Application of computational fluid dynamic modelling to improve flow and grit transport in Terrence J. O'Brien Water Reclamation Plant, Chicago, Illinois

The Terrence J. O'Brien Water Reclamation Plant (WRP) serves a population of around 1.3 million people and service area of 368.8 km² in Chicago, IL. Metropolitan Water Reclamation District of Greater Chicago, the agency responsible for the maintenance and operation of the WRP, observed non-uniform distribution of grit deposition between the six grit tanks. Single- and multiphase flow simulations were used to investigate the non-uniform grit distribution and to evaluate potential solution alternatives to ensure the plant operates at an optimal capacity. The simulations revealed the formation of secondary currents due to a bend in the approach conduit; this explained the preferential sediment conveyance along the left side of the conduit and higher deposition at the southernmost grit tanks. Baffles at the centre of the approach conduit and a constriction wall along the left side were recommended for breaking the secondary currents and uniform distribution of the grits.