Journal of Environmental Engineering

Residential surface soil regulatory guidance values (RGVs) specify the threshold at which soil contamination requires action. Usually, these are risk-based values based on child ingestion, inhalation, and dermal exposure. Benzene, toluene, ethylbenzene, and xylenes (BTEX) are among the five most commonly regulated soil contaminants in the United States and worldwide. More than 100 regulatory jurisdictions have established surface soil RGVs for BTEX compounds. Analysis of these values indicates that they vary by several orders of magnitude and appear to fit a lognormal random variable model with values well dispersed across the number spans. The RGVs applied to benzene are statistically distinct from those applied to TEX contamination, but the TEX values appear to be statistically indistinguishable. The magnitude of difference between TEX RGVs of different jurisdictions appears to be more significant than differences in the T, E, and X values specified by any one jurisdiction. Although value distributions are dominated by randomness, some contain clusters of points that are unlikely to be random and may represent consensus on appropriate values. Where “consensus clusters” exist, they should be identified and explored. The mechanistic explanations for cluster values may yield methods of reducing RGV variability.

Elevated and variable aqueous and granulometric concentrations of phosphate species (P) are commonly observed in urban rainfall runoff. Though physical operations such as sedimentation can potentially separate particulate P, aqueous P requires a unit process approach such as adsorption. Therefore, adsorption of aqueous P on aluminum oxide coated media (AOCM), a porous soil-type substrate coated with aluminum oxide, is investigated. Parameters studied include media size, phosphate concentration as total dissolved phosphorus (0–25 mg/L), pH (5–9), ionic strength (0.000 5–0.2 M as KCl), and the presence of coexisting ions such as ${\text{Ca}}^{2+}$ , ${\text{SO}}_4^{2-}$ , and ${\text{NO}}_3^{1-}$ . Results indicate that adsorption (mg/g) increased with decreasing AOCM size and decreasing pH. ${\text{Ca}}^{2+}$ enhanced P adsorption by forming ternary complexes; ${\text{SO}}_4^{2-}$ inhibited P adsorption by competing for available adsorption sites. Ionic strength and ${\text{NO}}_3^{1-}$ had minor to negligible effects on adsorption equilibrium, respectively. Chemical adsorption between P and AOCM resulted in low desorption potential. Adsorption data were modeled with Freundlich isotherms. After batch adsorption by AOCM, results indicate that P could be significantly reduced, meeting most surface water discharge requirements.

Wood chips were evaluated for their ability to attenuate heavy metals in roadway runoff. Column experiments with controlled synthetic runoff composition and flow rate were used to assess effects of flow rate (intercepted sheetflow from a 3-m wide roadway section), runoff salt concentration, wood exposure to alternating wetting and drying cycles, wood aging, competition among dissolved heavy metals, and removal of particle-associated heavy metals. Overall, wood chips damped the “pulse” of copper in the synthetic runoff such that the effluent was characterized by lower concentrations (3–25% of input) over longer periods of time, but with little retention of the total copper mass. The most effective treatment was wood chips aged up to 9 months. Increased aging and chip water content reduced effluent concentrations, relative to no treatment. Flow rate had no effect on effluent concentrations. The presence of salt $\left(>2\text{mS}/\text{cm}\right)$ or dissolved lead $\left(500\mu \text{g}/\text{L}\right)$ in the runoff caused greater copper effluent concentrations than the no treatment case. Removal of suspended particles (and associated contaminants) was greater than 85% with an estimated capacity of $0.16\text{g}/{\text{g}}_{\text{wood}}$ . Field evaluation with concentrated flow to a gutter containing a wood chip treatment showed little effect on total or dissolved copper and zinc runoff concentrations and indicated that wood chips may be a source of contaminants in subsequent storm events. Applications of wood chips to treat roadway runoff would not provide a significant decrease in total maximum daily load contributions (e.g., kg/d); however, there may be some scenarios for which wood chip treatments to decrease peak storm water concentrations of dissolved heavy metals in sheetflow runoff is desirable.

Wet detention basins are among the most common best management practices (BMPs) being implemented as means of complying with United States Phase II storm-water rules and impending Total Maximum Daily Load limits. The effectiveness of these basins for removal of microbial contaminants, one of the most frequent causes of water quality impairment, may be significantly affected by the degree to which microbes associate with particles in storm water. Little is known with regard to where microbial-particle associations are initiated within the storm-water transport chain as flow travels from upland sources (e.g., lawns, parking lots) through storm sewer systems and BMPs and finally on to receiving waters. A similar lack of information exists on the relative concentrations of microbes at each point in the transport chain. Both of these factors have important implications for the location of wet detention basins within a watershed, as well as their anticipated effectiveness. This study tracked the concentrations and partitioning behavior of three indicator organisms (fecal coliform, E. coli, and enterococci) at several locations in the transport chain and also explored the impacts of partitioning on wet pond removal efficiency. Results suggest that microbial-particle association is primarily initiated at upland sources and the degree of microbial partitioning does not vary greatly throughout the transport chain; therefore, treatment ponds will likely be most effective if located near upland contaminant sources. The overall reduction in microbial concentration brought about by the ponds was less than that assumed by most regulatory agencies, but the ponds did show some evidence of preferentially removing particle-associated fecal coliform and E. coli, suggesting that sedimentation is a key removal process. These findings should provide insights useful in the design and implementation of storm-water management strategies.

To meet the need for an operating protocol to measure the distributions of suspended solid settling velocities within urban drainage, the CEREVE research laboratory has developed and validated the VICAS protocol. This procedure makes it possible, through the use of a compact, inexpensive and easy-to-operate settling column, to measure the settling velocity of suspended solids conveyed by either storm water or combined sewage, immediately after collecting a reduced volume sample (4.5 L), and without any pretreatment steps. Two measurement data processing methods were developed and may be easily implemented by means of a series of macros written in Excel. Tests were also conducted for the purpose of evaluating the level of measurement uncertainty specific to the protocol.

The knowledge of solid behavior in combined sewer overflow (CSO) chambers is a great challenge for the protection of receiving watercourses. Moreover, great attention must be given to the occurrence of deposits on the bed of the chamber because they may lead to operation problems. In this paper, we investigate the capability of a particle tracking approach to determine the solid separation in CSO chambers. This is done by comparing simulations and experimental data collected in three small-scale models, as reported by Kehrwiller 1995. The trap, reflect, and bed shear stress (BSS) boundary conditions are compared. We propose to use the Shields relationship for evaluating the critical BSS. Finally, we propose a methodology for predicting the solid separation in CSO chambers using computational fluid dynamics.

Rejection of selected $N$ -nitrosamines, a group of probable human carcinogens, and their precursors by nanofiltration (NF) and brackish water reverse osmosis (BWRO) membranes was evaluated using a bench-scale cross-flow filtration apparatus. The tested nitrosamines included $N$ -nitrosodimethylamine, $N$ -nitrosomethylethylamine, $N$ -nitrosopyrrolidine, $N$ -nitrosodiethylamine, $N$ -nitrosodi- $n$ -propylamine, and $N$ -nitrosodi- $n$ -butylamine. The target nitrosamine precursors included secondary amines such as dimethylamine, methylethylamine, diethylamine, and dipropylamine. Rejection of nitrosamines varied greatly depending on the tested membranes (9–75% for NF membranes and 54–97% for BWRO membranes) and the molecular weight of nitrosamines. Experimental data obtained with the BWRO membranes matched well with an irreversible thermodynamic model coupled with film theory. The model further suggested that effective diffusion of nitrosamines through the BWRO membranes is responsible for the relatively low rejections observed experimentally, and the aqueous diffusivity of nitrosamines could be used as an accurate measure of nitrosamine permeability through these membranes. The steady-state rejection of all the tested nitrosamine precursors reached over 98%. This study suggests that a strategy for membrane-based water treatment processes to reduce nitrosamines should consider the removal of precursors before nitrosamines are formed during subsequent disinfection and water distribution.

The presence of toxic hexavalent chromium poses a great challenge in biological wastewater treatment. In this study, the performance of a membrane bioreactor (MBR) for the treatment of synthetic domestic wastewater in the presence of chromium was investigated. The carbonaceous pollutant removal is not affected by Cr(VI) with concentration ranging from 0.4 to 10 mg/L; it becomes slightly lower when the Cr(VI) is 50 mg/L. The nitrification efficiency of above 99% can be achieved when the waste stream is free of the metal or contains 0.4 mg/L chromium. When its concentration is 10 mg/L, nitrification efficiency above 50% is found; however, it becomes deteriorated in the presence of 50 mg/L chromium. The positive biomass growth, though lower than conventional activated sludge process, can be achieved at Cr(VI) concentration less than 10 mg/L; a decline in the cell growth occurs when the metal concentration is increased to 50 mg/L. Significant accumulation for the metal is observed when its concentration is 0.4 mg/L; however, almost no metal removal is observed when the concentration is above 10 mg/L. During eight-month continuous operation, the presence of Cr(VI) has an insignificant effect on the flux. The nitrifiers in the MBR are more sensitive to the presence of Cr(VI) than heterotrophs.

A mechanistic oxygen transfer model was developed and applied to a flow-through hollow-fiber membrane-aerated biofilm reactor. Model results are compared to conventional clean water test results as well as performance data obtained when an actively nitrifying biofilm was present on the fibers. With the biofilm present, oxygen transfer efficiencies between 30 and 55% were calculated from the measured data including the outlet gas oxygen concentration, ammonia consumption stoichiometry, and oxidized nitrogen production stoichiometry, all of which were in reasonable agreement. The mechanistic model overpredicted the oxygen transfer by a factor of 1.3 relative to the result calculated from the outlet gas oxygen concentration, which was considered the most accurate of the measured benchmarks. A mass transfer coefficient derived from the clean water testing with oxygen sensors at the membrane-liquid interface was the most accurate of the predictive models (overpredicted by a factor of 1.1) while a coefficient determined by measuring bulk liquid dissolved oxygen underpredicted the oxygen transfer by a factor of 3. The mechanistic model was found to be an adequate tool for design because it used the published diffusion and partition coefficients rather than requiring small-scale testing to determine the system-specific mass transfer coefficients.

Consumer batteries in urban litter can be significant sources of storm-water pollution. Recent studies have reported annual urban battery litter rates as high as 215 batteries per hectare of pavement and 0.4 batteries per meter of street curb. On average, 75% of these batteries are leaking or have already discharged their internal reactants. However, many battery sizes, brands, and power chemistries are littered and this diversity makes it difficult to quantify their cumulative pollution potential. The amount of zinc released from AA size alkaline and zinc chloride/zinc carbon (ZnCl/ZnC) batteries which account for approximately 90% of urban battery litter is examined. Results are presented for batch rupture release extractions of 52 alkaline battery products yielding zinc releases of 20–40 mg/L and 57 ZnCl/ZnC products yielding zinc releases of 400–1,400 mg/L. Results of continuous flow column extractions are also presented to gauge releases following initial battery rupture. Disassembly analyses are used to bound the total zinc release potential of common battery products. Results indicate that ZnCl/ZnC batteries release more zinc when they are first ruptured, but if deterioration is complete, alkaline batteries can release approximately 25% more zinc. Therefore, the relative importance of these two classes of batteries depends on site-specific factors such as the proportion of each in litter, battery deterioration rates, and the length of time that battery litter remains unremediated by maintenance.

Recent studies have shown that the annual rates of consumer battery litter on urban pavements can be as high as 215 batteries per hectare of pavement and 0.4 batteries per meter of curb. As littered batteries deteriorate, they release components (Ag, Ba, Cd, Cr, Cu, Hg, Li, Mn, Na, Ni, Pb, Ti, and Zn) that can be significant sources of storm-water contamination. Results of ambient environmental and laboratory-accelerated corrosion studies are presented to quantify the mechanisms that yield chemical deterioration of littered batteries. The analysis concentrates on AA size alkaline and zinc chloride/zinc carbon (ZnCl/ZnC) cells since these are the most commonly littered batteries. Results indicate that littered batteries exposed to ambient well-drained environmental conditions for more than two months will develop surface corrosion over most of their surface but fewer than 10% will be ruptured by corrosion within the first 6 months. This agrees well with field observations. Exposure under poorly drained conditions yields more rapid deterioration but it requires exposure to more aggressive conditions such as those produced by road salts to reproduce the high degree of deterioration observed in some battery litter.

The current practice for monitoring of subsurface plumes involves the collection of water samples from sparsely distributed monitoring wells and laboratory analysis to determine chemical concentrations. In most field situations, cost and time constraints limit the number of samples that could be collected and analyzed for continuous monitoring of large, transient plumes. With the development of wireless sensor networks (WSNs), that allow sensors to be incorporated into a distributed wireless communication and processing system, the potential exists to develop new, efficient, economical, large-scale subsurface data collection and monitoring methods. This paper presents a proof-of-concept study conducted in a two-dimensional synthetic aquifer constructed in an intermediate scale test tank to demonstrate the feasibility of using WSN for subsurface plume monitoring. The tank was packed to represent a heterogeneous aquifer, and a sodium bromide tracer was used to create a plume. A set of ten wireless sensor nodes (motes) equipped with conductivity probes to measure electrical conductivity formed the network. Software for automated data acquisition was developed and tested. Results of two experiments conducted using this test system are presented. The lessons learned from the first experiment were used to make modifications to the way the sensors were placed, how they were calibrated and how the sensors were interfaced with the data acquisition system. The findings are used to identify future research directions and issues that need to be addressed before field implementations of a WSN based data collection system for plume monitoring.

Several chemical and biological methods have been developed in the last decade to evaluate heavy metals mobility and bioavailability in contaminated soils. In this study, two methods, Biomet sensors and chemical sequential extraction [potentially bioavailable assessment sequential extraction (PBASE) method], were used to predict heavy metals bioavailability in the surface and heavy metals mobility in the subsurface of smelter-contaminated soils, respectively. The heavy metals considered (arsenic, copper, iron, lead, and zinc) were those detected in a previous sampling campaign performed in the contaminated area. Biomet biosensor results indicated that 15–25% of Cu and Zn were bioavailable for plants and animals uptake in the soil surface, whereas higher values were obtained for As and Pb $\left(>60\%\right)$ . In the soil subsurface, iron was identified as the less mobile element, followed by As and Pb, since they were mainly present in the nonsoluble fractions of PBASE method. In contrast, Cu and Zn showed similar distribution between the soluble and nonsoluble fractions. Therefore, PBASE and Biomet are useful and complementary methods which supply different information about heavy metals occurrence in contaminated soils: the first method indicates their potential mobility, whereas the second one shows their potential bioavailability for biota.

In this study, microcosm experiments were conducted to evaluate the effectiveness of (1) nutrients, hydrogen peroxide $\left({\text{H}}_2{\text{O}}_2\right)$ , and cane molasses addition; (2) soil washing by biodegradable surfactant [Simple Green (SG)]; and (3) soil pretreatment by Fenton-like oxidation on the bioremediation of fuel-oil contaminated soils. The dominant native microorganisms in the fuel-oil contaminated soils after each treatment process were determined via polymerase chain reaction, denaturing gradient gel electrophoresis, and nucleotide sequence analysis. Results show that approximately 32 and 56% of total petroleum hydrocarbon (TPH) removal (initial concentration of $\mathrm{5,000}\text{mg}{\text{kg}}^{-1}$ ) were observed in microcosms with the addition of nutrient and cane molasses $\left(\mathrm{1,000}\text{mg}{\text{L}}^{-1}\right)$ , respectively, compared to only 9% of TPH removal in live control microcosms under intrinsic conditions (without amendment) after 120 days of incubation. Addition of cane molasses would cause the increase in microbial population and thus enhance the TPH degradation rate. Results also show that approximately 61% of TPH removal was observed in microcosms with the addition of ${\text{H}}_2{\text{O}}_2\left(100\text{mg}{\text{L}}^{-1}\right)$ and nutrient after 120 days of incubation. This indicates that the addition of low concentration of ${\text{H}}_2{\text{O}}_2\left(100\text{mg}{\text{L}}^{-1}\right)$ would cause the desorption of TPH from soil particles and increase the dissolved oxygen and subsequent bioremediation efficiency in microcosms. Approximately 95 and 69% of TPH removal were observed in microcosms with SG $\left(100\text{mg}{\text{L}}^{-1}\right)$ and higher dose of ${\text{H}}_2{\text{O}}_2\left(900\text{mg}{\text{L}}^{-1}\right)$ addition, respectively. Moreover, significant increases in microbial populations were observed and two TPH biodegraders (Pseudomonas sp. and Shewanella sp.) might exist in microcosms with SG or ${\text{H}}_2{\text{O}}_2$ addition. This indicates that the commonly used soil remedial techniques, biodegradable surfactant flushing, and Fenton-like oxidation would improve the TPH removal efficiency and would not cause adverse effects on the following bioremediation process.

Toluene and naphthalene degrading (ND) bacteria, obtained from contaminated lake sediment, were used to degrade both monoaromatics and polycyclic aromatic hydrocarbons (PAHs) and the effects of cosubstrates and cocultures were examined. When toluene and naphthalene enrichments were used, the effect of the substrate interaction on their metabolism was found to be inhibitory and yet the cocultures were stimulatory, especially for toluene enrichment degradation of naphthalene (with toluene). Pseudomonas putida M2T14, a toluene degrading isolate, could efficiently degrade benzene and toluene but not naphthalene. Nonetheless, when toluene was present, this monoaromatic degrader became capable of degrading PAHs, among which the methyl substituted PAHs (mPAHs) were preferred to their corresponding unsubstituted PAHs (uPAHs). Pseudomonas azelaica ND isolate could degrade benzene, toluene, and all test PAHs. Although the uPAHs were preferred, the degradation rates of mPAHs were greatly increased via substrate interactions with naphthalene. The interaction modes of dual aromatic hydrocarbons (AHs) degraded by P. putida M2T14 and P. azelaica ND were cometabolism, synergism, no effect, inhibition, and antagonism. However, when a negative effect of biodegradation from the interaction of these AHs was found on one isolate, a positive effect would be found on the other. When benzene was present, it exhibited inhibitory effects on aromatic hydrocarbon biodegradation by M2T14 and ND isolates. A study of the biodegradation of the ternary mixture of benzene, toluene, and naphthalene by both isolates together illustrated that not only was inhibition relieved but that degradation of each compound was also greatly enhanced. Degradation by the toluene and the ND bacteria could be facilitated by complementary substrate interactions between monoaromatics and PAHs and by bacterial association. These model organisms may be very useful for the study of complex aromatic hydrocarbon degradation and for bioremediation purposes.

Remediation of source areas is challenging because lingering contaminants are often present as nonaqueous phase liquid (NAPL) and sorbed mass, and therefore difficult to remove via biodegradation or other commonly used remedial methods. Experimental results indicate that enhanced dissolution of a model NAPL, trichloroethene (TCE), can occur through the addition and/or subsequent fermentation of a dilute molasses solution. Enhanced mass transfer occurs by two mechanisms, depending upon whether the molasses solution is fresh or has fermented. The addition of fresh molasses worked to increase TCE solubility $\left(>200\%\right)$ , thereby increasing mass transfer from the NAPL phase. Mixing TCE NAPL with a fermented molasses solution, however, increased TCE mass flux via the formation of a NAPL/aqueous phase emulsion. In addition, fermented liquid may have also decreased the soil partitioning coefficient $\left(K_d\right)$ of TCE, indicating that enhanced transfer of sorbed mass to the aqueous phase could also occur in the presence of fermented molasses. These results provide guidance on how remedial systems may be optimized to increase NAPL and sorbed-mass dissolution and are therefore important, particularly when bioremediation is used to polish residual source zones.

Many problems are associated with pig manure production like high biochemical oxygen demand, chemical oxygen demand, nitrogen, and phosphorus contents. Manure produces may be used in land spreading for agricultural purposes. Over application of liquid manure or runoff caused by precipitation contribute notably to surface or overland flow of phosphorus. In this study, the LISOX process is proposed for use in medium size farms, namely a 2,000-head swine farm. The LISOX process uses biological passive flotation, without any gas addition, to enable the flocs to rise to the surface. Results show that this technology is able to considerably reduce the solids content in the final effluent to $1.1\pm 0.3\%$ and reached solids content of $17.9\pm 2.6\%$ in the combined solid manure obtained at the end of the LISOX process. Total phosphorus $\left(P_t\right)$ concentrations have been reduced from $1,234\pm 428\text{mg}/\text{L}$ to $146\pm 46\text{mg}/\text{L}$ in the final effluent, while a value of $P_t$ of $20.6\pm 7.9\text{g}/\text{kg}$ has been obtained in the final solid fraction of the treated manure. The initial ammonium ion/total phosphorus ratio of $2.3\pm 1.0$ has been increased to respectively $16.4\pm 4.6$ and $17.6\pm 5.4$ after the primary and the secondary flotation, which is clearly much higher than the target value $\left({\text{NH}}_4/P_t>7\right)$ .

Cell immobilized lipase-producing bacteria on three different matrices were incorporated in a fat-, oil-, and grease (FOG) trap system for restaurant wastewater treatment. During a 16-day laboratory-scale experiment for the treatment of synthetic FOG wastewater containing soybean oil, no significant difference (two-tailed $t$ test at 95% confidence interval) in the FOG removal between two systems was observed at FOG influent $\le 1,000\text{mg}/\text{L}$ . However, the typical trap showed lower FOG removal efficiency than the matrix-based system when the influent FOG concentration was increased to $\ge 5,000\text{mg}/\text{L}$ . In addition, the matrix-based trap system was able to sustain a stable high FOG removal, with $<100\text{mg}/\text{L}$ effluent, even at 10,000 mg/L influent FOG. Based on FOG heights measured and mass balance calculations, 97.4 and 99.5% of the total FOG load for 16 days were removed in a typical trap and matrix-based system, respectively. About 93.6% of the removal in the matrix-based was accounted to biodegradation. The 30-day full-scale operations demonstrated a distinguishably better performance in the matrix-based system ( $92.7\pm 9.06\%$ of $1,044.8\pm 537.27\text{mg}$ FOG/L) than in the typical trap system ( $74.6\pm 27.13\%$ of $463.4\pm 296.87\text{mg}$ FOG/L) for the treatment of barbeque restaurant wastewater. Similarly, matrix-based system revealed higher chemical oxygen demand removal $\left(85.9\pm 11.99\%\right)$ than the typical trap system $\left(60.4\pm 31.26\%\right)$ . Characterizations of the influent, emulsified, adsorbed and effluent FOG indicated that straight saturated fatty acids constituted the cause of clogging problems in the FOG-trap and piping system.

Terrigenous inorganic particles delivered during runoff events cause problems of high turbidity in many lakes and reservoirs. A turbidity model, composed of a two-dimensional hydrothermal/transport submodel and a turbidity submodel, is developed and tested for Ashokan Reservoir, New York, that experiences elevated turbidity levels following runoff events. A robotic monitoring network, rapid profiling instrumentation, and individual particle analyses are used to support the modeling, by specifying turbidity loads and in-reservoir patterns and features of the particles that guided representation of settling. The turbidity-causing particles are clay minerals, $1–10\mu \text{m}$ in diameter. The hydrothermal/transport submodel that serves as the physical framework for the overall model, was separately validated for a 13-year period. The turbidity submodel considered three particle-size/settling velocity classes of turbidity, consistent with the independent individual particle characterizations. Robust performance is demonstrated for the overall turbidity model, as it simulates well the wide range of patterns observed in the reservoir and withdrawal, associated with a number of major runoff events from the same 13-year period. The model will be used to support forecasting in the evaluation of management alternatives intended to abate the problem.

Storm-water filters and biofilters are limited by physical clogging. Several models have been proposed to predict the flow rate through the media throughout its lifespan. Urbonas (1999) modeled flow rate through a downflow sand filter as a function of the suspended solids loading on the media surface using a power equation. This paper confirms this equation in describing the flow rate through mixed-media downflow filters at a laboratory scale but with unique coefficients for different media. Confounding effects of influent solids concentration and filter surface diameter on the relationship between flow rate and suspended solids loading were seen, indicating that other factors are important in describing that relationship. Maintenance issues also were investigated, with the results showing that removal of about 5–10% of the surface of the media had little long-term impact on flow rate recovery.