A Granulometry-Based Selection Methodology for Separation of Traffic-Generated Particles in Urban Highway Snowmelt Runoff

Traffic activities generate a wide gradation of anthropogenic particulate matter that is entrained in highway snow and snowmelt. Granulometric-based analyses of this particulate mattercan provide guidance for selection and design for snowmelt solid/liquid separation processes. This study presents a granulometry-based analysis of snow melt particles from 10 highway shoulder sites in urban Cincinnati (State of Ohio, U.S.A.) generated from a 46 cm, 48 hr snowfall with a highwayshoulder residence time of 102 hr. Each site was exposed totraffic and maintenance activities (plowing and de-icing saltsonly). Despite variations in gradations and particle indices, measured l _nv-N _t (number-volume mean size-particle counts) values for all sites were closely modeled using a two-parameter power law model. The model exponent, β, ranged from 2.22 to 2.64 indicating that a significant fractionof surface area is associated with the coarser gradation of particles. Modeled results support previous experimental data indicating the predominance of surface area and heavy metal mass is associatedwith the coarser fraction of particles. Results indicated a statistically significant difference in densities for coarse (2.86 gm cm^-3) and fine particles (2.75 gm cm^-3) (P < 10^-11).A methodology is presented in the form of a process selection diagram to evaluate mechanisms of particle separation. It was determined that sedimentation could remove 90% of particles, bymass, within 2 hr for a typical roadway drainage design. The influence of particle specific gravity on sedimentation efficiency is illustrated for a range of specific gravities from 1.1 to 4.0. Although the very high concentrations of particulate matter in highway snow melt do not make it amenableto straining or direct filtration, such processes may be feasible as a secondary treatment for snowmelt or storm water effluent discharges to receiving waters.     

In vitro antibiotic susceptibility of field isolates of Mycoplasma synoviae in Argentina

Minimum inhibitory concentrations (MICs) were determined in vitro for 7 antibiotics (aivlosin, enrofloxacine, tylosin, tiamulin, kitasamycin, chlortetracycline, and oxytetracycline) against eight recent local Argentinean isolates and two standard strains of Mycoplasma synoviae. Aivlosin (3-acetyl-4"-isovaleryl tylosin tartrate), tylosin, and tiamulin showed the lowest MICs with MIC90s of 0.006, 0.012, and 0.05 microg/ml, respectively. Except one strain that showed resistant values to chlortetracycline (> or = 12.5 microg/ml), all the analyzed strains were susceptible in different degrees to all the antibiotics tested. In this study, the improved activity of the tylosin-derived drug, aivlosin, was confirmed because it showed, in most strains, MIC values half those for tylosin.     

Cement Stabilization of Runoff Residuals: A Study of Stabilization/Solidification of Urban Rainfall–Runoff Residuals in Type 1 Portland Cement by XRD and 29Si NMR Analysis

Urban rainfall–runoff residuals contain metals such as Cr, Zn, Cu, As, Pb and Cd and are thus reasonable candidates for treatment using Portland cement-based solidification–stabilization (S/S). This research is a study of S/S of urban storm water runoff solid residuals in Portland cement with quicklime and sodium bentonite additives. The solidified residuals were analyzed after 28 days of hydration time using X-ray powder diffraction (XRD) and solid-state ²⁹Si nuclear magnetic resonance (NMR) spectroscopy. X-ray diffraction (XRD) results indicate that the main cement hydration products are ettringite, calcium hydroxide and hydrated calcium silicates. Zinc hydroxide and lead and zinc silicates are also present due to the reactions of the waste compounds with the cement and its hydration products. ²⁹Si NMR analysis shows that the coarse fraction of the waste apparently does not interfere with cement hydration, but the fine fraction retards silica polymerization.     

Size Distribution of Wet Weather and Dry Weather Particulate Matter Entrained in Combined Flows from an Urbanizing Sewershed

Urban drainage transports a complex and heterogeneous mixture of aqueous-phase chemicals and also solid-phase particulate matter (PM). In this study, event-scale particle size distribution (PSD) of wet and dry weather flows are measured, modeled, and compared. The flows are generated from a complex urbanizing sewershed (Liguori catchment) in Cosenza, Italy. Results indicate PSDs are heterodisperse, ranging from colloidal to sand-size PM. On an event scale, dry weather PSDs are coarser than wet weather flows, yet within each flow class results indicate flow-limited behavior and only nominal variability during and between events. PSDs from each event and flow category are modeled with a cumulative gamma distribution. Results produced nonparametric distributions of shape (γ) and scaling (α) parameters as well as a d ₅₀ index. Wet weather flows generated statistically significantly higher distributions of γ and α and statistically significantly lower d ₅₀. Nonparametric parameter distributions illustrate greater, yet still nominal variability for wet weather flows.     

Granulometry of Non-colloidal Particulate Matter Transported by Urban Runoff

Water, Air, & Soil Pollution - This study examined the granulometry of non-colloidal particulate matter (PM) from four urban transportation land use catchments (source areas) in Baton Rouge,...     

Heavy Metal Contamination in Soils of Urban Highways Comparison Between Runoff and Soil Concentrations at Cincinnati,Ohio

Rainfall runoff from urban roadways oftencontains elevated amounts of heavy metals in both particulate anddissolved forms (Sansalone and Buchberger, 1997). Because metalsdo not degrade naturally, high concentrations of them in runoffcan result in accumulation in the roadside soil at levels thatare toxic to organisms in surrounding environments. This studyinvestigated the accumulation of metals in roadside soils at asite for which extensive runoff data were also available.For this study, 58 soil samples, collected from I-75 nearCincinnati, Ohio, were examined using X-ray fluorescence, C-Sanalyzer, inductively coupled plasma spectroscopy, atomicabsorption spectrometry and X-ray diffraction. The resultsdemonstrated that heavy metal contamination in the top 15 cm ofthe soil samples is very high compared to local backgroundlevels. The maximum measured amount for Pb is 1980 ppm (at 10–15 cm depth) and for Zn is 1430 ppm (at 0–1 cm depth). Metal content in the soil falls off rapidly with depth, and metalcontent decreases as organic C decreases. The correlation toorganic C is stronger than the correlation to depth. The resultsof sequential soil extraction, however, showed lower amounts ofPb and Zn associated with organic matter than was expected basedon the correlation of metals to % organic C in the whole soil.Measurement of organic C in the residues of the sequentialextraction steps revealed that much of the carbon was not removedand hence is of a more refractory nature than is usual inuncontaminated soils. Cluster analysis of the heavy metal datashowed that Pb, Zn and Cu are closely associated to one another,but that Ni and Cr do not show an association with each other orwith either organic C or depth. ICP spectroscopy of exchanged cations showed that only 4.5%of Pb, 8.3% of Zn, 6.9% of Cu and 3.7% of Cr in the soil isexchangeable. Combined with the small amounts of metals bound tosoluble organic matter, this result shows that it is unlikelythat these contaminants can be remobilized into water. At thissite, clays are not an important agent in holding the metals inplace because of low amounts of swelling clays. Instead, insoluble organic matter is more important. Mass balancecalculations for Pb in soil showed that most of the Pb came fromexhausts of vehicles when leaded gasoline was in use, and thatabout 40% of this Pb is retained in the soil.This study shows that, highway environments being a relativelyconstant source of anthropogenic organic matter as well as heavymetals, heavy metals will continue to remain bound to organicmatter in-situ unless they are re-mobilized mechanically. Removalof these heavy metals as wind-blown dust is the most likelymechanism. Another possibility is surface run-off carrying themetals into surface drainages, bypassing the soil. This studyalso shows that for those countries still using leaded gasoline,important reductions in Pb contamination of soils can be achievedby restricting the use of Pb additives.     

Granulometric Relationships for Urban Source Area Runoff as a Function of Hydrologic Event Classification and Sedimentation

This study investigated particulate matter (PM) granulometry delivered in source area runoff as a function of hydrologic transport and settling. At a Baton Rouge, LA paved urban watershed, event runoff volume and PM load were “fully captured” and recovered in settling tanks. Events were differentiated as mass-limited (ML) or flow-limited (FL) and PM differentiated into suspended (1 to ~25 μm), settleable (~25 to 75 μm), sediment (75 to 4,750 μm) fractions; and also particle size distributions (PSDs). Suspended sediment concentration (SSC)-turbidity relationships were unique for FL events compared to ML events; while 60 min of quiescent settling produced a single distinct relationship across all events. ML events transported higher proportions of settleable and sediment mass compared to higher suspended mass for FL events. Event-based ratios of settled and unsettled turbidity as well as SSC mass were statistically different for ML and FL events. For the same settling conditions, treatment of ML and FL events were statistically different. Results demonstrated that PM separation by a unit operation was a deterministic function of granulometry, hydrodynamics, unit operation mechanisms and loads, but significantly influenced by the indeterminate nature of local climate; and hydrology which drives PM delivery and is not known a priori. Combining the influences of scour and lack of maintenance, unit operation performance is non-stationary and cannot be described by a single value. Treatment should be tied to an effluent concentration; granulometry and load.     

Speciation of Zinc and Copper in Stormwater Pavement Runoff from Airside and Landside Aviation Land Uses

The transport, bioavailability and fate of aqueous metals in rainfall-runoff are determined, in part, by speciation. In the framework of a monitoring program to investigate the predominant species of zinc, copper, and water chemistry in runoff subject to aviation land use and activities, two rainfall-runoff monitoring stations were installed at the international airport of Genoa (Italy). One catchment was a boarding area (airside) apron and the other a parking area for vehicles (landside). Utilizing water chemistry analyses, ion balances and speciation modelling for a series of five event loadings for each site, results indicated that Zn²⁺ dominated Zn speciation and Cu complexes with carbonate or dissolved organic matter, dominated Cu speciation. With respect to wash-off processes a mass limited behaviour was generally observed for particulate matter (measured as TSS) and TOC; while the mass delivery of aqueous metal species tended to be more proportionate with respect to runoff volume.     

Physically-Based Particle Size Distribution Models of Urban Water Particulate Matter

Water, Air, & Soil Pollution - The aim of this study was to evaluate the effect of pretreatment on the phytotoxicity and leaching of nitrogen and phosphorus in biosolids from anaerobic...     

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

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.