Figure 1. Amiad’s “focus backflush” technology uses the principles of simple physics for cleaning.

The City of St. Cloud, Fla. recently specified Amiad Filtration Systems’ ( filter products for an expanded 20.25 MGD water reuse system at its Michigan Avenue Wastewater Treatment Plant. The automatic self-cleaning system employs six model units with a filtration degree of 200 microns. The cleaning mechanism consists of a suction scanner “focus backflush” technology, which takes advantage of simple physics to enable cleaning (Figure 1). The decision to specify the Amiad systems for the expansion project was based on the experience of a smaller and successfully operating system previously installed in October 2003.

The “focus flush” concept that Amiad’s technology uses exhibits 100 percent cleaning via suction scanner technology. The cleaning nozzle is designed within close tolerances to cylindrical screen for high efficiency of backflushing.

During a backflush cycle, water moves both tangentially and directly into the orifice of the nozzle due to the large difference between operating and atmospheric pressures. Expanding this concept further, the high velocity (50ft/sec2) combined with the spiral movement of the nozzle(s) across every square inch of screen area effectively removes the entire filter cake without any interruption of flow through the filter units. Typically, backflushing wastewater is less than 1 percent of total flow.