Journal of Environmental Engineering

Landfill leachates are often discharged through sewers or by trucks to publicly owned treatment works (POTWs) after on-site biological treatment. This discharge of landfill leachate is widely accepted because of its cost-effectiveness and reliability, but potential impacts of this practice include additional nutrient loading and interference with ultraviolet (UV) disinfection during subsequent biological treatment. Leachate was fractionated into humic acid (HA), fulvic acid (FA), and hydrophilic (Hpi) fractions based on chemical composition and solubility to determine the hydrophobicity distribution. The analysis showed that the specific ${\mathrm{UV}}_{254}$ absorbance (${\mathrm{SUVA}}_{254}$) of the humic substances (HA and FA) was significantly higher than the Hpi fraction. The UV quenching materials were found to be resistant to biological treatment for the majority of leachates studied. Removal of humic substances was associated with decreased UV quenching and the aromatic content of landfill leachates after biological treatment. The size distribution of the hydrophilic fraction suggests that the majority of organic nitrogen in landfill leachate is associated with the low-molecular-weight ($<1\mathrm{kDa}$) hydrophilic fraction.

The possibility of using granular dead anaerobic sludge (GDAS) biosorbent as a permeable reactive barrier (PRB) to remove phenol from contaminated shallow groundwater was investigated. Batch tests were performed to characterize the equilibrium sorption properties of GDAS and sandy soil in phenol-containing aqueous solutions. The Langmuir isotherm model gives a better fit for the sorption data of phenol by GDAS and soil than other models under the studied conditions. One-dimensional column experiments were performed at a pilot scale, and an integrated model based on the solution of an advection-reaction-dispersion mass balance equation, using the finite-element method, was developed to study the space and time normalized concentration of phenol within groundwater. Numerical and experimental results proved that the PRB plays a potential role in the restriction of the contaminant plume migration. Also, these results showed that the removal of phenol by PRB was increased as function of its thickness and that the barrier starts to saturate with contaminant as a function of the travel time. However, a good agreement between the predicted and experimental results was recognized with the root-mean squared error (RMSE) not exceeding 0.0460 and Nash-Sutcliffe efficiency not less than 0.9201.

This paper presents a new way of modeling in-stream bacteria concentrations by examining a watershed in terms of wet and dry hydrologic states. Flow-duration curves were developed for four catchments of the Little River Experimental Watershed in Tifton, Georgia, and HSPF and SWAT bacteria models were built for the catchments. The flow-duration curves were used to designate wet and dry states of the catchments based on flow conditions instead of calendar day, the bacteria data sets were divided into wet and dry groups accordingly, and the models were calibrated to the wet and dry states. Water-quality parameter sensitivities revealed that each model placed varying emphasis on the parameters in each state according to the model’s structure, and certain parameters were insensitive in both wet and dry states. A custom parameter added to the models to represent background in-stream and/or distributed loads was consistently sensitive across hydrologic states and improved model predictions in both computer models. Seven of the eight scenarios considered attained better model predictions in the wet state than the dry state as evaluated by a log-transformed Nash-Sutcliffe efficiency. The results show that fundamental aspects of the models’ performance are revealed in light of the analysis by hydrologic state and can provide future guidance for the collection of better datasets for use in bacteria modeling.

Electrochemical-oxidation experiments was conducted for degradation of 16 priority polycyclic aromatic hydrocarbons (PAHs) using a dimensionally stable anode (DSA)-type $\mathrm{Ti}/{\mathrm{SnO}}_2\text{-}{\mathrm{Sb}}_2{\mathrm{O}}_5\text{-}{\mathrm{RuO}}_2$ electrode. In the research reported in this paper, for electrooxidation, anode was coated with metal oxides ${\mathrm{SnO}}_2$, ${\mathrm{Sb}}_2{\mathrm{O}}_5$, and ${\mathrm{RuO}}_2$ in laboratory using titanium as substrate dip coating thermal decomposition method. Laboratory-scale batch reactor was used for degradation studies at pH 3, 6, and 9. Surface morphology and composition of the anode coatings were characterized by variable pressure field emission scanning electron microscopy and energy dispersive X-ray spectroscopy, respectively. Coating microstructure was analyzed by X-ray diffraction. Stability of coating was analyzed by Raman spectroscopy. Gas chromatography–mass spectrometry results revealed that almost 80, 73, and 82% PAHs removal was found without using electrolyte at pH 3, 6, and 9, respectively. While using electrolyte removal efficiency gone to 93, 87, and 93% at pH 3, 6, and 9, respectively. To study the optimum conditions for electrochemical degradation of PAHs from produced water, Box-Behnken design was used. Experiments were designed for each anode as function of independent variables such as current density, pH, and electrolysis time. Quadratic model was suggested best-fit model. The results of the ANOVA for PAHs revealed that the model was highly significant.

Based on previously developed monitoring system comprising three microfluorescent silica detectors, this paper proposed an improved real-time fluence monitoring method for running ultraviolet (UV) reactors. Adoption of this new method would significantly decrease the number of biodosimetry tests while increase the monitoring accuracy. The method constants were first determined by biodosimetry; thereafter, a long-term (about 16 months) experiment was conducted to evaluate the continuous performance of the proposed method under simulated practical conditions. The results indicate that the daily average fluence dropped gradually from 248 to $30\mathrm{mJ}/{\mathrm{cm}}^2$ over the whole operational period, which arose principally from the lamp output attenuation and serious sleeve fouling. Furthermore, the real-time monitoring data of 1 representative week were analyzed, which could provide useful instructions for the operation and maintenance of UV facilities. This paper demonstrates that the proposed method could monitor well the real-time fluence with a low cost but a high accuracy.

Impervious cover (IC) has been shown to increase runoff volumes, peak discharges, and pollutant loads to streams, which can lead to degraded water quality and biological integrity. Stormwater control measures (SCMs) have been developed to mitigate the hydrologic and water quality impacts of urban areas and IC. This paired watershed study evaluated the impacts of multiple SCM retrofits on water quality at a catchment scale in a 0.53 ha urban residential drainage area. In February 2012, an in-street bioretention cell (BRC) retrofit, four permeable pavement parking stalls, and a tree filter device were installed to treat residential street runoff in Wilmington, North Carolina. In the retrofitted catchment, 94% of the directly connected impervious area (DCIA) and 91% of the total drainage area were retrofitted for water quality treatment. Underlying soils in the study area were sand. After the SCM retrofits were constructed, concentrations of total Kjeldahl nitrogen (TKN), total phosphorous (TP), total suspended solids (TSS), copper (Cu), lead (Pb), and zinc (Zn) significantly decreased by 62%, 38%, 82%, 62%, 89%, and 76%, respectively. Concentrations of dissolved pollutants [nitrate-nitrite-nitrogen (${\mathrm{NO}}_{2,3}\text{-}\mathrm{N}$), total ammoniacal nitrogen (TAN), and orthophosphate ($\mathrm{O}\text{-}{\mathrm{PO}}_4^{3-}$)] did not change. Mass exports of TKN, TAN, $\mathrm{O}\text{-}{\mathrm{PO}}_4^{3-}$, TP, TSS, Cu, Pb, and Zn significantly decreased by 79%, 60%, 54%, 72%, 91%, 54%, 88%, and 77%, respectively. Improvements in water quality were due to decreases in particulate and particulate-bound pollutant concentrations and loads. This study has shown that a limited number of SCMs installed within a street right-of-way can mitigate a substantial portion of the water quality impacts caused by existing residential development.

The transport of bimetallic nano-$\mathrm{Fe}/\mathrm{Cu}$ particles through coarse sand-packed columns was investigated simulating particle transport under 25 injection strategy scenarios. The considered transport mechanisms included retention on and release from the solid grains, modeled by a dual-site advection-dispersion-deposition equation, and clogging of the porous medium. The transport kinetics and parameters used in the research reported in this paper were calibrated against experimental data, previously reported, and simulated using computer software. The influence of the injected particle concentration (2–$12\mathrm{g}/\mathrm{L}$), flow rate (43.2–$172.8\mathrm{m}/\mathrm{day}$), duration, and eventual alternation of injection and flushing periods was analyzed. The impact of each scenario was quantified in terms of particle mobility, porous medium clogging, water pressure, and uniformity of distribution of the particles in the porous medium. The results of this paper indicate that when injecting under conditions typical of a full-scale aquifer remediation, nanoparticle mobility and distribution are optimized and clogging is minimized by using high flow rates, low concentrations, and frequent injection steps without intermediate flushing.

A simple relationship, referred to as a mass conversion factor (MCF), is presented to convert optically based particle measurements to mass concentration. It is calculated from filter-based samples and optical particle counter (OPC) data on a daily or sample period basis. The MCF allows for greater temporal and spatial mass concentration information than typical filter-based measurements. Results of MCF calculations from several field studies are summarized. Pairwise comparisons from a collocated study with multiple OPCs and mass samplers suggest the minimum variability of the MCF is 5–10%. The variability of the MCF within a sample period during a field study with distributed samplers averaged 17–21%. In addition, the precision of the Airmetrics MiniVol Portable Air Sampler for particulate matter (PM) was typically $<10\%$. Comparisons with federal reference method (FRM) samplers showed that MiniVols yield ${\mathrm{PM}}_{2.5}$ concentrations essentially equivalent to FRMs with slightly greater deviations from the FRM for ${\mathrm{PM}}_{10}$ under tested ambient conditions.

Chromium is one of the most toxic and carcinogenic heavy metals. Conventional techniques which are commonly applied for removal of chromium ions from aqueous matrices have several drawbacks whereas biosorption has a high performance for metal extraction. Three fungal strains, i.e., (1) Aspergillus ustus (Asp), (2) Fusarium verticillioides (Fus), and (3) Pencillium funiculosum (Pen), have been immobilized on nanosilica (NSi) surface to develop highly effective three biosorbents, i.e., (1) NSi-Asp, (2) NSi-Fus, and (3) NSi-Pen. They are used for solid phase extraction and selective removal of Cr(III) and Cr(VI) ions. Surface characterization and immobilization of fungal cells on nanosilica were examined and confirmed by using scanning electron imaging and Fourier-transform infrared analysis. Biosorption and removal of chromium ions were followed up via batch experiment under the influence of pH, contact time, biosorbent dosage, and initial metal ion concentration. The maximum biosorption capacity values of Cr(III) were 2,466.7, 2,666.7, and $\mathrm{1,866.7}\mathrm{\mu mol}{\mathrm{g}}^{-1}$ by using NSi-Asp, NSi-Fus, and NSi-Pen, respectively. These were observed at pH 7.0, while those for Cr(VI), 6,466.7, 6,400.0, and $\mathrm{3,800.0}\mathrm{\mu mol}{\mathrm{g}}^{-1}$, were observed at pH 2.0. Fast sorption equilibria were established at about 15 min and their data were well described by both Langmuir and Freundlich isotherms. Potential applications for speciation and selective extraction of chromium ions from real wastewater samples were successfully accomplished.