Representation of Particulate Matter COD in Rainfall Runoff from Paved Urban Watersheds

Abstract

For a half century, total suspended solids (TSS) has been the most commonly utilized particulate matter (PM) gravimetric index for wastewater. While TSS has been extended to urban runoff, runoff phenomena are unique. Runoff is unsteady and transports heterodisperse inorganic granulometry, giving rise to the PM index, suspended sediment concentration (SSC). With respect to PM-associated chemical oxygen demand (COD p ) in runoff, it is hypothesized that, while the TSS method can represent effluent COD p , the SSC method is required to represent influent COD p . COD p and PM indices (TSS and SSC) for runoff events with mass balances and manual sampling are analyzed to investigate this hypothesis. This study examined a series of rainfall-runoff events captured from an instrumented fully paved urban catchment subject to traffic loadings in Baton Rouge, LA. Results indicate TSS generated substantial event-based mass balance errors for COD p and Δm p (mg/g) across a hydrodynamic separator (HS) as compared to SSC.TSS underestimates sediment-bound COD (>75 µm), a significant portion (maximum of 63% and median of 50%) of influent load. Negative bias by the TSS method for influent COD p load increases as the heterodisperse particle size distribution becomes coarser. Above a PM of 250 mg/L, underestimation of COD p by the TSS method is statistically significant. Utilizing the SSC method, COD p reduction by a HS upstream of a batch clarifier (BC) indicates that a HS does not provide COD p reduction, compared to a BC with 60 min of residence time. Representative PM and COD P assessment suggests frequent BMP and drainage system maintenance to ensure proper operation and reduce pollutant elution.

Continuous field estimation of dissolved organic carbon concentration and biochemical oxygen demand using dual‐wavelength fluorescence, turbidity and temperature

“…In lowland rivers a large proportion of BOD is thought to be particulate (Sullivan, Snyder, & Rounds, ) and associated with degraded phytoplankton cells (Volkmar & Dahlgren, ). In urban rivers generally, BOD is highly variable and largely driven by storm water dynamics (Lee & Bang, ) and associated particulate transport (sediment/biofilm associated organic material and microbes) from impervious surfaces, storm drains, and deposited sediments (Sakrabani, Vollertsen, Ashley, & Hvitved‐Jacobsen, ; Kim & Sansalone, ). Given the diversity of OM sources within urban catchments (Goldman, Rounds, & Needoba, ; McElmurry, Long, & Voice, ) robust in‐situ or real‐time monitoring methods are required to improve: (i) process understanding (e.g., climate – source – pathway); (ii) legislative monitoring capacity; and (iii) assessment of river restoration initiatives (Khamis et al, ).…”

Management of combined sewer overflows based on observations from the urbanized Liguori catchment of Cosenza, Italy

“…These modern conditions generate a hetero-disperse and inorganic PM for source area discharges that is progressively transformed to finer gradations in the urban conveyance system while representing a chronic oxygen demand ). Furthermore, the COD p is distributed across the PSD, suggesting strategies to target particle size ranges based on treatment objectives (Kim & Sansalone 2009). PSDs are required when evaluating unit operations designed for PM separation (Pathapati & Sansalone 2009a,b).…”