Journal of Environmental Engineering

This paper summarizes the results of numerous simulations to assess the hydraulic performance of fully permeable highway shoulder retrofits designed to capture all the rainfall runoff falling onto conventional highway surface pavements. The simulations were performed using commercially available HYDRUS software that uses unsaturated flow theory. The hydraulic properties of subgrade soil and pavement materials were measured in the laboratory and used as input for numerical simulation. The simulations were performed for three rainfall regions in California representing high, medium, and low annual rainfall events. The simulations were performed based on 24-h actual rainfall data using 2-, 50-, and 100-year storm recurrences to determine the critical thickness of aggregate needed to capture the highway runoff volume without surface ponding and/or overflow. Sensitivity analyses were performed to evaluate the influence of material, hydrologic, and geometric factors on the critical aggregate base thickness. Results indicated that an aggregate depth of about 1.5 m was adequate for most California areas with two-lane highways. Sensitivity analyses also revealed that the saturated hydraulic conductivity ($K_s$) of the subgrade soil is the most important parameter to be considered in the design of fully permeable pavements, with a minimum effective allowable value of approximately ${10}^{-5}\mathrm{cm}/\mathrm{s}$.

Urban drainage appurtenances separate particulate matter (PM) and detritus unintentionally and by design. Such PM separation impacts conveyance, treatment, and maintenance practices. This study examines two common appurtenances: Gully pots (or catch basins) and screened hydrodynamic separators (HS). Under steady and controlled physical model testing, PM separation was measured for influent granulometry [particle size distributions (PSDs), PM specific gravity]. Catch basin separation ranged from 40 to 99% for a monodisperse (well-graded sand, SW) PSD and 60 to 83% for a hetero-disperse PSD. With similar testing, a clean HS (to avoid scour dominating PM separation), the HS was also loaded with a heterodisperse sandy silt (ML) and tested as a function of flow, with separation of 40 to 65%, as compared to 70 to 99% for the SW, similar to the catch basin. Physical model results were compared to the surface overflow rate (SOR) model, illustrating that the SOR overestimated PM separation by 3–13%. The SOR was extended to unsteady runoff events. For unsteady loading of an HS with complex hydrodynamics and short residence times, the SOR overpredicted measured PM separation by 3–22% on the basis of PM granulometry. For maintenance and coarse PM load inventories, the SOR can reasonably predict the fate of coarse PM, subject to Type I settling in an HS and catch basin units with similar PM separation behavior. If suspended PM mass dominates the particle size distribution (PSD), is the focus of treatment, or for units with long residence times, the continuous phase hydrodynamics must be coupled with a discrete phase model, requiring analytical or numerical models such as computational fluid dynamics (CFD). For conditions illustrated herein, the SOR is reasonably robust.

Highway storm water runoff represents a significant source of dissolved copper to surface waters. It is well-established that even low concentrations of dissolved copper can be toxic to many aquatic organisms. In the Pacific Northwest of the United States, recent research has focused on the effects of low-level copper exposure to salmonids listed as threatened or endangered under the Endangered Species Act (ESA). In light of these recent studies, increasingly stringent guidelines for the discharge of highway storm water runoff have been imposed as part of ESA assessments of transportation projects. Assessing factors that may affect dissolved copper concentrations in storm water provides a practical framework for predicting when and where copper toxicity could be problematic. A storm water sampling effort was performed to examine the influence of site locale, traffic density, storm hydrology, the “first-flush” effect, and water quality parameters on measured dissolved copper concentrations in highway storm water runoff. In general, runoff from urban/high traffic sites and first-flush samples exhibited higher copper concentrations than other samples. Increased dissolved copper concentrations were highly correlated with both dissolved organic carbon (DOC) and alkalinity. However, multiple linear regression modeling suggests that only the correlation with DOC has the potential to be causative. These findings will help inform state and federal transportation and environmental protection agencies regarding the conditions under which elevated copper concentrations and potential copper toxicity are most likely to occur.

The objective of this research was to investigate, at the laboratory scale, the performance of an electrochemical process for enhancing dewaterability and stabilizing wastewater sludge from municipal wastewater treatment plants. This process has the advantage of simultaneous disinfection and odor removal from sludge. The equipment consisted of a 12-L cylindrical electrolytic cell containing a $\mathrm{Ti}/{\mathrm{RuO}}_2$ anode and Ti cathode. Current intensities varying from 5.0 to 10 A were tested in the absence and presence of the electrolytes ${\mathrm{H}}_2{\mathrm{SO}}_4$ [$10–27\mathrm{kg}/\mathrm{ton}$ of dry matter (tDM)] and NaCl ($88–354\mathrm{kg}/\mathrm{tDM}$). Best performance with respect to sludge treatment and stabilization was obtained when the electrolytic cell was operated for 60 min at 8.0 A, with energy consumption of $856\mathrm{kWh}/\mathrm{tDM}$, in the presence of 177 kg $\mathrm{NaCl}/\mathrm{tDM}$ and $23.3\mathrm{kg}{\mathrm{H}}_2{\mathrm{SO}}_4/\mathrm{tDM}$. The electrochemical treatment induces particles to agglomerate and enhances the filterability of wastewater sludge during dewatering in the presence of the cationic polymer Percol 789 ($2.5\mathrm{kg}/\mathrm{tDM}$). The process was efficient in increasing the dryness of sludge. A 6 to 10% increase in total solids in dehydrated sludge was expected. The electrochemical process was also found to be effective in removing indicator pathogens ($\mathrm{\text{abatement}}>4–5\mathrm{\text{log units of total and fecal coliforms}}$) and unpleasant odors. At the same time, it preserved the fertilizing properties of the sludge by maintaining concentrations of inorganic nutrients (total phosphorus and total Kjeldahl nitrogen) and organic matter (chemical oxygen demand) in dewatered sludge.

A mathematical model for calculating gas pressure profiles in layered landfill systems is presented. Solutions to scenarios considering a zero-pressure top boundary condition and a zero gas flux or fixed gas pressure bottom boundary condition are presented. Two cases, specified gas pressure and specified inward gas flux, are addressed for scenarios involving horizontal gas collection systems. A series of application examples demonstrate how the proposed model can be used to investigate the influences of (1) variation of gas generation rate with respect to depth and time, (2) soil covers, (3) horizontal collection layers, and (4) geomembrane and geosynthetic clay liner covers on gas pressure distribution in landfills. The proposed model provides a useful tool to landfill engineers in designing landfill gas management systems and in particular when selecting and specifying gas collection system spacing and pumps.

This study presents the degradation and mineralization results of phenol-containing fire fighting wastewater (FWW) generated from quenching a fire outbreak in an oil storage facility. The chemical oxygen demand (COD) and phenol content of the wastewater were above the Malaysian Standard B discharge limits of 100 and $1\mathrm{mg}{\mathrm{L}}^{-1}$ for COD and phenol, respectively. The Fenton oxidation method was chosen as the treatment technique, and a response surface methodology was used to optimize the response of the dependent variables: namely, COD, phenol, and total organic carbon (TOC) percentage removals. Based on the wastewater COD, three controlling variables, namely, $t_r$ and the mass ratios of [${\mathrm{H}}_2{\mathrm{O}}_2$]:[FWW] and [${\mathrm{H}}_2{\mathrm{O}}_2$]:[${\mathrm{Fe}}^{2+}$], were studied at values of 0.5 to 8, 2 to 12, and 5 to 20 h, respectively. The results obtained for the treated samples showed complete phenol degradation. However, the optimum percentage of TOC and COD reduction were 53.4 and 77.5%, respectively. The low TOC removal was attributed to partial hydroxylation, which generated more aliphatic components that then retarded the mineralization of the organic load. Kinetic studies using the Generalized Lumped Kinetic Model showed that the apparent kinetic constants, for the initial oxidation step ($k_1^{\prime }$) and for the final oxidation step ($k_2^{\prime }$), are $11.2\times {10}^{-3}{\mathrm{h}}^{-1}$ and $6.4\times {10}^{-3}{\mathrm{h}}^{-1}$, respectively. These results indicate that the reaction rate leading to the hydroxylation of the organic load is approximately twice as fast as the rate of intermediate product conversion to the final product. The fast initial rate ($k_1^{\prime }$) accounted for the complete phenol degradation, and the relatively slow second rate ($k_2^{\prime }$) resulted in incomplete mineralization of some of the intermediate organic by-products.

Prediction of a conservative solute transport in the subsurface is investigated by applying a Kalman filter (KF) that uses time-correlated-error and a KF that uses Gaussian error. The observation data generated from an analytical solution of a two-dimensional advection-dispersion equation with additive time-correlated random errors were used as the measurement equation for the KF with time-correlated measurement errors and the KF with white Gaussian errors. A measurement-differencing algorithm was adopted in deriving a discrete time varying KF with time-correlated measurement errors for predicting contaminant transport in the subsurface in the case of observations with time-correlated errors. Simulation results indicated an improved root mean square error (RMSE) profile of KF with time-correlated errors over KF with white Gaussian error. The KF with time-correlated-error reduced the error in the prediction by 11.4% when compared to the KF with white Gaussian error. The stability analysis of the two filters indicated that both filters were stable and convergent for the entire simulation duration.

Laboratory experiments were performed to demonstrate an experimental method for measuring the UV dose-response behavior among air-exposed microorganisms, and to quantify the effect of relative humidity on this behavior. These experiments included two nonpathogenic microorganisms as surrogates for airborne microbial pathogens: Bacillus subtilis spores and coliphage MS2. UV dose-response behavior of these microorganisms was measured as a function of relative humidity (RH). Microorganisms were transferred to membrane filters at less than monolayer coverage and were subjected to exposure to UV radiation delivered from a collimated beam to a planar surface in a humidity-controlled environment at two germicidally active wavelengths: 254 nm and 282 nm. Dose-response data for Bacillus subtilis spores and coliphage MS2 exposed to UV radiation were fit to the Phenotypic Persistence and External Shielding (PPES) model. B. subtilis spores showed a modest effect of RH on the UV dose-response behavior, whereas essentially no effect of RH was evident for air-exposed MS2 for their UV dose-response behavior at 254 nm or 282 nm.

The present work is the first to examine temporal variability of bacterial diversity in a free-chlorinated drinking water distribution system over multiple years. The authors examined seasonal and monthly bacterial diversity by using three different molecular methods. 16S rRNA gene clone library analysis identified the bacteria in Pittsburgh seasonal water samples, collected in fall 2006, and winter, spring, and summer 2007 and an event sample collected following a major pipe break, as primarily members of the alpha-, beta-, and gammaproteobacteria classes, which agrees with previous studies of smaller numbers of bulk water samples over shorter durations. However, in this study, seasonal shifts in relative populations were observed with decreased alphaproteobacteria and increased betaproteobacteria diversity in the winter sample compared to the other seasonal samples, which may be caused by changes in chlorine dosing. Further, in 11 monthly samples collected at the same location from September 2008 to August 2009, quantitative polymerase chain reaction (qPCR) results indicated that alpha- and betaproteobacteria predominated over the year, except in May and October, when changes in chlorine dosing as a result of temperature shifts may have influenced bacterial diversity. Denaturing gradient gel electrophoresis (DGGE) cluster analyses suggested that the monthly samples cluster seasonally with greater than 85% similarity between March and April, June and July, and December and January. These results demonstrate the consistent presence of alpha-, beta-, and gammaproteobacteria in drinking water distribution systems across seasons during routine operational conditions and suggest that changes in bacterial class distributions may be useful indicators of system disruptions.

It has been proven that the concept of using a high pressure water jet (HPWJ) to pretreat wastewater for the enhancement of ultraviolet (UV) disinfection of wastewater is an effective and cost-efficient alternative compared with the widely studied ultrasonic method. This study addresses: (1) the effectiveness of the pretreatment with a low pressure water jet (LPWJ) under similar experimental settings to the previous HPWJ study, (2) the water pressure impacts on bacteria in the treated wastewater, and (3) the difference in electrical energy consumption under treatment with different pressures. The results show that with the tested primary clarifier overflow (PCO), there were no real differences in enhancement of UV disinfection with LPWJ pretreatment operating under a tested pressure range from 0.97 to 6.80 MPa. More than 1 log unit improvement of UV disinfection efficiency can be achieved under all the tested pressures compared with treatment by UV irradiation alone when the UV dose is in the $20\sim 30\mathrm{mJ}/{\mathrm{cm}}^2$ range. The general hypothesis for the enhancement of UV disinfection using a water jet is attributable to two factors: (1) reduction in the particle shield/shadow effects by breaking up the larger particles and (2) reduction in the resistance to UV irradiation by weakening the bacteria. Unfortunately, there is no easy and reliable way to test bacterial viability. In this study, an indirect method was proposed, and corresponding experiments were conducted for an investigation of the impact of water jet force on the bacteria. Results show that for the tested pressure range from 0.97 to 6.80 MPa, there was no confirmation that the bacteria in PCO were weakened after being treated by the water jet. The main function of the water jet pretreatment was to affect a reduction of particle size in the treated water, instead of weakening the bacteria themselves.

This paper presents a comparison of the effects of ozonation [0.4–3.0 mg ozone $({\mathrm{O}}_3)/\mathrm{mg}$ (DOC)] and titanium dioxide–catalyzed ozonation (${\mathrm{TiO}}_2\mathrm{\text{-}}{\mathrm{O}}_3$) (0.4–3.0 mg ${\mathrm{O}}_3/\mathrm{mg}$ DOC; 1.0 mg ${\mathrm{TiO}}_2/\mathrm{L}$) at pH 7.46 on the removal of natural organic matter (NOM) from groundwater from the central Banat region (northern Serbia). This groundwater is rich in NOM ($9.85\mathrm{mg}/\mathrm{L}$ DOC), which is mostly of hydrophobic character (65% fulvic acid, 14% humic acid fraction). Ozonation and ${\mathrm{TiO}}_2\mathrm{\text{-}}{\mathrm{O}}_3$ resulted in almost identical degrees of DOC content reduction (up to 30%), with the maximum efficacy of both processes achieved with 3.0 mg ${\mathrm{O}}_3/\mathrm{mg}$ DOC. The application of oxidation treatments resulted in complete humic acid oxidation, and increased the content of the hydrophilic fraction (up to 72%). The use of ${\mathrm{TiO}}_2\mathrm{\text{-}}{\mathrm{O}}_3$ did not result in an improvement in the removal of trihalomethane precursors in comparison with ozonation (up to 48%) but produced less brominated species, whereas use of the ${\mathrm{TiO}}_2\mathrm{\text{-}}{\mathrm{O}}_3$ process resulted in better removal of haloacetonitrile precursors (up to 44% removal) than did ozonation, which had less effect.

To evaluate sediment removal in dry detention basins, one of the most frequently used Best Management Practices (BMPs), a particle pathline model using plug flow assumption was proposed in a previous study. The model requires numerical integration, thus it may not be convenient for quick evaluation and design of detention basins. To overcome the difficulty a simpler continuous stirring tank reactor (CSTR) model is proposed and used to compare outflow Suspended Sediment Concentrations (SSCs) from different size storms using a nondimensionalized time scale. The CSTR model satisfactorily predicts sediment removal and outflow SSC measured using a physical model. The paper presents the time nondimensionalization and CSTR model application processes and discusses the critical characteristics of the proposed models.