Journal of Environmental Engineering

Pesticide runoff loads from grass surfaces were estimated through simulation experiments for 37 chemicals registered for use on U.S. lawns and golf courses. Simulation runs were made for each chemical and surface (lawns, greens, fairways) using 100-year weather records generated for nine U.S. cities. Results were summarized as mean annual and 1-in-10 year annual maximum daily pesticide loads. These loads varied greatly with pesticide, grass surface, and city, ranging from less than one to over $400\mathrm{g}/\mathrm{ha}$ for mean annual loads and from less than one to over $500\mathrm{g}/\mathrm{ha}$ for 1-in-10 year maximum daily loads. Mean annual loads averaged over the 37 chemicals and three grass surfaces were found to be closely related to growing season precipitation. Variations among the nine cities were well-captured by three general climate categories: humid, represented by Atlanta and Houston; mesic, as with Albany, Columbus, Madison, and Olympia; and dry, represented by Bismarck, Fresno, and Roswell. Mean annual pesticide runoff was 19, 6, and $2\mathrm{g}/\mathrm{ha}$ in the humid, mesic, and dry regions, respectively.

A new technique for quantifying pathogen sources to streams is proposed and demonstrated. Hydrograph separation is used to partition measured streamflow into surface runoff and base flow, and characteristic pathogen concentrations are assigned to each flow component along with a background source flux. The maximum-likelihood characteristic concentrations and background flux are determined from measured instream pathogen concentrations. This approach is shown to yield comparable to superior performance in predicting instream pathogen concentrations compared with much more complex terrestrial fate and transport models. Application of the proposed approach to six catchments yields Nash-Sutcliffe efficiencies of the log-transformed fecal-coliform concentrations in the range of 0.21 to 0.48. The characteristic fecal-coliform concentrations in surface runoff are in the range of $200–700\mathrm{cfu}/\mathrm{dL}$ and the base-flow characteristic concentrations are in the range of $20–100\mathrm{cfu}/\mathrm{dL}$. It is shown that the frequency distribution of bacteria concentrations derived from sample measurements can sometimes differ significantly from their long-term frequency distribution.

This paper tests a simple two-parameter regression model, based on rainfall intensity, for calculating event loads of total suspended solids, total phosphorus, and total nitrogen from urban catchments. It also examines the sensitivity of the model to its two parameters and to the rainfall time step. This was done by using large data sets collected at six urban catchments in temperate Melbourne. It was found that the two-parameter model typically explains approximately 90% of the variation in event loads at a site. The model also predicts the within-event behavior of pollutants when the flow lag time is taken into account, with $R^2$ correlations greater than 0.6 in most cases for both loads and concentrations at a six minute time step. Despite its acknowledged correlation with flow, rainfall intensity over short time steps is shown to be the primary driver of pollutant mobilization, and provides a practical means of predicting pollutant loads by using readily available data.

The water quality performance of best management practices (BMPs) has been frequently assessed by the removal efficiency metric. Recent findings show that the removal efficiency metric is flawed because it does not account for background water quality, eco-region differentiation, and background, or “irreducible,” concentrations. Additionally, the removal efficiency metric inherently assumes a definite association exists between influent and effluent pollutant concentrations. Such a relationship between influent and effluent concentrations has been minimally studied for bioretention, the most common storm-water control measure associated with low-impact development (LID). This study analyzes influent and effluent total nitrogen (TN) and total phosphorous (TP) concentrations from 11 bioretention cells in the mid-Atlantic United States. Pooled data showed only a slight association between influent and effluent TN. Essentially no relationship exists between influent and effluent TP concentration. Both findings indicate that the percent-removal metric is a faulty means of evaluating bioretention performance. Twelve general linear models (GLMs) were created where influent TN and TP were the predictors of respective effluent TN and TP concentrations. Only one GLM was considered to be “good,” defined as 67–90% of the variation in effluent concentrations being explained by respective influent concentrations ($R^2=0.72$). In addition, there were two “fair” models, five “poor” models, and four “very poor” models. No “very good” models were found for TN or TP. Furthermore, as influent nutrient concentration in runoff increases, the removal efficiency increases for TN and TP. “Dirtier” influent TP concentrations were effectively reduced; conversely, “cleaner” TP influent concentrations increased, both tending toward a (possibly media-controlled) baseline effluent concentration (0.10 to $0.18\mathrm{mg}/\mathrm{l}$). TN effluent data also may have been tending toward a common concentration; however, the value was not as discernible.

In response to water quality and quantity issues within the Stroubles Creek watershed in Blacksburg, Virginia, a retrofit bioretention cell (BRC) was installed to collect and treat runoff from an existing parking lot. The BRC was completed in July 2007, and 28 precipitation events were monitored between October 2007 and June 2008. For each storm, inflow and outflow flow-weighted composite samples were collected and analyzed for suspended sediment, total nitrogen, and total phosphorus. The inflow and outflow concentrations and loads, as well as total inflow and outflow volumes and peak flow rates, were analyzed to evaluate BRC efficiency. Overall, the BRC successfully reduced flow volumes and peak flow rates leaving the parking lot by 97 and 99%, respectively. Cumulative mass reductions for sediment, total nitrogen, and total phosphorus all exceeded 99% by mass. The findings of this study have significant implications for areas with karst geology: (1) current design recommendations of lining the bottom of BRCs with clay may not be sufficient to prevent large amounts of water from infiltrating into surrounding soils; and (2) in areas with significant elevation changes, designing BRCs deeper than the typical 0.6–1.2 m increases the feasibility of retrofits and provides substantial water quality and quantity benefits.

An apparatus was designed, manufactured, and implemented to isolate pH during electrokinetic in situ chemical oxidation (EK-ISCO). ${\mathrm{H}}^{+}$ and ${\mathrm{OH}}^{-}$ electromigration were used to determine the adequacy of the designed apparatus for pH isolation. A series of pH-isolation and normal-mode (no pH-isolation) experiments were undertaken and compared. It was found that pH isolation was achieved when the electrode reservoirs were separated by porous media combined with the purging of the electrode reservoir fluid. The electromigration retardation factor of ${\mathrm{H}}^{+}$ and ${\mathrm{OH}}^{-}$ was calculated for the porous media using the observed pH breakthrough times. The retardation factor for ${\mathrm{H}}^{+}$ was also calculated by considering mass flux data. The retardation factors for ${\mathrm{H}}^{+}$ and ${\mathrm{OH}}^{-}$ were found to be 28.3 and 95, respectively, when using the breakthrough time. The retardation factor for ${\mathrm{H}}^{+}$ was calculated to be 36.7 using the mass flux data.

Methyl-$t$-butyl ether (MTBE) is an additive to gasoline that serves as an oxygenate to increase the octane rating and improve combustion efficiency. Assessment of MTBE biodegradation under aerobic conditions was performed in lab-scale biomass concentrator reactors (BCRs). These reactors were bench-scale microcosms that retain and concentrate biomass thereby enabling biodegradation to sub-$\mu \mathrm{g}/\mathrm{L}$ level. The BCRs were run under low hydraulic retention times with a synthetically prepared feed containing $500\mu \mathrm{g}/\mathrm{L}$ of several oxygenates, MTBE, diisopropyl ether (DIPE), ethyl-$t$-butyl ether (ETBE), $t$-amyl methyl ether (TAME), $t$-amyl alcohol (TAA), and the primary gasoline constituents benzene, toluene, ethyl benzene, and $p$-xylene (BTEX). The BCRs were effective in the removal of the aforementioned contaminants to concentrations lower than the targeted $5\mu \mathrm{g}/\mathrm{L}$, which is below the U.S. Environmental Protection Agency (EPA) taste and odor threshold of $20–40\mu \mathrm{g}/\mathrm{L}$. Reactor performance was also evaluated under shock loading and intermittent feeding (starvation tests) of the contaminants of concern to evaluate the reactor’s robustness in recovering from such stresses. The BCRs were found to be highly resilient to fluctuations in substrate and flow conditions.

The amount of organic vapors that are emitted to the atmosphere can be reduced with the use of electrothermal-swing adsorption (ESA) with activated carbon fiber cloth (ACFC). This paper describes a pilot-scale ESA system that was scaled up based on two ESA bench-scale systems. Each ESA system consists of two vessels with four ACFC cartridges. The bench-scale and pilot-scale systems were tested with adsorption and desorption cycles using gas streams containing 73–10,000 ppmv and from 170–940 ppmv methyl ethyl ketone, respectively. Total flow rate ranged from $5\mathrm{sL}/\min$ to $140\mathrm{sL}/\min$ for the bench unit and $1,700\mathrm{sL}/\min$ for the pilot unit. Scale-up procedure of an ESA system from the bench-scale to the pilot-scale is presented for the first time. Scale-up was based on throughput ratio, length of unused bed, adsorption capacity, pressure drop, superficial gas velocity in the ACFC, organic vapor removal efficiency, duration of the adsorption cycle, duration of the regeneration cycle, liquid recovery efficiency, electrical power/energy applied to the ACFC cartridges, and temperature of the ACFC cartridges.

A novel method is presented for pyrolyzing and activating waste tires for adsorptive removal of aqueous contaminants. The adsorption characteristics of a cationic dye (methylene blue, MB) by pyrolytic tire char were evaluated. Mechanistic insights into the adsorption of MB onto char made from pyrolyzed tires are discussed on the basis of equilibrium and kinetic studies. A comparative evaluation of the performance of unoxygenated, pyrolyzed chars (NoPPO) and oxygenated chars (P550250) is reported. Despite having similar surface areas between the oxygenated and unxoygenated chars, the adsorption capacity of the former was much higher than that of the latter. However, adsorption of MB is thermodynamically unfavorable ($\Delta G>0$) although oxygenation lowers the free energy of adsorption. MB sorption onto P550250 is inhibited by an external film, which was not observed in the case of NoPPO. An increase in the solution temperature was found to reduce the adsorption rates of MB onto P550250 but increase the sorption capacity of NoPPO. Overall, oxygenation was found to improve the sorption of MB onto pyrolytic chars.

In this study, an inexact fuzzy-probabilistic programming (IFPP) method is advanced for developing optimal municipal solid waste (MSW) management strategy with uncertain information. The IFPP can support the assessment of risk of violating constraints associated with fuzzy and random features. The developed method is applied to a case study of long-term MSW management planning in the city of Changchun, China. Violations for transfer-station capacity constraints are allowed under a range of probability and possibility levels, which are related to trade-offs between the system cost and the constraint-violation risk. The results indicate that useful solutions for planning the MSW management practices have been generated. They are valuable for supporting the identification of efficient waste-flow allocation patterns, the long-term capacity planning of the city’s waste management system, and the formulation of local policies regarding waste management under uncertainty.

In many situations the design of culverts prevents the upstream migration of fish because water velocity in the barrel is greater than that of the natural channel. One way to reduce the water velocity within the culvert is to install spoiler baffles on the base. The current investigation uses a three-dimensional numerical tool to examine the influence of the baffle geometry on flow within culverts of varying diameters. The results indicate that spoiler baffles can reduce velocities in the culvert dramatically. The final choice of design hinges on the need of the fish and the discharge capacity of the culvert.