through the sand filter to establish a bed expansion of 50%. For this the first experiment, manual measurements of flow rate were performed by unhooking the influent water tube into the sand filter and allowing the influent to fill a large graduated cylinder over the course of a minute. The flow rate was found to be 225 ml/min. ( In order to minimize changes made to the system, flow rate measurements for future experiments will be the second experiment were taken at the system effluent tube. ) The flow rate with Sand 40 was found to be roughly 225 ml/min and 485 ml/min for Sand 30.
Run the Process Controller method file here on the "On" state. The "On" state regulates the air pressure in the aerator by releasing small amounts of air through a valve when the system exceeds the maximum aerator air pressure of 102 kPa. The water level in the aerator is controlled in a similar manner; however, the water wasting valve is also subject to a duty cycle in which the valve will open for a set period of time and close for a set period of time. If the "on" condition for the wasting valve is not met (that is, if the water level does not exceed the regulated height), the wasting valve will remain closed.
...