Screening and Comminution
In order for water and wastewater treatment plants to operate effectively, it is necessary to remove or reduce early in the treatment process large suspended solid material that might interfere with operations or damage equipment. Removal of solids may be accomplished through the use of various size screens placed in the flow channel. Any material removed may then be ground to a smaller size and returned to the process stream or disposed of in an appropriate manner such as burying or incineration. An alternative to actual removal of the solids by screening is to reduce the size of the solids by grinding them while still in the waste stream; this grinding process is called comminution (1, 2, 3, 4, 5, 6, 7, 8). Coarse screens (bar racks) and comminutors are usually located at the very beginning of a treatment process, immediately preceding the grit chambers (Fig. 1). To ensure continuous operation in a flow process, it is desirable to have the screens or comminutors installed in parallel in the event of a breakdown or to provide for overhaul of a unit. With this arrangement, flow is primarily through the comminutor and diverted to the coarse (bar) screens only when necessary to shut down the comminutor. Fine screens are usually placed after the coarse (bar) screens.
KeywordsHead Loss Maximum Water Depth Average Water Depth Approach Velocity Water Pollution Control Federation
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