Journal of Environmental Engineering

In this study, the release of metals and metalloids from full-scale portland cement concrete pavements containing coal combustion products (CCPs) was evaluated by laboratory leaching tests and accelerated loading of full-scale pavement sections under well-controlled conditions. An equivalent of 20 years of highway traffic loading was simulated at the OSU/OU Accelerated Pavement Load Facility (APLF). Three types of portland cement concrete driving surface layers were tested, including a control section [i.e., ordinary portland cement (PC) concrete] containing no fly ash and two sections in which fly ash was substituted for a fraction of the cement; i.e., 30% fly ash (FA30) and 50% fly ash (FA50). In general, the concentrations of minor and trace elements were higher in the toxicity characteristic leaching procedure (TCLP) leachates than in the leachates obtained from synthetic precipitation leaching procedure and ASTM leaching procedures. Importantly, none of the leachate concentrations exceeded the TCLP limits or primary drinking water standards. Surface runoff monitoring results showed the highest release rates of inorganic elements from the FA50 concrete pavement, whereas there were little differences in release rates between PC and FA30 concretes. The release of elements generally decreased with increasing pavement loading. Except for Cr, elements were released as particulates $(>0.45\mathrm{\mu }\mathrm{m})$ rather than dissolved constituents. The incorporation of fly ash in the PC cement concrete pavements examined in this study resulted in little or no deleterious environmental impact from the leaching of inorganic elements over the lifetime of the pavement system.

A spatially distributed and continuous hydrologic model focusing on total maximum daily load (TMDL) projects was developed. Hydrologic models frequently used for TMDLs such as the hydrologic simulation program—FORTRAN (HSPF), soil and water assessment tool (SWAT), and generalized watershed loading function (GWLF) differ considerably in terms of spatial resolution, simulated processes, and linkage flexibility to external water quality models. The requirement of using an external water quality model for simulating specific processes is not uncommon. In addition, the scale of the watershed and water quality modeling, and the need for a robust and cost-effective modeling framework justify the development of alternative watershed modeling tools for TMDLs. The hydrologic and water quality integration tool (HydroWAMIT) is a spatially distributed and continuous time model that incorporates some of the features of GWLF and HSPF to provide a robust modeling structure for TMDL projects. HydroWAMIT operates within the WAMIT structure, developed by Omni Environmental LLC for the Passaic River TMDL in N. J. HydroWAMIT is divided into some basic components: the hydrologic component, responsible for the simulation of surface flow and baseflow from subwatersheds; the nonpoint-source (NPS) component, responsible for the calculation of the subwatershed NPS loads; and the linkage component, responsible for linking the flows and loads from HydroWAMIT to the water quality analysis simulation program (WASP). HydroWAMIT operates with the diffusion analogy flow model for flow routing. HydroWAMIT provides surface runoff, baseflow and associated loads as outputs for a daily timestep, and is relatively easy to calibrate compared to hydrologic models like HSPF. HydroWAMIT assumes that the soil profile is divided into saturated and unsaturated layers. The water available in the unsaturated layer directly affects the surface runoff from pervious areas. Surface runoff from impervious areas is calculated separately according to precipitation and the impervious fractions of the watershed. Baseflow is given by a linear function of the available water in the saturated zone. The utility of HydroWAMIT is illustrated for the North Branch and South Branch Raritan River Watershed (NSBRW) in New Jersey. The model was calibrated, validated, and linked to the WASP. The NPS component was tested for total dissolved solids. Available weather data and point-source discharges were used to prepare the meteorological and flow inputs for the model. Digital land use, soil type datasets, and digital elevation models were used for determining input data parameters and model segmentation. HydroWAMIT was successfully calibrated and validated for monthly and daily flows for the NSBRW outlet. The model statistics obtained using HydroWAMIT are comparable with statistics of HSPF and SWAT applications for medium and large drainage areas. The results show that HydroWAMIT is a feasible alternative to HSPF and SWAT, especially for large-scale TMDLs that require particular processes for water quality simulation and minor hydrologic model calibration effort.

Water quality models are important tools used for developing total maximum daily loads (TMDLs), which are used to implement water quality standards. The writers have developed a tool which spatially interpolates output from the Chesapeake Bay Program Watershed Model (WSM) and requires little time, data, or training. In contrast, the WSM requires extensive time, data, and training to run. This study examines if the writers’ tool provides accurate estimates of pollutant loads as compared to observed pollutant loads calculated using two different rating curve methods. The accuracy of the tool was assessed based on Nash–Sutcliffe coefficients. This study found that the tool provided moderate estimates of total nitrogen, poor estimates of total phosphorus, and that the rating curve method used to calculate observed loads affected the conclusion of the accuracy of the writers’ tool for predicting total sediment. A key finding of this study is that the widely used load-derived method for calculating observed loads exhibits spurious correlation. The writers discuss the imperative need to use sound statistical methods when estimating pollutant loads and TMDLs, and suggest an alternative approach for developing rating curves which is not subject to the problem of spurious correlation.

The performance of four sedimentation basins (SBs) at a Pennsylvania Department of Transportation I-99 highway construction site was evaluated based on their particle removal ability. Suspended solids data from the basins indicated poor particle removal, peaks in suspended solid concentration that correlated with rainfall peaks and possibility of sediment resuspension. The current Pennsylvania Department of Environmental Protection basis for basin design is the allocation of $28{\mathrm{m}}^3$ $\left(\mathrm{1,000}{\mathrm{ft}}^3\right)$ of sediment storage zone and $140{\mathrm{m}}^3$ $\left(\mathrm{5,000}{\mathrm{ft}}^3\right)$ of drainage zone per disturbed acre of the drainage basin. Overflow rate, which is a scientific basis for particle removal, is currently not considered in the design of basins. This paper presents a methodology for developing an integrated design for SBs, applying rainfall probability plots to determine an appropriate basin settling volume. The revised universal soil loss equation is used to identify sediment zone volume, and an overflow rate is determined to design basin surface area. The method presented is a comprehensive procedure for designing SBs with flexibility to choose the extent of particle removal and runoff capture, and to vary construction costs.

Structural best management practices (BMPs) have become a tool for stormwater managers to achieve water quality improvement and regulatory compliance. Existing empirical evaluation of BMP performance is valuable, but has limited applicability to predict BMP performance over extended durations under a variety of storm types. This study applies a dynamic model to simulate BMP performance over a 10-year period. The BMP model used hourly output from a calibrated and validated land-use model to evaluate two BMP types: a retention facility and a flow-through swale. The model evaluated each BMP alone and in series targeting volume, total suspend solids, and total copper. Effectiveness was based on load reduction, event mean concentrations, and frequency of exceedence of relevant water quality standards. The model predicted over 60% removal of solids and copper over most conditions; however, effectiveness was reduced during large storms and wet years. Although performance was similar based on load reduction and water quality standard exceedence, the latter was most sensitive to storm size. This study demonstrates that BMP modeling can help managers understand expected BMP performance over a range of storms, time periods, and design parameters, and, perhaps more significantly, evaluate BMPs in series.

Solute transport and dispersion processes affect the performance of a wide range of water engineering structures. Some urban drainage network models transport the pollutants by advection only, whereas others also account for the effects of dispersion, although there is only limited knowledge regarding appropriate values for dispersion parameters. Computational fluid dynamics (CFD)-based software tools enable engineers to simulate flow patterns and associated pollutant transport mechanisms within both natural and engineered hydraulic structures. It is feasible to use CFD to represent solute transport using two contrasting approaches, an unsteady species (scalar) transport model or a discrete phase (Lagrangian particle tracking) model. This paper outlines these two approaches, using the example of a storage tank to demonstrate, compare, and validate the two approaches, and to explore a number of issues associated with interpretation of the simulation outputs. It is concluded that both CFD-based approaches may be usefully utilized for the design and modeling of urban drainage systems.

The long-term effectiveness of an ${\mathrm{FeSO}}_4+{\mathrm{Na}}_2{\mathrm{S}}_2{\mathrm{O}}_4$ reductant solution blend for in situ saturated zone treatment of dissolved and solid phase $\mathrm{Cr}\left(\mathrm{VI}\right)$ in a high pH chromite ore processing solid waste fill material was investigated. Two field pilot injection studies were conducted that showed sustained treatment of $\mathrm{Cr}\left(\mathrm{VI}\right)$ over evaluation periods of more than 1,000 days. No well or aquifer formation clogging was observed during injection although treatment was limited to the pore volume displacement radius of the injected reductant. Analysis of posttreatment core samples suggested $>85\%$ treatment effectiveness of solid phase $\mathrm{Cr}\left(\mathrm{VI}\right)$ , whereas lab tests suggested treatment of the solid phase $\mathrm{Cr}\left(\mathrm{VI}\right)$ can be complete provided the chromite ore processing solid waste sediments are sufficiently dosed with the reductant. The sustained treatment of dissolved phase $\mathrm{Cr}\left(\mathrm{VI}\right)$ migrating through the treatment zones for more than 1,000 days following injection provided strong evidence of a residual treatment capacity having been imparted to the formation solids. Scanning electron microscopy–energy dispersive x-ray spectroscopy analyses of posttreatment core samples indicated that much of the $\mathrm{Cr}\left(\mathrm{VI}\right)$ may be removed through the formation of a Cr-bearing precipitate, possibly a complex carbonate, characterized by an $\mathrm{Fe}:\mathrm{Cr}$ molar ratio of roughly 1:1.

Bench scale fermentation of primary, mixed, and secondary (raw and hydrolyzed) sludge and starch industry wastewater was carried out using Bacillus thuringiensis (Bt) var. kurstaki HD-1 to test their feasibility as potential growth substrates on the basis of rheology and process performance in comparison to soyameal (semisynthetic) commercial medium. All fermented media exhibited pseudoplastic pattern, followed power law for viscosity with greater shear thinning for primary sludge (raw and hydrolyzed). Improved rheology correlated well with the fermented broth morphology. The total cell and viable spore counts, oxygen consumption, maximum specific growth rate $\left({\mu }_{\max }\right)$ , and entomotoxicity were, respectively, 2, 4, 1.5–2, and 3 folds lower in primary sludge in contrast to mixed sludge, rendering primary sludge unsuitable as raw material for Bt fermentation and eventual formulation. Further, the rheology studies of secondary sludge and starch industry wastewater proved them to be good Bt fermentation alternatives.

The toxicity characteristic leaching procedure (TCLP) is normally used to evaluate if sludge should be managed as hazardous waste. This study examines immobilization mechanisms of arsenic onto arsenic-iron hydroxide sludge, the byproduct of arsenic removal by coagulation with ferric chloride. The leaching mechanism of arsenic from the sludge due to the TCLP is also investigated. Microscopic characterization techniques including scanning electron microscopy equipped with energy dispersive spectroscopy (SEM-EDS), X-ray diffraction (XRD), and Fourier transform infrared spectroscopy (FT-IR) were employed to characterize the sludge samples with the $\mathrm{As}\text{-}\mathrm{to}\text{-}\mathrm{Fe}$ ratios of 0.07 to 0.15 before and after the TCLP. SEM-EDS and FT-IR results suggested that arsenic-iron hydroxide sludge be ferric hydroxide, whose surface is inner or outer spherically sorbed by arsenic, rather than the precipitate of insoluble iron-arsenic compounds such as $\mathrm{Fe}(\mathrm{AsO}{)}_4$ . This is also confirmed by XRD results, which revealed that none of such crystalline iron-arsenic compounds were detected in the arsenic-iron hydroxide sludge. Therefore, adsorption among other possible arsenic immobilization mechanisms, namely, precipitation, coprecipitation, and occlusion, is supposed to play the major role. Due to the TCLP, the arsenic concentrations ranging from 0.26 to $2.54\mathrm{mg}∕\mathrm{L}$ were leached out of the sludge samples with the $\mathrm{As}\text{-}\mathrm{to}\text{-}\mathrm{Fe}$ ratios ranging from 0.07 to 0.15, respectively. The changes of FT-IR patterns of the sludge after the TCLP suggested that during the TCLP, desorption and resorption of arsenic occurs. The relationship between arsenic in TCLP leachate and that remaining in the leached sludge can be modeled by Langmuir isotherm, an adsorption isotherm. This indicates that desorption and resorption of arsenic onto the leached sludge is the main phenomenon controlling arsenic leachability due to the TCLP.

The sorption of ${\mathrm{Pb}}^{2+}$ , ${\mathrm{Cd}}^{2+}$ , and ${\mathrm{Sr}}^{2+}$ ions from aqueous solutions by carbonate-substituted calcium hydroxyapatite (HAP) obtained by the hydrothermal decomposition of urea and calcium–ethylenediaminetetraacetic acid chelates was investigated. The shift of the point of zero charge $\left({\mathrm{pH}}_{\mathrm{pzc}}\right)$ of HAP toward lower pH values in solutions of ${\mathrm{Pb}}^{2+}$ and ${\mathrm{Cd}}^{2+}$ ions, which was more pronounced for ${\mathrm{Pb}}^{2+}$ ions than for ${\mathrm{Cd}}^{2+}$ ions, indicates that specific adsorption of these cations on HAP had occurred. There was no shift of the ${\mathrm{pH}}_{\mathrm{pzc}}$ in the solution containing ${\mathrm{Sr}}^{2+}$ ions, suggesting that specific adsorption of this cation on HAP had not occurred. The sorption isotherms suggest that the sequence of the efficiency of sorption by HAP is ${\mathrm{Pb}}^{2+}>{\mathrm{Cd}}^{2+}>{\mathrm{Sr}}^{2+}$ . Ion exchange is the main mechanism of removal of ${\mathrm{Sr}}^{2+}$ ions from aqueous solution by apatite, whereas during the sorption of ${\mathrm{Cd}}^{2+}$ ions, this mechanism occurs simultaneously with the process of specific adsorption. The interaction of the apatite with ${\mathrm{Pb}}^{2+}$ ions includes the previously mentioned mechanisms and dissolution of the apatite, followed by the precipitation of lead hydroxyapatite.

The present study aims to select the most appropriate aggregation function for estimation of the Ganga River pollution index (GRPI). Following the Delphi technique based on expert opinion, 16 water pollutant variables are selected; the weights of each pollutant variable based on their relative significance are determined, and the average subindex curves for each variable are drawn. Using the weights, average parameter’s value and the corresponding subindex value, 18 different aggregation functions are tested and analyzed. Literature reveals that most aggregation methods suffer from ambiguity and eclipsing problems due to faulty selection of aggregation function. From the results of the present analysis, 12 aggregation functions are screened out on the basis of ambiguity and eclipsing, constant functional behavior, and nonaccountability of weights in functions criteria. Finally, the remaining 6 aggregation functions are subjected to sensitivity analysis. From the results of sensitivity analysis, it is concluded that the weighted arithmetic mean function, being a true linear, least ambiguous and eclipsing free function, is the most representative aggregation function for estimation of GRPI for River Ganges.