Journal of Environmental Engineering

Residential surface soil regulatory guidance values (RGVs) specify the threshold at which soil contamination requires action. Usually, RGVs are risk-based values based on child ingestion, inhalation, and dermal exposure. The U.S. Environmental Protection Agency, 45 U.S. states, and 27 other nations have developed arsenic surface soil RGVs. Regulating arsenic poses unusual problems because it presents both cancer and noncancer risks, and its background concentration often exceeds health-based risk levels. Statistical analyses are presented to characterize 119 arsenic surface soil RGVs. State values vary between 0.039 and 200 mg/kg. Worldwide values vary between 1.7 and 687 mg/kg. The U.S. and worldwide values resemble lognormal probability distributions but the data cannot be mingled since worldwide values are significantly higher. An analysis of 40 arsenic background studies yielding averages between 1.3 and 45.1 mg/kg is also presented. Monte Carlo simulations of screening model calculations are used to explore the impact of coefficient uncertainty. Results indicate that 95% of cancer-based results should fall between 0.004 and 2.7 mg/kg and 95% of noncancer results should fall between 1.0 and 40 mg/kg. Although U.S. state arsenic RGVs vary by 3.7 orders of magnitude, most values appear to fall within the bounds of plausible risk- and background-based values.

This paper reviews the evolution of bioretention systems, a promising at-source storm-water best management practice. The introduction of bioretention systems in the 1990s by Prince George’s County, Md. is examined along with the motivations behind the development of the systems. A summary of the research findings on the performance of bioretention systems is provided including proposed design modifications to improve the field performance. Also included is an overview of past and current bioretention design guidelines in North America, as well as a discussion of issues surrounding the public adoption and implementation of bioretention systems. Potential alternative uses for the systems are highlighted and a review of bioretention modeling work is provided. Finally, the paper outlines research needs and anticipated future work necessary to bring about the widespread use of bioretention systems.

This study aimed to investigate the contribution to estrogen removal from the activated sludge of an estrogen-degrading bacterium, Novosphingobium sp. Strain JEM-1, isolated by the writers from the activated sludge. The cell numbers of the Strain JEM-1 were investigated in two full-scale wastewater-treatment plants using real-time PCR. Strain JEM-1 appears to be commonly distributed in the activated sludge. The cell numbers of Strain JEM-1 in the oxidation ditch process were higher than those in the conventional activated sludge (CAS) process, and the effluent concentrations of E1 in the CAS process tended to decrease with increased cell numbers of Strain JEM-1. In a bench-scale experiment to investigate bioaugmentation with Strain JEM-1, there was a significant difference in the effluent concentrations of estrogens between the experimental series and the control series. Linear relationships were observed between cell numbers of Strain JEM-1 and the efficiency of removal of estrogens. These results suggest that Strain JEM-1 contributes to the estrogen removal in the activated sludge.

Toxic arsenic occurs in drinking water from natural and/or anthropogenic sources. It causes health problems worldwide. Among the existing arsenic removal techniques adsorption is the commonly used one. $\gamma {\text{-Fe}}_2{\text{O}}_3$ nanoparticles were found recently to be a good adsorbent for arsenate because of its relatively high adsorption capacity and simple separation of the particles from the treated water. The aim of the study was to investigate the arsenate adsorption mechanism on the crystal $\gamma {\text{-Fe}}_2{\text{O}}_3$ nanoparticles. Adsorption experiments were carried out with three different kinds of maghemite nanoparticles: (i) homemade one with mechanochemical method; (ii) homemade one with sol-gel process; and (iii) a commercially available one. The adsorption process was monitored by characterizing with Fourier transform infrared, x-ray photoelectron spectroscopy, x-ray diffraction, transmission electron microscopy, and zeta potential analyzer. No crystal and amorphous precipitation were found on the iron oxide surfaces. The inner-sphere complex formation was found to be the predominant mechanism of adsorption.

A pilot-scale liquid-solid circulating fluidized bed (LSCFB) bioreactor was employed for biological nutrient removal from municipal wastewater at the Adelaide Pollution Control Plant, London, Ontario, Canada. Lava rock particles of $600\mu \text{m}$ were used as a biomass carrier media. The system generated effluent characterized by $<1.0\text{mg}$ ${\text{NH}}_4\text{N}/\text{L}$ , $<6.0\text{mg}$ ${\text{NO}}_3\text{N}/\text{L}$ , $<1.0\text{mg}$ ${\text{PO}}_4\text{P}/\text{L}$ , $<10\text{mg}$ TN/L, and $<10\text{mg}$ SBOD/L at an influent flow of $5{\text{m}}^3/\text{d}$ , without adding any chemicals for phosphorus removal and secondary clarification for suspended solids removal. The impact of the dynamic loading on the LSCFB effluent quality and its nutrient removal efficiencies were monitored by simulating wet weather condition at a maximum peaking factor of 3 for 4 h. The achievability of effluent characteristics of 1.1 mg ${\text{NH}}_4\text{N}/\text{L}$ , 4.6 mg ${\text{NO}}_3\text{N}/\text{L}$ , 37 mg COD/L, and 0.5 mg ${\text{PO}}_4\text{P}/\text{L}$ after 24 h of the dynamic loading emphasize the favorable response of the LSCFB to the dynamic loadings and the sustainability of performance without loss of nutrient removal capacity.

Experimental data pertaining to two pairs of solid-substrate sulfate-reducing biocolumns for remediation of mine drainage were used for calibrating and testing new reactive transport models based on sulfate reduction and sulfide precipitation linked to rate-limiting solid-substrate hydrolysis. First-order (F) and Contois (C) kinetics for decomposition as well as different numbers of pools of decomposable materials were proposed in different models (F1–F3 and C1–C3). Effluent sulfate concentrations for one of the columns were used as the basis for calibrating the different models and, due to limitations in the calibration data set, the number of adjustable model parameters was limited using parameter tying. Calibrated models were ranked using Akaike information criterion, and Model C2, followed by Model C1, based on Contois kinetics, emerged as the models that were supported to a greater extent by the data. For an independent experimental data set, model testing was performed using Models C2 and C1 with parameters from the previous calibration resulting in good approximations of effluent sulfate. For the calibration data set, longer-term model predictions for effluent sulfate, decomposable substrates, and microbial populations also were performed. The reactive transport models represent a potentially valuable tool for the design of solid-substrate bioreactors used for the treatment of mining influenced water, although future model validation using longer-term field data sets will be necessary to confirm the model predictions.

A numerical watershed model was used to evaluate the potential influence of various point and nonpoint sources including on-site wastewater systems (OWS) on stream nitrate concentration in Turkey Creek Watershed, Colorado. A watershed analysis risk management framework model was used for this study, and was calibrated to observed stream nitrate concentrations using an automatic calibration tool. Parameter sensitivity analysis was done to select critical parameters for calibration and to reduce uncertainty in the simulated results. Sensitivity analysis of nitrate transport and transformation parameters showed that stream nitrate concentration is highly sensitive to cation exchange capacity, nitrification rate, base saturation of ammonium, initial concentration of ammonium in the soil, and some of the crop growth related parameters. The calibrated model was used to evaluate scenarios related to OWS including the impacts of population growth and new development and impacts of conversion of OWS to conventional sewers. The results showed that there would be a significant increase in stream nitrate concentration with increasing population. Conversion of OWS to sewers increased stream nitrate concentration but decreased nitrate concentration in the bottom soil layer indicating that OWS are beneficial with respect to stream nitrate concentration but may increase nitrate concentrations in groundwater.

This study evaluated the constituent make up of simulated rainwater runoff from Class C fly ash–stabilized and nonstabilized clay soil using laboratory test pads to assess the potential for impacts to surface water from the use of uncovered fly ash–stabilized soils as potential roadbed material. Recirculated runoff from test pads was sampled and tested during three simulated rainfall events over an 84-day trial period. All samples were analyzed for trace metals. Analytical results from the simulated runoff were screened to identify five indicator parameters in the runoff that were used as the basis for assessing potential environmental effects to surface waters. Runoff water results from fly ash–stabilized test pads for these indicator parameters were compared to water quality benchmarks. Based on the low concentrations measured in runoff relative to applicable criteria, and on the conservative nature of the experimental methods relative to typical field conditions, we concluded that surface runoff from fly ash–stabilized soil would not present significant adverse effects to surface water if used uncovered on low traffic exposed surfaces.

A modeling framework that combines both two-dimensional (2D) and one-dimensional (1D) numerical models for the evaluation of organic-matter transport across the bed-water interface is presented. Emphasis is placed on capturing oxygen demand in the water column associated with the resuspension of organic sediments from the bottom. The proposed numerical approach solves the hydrodynamics coupled with sediment transport and water quality dynamics and represents a substantial improvement to the state of the art of water quality modeling methodologies available in the literature. A biochemical oxygen demand (BOD)–dissolved oxygen (DO) water quality module is incorporated into the 2D depth-averaged numerical model STREMR-HySedWq. The model is applied to the South Fork of the South Branch of the Chicago River, known as Bubbly Creek, with the goal of modeling combined sewer overflow (CSO) events and their impact on DO levels in the short-term (hours or days). Given the intermittent nature of this kind of events, STREMR-HySedWq was used for modeling the overflow phase, while the period following a given CSO event, when water is essentially quiescent in the creek, was modeled with a simpler 1D, area-averaged, dispersion-reaction BOD-DO model. The proposed conceptual and numerical approach is capable of capturing the key processes, thus providing both useful preliminary results as well as important guidance to assess potential water quality improvement and sediment management solutions in Bubbly Creek, Illinois.

Pilot- and laboratory-scale granular activated carbon (GAC) studies were conducted to determine the extent of 2-methylisoborneol (MIB) removal from two conventionally treated waters. Two different GACs were evaluated, a wood-based carbon and a coal-based carbon. Greater MIB removal was observed with the wood-based GAC which contradicts previous studies using the powdered forms of the carbons. Equilibrium and kinetic parameters were derived from laboratory-scale adsorption isotherm and short bed adsorber (SBA) experiments, respectively, and used to describe the adsorption of MIB. However, the derived parameters were unable to accurately predict the removal of MIB in the pilot-scale columns using the homogenous surface diffusion model. This suggested that there were inherent limitations with the SBA experiments, in particular, the small volume of GAC and high filtration rates employed. Larger laboratory column experiments were shown to accurately simulate the pilot-scale columns. Adsorption still played a vital role in the removal of MIB, even though the GAC had been exhausted for the removal of organics in terms of dissolved organic carbon and ultraviolet absorbance measurements. Even after a 6-month operation, complete MIB removal was observed with up to 80% attributed to adsorption, and the remaining 20% attributed to biodegradation.

The mixture of scrap iron and particle carbon, termed internal electrolysis, has been used in the pretreatment of industrial wastewater to improve the biodegradability. However, the clogging of fillings reduces treatment efficiency, and filling replacement is inconvenient in engineering application. This study developed a novel internal electrolysis system, in which iron and carbon were separately placed and connected with a wire. Results showed that the removal of paranitrophenol by iron was significantly enhanced by the connection of carbon. The removal by iron connected with carbon was approximately equivalent to that by iron contacted with carbon. The removal of nitrobenzene and the production of aniline proved the reduction in nitro to amino group. The sites for contaminant removal were found to be on iron surface rather than on carbon surface. The connection of carbon to iron facilitated the corrosion of iron and led to the formation of more Fe oxyhydroxide and the release of more electrons from iron, both of which attributed to contaminant removal. The engineering application using the novel internal electrolysis demonstrated an average chemical oxygen demand removal of 60% and a significant increase in wastewater biodegradability. This novel internal electrolysis system was preliminarily proved feasible and convenient.

The capillary suction time (CST) and the specific resistance to filtration (SRF) tests are both commonly used to estimate sludge dewaterability. Both tests are known to be empirically related but the SRF is much more expensive and time consuming compared with the CST test. The aim of this study was therefore to develop a prediction methodology to obtain SRF test results from the data generated by CST tests under different experimental conditions. This study is based on empirical data sets linking CST with SRF. The prediction equations were developed by first estimating filterability from CST values and then relating it with SRF values using regression analyses. The relationships between the results of the CST and SRF tests were best described using an empirical model, which incorporated logarithmic and squared terms to account for the nonlinear relationship between filterability, total suspended solids, and temperature. The findings were statistically significant $\left(p<0.05\right)$ and the model satisfied all the statistical assumptions. Therefore, the model can be used to predict SRF from CST values.

An immobilization cell was successfully coupled to a controlled stress rheometer to quantify rheological properties of a sludge during its dewatering. An anaerobically digested sludge and a synthetic sludge were analyzed and conditioned at various doses with a cationic flocculant. Direct strain-controlled oscillatory analyses could not be performed due to rapid dewatering, but controlled shear rate analysis quantified the increases in sludge viscosity as the solid’s concentration increased. Immobilization times determined by these experiments—viscosity versus dewatering time—agree with capillary suction times, since both indicate the time required for water removal ( $r^2$ from 0.81 to 0.99). However, capillary suction time tests were more strongly influenced by filtrate viscosity at high polymer doses. The immobilization cell allowed quantified amounts of shear to be imposed during dewatering, with greater shearing found to provide more rapid immobilization. This finding is consistent with the design of belt filtration dewatering devices, but demonstrates that current models do not account for a critical aspect of this process.

Degradation of aqueous solutions of a commercial azo-reactive textile dye, Remazol Red F3B, by the Fenton and photo-Fenton processes, has been investigated. Fenton-type reaction rates are strongly dependent on pH, temperature, and initial concentrations of the ${\text{Fe}}^{2+}$ , ${\text{H}}_2{\text{O}}_2$ , and dye. The effects of varying these parameters on the degradation performances of these two processes have been studied, and the optimal operational conditions have been found. The optimal conditions for these processes were obtained at $\text{pH}=3$ . A comparative study of the Fenton and photo-Fenton reactions has also been carried out using a photoreactor. The Fenton process is highly efficient for removal of the color, chemical oxygen demand, and total organic carbon of a Remazol Red F3B solution. The photo-Fenton process proved to be more efficient, and proceeds at a much higher oxidation rate than the Fenton process. The photo-Fenton process allows 90% degradation of chemical oxygen demand in about 20 min of reaction time.