Journal of Environmental Engineering

The presence of emerging contaminants (ECs) in the environment, especially in the water and wastewater matrices, has become a major headache for the competent authorities, because even with the mildest of exposure aquatic organisms, as well as humans, can exhibit chronic/acute toxicity. In the last few years constructed wetlands (CWs) have become a popular method to eradicate ECs from water and wastewater, because they are an environmentally benevolent, economically feasible, and aquatic plant-based natural technology. However, information is not readily available on how to configure a CW (or combination of CWs, for hybrid CWs) to ensure the substantial removal of ECs. Thus, the present review analyzes how the various physicochemical properties of ECs govern their major removal pathways in different CWs and how the design configuration of a CW can lead to better EC removal. Finally, some recommendations regarding the possible configuration or combination of CWs on the basis of the ECs’ known physicochemical properties are made. This review article will help in selecting the proper combinations of CWs to eliminate the ECs of concern (known or unknown) from the aquatic matrices.

Metal porphyrin structure is believed to be the active site for microbiological reductive dechlorination. In this work, a biomimetic Hemin catalyst was used for the electrochemical dechlorination of trichloroethylene (TCE). Cyclic voltammetric analysis demonstrates the high electrochemical reactivity of Hemin toward reductive dechlorination of TCE, which is further confirmed by controlled potential electrolysis. TCE can be fully dechlorinated to acetylene, ethylene, and ethane. Density functional theory calculations show the appearance of unpaired electron spins on coordinatively unsaturated Fe sites. The breakage of the Fe–Cl bond in Hemin with the formation of coordinatively unsaturated ${\mathrm{Fe}}^{\mathrm{II}}$ sites shows reactivity toward TCE-to-dichloroethylene (DCE) conversion, but ${\mathrm{Fe}}^{\mathrm{II}}$ sites with the coordination to Cl atoms have no reactivity. Lowering the applied potential to $-2.1\mathrm{V}$ generates coordinatively unsaturated ${\mathrm{Fe}}^{\mathrm{I}}$ sites, showing much higher reactivity toward TCE reduction compared with ${\mathrm{Fe}}^{\mathrm{II}}$ sites. The energy barrier involving complete dechlorination of TCE was decreased from 1.83 eV by ${\mathrm{Fe}}^{\mathrm{II}}$ sites to 0.86 eV by ${\mathrm{Fe}}^{\mathrm{I}}$ sites. ${\mathrm{Fe}}^{\mathrm{I}}$ sites can continue to contribute to TCE dechlorination in electrochemical systems. Our study provides a novel biomimetic electrochemical approach for the dechlorination of TCE in groundwater.

The Mariner field is a newly completed oil field in the UK continental shelf with an estimated reserve of 396 million cubic meters (2.5 billion barrels) of oil. Despite the energy security benefits its development provides to the UK, it constitutes a challenge to environmental conservation due to the existential threat of an oil spill. To plan an effective oil spill response operation, it is essential to have a sophisticated knowledge of the behavior of an oil spill in the Mariner field. More importantly, only a few studies exist that sufficiently describe the oil behavior in the Mariner field under varying environmental conditions, due to its recent development. This study aims to predict the behavior (fate and trajectory) of a heavy oil spill from the floating storage unit platform in the Mariner field. For this purpose, General NOAA Operational Modeling Environment (GNOME) and Automated Data Inquiry for Oil Spills (ADIOS) were selected as the simulation tools to predict the trajectory and fate behaviors of oil for 5 days in October under the forcing of two different ocean models, namely Real-Time Ocean Forecasting system (RTOFS) and Hybrid Coordinate Ocean Model (HYCOM). Results indicated that approximately 87% of the spilled oil remained at sea after 5 days. This apparent persistent behavior of the oil on water raises a concern for marine organisms like seabirds, whose vulnerability has been found to peak in October. This implies the need for swift response action if such organisms must be protected. Furthermore, shoreline beaching was not recorded within the 5 days of observation; however, the oil slick was found to encroach the Norwegian territorial waters. This indicates the need to plan for implementation of UK–Norway joint contingency plan to combat a future oil spill of this manner. This work could serve as a reference or guide to oil spill responders to inform the process of systematic environmental conservation planning in the Mariner field, UK continental shelf.

Electrochemical oxidation (EO) is the most promising treatment for pharmaceutical removal in an aqueous matrix, though there are limited studies investigating the EO of pharmaceuticals in a real matrix such as reverse osmosis concentrate (ROC). High electrical conductivity causes less energy consumption for EO and massive chloride concentration in ROC make it suitable for its use as an electrolyte. The application of ROC as an electrolyte for the EO of diclofenac sodium (DCF) using an indigenously prepared $\mathrm{Ti}/\mathrm{Ru}\text{-}\mathrm{Sn}\text{-}\mathrm{Sb}\text{-}{\mathrm{O}}_x$ anode is explored in this study. The removal rate increased with an increase in current density from 5 to $10\mathrm{mA}/{\mathrm{cm}}^2$ for both DCF and intermediate products (IPs). The 0.005 $p$-value obtained using a paired $t$-test indicated that the results obtained using methanol as a quenching agent matched those obtained by immediate analysis (without quenching) at a 99.5% confidence level. Thus, methanol is the most suitable quenching agent in this study. The composition of electrolyte in terms of sulfate to chloride mass ratio was found to affect the removal of DCF and IPs. The maximum removal (approximately 95%) of DCF was obtained in the presence of a sulfate-to-chloride mass ratio ranging from 0.85 to 1.35. The phytotoxicity level increased from 3% to 9% after 120 min of EO, which is not significant compared with similar previous studies.

The removal effects of livestock wastewater dominated by tetracycline antibiotic in microbial fuel cell (MFC) and the fate of antibiotic-resistance genes (ARGs) and mobile genetic elements (MGEs) were evaluated by high-throughput quantitative polymerase chain reaction (PCR). In total, 132 kinds of ARGs and seven kinds of MGEs were detected in the untreated livestock wastewater. A decrease in the number of ARGs and MGEs was observed after MFC treatment, among which MGEs decreased by 71.4%. Chloramphenicol-resistance genes and MGEs both dropped in relative abundance, by 58.6% and 55.5%, respectively. The absolute abundance of sulfonamide-resistance genes fell from ${5.9\times 10}^5{\mathrm{copiesL}}^{-1}$ to ${3.7\times 10}^5{\mathrm{copiesL}}^{-1}$. Vancomycin-resistance genes ($130\pm 10{\mathrm{copiesL}}^{-1}$) and beta-lactamase-resistance genes ($180\pm 10{\mathrm{copiesL}}^{-1}$), on the other hand, were not effectively eliminated. After the tetracycline concentration was increased to ${6\mathrm{mgL}}^{-1}$, the chemical oxygen demand (COD) removal rate reached up to 88.8%. The corresponding maximum power density value was ${763.695\mathrm{mWm}}^{-3}$. A clear alteration in the microbial community structure was noticed as tetracycline concentrations increased. Illumina sequencing indicated that Pandoraea (12.4%), Chitinophaga (12.8%), Dyella (7.3%), and Chryseobacterium (5.4%) were the dominant genera. They were critical for ensuring the reactor’s stable operation and played a significant role in tetracycline degradation in MFC. Results showed that the MFC system had strong resistance to antibiotic toxicity and high potential to control ARGs. Although MFC’s removal efficiency for high tetracycline concentration was limited in this work, MFC was found to have an essential role in lowering ARGs and limiting horizontal gene transfer.

The present study deals with the generalized one-dimensional (1-D) advection fractal dispersion (AFD) equation. The numerical simulation is carried out to simulate the plume’s fate and transport phenomenon in a finite porous medium. The present model is developed for chemical substitute migration in soil with spatial varying advection and its corresponding fractal dispersion. Moreover, it is adequate for deliberating spatial varying sorption and first-order biological degradation due to reaction processes in the soil. As in generalized dispersion theory, the dispersion term is expressed to be directly proportional to seepage velocity by some power $\alpha$, where $\alpha$ varies from 1 to 2. The present numerical study is capable of dealing with various types of advection and its corresponding fractal dispersion. Initially, we have assumed that the aquifer was pollutant-free. At the inlet of the domain, some pollutant source has been considered, and at the outlet boundary, it is assumed that the pollutant concentration disappears to zero. The pollutant concentration distribution has been observed in different types of porous medium as well as for various hydrological parameters. The current generalized AFD model is based on the implicit finite difference technique, which can illustrate chemical migration in the soil to the groundwater, and further, the MATLAB version R2013a(8.1.0.604) Pdepe tool technique validates it. A special case study is also discussed regarding the migration of Iron (Fe) and Zinc (Zn) in the soil. Afterwards, the numerical model is used to illustrate the breakthrough curves (BTCs) for the various transport parameters, and the accuracy of the model problem is also discussed using root mean square error (RMSE).

The effects of different types of earthen landfill covers and vapor on landfill gas emissions are not well understood. In this study, an existing theoretical model of water and multicomponent gas (methane, carbon dioxide, nitrogen, and oxygen) flow was improved by incorporating vapor flow. The model was validated using a published soil column test simulating landfill gas emissions through landfill covers. Numerical simulations were conducted to investigate landfill gas emissions through a single clay-layer cover, a cover with capillary barrier effects (CCBE), and a three-layer cover during continuous drying. The CCBE retained the lowest water content after drying, whereas the bottom clay layer in the three-layer cover stayed almost saturated due to the protection afforded by the top two layers. Accordingly, methane emissions from the CCBE were the highest, whereas those from the three-layer cover were the lowest. Ignoring vapor will predict a drier soil state, and hence will cause methane emissions to be overestimated by 1–2.5 times. Effects of vapor became more significant as the overall gas coefficient of permeability of the cover increased.

In this paper, the well-known Benchmark Simulation Model No. 1 (BSM1) was modified with a new model for the secondary clarifier to improve its prediction capability. The Bürger-Diehl settler model was integrated with the activated sludge models to represent a complete model of an activated sludge train. Based on this integrated model, twin-level control strategies were developed to enhance the model effluent quality. The secondary controllers at the lower level were proportional integral (PI) and model predictive control (MPC), and the primary controllers at the supervisory level were MPC and fuzzy controllers. The controllers were developed on the identified plant models using prediction-error methodology. Based on these, different controller combination strategies such as PI-Fuzzy, MPC-Fuzzy, PI-MPC, and MPC-MPC were evaluated. Results indicated that the Bürger-Diehl settler model achieved better effluent quality than the traditional Takacs settler model due to a significant reduction in effluent violations. In terms of overall performance, the PI-Fuzzy controller combination was able to deliver improved plant performance.

Walnut shell biochar (WBC) was used to adsorb metolachlor (MET) in soils with different kaolin contents. 0%, 10%, and 20% of kaolin were added to the pretreated soil to prepare experimental soil. Adsorption kinetics, pH value, adsorbent dosage, ionic strength, and isotherm adsorption models are all used to characterize the adsorbent, and the removal effects of WBC on MET in different experimental soils were studied. The saturation adsorption capacities of MET on WBC in the soil with 0%, 10%, and 20% kaolin are 39.38, 44.44, and ${52.08\mathrm{mg}\mathrm{g}}^{-1}$, respectively, according to the fitting findings of the Langmuir isotherm model. In the experiment, the kaolin can increase the adsorption of MET by the soil itself and promote the MET adsorption by WBC. This study provides a theoretical basis for minerals’ influence on the adsorption of biochar under natural conditions.

The aging of sewer networks in old residential neighborhoods in China causes frequent problems with their integrity and functionality, such as sanitary sewer overflows and hydraulic overloading of wastewater treatment plants. In order to assess the performance of the sewer system in an old residential area in Ningbo, China, and to evaluate the effectiveness of the sewer system upgrade, the sewer system was continuously monitored for about 8 months. The quantity and quality of wastewater were comprehensively analyzed. The rainfall-derived inflow and infiltration (RDII) characterization was identified in the sewershed by using the $R\text{-}\text{value}$ method and the triangle method. The $R\text{-}\mathrm{values}$ before and after the sewer upgrade were about 28% and 7%, respectively. The effects of the sewer upgrade were also quantified through comparing the concentration of pollutants before and after the program. The findings of this study will help to understand the performance of small-scale urban drainage systems, especially in old residential areas and/or in developing countries, and to provide guidance for future system upgrades.

Although the reuse of reclaimed water is one of the ways to solve the water crisis, secondary effluents still contain opportunistic pathogens that pose a potential threat to human health. Herein, we use slow filtration-disinfection as an advanced treatment to explore the removal of opportunistic pathogens such asLegionellaorPseudomonas aeruginosa. We show that, at the same filtration rate, removal is more effective (1) with aerobic heterotrophic biofilm rather than with denitrification or nitrification ones, (2) at the slowest filtration rate of $5\mathrm{cm}/\mathrm{h}$, and (3) when pathogens adhere to particles. According to the opportunistic pathogens content in the water after adding the disinfectant, the optimal dosage of sodium hypochlorite (NaClO) ($8.0\mathrm{mg}/\mathrm{L}$, calculated as available chlorine concentration) and ultraviolet (UV) ($40\mathrm{mJ}/{\mathrm{cm}}^2$) was determined. To remove opportunistic pathogens, NaClO disinfection in slow filtration water is more effective at lower pH and higher temperature, whereas UV disinfection in slow leaching water is more effective at lower pH and turbidity. Combining slow filtration and disinfection was effective in removing opportunistic pathogens in the secondary effluent, and UV radiation was more effective than NaClO. Removal rates of Legionella and P. aeruginosa by UV exposure were 98.6% and 98.1%, respectively. Although Pseudomonas, Acidovorax, Sphingomonas, and Lactobacillus were also present in the other types of biofilms, they were more abundant in aerobic heterotrophic biofilm and had some inhibitory effect on opportunistic pathogens. Finally, turbidity, but not dissolved organic carbon (DOC), was correlated with opportunistic pathogens in water. In summary, the combined process of slow filtration-disinfection can effectively reduce the content of opportunistic pathogens in the secondary effluent and ensure microbiological safety.

Heavy metals in industrial waste cause environmental damage because they metals are toxic, nonbiodegradable, and are bioaccumulated. As such, treatments are needed to reduce heavy metals to legally acceptable levels before disposal. As such, the aim of this study was to assess copper ion adsorption in aqueous solution using Ranufe bentonite (raw, sodium and pillared), which is abundant in Northeastern Brazil. Sodium bentonite was obtained using ionic exchange with sodium acetate and pillared bentonite was formulated with a pillarizing agent (aluminum hydroxide and sodium). Treatment efficiency was assessed using Brunauer–Emmett–Teller (BET), X-ray fluorescence (XRF), and X-ray diffraction (XRD) analyses. The surface area obtained by BET showed behavior characteristics of a mesoporous material. XRD exhibited basal spacing consistent with the pattern of clays. XRF analyses confirmed the changes on the raw bentonite surface, proving its transformation in the sodium and pillared forms. Adsorption capacity was assessed as a function of pH, contact time, adsorbent mass, initial metal concentration, ligand and co-ion effects on copper removal efficiency, reaching a maximum rate of 85.76%. Adsorption isotherms were fit to the Langmuir model, assuming adsorption on homogeneous surfaces in the form of monolayers, with maximum adsorption capacity of $12.92\mathrm{mg}/{\mathrm{g}}^{-1}$ (raw bentonite) and $24.51\mathrm{mg}/{\mathrm{g}}^{-1}$ (sodium bentonite). The kinetic study demonstrated that bentonite (raw and sodium) fit the pseudo-second-order kinetic model, indicating a process governed by ionic exchange between copper and the ions present in the bentonite layers. The thermodynamic adsorption parameters demonstrated that adsorption using raw and sodium bentonite is endothermic (favored by the rise in temperature) and nonspontaneous (energy is needed to promote adsorption). In a study on desorption, four adsorption and desorption cycles were sufficient to assess the regeneration capacity of the material, showing a decrease in adsorption capacity from the first to last cycle from 69.47% to 41.33% (raw bentonite) and from 48.36% to 22.46% (sodium bentonite). A decline in adsorption capacity is related to chemical degradation caused by acid solutions and mechanical agitation during the adsorption cycles.

Evaluations of analytical performance through interlaboratory comparisons and proficiency tests are underway globally for biomolecular-based methods [e.g., reverse-transcription quantitative polymerase chain reaction (RT-qPCR)] used in the surveillance of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in wastewater. These evaluations often rely on sharing a common reference wastewater sample that is split among participating laboratories. A known quantity of recovery surrogates can be introduced to the wastewater matrix by the coordinating laboratory as an exogenous control in a spike-and-recovery approach; however, split-sample comparisons are increasingly performed to evaluate in situ quantities of SARS-CoV-2 genetic signal native to the sample due to the lack of a universally accepted recovery surrogate of SARS-CoV-2. A reproducible procedure that minimizes the variability of SARS-CoV-2 genetic signal among split wastewater aliquots is therefore necessary to facilitate the method comparisons, especially when a large number of aliquots are required. Emerging literature has suggested that SARS-CoV-2 genetic signal in wastewater is linked to the solids fraction. Accordingly, a protocol that allows for equal distribution of solids content evenly among wastewater aliquots was also likely to facilitate even distribution of the SARS-CoV-2 genetic signal. Based on this premise, we reviewed existing sample splitting apparatus and approaches used for solids-based parameters in environmental samples. A portable batch reactor was designed, comprised of readily accessible materials and equipment. This design was validated through splitting of real wastewater samples collected from a municipal wastewater treatment facility serving a population with reported cases of COVID-19. This work applies well-established solid-liquid mixing theory and concepts that are likely unfamiliar to molecular microbiologists and laboratory analysts, providing (1) a prototype adaptable for a range of sample quantities, aliquot sizes, microbial targets, and water matrices; and (2) a pragmatic demonstration of critical considerations for design and validation of a reproducible and effective sample splitting protocol.