Grit Collection

After the wastewater is pumped to 10 feet above ground level, it flows into a discharge channel that leads to the grit collector. Grit consists of sandy materials and other particulates that readily settle from the wastewater. Although some grit may be discharged to the sewer system by users, most grit is washed into the system along with groundwater infiltration. Since grit is inorganic, it cannot be removed in the biological treatment processes. If it is not removed prior to biological treatment, it accumulates in the process units, particularly the sludge digesters, and tends to cause excessive wear on the equipment. The grit is allowed to settle in a grit tank by slowing the velocity of the wastewater flow to approximately one foot per second. The inorganic grit settles at this velocity, but the organic material requiring further treatment does not. The grit is removed from the tanks and washed to remove residual organic material. As with screenings, the grit is disposed of as a solid waste. The BCUA currently has four units ranging from 35’ to 45’ in diameter.

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