Grit in biosolids was destroying the dewatering centrifuge at the Council Bluffs (Iowa) Water Pollution Control Plant. Damage to the scroll bowl and other wear cost $30,000 to $40,000 per rebuild, sometimes done twice a year. Grit also accu-mulated in the anaerobic digesters, reduced their capacity, and was difficult and costly to remove.
When the plant began a preliminary treatment process upgrade, division superintendent Hank Pangelina worked with the consultant to find a grit removal solution to install using existing structures. The consultant liked vortex separators because of their long history. That equipment, however, relies on velocity to remove grit. Efficiency
