Redesign of infrastructure with green technology for hydrologic and constituent load reduction

Abstract

Computational fluid dynamics (CFD) is an emerging tool to predict the coupled hydrodynamics and particulate matter (PM) fate in unit operations (UOs) subject to rainfall-runoff events. Most studies examine unit operations on an event-basis. This study also includes event-based analysis extended to time domain continuous simulation using the Stormwater Management Model (SWMM) to evaluate unit operation performance on a long-term basis with and without maintenance. A validated computational fluid dynamics model simulated particulate matter fate in a rectangular clarifier (RC) and a screened hydrodynamic separator (SHS) for a representative year of runoff in a North Florida source area. The clarifier and SHS are fundamentally different unit operations with differing behavior, applications and functionality. The objective of the study is to illustrate the modeling of these two unique, but common units. The large footprint clarifier with volumetric capacity is a primary treatment unit operation while the SHS is a pretreatment gross solids trap without storage. Results indicate that the SHS is prone to washout without frequent maintenance. While neglecting particulate matter washout from the SHS overestimates SHS annual performance this was not the case for the clarifier. For unit operations, computational fluid dynamics and time domain continuous simulation models are tools to estimate fate of particulate matter and nutrients on an annual basis. Examined on an annual basis the mean cost (USD) to recover 1.0 lb (0.45 kg) of particulate matter (PM) (irrespective of particle size since the SHS is a gross solids trap) is $4 (SHS), $10 (clarifier) and for comparison, $15 (radial cartridge filter) without pre- or primary treatment required (and associated costs) by such filters. This compares to street sweeping at $0.10 to recover 1.0 lb of PM.