Journal of Environmental Engineering

This paper reviews the application of computational fluid dynamics (CFD) to numerically model the two-phase flow of water and sediment in the complex environment of a stormwater retention pond. The review is intended to draw the attention of the hydraulic engineering community, specifically those involved in pond design, to the recent advancements in computational modeling of sediment transport in ponds. It provides an up-to-date survey of current simulation capability, focusing on the potential of fully three-dimensional methods for solving sediment transport in complex pond flows. An additional goal of this paper is to alert new researchers engaged in stormwater retention pond design to the research opportunities presented by CFD. Even though pond configurations have become more complex to improve their performance, many studies have continued to rely solely on single-phase models. At the present time, unsteady three-dimensional two-phase models are becoming available to study these problems. Of the multiphase models that might be considered, the particle tracking (Eulerian-Lagrangian) method and two-fluid (Eulerian-Eulerian) method both are potentially applicable to modeling sediment transport in pond-type flows. To date, only the particle-tracking method has been applied to stormwater retention ponds. The two-fluid method is capable of simulating sediment transport in retention ponds. It would be advantageous for a simulation of large-scale ponds in which the number of particles required for particle-tracking becomes excessive. Currently, fully three-dimensional CFD methods are being successfully used to model a variety of multiphase flows in mechanical and chemical engineering, as well as some specific applications in hydraulic engineering. Its application to predict sediment transport in a retention pond shows significant promise, especially when the effect of turbulence becomes challenging to model.

In this paper, simultaneous wastewater treatment and power generation of fed-batch microbial fuel cells (MFCs) have been analyzed by introducing a stepwise variation in temperature, pH, and cathodic electrolyte. Different ranges of operational parameters were applied to enriched biofilm (30 days) for 2 weeks to evaluate system performance through polarization studies and chemical oxygen demand (COD) removal rate. Increasing the electrolyte temperature from 37°C to 45°C resulted in higher voltage output ($394.5\pm 6.1\mathrm{mV}$) and increased COD removal efficiency (84.5%). The cell potential of MFCs was also enhanced up to 398.9 mV by optimizing anodic pH to 7. Further increase in the current production ($0.04\pm \le 0.01\mathrm{mA}$) was observed with cathodic electrolyte 100 mM phosphate-buffered saline $(\mathrm{PBS})+100\mathrm{mM}\mathrm{NaCl}$ of higher reductive strength, primarily as a result of the overcoming system proton transfer limitation. This study provides a detailed parametric analysis of operating parameters and assists in process optimization.

This study identified biotransformation products formed from three anthropogenic trace organic compounds (TOrCs) (benzotriazole, triclosan, and trimethoprim) in aerobic and anoxic sludge from a biological nutrient removal (BNR) wastewater treatment system. Liquid chromatography coupled to quadrupole time-of-flight mass spectrometry (LC-QTOF) was used to identify intermediate transformation products. A user-defined compound library was used to target unknowns in samples with a mix of TOrCs without requiring chemical standards and developed using EAWAG-BDD predictive software, which included 37 potential transformation products. Biotransformation batch experiments were conducted using activated sludge from anoxic and aerobic redox regimes of a BNR treatment plant located in Southern Nevada, United States. Four intermediates were observed for benzotriazole in both aerobic and anoxic activated sludge, which consisted of two isomers of hydroxy benzotriazole and two isomers of methoxy benzotriazole. Four intermediates were observed for trimethoprim under aerobic conditions, which formed 2,4-diaminopyrimidin-5-yl)(3,4,5-trimethoxyphenyl)methanol (TMP 306) and 2,6-diamino-5-hydroxy-5-(3,4,5-trimethoxybenzyl)-5,6-dihydropyrimidin-4(1H)-one (TMP 324) and two demethylation isomers of desmethyl trimethoprim. Triclosan had one confirmed transformation product, triclosan-o-sulfate, formed in both conditions. The identification of these transformation products will allow for more thorough risk assessments to be performed for the target TOrCs.

The microbial communities involved in the composting of manure remain poorly understood. This study conducted aerobic composting of dairy manure and sawdust. Four 16S rRNA gene clone libraries were constructed from samples at Days 6, 14, 21, and 42, and a total of 375 clones were sequenced. The bacterial community structure and composition varied significantly during the composting process. Larger differences at the genus level were observed in each sample. Early in the thermophilic stage (Day 6), three main genera, Pseudomonas, Sphingobacterium, and Bacillus, were identified. Most clones affiliated with genera Cellvibrio, Devosia, Rheinheimera, and Luteimonas were detected at the thermophilic stage (Day 14). Dominant bacteria at the cooling stage (Day 21) were more diverse at the genus level, and included Flavobacterium, Myroides, Cellvibrio, Sphingobacterium, Rhodothermus, Bacillus, and Clostridium. Cellvibrio. spp increased to the highest abundance (12.4%) at the manured stage (Day 42). These results could provide a better understanding of bacterial communities during manure composting.

For the first time, a comprehensive study of 35 multiparameter isotherm models was conducted to describe the dynamics of the adsorption of acridine orange (AO) dye on an abundantly available agricultural waste, i.e., overripe Abelmoschus esculentus seedpods. The purpose of this work is to assess the most reliable model for the design and development of an effective batch adsorber system. Analysis of experimental isotherm data was done by scrutinizing one-, two-, three-, four-, and five-parameter models at three different temperatures to understand specific parameters for the design process. Detailed error analysis is carried out to check the accuracy and adequacy of the best fitting isotherm model for experimental data. The isotherm data are in good agreement with the Fritz-Schlunder-V model. Later, experimental data are extensively investigated for dye-biosorbent/dye interactions through Fowler-Guggenheim, Flory-Huggins, Kiselev, Frumkin, Hill-de Boer, and El-Awady isotherm modeling. As a result, the adsorption phenomenon that provides evidence of a multilayer formation shows an attractive interaction between the adsorbed species and the adsorbent surface. Most importantly, an artificial neural network (ANN)-based empirical model was developed to illustrate the dye sequestration process. The ANN-predicted and experimentally observed results were compared ($R^2=0.9964$) to test the accuracy of the model.

Potential environmental risks posed by graphene oxide (GO) should be evaluated. Wastewater treatment plants will be one of the last barriers for GO wastes. Hence, this study investigated the effects of GO on ammonia removal and bacterial community in a simulated wastewater treatment process. Reactors were fed with influents containing 0, 5, and $25\mathrm{mg}/\mathrm{L}$ of GO ($12\mathrm{h}$ cycles) for 11 days. Results showed that the ammonia removal efficiency increased as the GO dose varied within $5–25\mathrm{mg}/\mathrm{L}$ in reactors after 7 days. The abundance of Firmicutes, Sphingobium, and Leuconostoc in reactors fed with GO at concentration of $25\mathrm{mg}/\mathrm{L}$ were significantly higher than that in control reactors, and the abundance of Sphingobium increased with the increasing concentration of GO in reactors; however, the abundance of Klebsiella decreased with the increasing concentration of GO in reactors. The results indicated that a reasonable microbial community restructured by GO might play a crucial role in promoting ammonia removal. The findings in this work help to promote the understanding of biological characteristics of GO.

Increasing energy demand and decreasing availability of fossil fuels along with growing concerns regarding environmental issues have boosted the production of biofuels, including biogas. In the present study, we aimed to produce biogas using mixtures of crude glycerol, stillage, and swine wastewater as substrates in order to evaluate their effect on wastewater treatment efficiency and gas yield. The optimal mix of these substrates was determined and the kinetics of biogas production was analyzed. The most desirable results in terms of methane production and removal of organic matter from the wastewater were obtained when using concentrations of 5% glycerol and stillage.

The mechanism of ${\mathrm{SO}}_2$ and NO removal by chemical absorption enhanced with electromigration in corona discharge has been studied. The experiments were performed to investigate the effect of discharge voltage, gas flow rate, and inlet concentrations on the removal efficiency of ${\mathrm{SO}}_2$ and NO in an electromigration-enhanced chemical absorption reactor. The results showed that electromigration can enhance the chemical absorption rate of ${\mathrm{SO}}_2$ and NO. Removal efficiency of ${\mathrm{SO}}_2$ and NO increased with the increase of discharge voltage; the efficiency increments of ${\mathrm{SO}}_2$ and NO may reach up to 23.6% and 24.2% at 21 kV, respectively. Under experimental conditions, the increase of gas flow rate and ${\mathrm{SO}}_2/\mathrm{NO}$ inlet concentrations had no significant effect on ${\mathrm{SO}}_2$ removal efficiency because of the strong electron affinity and solubility, while the NO removal efficiency was significantly reduced with the increase in these parameters.

The recovery of copper by-products from wastewater was achieved by carrying out an adsorption process coupled with an electrochemical system using modified grapefruit peels for metal recovery in a continuous flow. The adsorption capacity of grapefruit peels was $52.48\mathrm{mg}{\mathrm{g}}^{-1}$, and it was possible to reuse it in repeated adsorption–desorption cycles (more than 17). The recovery of copper from the saturated adsorbent was possible by means of a two-step process: first, desorption was carried out using 0.1 M HCl, achieving 90% of Cu(II) eluted in a concentrated solution, and then, an electrolytic process was carried out, achieving up to 65% of metal recovery as electrolyzed copper with high purity. The adsorbent material and eluted solution could be reused. In a final step, the exhausted adsorbent was processed through thermal degradation; copper adhered to the material acted as a catalyst, which reduced the energy consumption and finally resulted in the formation of copper oxide with 54% weight for weight (w/w) copper purity.

The limiting nutrient in North Biscayne Bay identified using the Redfield ratio does not correspond to a significant quantitative relation between measured concentrations of the identified nutrient and chlorophyll $a$. Strategies for reducing chlorophyll $a$ could focus on the nutrients that are significantly correlated with chlorophyll $a$. To identify the terrestrial sources of nutrient loads, a novel application of the load-duration curve (LDC) is shown to effectively differentiate between surface runoff and groundwater sources of nutrients in urban drainage canals. It is shown that septic tanks and stormwater-management exfiltration trenches can yield comparable nutrient loadings to groundwater, which might subsequently impact nutrient concentrations in the adjacent bay.

Batch equilibrium tests with various soil-liquid ratios ($\mathrm{S}/\mathrm{L}=1:2.5$, $1:5$, $1:10$, and $1:20$) and column tests with a flow interruption and rest period were performed to evaluate the adsorption behavior of kaolin. Identical isotherms were obtained from the batch equilibrium tests, illustrating that the S/L ratio has minimal impacts on adsorption behavior if complete mixing is ensured. In the column tests, a long non-Fickian tailing was observed in the breakthrough curve, and a decrease in the concentration of the liquid phase was observed in the closed system during the flow interruption and rest period although the column achieved local equilibrium. These results demonstrated that sorption equilibrium in the soil columns was not reached even when a stable exit concentration was achieved. The dual porosity (DP) concept was used to interpret the test results. Insufficient adsorption in the immobile phase is the major cause of the relatively low adsorbed concentration in short-term column tests, and a higher ratio of mobile phase voids compared to that of mobile phase adsorption capacity leads to a lower apparent retardation factor. The long-term transfer between the two phases is another key point that should be accounted for in the data analysis and modeling of column tests. Differences in immobile phase adsorption levels between tests under laboratory conditions and those under in situ conditions lead to discrepancies, which may confound the apparent retardation factor.

Key technological breakthroughs, such as hydraulic fracturing (HF) and horizontal drilling, have facilitated the extraction of shale gas. The boost of the shale gas industry has changed global energy markets and led to a decline in natural gas and oil price. Endowed with massive shale gas resources, China is ambitious to develop its shale gas industry, driven by growing energy demand and critical environmental conditions. However, an increasing number of pollution problems coming along with extraction has threatened our environment with atmospheric pollution, water risk, induced seismicity, occupational health, safety, and so on. Because HF needs millions of tons of water and produces a large quantity of effluents, water management becomes one of the most threatened problems. Also, wastewater treatment has become a key factor restricting the development of China’s shale gas industry. In response, international and domestic enterprises have developed a variety of management processes, which are divided into three categories: reinjection, reuse in hydraulic fracturing, and discharge after treatment. In this paper we first summarize Chinese shale gas development, then analyze the production of shale gas wastewater through major extraction techniques. Finally, a review was conducted on current wastewater treatments utilized in China, and advice is offered for future treatment techniques.

This research focused on the improvement of catalytic activity and ${\mathrm{N}}_2$ selectivity in catalytic denitrification by zero-valent iron (${\mathrm{Fe}}^0$) and bimetallic catalyst. Analysis of optimal operating conditions indicated that Pd-Cu/graphene showed better catalytic performance (catalytic activity: $0.44\mathrm{mg}/\mathrm{L}·\mathrm{g}·\min$, ${\mathrm{N}}_2$ selectivity: 70%) than other catalysts under the same following conditions: $4\mathrm{g}/\mathrm{L}{\mathrm{Fe}}^0$, $3\mathrm{g}/\mathrm{L}$ catalyst, $3:1$ $\mathrm{Pd}:\mathrm{Cu}$ (Pd: 5% by weight), 2-h reaction time, and 5.1 pH. This may be due to graphene’s larger specific surface area, good chemical stability, thermostability, and strong electron transfer illustrated via characterization of ${\mathrm{S}}_{\mathrm{BET}}$, SEM, FTIR, and TG. Finally, experiments on regeneration and reuse of catalysts indicated that acidic washing helped to regenerate the catalysts. However, except for Pd-Cu/diatomite, the catalytic performances of other catalysts appeared to be lower than their original catalysts.

This study investigated the simultaneous production of lipases and biosurfactants and the use of culture media containing biocompounds (without precipitation and purification processes) in the bioremediation of contaminated soil. Different concentrations of agroindustrial raw materials, moisture, oil inducers, and nitrogen were studied. The bioremediation assay was evaluated for 90 days, using biodiesel as a contaminant, adding fermented solid culture medium in soil and comparing it to natural attenuation. The culture media was composed of wheat bran:corncob (proportion $80:20$), 5% inducer, and 60% moisture, inoculated with Aspergillus niger, allowing the simultaneous production of biosurfactants [$6.67\pm 0.06$ Units of Emulsifying activity (UE)] and lipases [$10.74\pm 0.54$ Units of Lipase (U)]. In the bioremediation assay, the highest degradation of contaminant (64.09%) was found after 60 days using 10% of the fermented solid culture medium containing lipases and biosurfactants. Coproduction of both biocompounds in the fermentation process was allowed, leading to cost reductions and the viability potential of the bioprocess on an industrial production scale, as well as its environmental application in the treatment of oily contaminants.

Bottom and combined ash samples from municipal solid waste incinerator (MSWI) facilities in Florida were compared with industry aggregate standards to determine suitability for use as a road base. Although MSWI ashes tested in this work generally conformed to these standards for bearing strength (i.e., limerock bearing ratios above 100%), blending with commercially available aggregates is proposed as a strategy for improving overall material homogeneity and quantity. This work presents that MSWI ash can exhibit acceptable parameters defined in existing specifications for road-base materials on their own or by blending with commercially available aggregates, bolstering existing supplies of base materials while contributing to landfill diversion. The overall trend for bearing strength decreases with increasing MSWI bottom ash replacement (except for recycled asphalt pavement), but there appears to be a positive correlation between blend coefficients of uniformity ($C_u$) and bearing strength ($R^2=0.5290$). This suggests that gradation and material types may be parameters for identifying potential blends for advanced testing and developing quality control and assurance standards for material production and construction.

Nanoscale zero-valent iron (nZVI) particles are one of the most efficient materials for water treatment. However, their poor resistance to oxidation is one of the major reported drawbacks. This study synthesized a series of nZVI particles modified by sulfides (S-nZVI) and then supported on activated carbon (AC/S-nZVI). Batch experiments of bromate removal by S-nZVI or AC/S-nZVI were performed. Three process parameters [dissolved oxygen (DO), S/Fe, and dose of S-nZVI] were optimized by the response surface methodology (RSM) combined with the Box–Behnken design (BBD). The highest bromate removal rate (90%) was achieved in 90 min with a $40\text{-}\mathrm{mg}/\mathrm{L}$ dose of the S-nZVI composites (S/Fe molar ratio of 0.09) and a DO value of $8.0\pm 0.5\mathrm{mg}/\mathrm{L}$. The mechanism of bromate reduction by AC/S-nZVI was discussed. The oxidation resistance was improved due to the presence of iron sulfides (${\mathrm{FeS}}_x$). The excellent bromate removal efficiency achieved by AC/S-nZVI likely is due to the synergistic effects of AC and S-nZVI. Overall, our work provides a promising, efficient method for removing bromate in high DO water.

This paper presents a failure quantification methodology to assess the impact of cyber-physical attacks (CPAs) on critical water infrastructures, such as water distribution networks, by mapping simulation-derived data onto metrics. The approach sets out a three-step profiling architecture to interpret the consequences of failures resulting from CPAs against several dimensions of integrity, adjusted through user-defined service levels. Failure is examined in terms of its magnitude, propagation, severity, and crest factor, while rapidity is used to infer available time slots to react. The methodology is operationalized through a dedicated tool designed to assist water-sector critical infrastructures gauge and assess CPAs. The approach is demonstrated on a benchmark water distribution system, and results and insights from the metrics are presented and discussed. It is argued that the approach and the tool that operationalizes its application can be useful to water companies that need to assess and compare cyber-physical threats and prioritize mitigation actions based on quantitative metrics.

Microbubbles (MBs) can spontaneously generate hydroxyl radicals ($·\mathrm{OH}$) with high oxidizing capacity. In this study, a novel oxidation-absorption process based on a microbubble system in the indirect removal mode was proposed for the simultaneous removal of nitric oxide (NO) and sulfur dioxide (${\mathrm{SO}}_2$). In this process, an air microbubble water system (AMBW) was produced by a microbubble generator (MBG) inhaling air and tap water and injected into an oxidation-absorption column reactor by the MBG, meanwhile the mixed gas composed of NO and ${\mathrm{SO}}_2$ passed through a micron-sized gas distributor at the bottom of the reactor and flowed into the AMBW. Important parameters including initial pH and temperature of tap water, operation time, NO concentration, ${\mathrm{SO}}_2$ concentration, and NaCl concentration were assessed to investigate the feasibility of the AMBW for the simultaneous removal of NO and ${\mathrm{SO}}_2$. The results showed that $·\mathrm{OH}$ generated from the collapsed MBs played a critical role in the removal and the simultaneous removal of NO and ${\mathrm{SO}}_2$ was successfully achieved with the AMBW. Even with only tap water used as the absorbent, the removal efficiencies of NO and ${\mathrm{SO}}_2$ reached 92.7% and above 99%, respectively, when the experiment conditions were initial water pH 11.5, initial water temperature 298 K, 600 ppm NO, and 3,000 ppm ${\mathrm{SO}}_2$. Compared with the microbubble system in the direct removal mode, this new system is more suitable for the treatment of flue gases with low NO concentration and high volume. Moreover, this novel process should have a good prospect of industrial application in the flue gas treatment due to its high efficiencies of desulfurization and denitration and some advantages such as low usage cost of the reagents, simple system, and small occupation space.

This study investigated the effectiveness of magnetite as ballast material through a technology called BioMag in nitrogen and phosphorus removal and in processing peak flows at a wastewater treatment plant using data from the Marlay-Taylor Water Reclamation Facility in Maryland. Using intervention analysis, the magnitude of the difference in effluent total nitrogen (TN) and total phosphorus (TP) before and after the magnetite technology retrofit was estimated, but with the time series forecast forward both before and after the upgrade, as opposed to a backward forecast of the series after the upgrade suggested by previous studies. The sludge volume index (SVI) and mixed liquor suspended solids (MLSS) were also examined to ascertain the effect of the magnetite technology on these parameters. The findings showed improved SVI and increased MLSS and that the upgraded facility is successfully treating peak flows while maintaining good effluent quality. The effluent TN and TP decreased by 98% and 77%, respectively. These results were compared to results from a backward forecast as well as results obtained from a simple difference between actual reported values.