Journal of Environmental Engineering

Biodosimetry is the currently accepted method for validation of fluence delivery in ultraviolet (UV) reactors for water disinfection. This method utilizes the inactivation of a surrogate microorganism to predict the reduction equivalent fluence and subsequent inactivation of a target pathogen. Two common surrogates—Bacillus subtilis spores and MS-2 coliphage—were used to examine the relationship between surrogate type and biodosimetry results. A pilot-scale LP UV reactor was investigated at two flow conditions (7.5 and $15\mathrm{gpm}$ ) and four different UV $253.7\mathrm{nm}$ water transmittance (UVT, $1\mathrm{cm}$ ) values between 82 and 91%. The calculated reduction equivalent fluence differed from a maximum of 30% at $7.5\mathrm{gal.}∕\min$ and 15% at $15\mathrm{gal.}∕\min$ between the surrogates tested, depending on the UVT. These differences were attributed to the sensitivity of organisms used, hydraulic inefficiences, and UV fluence distribution in the reactor, thus the choice of validation microbe may impact the determination of reduction equivalent fluence in UV reactors.

Field data and existing theory suggest that pavement texture governs the seasonal persistence of deicing agent solids and the storm scale variability of the specific conductivity of highway runoff. We measured precipitation, runoff, and specific conductivity for 50 storms over four deicing seasons at a highway drainage system in southeastern Massachusetts. An average pavement texture of $2.44\mathrm{mm}$ was measured and $5.17\times {10}^5\mathrm{kg}$ of calcium magnesium acetate, salt, and premix applications was reported as well. Catchments and a depression storage layer model the highway drainage system, which routes hyetographs and slowly dissolving deicing agent solids to storm scale hydrographs and specific conductivity pollutographs. We equate the average pavement texture to the depression storage layer depth, which receives applied deicing agent solids, controls their dissolution during a storm, and governs their seasonal scale persistence. The observed average pavement texture, precipitation, and deicing agent applications yield first flush (storm scale) specific conductivity values in the depression storage layer that range from a winter maximum of $15\mathrm{mS}∕\mathrm{cm}$ to summer values two orders of magnitude lower. The winter maximum, or seasonal scale first flush of specific conductivity, would be lower for rougher pavement due to slower dissolution. The rougher pavement would also induce stronger persistence of deicing agent solids throughout the year, so that appreciable storm scale first flushes would occur in the summer.

This study has conceptually reviewed issues related to implementation of a groundwater mound monitoring well (GMMW) for monitoring recharged water from a surface spreading basin with emphasis on uncertain hydrogeological conditions. For this, we selected a recharge site in the City of Mesa, Ariz., that is characterized with near-surface clay lenses of low permeability. A geostatistical simulation technique was used for generating hydrogeological fields under the recharge basin, using soil boring logs and historical hydrological data. More than 50 hydrogeological fields were generated and used for modeling. Five scenarios were formulated with varying parameter values and different initial and boundary conditions, and each scenario was evaluated with the 50 hydrogeological fields generated. Results of this study indicate that travel times to the mound may vary by over one order of magnitude and the use of a GMMW will only be practical for regulatory compliance in a homogeneous system.

Years of wastewater discharge at the Department of Energy’s Pantex Plant have contaminated the vadose zone and underlying perched aquifer with hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX). Because the vadose zone is acting as a continual source of groundwater contamination, removing RDX from the unsaturated zone is paramount to prevent further contamination. We determined the efficacy of ozone to degrade and mineralize RDX. Solution experiments showed that ozone ( $27\mathrm{mg}{\mathrm{L}}^{-1}$ ; $150\mathrm{mL}{\min }^{-1}$ ) was effective in mineralizing 80% of the RDX $\left(30\mathrm{mg}\mathrm{RDX}{\mathrm{L}}^{-1}\right)$ provided that some Pantex soil was present to buffer the solution pH. Soil columns treated with ozone produced 50% RDX mineralization within 1 day and $>80\%$ within 7 day. Experiments designed to evaluate aerobic biodegradation following partial ozonation of a RDX solution showed that ozone-generated RDX products were much more biodegradable than untreated controls in aerobic microcosms (35 versus $<0.3\%$ cumulative mineralization). These results support the use of ozone as a remedial treatment for the contaminated vadose zone at the Pantex facility.

The adsorption isotherm models available in the literature have generally developed for sorption onto metallic surfaces or activated carbon-based sorbents. However, biosorptive uptakes involve interactions of biopolymer-based surfaces with different types of pollutants, which are quite different from metal surfaces or activated carbon. So, in the present study, 16 different types of adsorption isotherm models have been studied. For a ready reference both types of sorbents, i.e., a biosorbent and activated carbon have been employed. Results show that in general the accuracy of models to fit experimental data improves with the degree of freedom. The Fritz–Schluender model gives the most accurate fit $(R^{2}0.85–0.99)$ to all experimental data in comparison to other models used both for activated carbon and the biosorbent. However, most widely used isotherm models, i.e., Langmuir and Freundlich, could be used to describe the sorption equilibrium of biosorptive processes with a fair degree of accuracy, owing to the mathematical ease in the use of these models. Trends of the applicability of various sorption equilibrium models to biosorptive uptakes are similar to those of activated carbon-based sorptions. Comprehensive equilibrium analysis has assisted in understanding the mechanistic aspects associated with different types of sorbents.

Multiparameter monitors (sondes) were installed at four sites in a stream in the Great Smoky Mountains National Park. These sondes recorded pH, turbidity, and other parameters every $15\min$ . The data were analyzed to determine the time-connected duration of excursions below various pH levels (pH 4.5, 5.0, 5.5, 6.0, and 6.5). The durations for excursions below each pH level were assigned probability quantiles and plotted. This created a concentration–duration–frequency curve similar to precipitation intensity–duration–frequency curves. The pH excursion events appear to follow a Poisson arrival process and were fitted to a corresponding exponential distribution. The mean event duration for each pH level is the fitting parameter, $\mu$ , for the exponential distribution, and $\mu$ followed an exponential trend with pH. The characteristics of the concentration–duration–frequency family of curves capture the information contained in the original data and potentially allow comparisons with toxicity data as well as a temporal and spatial comparison.

In this work we present a new reliable analytical evaluation of the oxygen sag equation for second-order biochemical oxygen demand reaction. A single series expansion relation is derived for dissolved oxygen sag equation in terms of binomial coefficients. The convergence of the series is tested by the concrete cases of parameters. The formulas obtained are numerically stable for $k_3{L}_{0}t<1$ . Numerical results are presented, and compared with results using alternative evaluation schemes.

This study investigates the interaction of natural organic matter with iron oxide (goethite) on chlorine decay, disinfection by-product (DBP) formation, and DBP compound speciation [total trihalomethanes (TTHM4) and haloacetic acids (HAA5)]. Batch experiments were conducted with goethite, multiple finished drinking waters, variable chlorine dose, and fixed pH 8. The overall objective was to assess natural organic matter (NOM) adsorption onto goethite and its effect on chlorine decay and DBP formation. Chlorine consumption always increased in the presence of goethite and is attributed to an increase in the reactivity and/or modification of adsorbed NOM. Adsorbed NOM also led to an overall increase in TTHM4, however, HAA5 formation was suppressed during the first $2\mathrm{h}$ . Chloroform was identified as the increasing species and dichloracetic acid was identified as the suppressed species. This study clearly shows that goethite, which is the predominant iron oxide of pipe deposits, alters both chlorine decay and DBP formation and should be considered when assessing water treatment plant operations and DBP monitoring site selection.

The performance of an abrasive is dependent on its properties as well as the operating conditions during blasting. This study was undertaken to simulate enclosed blasting operations using steel shot and grit on rusted and painted steel panels; and collect and measure total particulate matter (PM) emissions at commonly used blast pressure and feed rate settings. U.S. EPA source sampling methods were used to sample emissions and estimate uncontrolled total PM emission factors. Regression equations expressing total PM emissions as function of blast pressure and abrasive feed rate were developed to estimate uncontrolled total PM emissions. The results of this study will be helpful in controlling emissions, developing emission inventories, developing best management practices, and selecting process parameters corresponding to minimum emissions for steel shot and grit.

A testing methodology is presented that supports the development of a field design for in situ gaseous treatment of sediments with diluted hydrogen sulfide. This approach involves the collection of column breakthrough test results at various flow rates, allowing a relationship to be developed between pore velocity of the carrier gas and velocity of the hydrogen sulfide reaction front that permits sizing to the field scale. A regression fit of a set of laboratory column breakthrough test data collected in this study is utilized to illustrate the development of a field design based on a two-dimensional radial flow analytical model. Information regarding treatment time and hydrogen sulfide consumption characteristics associated with in situ gaseous treatment can then be obtained from this model and used as a basis for estimation of treatment schedule and costs. The regression relationship can also be utilized in numerical models in more complex geometries to support the field design of in situ gaseous treatment operations.

Concentrations of polychlorinated dibenzo- $p$ -dioxins and dibenzofurans in runoff were measured at 10 small flood control drainage channels in the Houston area. Total toxicity equivalent concentrations in runoff ranged from $0.01\text{to}0.11\mathrm{pg}∕\mathrm{L}$ for the dissolved phase and from $0.02\text{to}0.88\mathrm{pg}∕\mathrm{L}$ for the suspended phase. The dissolved concentrations were lower than their respective suspended concentrations, with average suspended/dissolved ratios between 5 and 152 for individual congeners. Average observed logs of organic-carbon (OC)-normalized suspended sediment-dissolved partitioning coefficients $\left(\log {\mathrm{K}}_{\mathrm{OC}}\right)$ varied between 5.47 and $7.83\mathrm{L}∕\mathrm{kg}$ OC. Dioxin concentrations in runoff were generally at the same level or lower than those measured in the receiving water body. Principal component analyses indicated that the signatures for dissolved runoff match those observed in dissolved ambient water in the channel, while the suspended-sediment runoff signatures are similar to those observed in dry air deposition in the Houston area.

Coal bed methane (CBM) is naturally occurring methane, contained in coal seams saturated with water. In order to extract the CBM, large quantities of water must be pumped from the coal seams. CBM water, produced in some areas of New Mexico, contains low total dissolved solids, which can potentially be used for rangeland irrigation. The water, however, has a high sodium adsorption ratio, which can result in severe deterioration of soil permeability with repeated irrigation. The St. Cloud zeolites exhibit a low selectivity of ${\mathrm{Na}}^{+}$ over ${\mathrm{Ca}}^{2+}$ (Vanselow selectivity coefficients of 0.26 and usable ${\mathrm{Na}}^{+}$ exchange capacity of $0.1\mathrm{meq}∕\mathrm{g}$ ) at the ionic strength of ${\mathrm{Na}}^{+}$ -laden CBM waters $\left(0.035\mathrm{M}\right)$ . Nevertheless, given the availability and low cost of natural zeolites, ion exchange experiments were conducted using packed columns to estimate a treatment cost. The operation and maintenance cost of the zeolite system was estimated to be about $3 per barrel (one barrel $=159$ liters) compared with $\$0.75–\$4∕\mathrm{bbl}$ for deep well injection (primary management practice) and $\$0.06–\$0.11∕\mathrm{bbl}$ for soil amendment. Based on these preliminary experiments, it is evident that the ion exchange process for ${\mathrm{Na}}^{+}$ removal, with natural zeolites as the media, is not economical due to the low sodium selectivity.

A simplistic and systematic procedure has been developed for the design and upscaling of a multichannel, continuous-flow electrocoagulation reactor of monopolar configuration for the removal of submicron particles from wastewater. Using wastewater generated from the chemical-mechanical planarization process as the target wastewater, a series of laboratory-scale studies were conducted to determine the required operating conditions for the efficient removal of the ultrafine silica particles. These operating criteria included charge loading $(⩾8\mathrm{F}∕{\mathrm{m}}^3)$ , current density $(⩾5.7\mathrm{A}∕{\mathrm{m}}^2)$ , hydraulic retention time $(⩾60\min )$ , as well as the initial pH (7–10). Furthermore, a steady-state transport equation with second-order reaction kinetics was employed to describe the rate of coagulation as the rate-limiting factor. The actual kinetic constant determined from the laboratory-scale experiments was approximately $1.2\times {10}^{-21}{\mathrm{m}}^3∕\mathrm{s}$ , which was three orders of magnitude smaller than that calculated based on Brownian coagulation. The model was subsequently validated with a series of experiments using a pilot-scale electrocoagulation reactor geometrically similar to the laboratory-scale reactor with nearly 20 times volumetric scaleup.

The sorptive capabilities of soils for organic contaminants can be greatly enhanced by treatment with cationic surfactants, and this has been suggested as a potential in situ approach for contaminant plume management. The hydraulic properties of soils modified by injection of hexadecyltrimethylammonium (HDTMA) were investigated using soil columns and a fixed-ring consolidometer. Oshtemo soil (87% sand, 10.5% clay, 2.5% silt) under two different effective stresses, was equilibrated with $1\mathrm{mM}$ $\mathrm{NaCl}$ and treated by recirculation of two different HDTMA soil concentrations, one above and one below the cation exchange capacity. No statistically significant changes in hydraulic conductivity occurred as a result of HDTMA treatment at any of the experimental conditions studied. These results suggest that sorptive zones created in situ with HDTMA may be hydraulically feasible.

We present the first large-scale comparison of a fluorescent dye [fluorescein $\left({\mathrm{C}}_{20}{\mathrm{H}}_{10}{\mathrm{O}}_5{\mathrm{Na}}_2\right)$ ] and a gas [sulfur hexafluoride $\left({\mathrm{SF}}_6\right)$ ] as tracers of advection and longitudinal dispersion from a dual tracer release experiment conducted in the tidal Hudson River. At the beginning of the experiment, $36\mathrm{kg}$ of fluorescein and $\sim 4.3\mathrm{mol}$ of ${\mathrm{SF}}_6$ were injected into the Hudson River at an averaged depth of $9.5\mathrm{m}$ , $\sim 1\mathrm{m}$ above the bottom, near Hyde Park, N.Y. After injection, fluorescein distributions were surveyed for 4 days (until it became undetectable) and ${\mathrm{SF}}_6$ distributions were surveyed for 10 days. The dye resolves initial vertical mixing on the day of injection, and then net advection and longitudinal dispersion, whereas ${\mathrm{SF}}_6$ provides information on net advection and longitudinal mixing on larger spatial scales and longer time scales. Quantitative estimates of transport processes (net advection and longitudinal dispersion) calculated from the two methods are consistent for the first three days, and start to deviate on the fourth day when the signal-to-noise ratio of the dye deteriorated.

The dissolution of ozone and the decomposition of 2-chlorophenol were noticeably enhanced for experiments conducted in the fixed packed contactor than those conducted in a bubble column. The rate of ozone transfer was increased with the increasing amount of Pall rings contained in the packed contactor and the decreasing gas/liquid ratio $(G∕L)$ because the gas–liquid interface may be renewed effectively. The decomposition of 2-chlorophenol by ozonation was found to be faster for experiments conducted in alkaline solutions while the decomposition of total organic carbon only slightly enhanced. However, the decomposition of total organic carbon only slightly increased for experiments conducted in alkaline solutions.

The glass encased magnet (GEM) batch reactor was designed to permit reactivity studies of granular iron with good mixing, and minimal abrasion. This study compared the GEM reactor with two conventional batch test designs (for granular iron studies). In the GEM reactor experiments, the reduction of 4-chloronitrobenzene with Connelly granular iron was found to proceed at about twice the maximum rate of the reaction mixed by orbital shaking or rolling, indicating that mass transfer was minimized in the GEM tests. In addition, the reproducibility of GEM tests was superior, possibly due to abrasion or other variations to the grain surfaces that occurred in the other types of tests. The biases and uncertainties in kinetic parameters estimated from the shaker and roller experiments were shown to be significant compared to the GEM derived parameters.