Lesson Learned: Drum Filter Optimization

For more information on the drum filter test, see Drum Filter Demonstration Site.

Filtration systems are not always a simple installation. Technologies require some manipulation to ensure that they are functioning at their maximum efficiency. The drum filter that was installation is one example. It succeeded in taking in washwater and filtering it through the screen. It was successful in rotating the barrel and spraying off the waste into a collection tray. However, initially the output of the collection tray contained excessive amounts of water. As the goal is to have a sludge-like material with the least amount of water possible to limit amounts of waste to dispose, adjustments were in order. The drum filter is able automated to rotate and spray on a regular schedule; the purpose of the optimization process is to find the setting that produces the most concentrated waste stream.

Table 1: The time between each spray cycle, approximate volume of waste output, volume of waste output per minute, and solids (depth in sample bottles) for each spray cycle setting

The first step was to investigate the settings that were most appropriate for the solid load and flow rate of the washwater. The drum filter was run at each of those settings for a few cycles and sludge samples were taken along with waste output volumes, spray cycle time, and time between rotations was recorded (Table 1). The samples were left to settle so the solids portion of the sludge could be observed (Figure 1).

Figure 1: Illustration of waste output at a spray cycle setting of (left to right) 5 seconds, 10 seconds, 15 seconds, 20 seconds, and 3 samples at 25 seconds.

Based on the results outlined in Table 1, the samples taken from the 5 second and 15 second rotation had the highest amount of solids in the sludge. The 5 second spray cycle has the lowest overall waste output. It was determined that this setting was the most efficient out of those tested.

Prior to optimizing the cycle setting, the change in total suspended solids between pre and post drum samples was 46%. The drum filter was run using the 5 second spray cycle setting and samples of the pre drum, post drum, and sludge were taken. After changing the setting, the change pre and post drum was 71%. Through manipulating the spray cycle, the efficiency of the system was greatly increased.

Figure 2: Total suspended solids in pre drum, post drum, and sludge samples prior to optimization on day 1 and after on day 2

Lesson Learned: As with many technologies, it takes time and careful measurements to set equipment to operate at optimal levels.