Читать книгу Automation of Water Resource Recovery Facilities - Water Environment Federation - Страница 241

Most grit systems have removal systems that do not operate continuously. Rather, the equipment is typically controlled to run on time. For example, a typical strategy may provide for grit removal for 10 minutes of operation every 1 hour under normal operation. In some systems, there may be several components of grit removal that work in series. For example, an auger may move the grit slurry to an area where the grit pump can pump the grit to a grit washer. In this event, there is typically a time lag between each component of the grit removal system. For example, the auger may start 3 minutes before the pump start and the washer may start 30 seconds after the pump start and continue for 2 minutes after the pump stops.

In some systems, an air or water jet may also be used to loosen compacted grit before pumping. In this instance, the air or water valve is typically opened for several seconds before starting the grit pump.

During high facility flows, it is common to greatly increase the frequency of grit removal operation. This is attributable to flushing the facility’s collection system, which tends to yield a much higher concentration of grit. Often, when facility flow is much greater than normal, the grit removal equipment operation is set for continuous operation.