Journal of Environmental Engineering

Bacillus anthracis spores represent an important bioterrorism agent that can be dispersed in air or water. Existing decontamination practices based on these spores have focused on chemical disinfectants; however, the basic characteristics of radiation-based disinfectants suggest potential advantages in their application for control of Bacillus spores. Experiments were conducted to examine the effectiveness of ultraviolet $\left({\mathrm{UV}}_{254}\right)$ radiation and $\gamma$ radiation for inactivation of Bacillus spores. Spores of Bacillus cereus were used for most experiments because of their similarity to B. anthracis. A limited number of experiments were also conducted using B. anthracis Sterne spores. In aqueous suspension, B. anthracis Sterne spores were observed to be slightly more resistant to ${\mathrm{UV}}_{254}$ than the spores of B. cereus. For the conditions of culture and assay used in these experiments, both spore types were more sensitive to ${\mathrm{UV}}_{254}$ radiation in aqueous suspension than the spores of B. subtilis, which are commonly used to characterize the performance of UV disinfection systems for water. Dried spores on surfaces were observed to be more resistant to ${\mathrm{UV}}_{254}$ than the same spores in aqueous suspension; it is likely that the increased resistance to UV of the dried spores was attributable to surface characteristics (porosity and texture) of the solid materials. $\gamma$ radiation was shown to accomplish similar rates of inactivation for spores in aqueous suspension and for dried spores on surfaces. Collectively, these results suggest that the application of UV or ionizing radiation may hold promise for decontamination following bioterrorism events.

The emissions of two types of organic solutes during the coagulation process were simulated using Jar Test equipment and two additives, coagulant and polymer, to evaluate the volatilization characteristics under various operating conditions. The solute volatilization rates were found to be a function of the liquid mixing intensity, the chemical properties of the additives, and the properties of solutes, including molecular weight $\left(M\right)$ , Henry’s law constant $\left(H\right)$ , and water solubility $\left(S\right)$ . The volatilization rates of the high $H$ solutes increased sharply as the mixing intensity increased. Moreover, the volatilization rates of selected compounds were only slightly dependent on the coagulant concentrations due to the inorganic property of the coagulant. On the other hand, the effective volatilization reduction of the high $H$ solutes in the existence of organic flocculant was a result of the enhancement of solutes solubility in water solutions. However, the above inhibition effects decreased significantly when the mixing intensity increased. Finally, the emission rates of the low $H$ solutes were weakly correlated with both the solution properties and the operating parameters, due to their high affinity with the solution and the major volatilization resistance existing in the gas phase. Two different approaches, i.e., the two-film theory and the modified Knudsen diffusion equation, were used to explain the solute volatilization characteristics in the simulation process.

Solute transport in natural streams is a complex phenomenon that involves both in-stream dispersion and mass exchange with the porous zones surrounding the water body. Due to the complex nature of the riverine systems several models may be used to simulate and analyze the transport of solutes with different degrees of complexity. The bedform-induced hyporheic transport is a stream-subsurface exchange mechanism that can be reproduced in controlled systems, such as laboratory flumes. Application of a simple Fickian diffusion model to laboratory data obtained with passive solutes and stationary bedforms proves successful within a range of durations of the contamination process. A dimensionless form of the diffusion coefficient, scaled with dynamic, physical, and geometric properties of the system is derived by comparison with another physically based model. A prediction of the dimensionless diffusion coefficient is obtained as a function of the timescale of the exchange process and is validated with a few sets of results from laboratory tests.

Particles in highway runoff contain various sorbed pollutants, and many best management practices (BMPs) are selected for particle removal efficiency, which makes particle size distribution a crucial BMP design parameter. Particles between 2 and $\mathrm{1,000}\mu \mathrm{m}$ in diameter were quantified for three rainfall events during the 2002–2003 rainy season at three highway sites in west Los Angeles. Rainfall, runoff flow rate, and a large suite of water quality parameters were also measured. An experimental protocol was developed for bottle cleaning, sample storage, and mixing that provided repeatable results. Particle aggregation occurred which required samples to be analyzed in less than $6\mathrm{h}$ ; the concentration of small particles decreased with a corresponding increase in the concentration of larger particles in stored samples. The particle concentration decreased as the storm progressed and the number of large particles decreased more rapidly than the total number of particles. Particles demonstrated a strong first flush. On average, 40% of the particles were discharged in the first 20% of the runoff volume.

As part of an ongoing watershed model comparison program for forested watersheds, Watershed Analysis Risk Management Framework (WARMF V5.18) and Hydrologic Simulation Program Fortran (HSPF V10) were independently applied to the Mica Creek Watershed in Idaho. A comprehensive model comparison was made in terms of watershed delineation, hydrologic formulations, model parameterization, meteorological data, hydrologic calibration, and hydrologic verification. Comparison was not made for water quality, which was not simulated in the HSPF application. It was concluded that WARMF is a mechanistic model structured to simulate the hydrologic processes, whereas HSPF is an empirical water budget model. The WARMF is suitable for application to forested watersheds. It successfully predicted stream flows comparable to measured values. The HSPF results were also good, if one ignores an unrealistic amount of water loss to inactive groundwater and an empirical treatment of rain-on-snow events.

The cometabolic transformation of high concentrations of 4-chlorophenol (4-cp) in the presence of phenol (growth substrate) was investigated in an immobilized cell hollow fiber membrane bioreactor. The biotransformation rates of 4-cp and phenol by free cells and immobilized cells were compared and it was found that biotransformation by immobilized cells was more efficient than that by freely suspended cells, especially at high substrate concentrations. Even when the initial substrate concentrations were both $\mathrm{1,000}\mathrm{mg}{\mathrm{L}}^{-1}$ , the substrates could still be transformed completely within $45\mathrm{h}$ in the hollow fiber membrane bioreactor. It was found that removal rates of the substrates were dependent not only on absolute substrate concentration, but also on the concentration ratios of 4-cp to phenol. With increased concentration ratios, phenol depletion rate decreased while 4-cp depletion rate increased. This was attributed to increased competitiveness of 4-cp in the competitive inhibition with phenol since the membranes had relatively better sorption for 4-cp over phenol. The bioreactor was operated batchwise for 18 times to investigate the feasibility of the bioreactor for long term operation. It was found that there was no significant decrease in the bioactivity, which demonstrates a potential for continuous operation.

Batch experiments were conducted to examine the oxidation of arsenite (As (III)) to arsenate (As (V)) by Alcaligenes faecalis strain O1201 isolated from soils. Pure cultures of O1201 completely oxidized As (III) to As (V) in the exponential growth phase at As (III) concentrations ranging from 10 to $\mathrm{1,000}\mathrm{mg}∕\mathrm{L}$ in less than 12 h. The growth of O1201 requires an organic substrate as the carbon and energy source, and the oxidation of As (III) was mainly observed in the exponential growth phase. As (III) concentration at $500\mathrm{mg}∕\mathrm{L}$ inhibited the growth of O1201, whereas its oxidation product As (V) did not show any inhibition effects even at concentration as high as $\mathrm{1,000}\mathrm{mg}∕\mathrm{L}$ . Kinetics studies of As (III) oxidation were performed under the optimal conditions for O1201 at pH 7 and 30°C in a chemical defined medium with citrate as the sole carbon source. The Monod expression coupled with a logistic growth model was used to analyze the kinetics of As (III) oxidation. The best fit parameters of half-velocity coefficient $K_c$ of $15\mathrm{mg}∕\mathrm{L}$ , maximum reaction rate coefficient $k_{\mathrm{mc}}$ of 0.47 mg As $\left(\mathrm{III}\right)∕\mathrm{mg}$ dry weight/h, and logistic growth rate coefficient $r$ of $0.22\text{–}0.34{\mathrm{h}}^{-1}$ were obtained using a nonlinear regression analysis.

Swine wastewaters contain varied and high amounts of organic matter (proteins, antibiotic compounds, organic acids) which are difficult to oxidize biologically or chemically. The discharge of such effluents is undesirable and can cause excessive oxygen demand in the receiving water. In order to produce an effluent suitable for stream discharge, electrochemical techniques have been explored at the laboratory pilot scale, for refractory residual organic compound removal in liquid swine manure (LSM) following a biofiltration process. Two types of electrolytic cells (monopolar and bipolar electrode cells) using aluminum and mild steel electrodes were studied. Effectiveness was measured in terms of chemical oxygen demand (COD) and biological oxygen demand (BOD) reduction. The amount of residue sludge produced and energy consumed have been also considered. Results showed that the best performances of COD and BOD removal from LSM were obtained using either aluminum bipolar (Al-BP) electrodes or mild steel monopolar (Fe-MP) electrodes operated at current intensities of 0.5 and $2.0\mathrm{A}$ , respectively, through $30\min$ of treatment. The COD removal yields varied from 65 to 68%, whereas BOD removal reached 87%. The optimal conditions determined for organic compound removal, including energy consumption and metallic sludge disposal, involved a total cost of only $\text{\$}0.24\text{and}\text{\$}0.29\text{United}\text{States}∕{\mathrm{m}}^3$ of treated LSM. The treatment using the Fe-MP system was found to be more economical and practical than the chemical treatment using $\mathrm{Fe}{\mathrm{Cl}}_3$ as a coagulating agent.

A one-dimensional multiphase numerical model is developed to simulate the vertical settlement involving liquid and gas flows in a deformable (settling) municipal solid waste (MSW) landfill. MSW is represented by a chemical composition, and a global stoichiometric reaction is used to estimate the maximum yield of gas generation. Following the general assumption accepted in the literature, the gas generated by waste decomposition is assumed to comprise of methane $\left(\mathrm{C}{\mathrm{H}}_4\right)$ and carbon dioxide $\left(\mathrm{C}{\mathrm{O}}_2\right)$ . The gas generation rate follows an exponentially decaying function of time. The gas generation model developed based on a first-order kinetic single-bioreactor approach includes the governing equations of gas migration, liquid flow, and landfill deformation. The Galerkin finite element method is used to solve the resulting equations. The model developed can be used to estimate the transient and ultimate settlements due to waste decomposition and gas generation in MSW landfills. The proposed model can estimate the waste porosity, gas pressure, liquid pressure, gas saturation, liquid saturation, and stress distributions in settling landfills. The results obtained for a deformable landfill are compared with a landfill having a rigid solid skeleton. Due to settlement, the depth of waste is 27% smaller in deformable landfills than that of the rigid ones.

A laboratory-scale trickle-bed air biofilter was evaluated for the removal of methyl isobutyl ketone (MIBK) from a waste gas stream. Six-millimeter $\left(6\mathrm{mm}\right)$ Celite pellets (R-635) were used as the biological attachment medium. Effects of MIBK volumetric loading rates on removal efficiency, biofilter reacclimation, biomass growth, and removal kinetics were studied under three different operating conditions, namely, backwashing and two intermittent periods (off chemical—no MIBK input; and off flow-no flow input). Backwashing of the biofilter once a week with full-medium fluidization removed the excess biomass and attained stable long-term performance with over 99% removal efficiency for loading rates less than $3.26\mathrm{kg}$ chemical oxygen demand $\left(\mathrm{COD}\right)∕{\mathrm{m}}^3\text{day}$ . The two intermittent periods could also sustain high removal efficiency for loading rates up to $1.09\mathrm{kg}\mathrm{COD}∕{\mathrm{m}}^3\text{day}$ without any backwashing. The recovery time increased with an increase in loading rates. Furthermore, the intermittent operations required a longer time to recover than backwashing. The pseudo-first-order removal rate constant decreased with an increase in volumetric loading rate. The removal kinetics showed an apparent dependency on the experimental operating conditions.

This paper presents the results of vehicle exhaust measurements that were used to establish emission standards for an inspection/maintenance (I/M) program. For this purpose, a total number of 100 private autos distributed across model years ranging between 1972 and 2002 were tested under idling conditions. The monitored indicators included air to fuel ratio (%), CO (%), $\mathrm{C}{\mathrm{O}}_2$ (%), HC (parts per million, ppm), $\mathrm{N}{\mathrm{O}}_x$ (ppm), and ${\mathrm{O}}_2$ (%). Private autos with model years greater than 1994 were found to be compliant with international standards and are relatively well maintained. Emissions from older models increased significantly with a lack of engine maintenance. The paper concludes with criteria for proposing I/M emission standards based on exhaust measurements taking country-specific socioeconomic characteristics into consideration.

The suppression of pyrite oxidation due to the formation of stable coatings of ${\mathrm{Fe}}^{3+}$ –silica and/or ${\mathrm{Fe}}^{3+}$ –hydroxy–silica complexes over pyrite surfaces in near-neutral and neutral solution pHs is well documented. On the contrary, there is currently no convincing experimental evidence that proves the existence of such a coating under low pH environments. Aqueous continuous flow kinetic experiments were conducted using coating solutions containing ${\mathrm{Na}}_2\mathrm{Si}{\mathrm{O}}_3\bullet 5{\mathrm{H}}_2\mathrm{O}$ and ${\mathrm{H}}_2{\mathrm{O}}_2$ at pH 6, 4, 3, and 2. Results showed that at pH 2, pyrite oxidation in the presence of silica is pseudofirst order and oxidation is not inhibited by silica. At pH 6, silica significantly reduced pyrite oxidation via a pseudofirst-order reaction that takes on several stages related to changes in the relative contributions of ${\mathrm{H}}_2{\mathrm{O}}_2$ and ${\mathrm{Fe}}^{3+}$ . Iron speciation data suggests a surface adsorption mechanism at pH 6 and an electrochemical mechanism at pH 2 for pyrite oxidation. Scanning electron microscopy and energy dispersive x-ray spectroscopy also support the kinetic model and showed the absence of any significant silica coating at pH 2.

In a laboratory study, manganese amended activated alumina (MAA), prepared by calcining $(400°\mathrm{C})$ manganese acetate-impregnated activated alumina, showed promise as a more effective medium than activated alumina (AA) for use in small municipal drinking water systems or point-of-use treatment, for removing arsenic [As(III) and As(V)] from groundwater. Batch adsorption/oxidation kinetic tests indicated that in fixed-bed operation, with a bed flowthrough time of $10–20\min$ , MAA would be a more effective medium than AA in removing arsenic [As(V), As(III), and As(III) and As(V) (present together)] from groundwater. In three cycles of downflow column test [bed depth $200\mathrm{mm}$ ; bed flowthrough time $20\min$ ; influent arsenic $1.0–0.6\mathrm{mg}∕\mathrm{L}$ As(III) and $0.4\mathrm{mg}∕\mathrm{L}$ As(V)], breakthrough bed volumes at the World Health Organization guideline value of $0.01\mathrm{mg}∕\mathrm{L}$ for arsenic in drinking water were 580, 550, and 485, and 825, 770, and 695, respectively, for AA and MAA. During regeneration (backwashing with a sodium hydroxide solution), 84–88% (for AA) and 86–89% (for MAA) of the removed arsenic was recovered. Manganese concentration in the MAA column effluent was low (below $0.02\mathrm{mg}∕\mathrm{L}$ ). A detailed study addressing the effects of some important factors (water pH, concentration and type of competing ions, and fouling by organics) on the process is needed.

The use of a gas partitioning interwell tracer test (PITT) has been proposed as a standard approach to the measurement of field-scale vadose zone water saturation fractions. The accuracy of the saturation measurement is largely dependent on the determination of the air–water partition coefficient, $K$ , of the tracers. In practice, $K$ is strongly influenced by the physical and chemical properties of the site water. In this study, column tests were conducted to investigate the impact of salinity on tracer partition coefficients for two promising gas phase candidate tracers, dibromomethane and dimethylether. Sodium thiosulfate was used as a salinity surrogate. The dynamic $K$ values of the two partitioning tracers were measured for sodium thiosulfate concentrations between 0% and 36% by weight. Methane was used as the nonpartitioning tracer for all experiments. $K$ values were found to decrease significantly with increasing sodium thiosulfate concentration. Similar correlations between $K$ values and sodium thiosulfate concentration were found for both of the partitioning tracers.