Critical Grit Removal Design Considerations for Retrofits and Additions at Existing Facilities

Many wastewater treatment facilities have aging or inefficient grit removal systems with excess solids build-up occurring in downstream sedimentation tanks, channels, aeration tanks and digesters with resulting abrasive wear on solids handling pumps and additional maintenance for cleaning. Inefficient grit systems also lead to a grit product that contains excess organics with odors in the materials handling areas.Retrofits and additions can often include limited space for construction of new processes, difficulty in maintaining existing grit removal during construction, phasing of tie-ins, and hydraulic limitations. The objective of this paper is to review critical grit removal design considerations including grit characterization, grit removal technologies, hydraulic considerations, grit pumping and conveyance, grit washing, and grit storage. Case studies at a wide range of facilities will be presented to illustrate the issues.