COMPUTATIONAL FLUID DYNAMICS (CFD) MODELING TO OPTIMIZE DESIGN OF BIOLOGICAL TREATMENT REACTOR

The City of Newport, Rhode Island is located on an island at the mouth of Narragansett Bay in the southeastern part of the state. The Newport Wastewater Treatment Facility (WWTF) is a secondary treatment facility utilizing the conventional activated sludge process to provide removal of pollutants. As part of an on-going Capital Improvement Program the City is having the existing Aeration tanks retrofitted with membrane style fine-pore diffusers to replace the existing mechanical aerators.Computational Fluid Dynamics (CFD) was used to analyze the flow characteristics of the four (4) aeration tanks at the Newport, RI WWTP after the existing mechanical mixing and aeration system is removed. Conditions with and without influent target baffles were modeled. The Capital Improvement Plan entails the replacement of the mechanical aerators with a fine bubble diffused aeration system. The initial design included inflow and outflow structures, combined with two mechanical mixers in each tank. After the removal of these mixers, the overall flow distribution pattern within each tank is important to assess. The CFD analysis looks at the relative flow pattern through the tank under both unbaffled and baffled conditions.