Journal of Environmental Engineering

For urban drainage, the role of granular media has expanded from particulate matter (PM) filtration to media also engineered for phosphorus (P) mass transfer. In this paper, equilibrium between P as total dissolved P (TDP) and granular substrate-based aluminum oxide (AlOx) media are investigated. Aluminum oxide coated media (AOCM) are clay- (${\mathrm{AOCM}}_{\mathrm{c}}$), pumice- (${\mathrm{AOCM}}_{\mathrm{p}}$), and concrete-based (${\mathrm{AOCM}}_{\text{pcc}}$), and their native substrates [uncoated media with a clay substrate (UCMs)] serve as control media. Equilibrium is modeled with Freundlich isotherms. Isotherms are evaluated in municipal wet weather (runoff), dry weather (wastewater), and a surrogate deionized (DI) water matrix as a control, each at neutral pH. Compared to UCMs, AlOx-coated (clay, pumice) and AlOx-admixture media (concrete) yield significantly higher equilibrium capacity. For runoff and wastewater, ${\mathrm{AOCM}}_{\mathrm{c}}$ and ${\mathrm{AOCM}}_{\mathrm{p}}$ generate lower capacity compared with the surrogate matrix due to competitive effects, and ligand exchange is hypothesized as a primary mass transfer mechanism. ${\mathrm{AOCM}}_{\text{pcc}}$ has higher capacity at higher TDP levels with surface precipitation hypothesized as a primary mechanism. For equal TDP levels, capacities of ${\mathrm{AOCM}}_{\text{pcc}}$ and ${\mathrm{AOCM}}_{\mathrm{c}}$ exceed ${\mathrm{AOCM}}_{\mathrm{p}}$. The native substrates of AlOx media and also the aqueous matrices have significant impacts on equilibrium. In contrast, Part II compares surface and physical indexes, equilibrium, and leaching for a wide range of media using a surrogate DI matrix. The two parameter Freundlich model is compared to a partitioning parameter to elucidate equilibrium for media with disparate capacities.

Part I focused on a Freundlich model of phosphorus (P) equilibrium between AlOx-media substrates and differing aqueous matrices: runoff, wastewater, and a reproducible deionized (DI) surrogate. In contrast, Part II examines equilibrium and leaching of a wide range of media using a single DI water matrix. Media are characterized, P removal quantified, leaching is examined, and equilibrium modeled. Media of high Al (${\mathrm{AOCM}}_{\mathrm{c}}$, alumina), Fe (coated perlite), or Ca [portland concrete cement-based media (${\mathrm{AOCM}}_{\text{pcc}}$)] content provided enhanced P capacity as compared to other media (tire crumb and zeolite-perlite- granular activated carbon). While zeta potential ($\zeta$) was stable from pH 5 to 9 for each aluminum oxide coated media (AOCM) and ranged from $+5\mathrm{mV}$ for ${\mathrm{AOCM}}_{\mathrm{c}}$ to 0 mV for ${\mathrm{AOCM}}_{\text{pcc}}$, $\zeta$ was largely negative for all other media and less stable for alumina and Fe-perlite. Despite enhanced capacity of media of high Al, Ca, or Fe content, metal leaching can be a concern. It was found that $\mathrm{Al}(1.09\pm 0.02\mathrm{mg}/\mathrm{g})$ and $\mathrm{Fe}(3.49\pm 0.05\mathrm{mg}/\mathrm{g})$ were leached from alumina and Fe-coated perlite, while Zn was leached from tire crumb, raising potential constraints for these media. For the media tested, the Freundlich binding capacity ($K_F$) varied by 2 orders of magnitude with heterogeneous site intensity profiles ($n$). In contrast to the two-parameter Freundlich model, a partitioning model ($K_u$) in Part II provides a single parameter to index equilibrium. $K_u$ varied by 3 orders of magnitude, also indicating large variability in P capacity between media. This range of media, commonly deployed for storm water systems, produced a wide range of equilibrium, leaching, and model parameters in a stable, reproducible surrogate matrix.

This study evaluates the removal of mercury from wastewater using chemical reduction and air stripping with a full-scale treatment system at the Savannah River Site. The existing water treatment system utilizes air stripping as the unit operation to remove organic compounds from groundwater that also contains mercury ($\mathrm{C}\sim 250\mathrm{ng}/\mathrm{L}$). The baseline air stripping process was ineffective in removing mercury from the water that exceeded a proposed limit of $51\mathrm{ng}/\mathrm{L}$. To test an enhancement to the existing treatment modality a continuous dose of reducing agent was injected for 6 h at the inlet of the air stripper. This action resulted in the chemical reduction of mercury to Hg(0), a species that is removable with the existing unit operation. During the injection period a 94% decrease in concentration was observed and the effluent satisfied proposed limits. The process was optimized over a 2-day period by sequentially evaluating dose rates ranging from 0.64–297X stoichiometry. A minimum dose of 16X stoichiometry was necessary to initiate the reduction reaction that facilitated mercury removal. Competing electron acceptors likely inhibited the reaction at the lower doses, which prevented removal by air stripping. These results indicate that chemical reduction coupled with air stripping can effectively treat large volumes of water to emerging part-per-trillion regulatory standards for mercury.

Experimental investigations undertaken to optimize the layout of floating treatment wetlands (FTWs) for maximum hydraulic performance of storm-water retention ponds are described. The study is the first to investigate how the arrangement of an FTW in a storm-water retention pond affects its hydraulic performance. The size, orientation, and arrangement of FTWs were investigated as well as the influence of inlet arrangements on the effects that the FTW has on the system hydraulics. For all the tests, the FTWs were positioned centrally across the width of the pond. The results show that FTWs can significantly improve the hydraulic performance of storm-water retention ponds. The hydraulic performance is shown to depend on the position, size, and placing arrangement of an FTW in the pond as well as the inlet arrangement.

In the last several years, computational fluid dynamics (CFD) has emerged as a potential tool to accurately predict the response of best management practices (BMPs) to highly unsteady rainfall-runoff (storm water) and particulate matter (PM) loadings. However, such predictive capability for BMPs as unit operation (UO) systems subject to highly unsteady loadings requires much higher computational time than for steady loadings. Therefore, to reduce computational time at a given level of predictive accuracy, an instantaneous response stepwise-steady method was tested to reproduce the unsteady load response of three geometrically different BMP UO systems. The units are baffled and screened hydrodynamic separator systems [(BHS) and (SHS)], respectively, as well as a granular media-based volumetric clarifying filter (VCF) system. The measured PM response was variable, a function of influent unsteadiness and the UO system geometry. Each hydrograph loading of a UO system was represented as a cumulative distribution function (CDF) which was discretized into a number of steady-flow steps using a discretization number (DN) for which an instantaneous response was modeled. DN was the model tuning parameter used to examine the stepwise-steady method. Despite variability in measured load-response for a UO system, a similar number of instantaneous response steady steps (DN of 35–40) were required to achieve a mean relative percent difference (RPD) of less than 10% between measured and modeled load response. For each UO system, the stepwise-steady method reduced computational time by an order of magnitude compared with a fully unsteady method.

The computer program AQUASIM was used to model biological treatment of perchlorate-contaminated water using zero-valent iron corrosion as the hydrogen gas source. The laboratory-scale column was seeded with an autohydrogenotrophic microbial consortium previously shown to degrade perchlorate. Consortium biokinetic parameters and data from column experiments were used to verify the model. The model was then used to simulate full-scale performance of an in-situ zero-valent iron permeable reactive barrier perchlorate-treatment system. Simulation results indicate full-scale field treatment systems have the potential to degrade significant concentrations of perchlorate in the presence of oxygen under a variety of operating conditions.

In this paper, photodegradation of dyes [Acid Red 14 (AR14) and Acid Red 18 (AR18)] has been studied using multiwalled carbon nanotube (MWCNT), ferrous ion ($\mathrm{F}{\mathrm{e}}^{2+}$), and hydrogen peroxide. The surface characteristics of MWCNT were investigated using Fourier transform infrared (FTIR) and scanning electron microscopy (SEM). UV-Visible (UV-Vis) and ion chromatography (IC) analyses were employed to investigate dye degradation. The effects of MWCNT, $\mathrm{F}{\mathrm{e}}^{2+}$, initial dye concentration, and salt on the photodegradation of dye were investigated. Formate, acetate, and oxalate were detected as aliphatic intermediates. The ${\mathrm{N}\mathrm{O}}_3^{-}$ and $\mathrm{S}{\mathrm{O}}_4^{2-}$ were detected as dye mineralization products. The results showed that $\mathrm{MWCNT}/\mathrm{F}{\mathrm{e}}^{2+}$ might be a suitable catalyst for dye degradation.

The objective of this work was to quantify the leaching of nine heavy metals from four desktop personal computer components (PCCs), namely, integrated drive electronics (IDE) cables, video cards, random-access memory (RAM), and CPUs, using two different leaching tests. One test was the toxicity characteristic leaching procedure (TCLP), which is widely used in the United States. The TCLP was augmented using a five-step sequential leaching procedure to further investigate the influence of increasing liquid-to-solid ($\mathrm{L}/\mathrm{S}$) ratios on the amount of metals leached. The other leaching test was based on European standards following the requirements of a European decision regarding acceptance of waste at landfills. The European leaching test was performed at the natural pH of the materials. Results showed that the masses of some metals leached during the TCLP were up to two orders of magnitude greater than the corresponding masses measured by the European leaching test. Lead and zinc were the dominant metals leached from all four PCCs. Video cards, RAM, and CPUs were classified as hazardous wastes according to the U.S. EPA’s TCLP limit for lead. Based on the limits of the European decision, IDE cables, video cards, and RAM chips were classified as nonhazardous and should be disposed of to nonhazardous waste landfills. CPUs should be disposed of to hazardous waste landfills. The amount of metals leached increased with an increasing liquid-to-solid ratio.

In this paper, amine-functionalized magnetic ferrite nanoparticle (AMFN) was synthesized. Dye removal ability of AMFN and magnetic ferrite nanoparticle (MFN) was investigated. Physical characteristics of AMFN were studied using Fourier transform infrared (FTIR) and scanning electron microscopy (SEM). Direct Red 31 (DR31), Acid Blue 25 (AB25), and Acid Red 14 (AR14) were used as model compounds. The kinetic and isotherm of dye adsorption were studied. The effects of operational parameter such as adsorbent dosage, pH and salt were evaluated. Adsorption kinetic of dyes was found to conform to pseudo second order kinetics. The maximum dye adsorption capacity ($Q_0$) was $0.271\mathrm{mg}/\mathrm{g}$ DR31, $0.756\mathrm{mg}/\mathrm{g}$ AB25 and $0.581\mathrm{mg}/\mathrm{g}$ AR14 for MFN and $185.185\mathrm{mg}/\mathrm{g}$ DR31, $161.290\mathrm{mg}/\mathrm{g}$ AB25 and $147.059\mathrm{mg}/\mathrm{g}$ AR14 for AMFN. It was found that dye adsorption onto MFN and AMFN followed Langmuir isotherm. The results showed that the AMFN being a magnetic adsorbent with high dye adsorption capacity might be a suitable alternative to remove dyes from colored wastewater.

Aerobic granulation has been extensively investigated in recent decades but most researchers have focused their studies on granule formation in laboratory-scale reactors using synthetic wastewaters at high organic loading rates (OLR) ($\mathrm{OLR}>2.5\mathrm{kg}\mathrm{COD}·{\mathrm{m}}^{-3}·{\mathrm{d}}^{-1}$). This research studied the aerobic granulation in a sequencing batch reactor (SBR) using real domestic wastewater with an OLR at or lower than $2\mathrm{kg}\mathrm{COD}·{\mathrm{m}}^{-3}·{\mathrm{d}}^{-1}$. The reactor was operated in three different stages (Stage I, II, and III), according to the applied OLR (1.4, 1.0, and $2.0\mathrm{kg}\mathrm{COD}·{\mathrm{m}}^{-3}·{\mathrm{d}}^{-1}$, respectively). After 140 days of operation (Stage II), the reactor biomass consisted mainly of compact mature granules (average diameter of 0.7 mm) with a good settling ability ($\mathrm{SV}{\mathrm{I}}_{30}$ approximately $53\mathrm{mL}·{\mathrm{g}}^{-1}$). The OLR increase caused a partial disintegration of the mature granules during the beginning of Stage III. However, the granules were able to quickly recover after the disturbance caused by the higher OLR. The reactor was effective at removing carbon and nitrogen compounds, especially when operated with an OLR of $2\mathrm{kg}\mathrm{COD}·{\mathrm{m}}^{-3}·{\mathrm{d}}^{-1}$, providing an average removal efficiency of 92% for $\mathrm{CO}{\mathrm{D}}_{\mathrm{D}}$ and 96% for $\mathrm{N}{\mathrm{H}}_4^{+}–\mathrm{N}$. The results demonstrated that aerobic granules can be formed, using real domestic wastewater, with an effective carbon and nitrogen removal.

Three coal fly ashes (FA) with different acid-base characteristics and unburned carbon contents, and their mixtures with a typical embankment soil, were analyzed for arsenic, copper, and chromium leaching as a function of pH using batch-type water leach tests. Final leachate pH of the samples was linearly correlated ($R^2=0.84$) to their water-soluble Ca (a surrogate for soluble CaO) and oxalate-extractable Fe concentrations (a surrogate for amorphous iron hydroxides). The leaching behavior of Cu, Cr, and As appear to be primarily governed by leachate pH, and no significant difference in terms of leaching trends was observed among different fly ashes solely attributable to different unburned carbon content. At acidic pH, increased Cu and Cr (presumably in the form of ${\mathrm{Cr}}^{\mathrm{III}}$) leaching were observed. ${\mathrm{Cr}}^{\mathrm{VI}}$ was determined as the predominant species in leachates. As and ${\mathrm{Cr}}^{\mathrm{VI}}$ were strongly retained below pH 7 and leached more at alkaline pH. According to ${\mathrm{Cr}}^{\mathrm{VI}}$ sorption test results, ${\mathrm{Cr}}^{\mathrm{VI}}$ retention capacity was higher for fly ashes with higher oxalate-extractable iron content. Thus, minimum metal release occurred from mixtures that produced leachates with pH values near neutral range. The leachate pH of acidic fly ash could be increased by adding soil or ash with neutral characteristics. The fly ash-to-soil ratio should be carefully adjusted because soil addition to ashes improved compactibility of the mixtures but also reduced the retention capacity for As and ${\mathrm{Cr}}^{\mathrm{VI}}$. Regardless, pH of naturally alkaline fly ash with high soluble CaO content could not be decreased to a neutral range and leached more metal, especially toxic ${\mathrm{Cr}}^{\mathrm{VI}}$.

This paper examines the application of atmospheric pressure microwave plasma (APMP) for disinfection of water contaminated by Bacillus globigii spores. The results were most promising when $\mathrm{He}-{\mathrm{H}}_2$ or ${\mathrm{O}}_2$ were used as plasma gases. The most probable cause for disinfection due to $\mathrm{He}-{\mathrm{H}}_2$ plasma can be attributed to the presence of germicidal ultraviolet radiation. On the other hand, the presence of metastable oxygen species (which are very reactive) in the oxygen plasma effluents was attributed as the most likely cause of sterilization of Bacillus globigii spores. By choosing the correct combination of gas mixtures and microwave power level, the authors were able to achieve greater than $\mathrm{lo}{\mathrm{g}}_5$ inactivation. AMPM may be a suitable alternative to traditional disinfection techniques (e.g. chlorination) when they are difficult or impracticable.