Journal of Environmental Engineering

Due to their large impervious coverage, highways are ideal sites for the transport of pollutants to either treatment units or direct discharge to waterways. Mercury, a highly toxic and ubiquitous environmental contaminant, is rarely studied in stormwater runoff. Removal of particulate-bound mercury in a dry detention basin was analyzed for the five size fractions: $<0.45\mathrm{\mu m}$, 0.45–8 μm, 8–20 μm, 20–100 μm, and $>100\mathrm{\mu m}$. The highest concentration of mercury for both influent and effluent is observed in the 8–20 μm size fraction. Treatment units are often characterized by suspended solids removal efficiency and particle-bound pollutants correlated to suspended solids removal; however, different suspended solids removal efficiency may occur in specific particle size fractions. Therefore, the benefits of treatment units may be different than originally anticipated, especially if the particle-bound concentrations are greater in fractions more efficiently removed. For sedimentation-based treatment units, the removal is dependent on size fraction, and when one size fraction is captured more efficiently, the removal rate calculated using the entire sample might indicate particle-bound pollutant removal quite different than actually occurring.

Methylene blue (MB), a cationic azo dye, is harmful to the environment and human health. In this study, carbon microspheres (CMS)@magnetite was prepared to remove MB. The performance of CMS@magnetite on MB removal and adsorption mechanisms was studied. Transmission electron microscopy, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, Brunauer-Emmett-Teller, X-ray diffraction, and vibrating-sample magnetometry were used to characterize the CMS@magnetite before and after adsorption with MB. The effects of different dosages and initial pH values on MB removal by CMS@magnetite were studied through batch experiments. Results reflected that CMS@magnetite had high removal efficiency on MB. In addition, adsorption isotherms, kinetics, and thermodynamics models were also studied. MB adsorption behavior was better described by the Langmuir model. The experimental data of MB adsorption by CMS@magnetite had a higher fitting degree with a pseudo-second-order kinetic model. In addition, reuse experiments were studied, which showed the advantage of good recycling ability of CMS@magnetite. MB was removed by CMS@magnetite through electrostatic adsorption and $\pi \text{-}\pi$ interaction. Because of high removal efficiency, easy separation, and high performance of recycling, CMS@magnetite can be potentially used to remove MB wastewater.

The zinc oxide method is one of the most popular flue gas desulfurization processes, especially for the control of low-content sulfur dioxide. In this process, zinc sulfite can be oxidized to form a soluble zinc sulfate, which can solve the problems of scale formation and pipe plugging. This paper aims to study the oxidation kinetics of zinc sulfite in the zinc-based wet flue gas desulfurization (FGD) process by varying the zinc sulfite concentration, initial pH, oxygen partial pressure, temperature, stirring speed, gas flow rate, and particle size. The oxidation results indicate that there is a critical sulfite concentration of 7.5%, below which the reaction rate is 0.32 order dependence from sulfite, while above which the order turns to $-0.78$. Meanwhile, the reaction rate is 1.0 order in the oxygen partial pressure. The initial pH and particle size have little effect on the oxidation rate, while the oxidation rate increases with the stirring speed, gas flow rate, and temperature. Moreover, the apparent activation energy is calculated to be $15.85\mathrm{kJ}·{\mathrm{mol}}^{-1}$. Integrated with the kinetic model, it is concluded that the oxidation rate of zinc sulfite is controlled by the mass transfer of oxygen in the liquid phase.

Waste disposal is a challenging environmental concern worldwide. Carbon-rich waste materials can be transformed into adsorbent and/or catalyst support to reduce treatment costs and promote waste recycling. In the present study, three waste materials—sewage sludge, black liquor (from pulp and paper mills), and sugar mill press mud—were converted into activated carbons which were used as support for the iron-impregnated heterogeneous Fenton-type photo catalysts. These materials were characterized and tested on synthetic wastewater containing 4-chlorophenol (4-CP) as the model compound and simulated pulp-bleaching effluent. The oxidation runs were performed at an initial reaction pH of 4.4 with stoichiometric ${\mathrm{H}}_2{\mathrm{O}}_2$ dose and catalyst mass loading of $1\mathrm{g}/\mathrm{L}$ for 2 h duration. The maximum total organic carbon removal of 69% and 32% was observed for 4-CP and simulated bleaching effluent, respectively, during photocatalytic oxidation with black liquor–derived catalyst. Thus, the use of black liquor–derived catalyst for bleaching effluent can help paper mill operators handle liquid as well as solid waste in a very efficient manner.

This study develops a system named Wuhan University of Technology Intelligent Tracer (WUT-iTracer) for identifying ships using high-fuel-sulfur-content (FSC) fuel oil in port waters. The system integrates a land-based sniffing monitoring module and a numerical simulation module. The land-based sniffing monitoring module collects and processes simultaneous several parameters from the automatic identification system (AIS) and micrometeorological monitoring system, which include the concentrations of gaseous pollutants emitted from ships, marine meteorological parameters, and dynamic and static information of ships. The numerical simulation module was developed based on a mobile ship emissions diffusion model, which estimates the concentration of ${\mathrm{SO}}_2$ at the location of the WUT-iTracer assuming the ship using compliant fuel. The relative difference between the measured and simulated concentration of ${\mathrm{SO}}_2$ is used to detect if the ship uses high-FSC fuel oil. The WUT-iTracer was installed on the shore of Yantian Port, Shenzhen, China, during June and August 2018. Ten ships were selected as samples to verify the efficacy of the WUT-iTracer. Based on these data, it was found that the ship can be treated as using high-FSC ($>0.5\%$) fuel oil if the relative difference between the measured and simulated ${\mathrm{SO}}_2$ concentration is larger than 44%. The field test shows that the WUT-iTracer works well for identifying ships with high-FSC fuel oil. However, further tests and developments are needed for the system to work in different ports and weather conditions.

Integrated fixed film activated sludge-oxic settling anoxic system (IFAS-OSA) is a new, modified system for excess-sludge reduction. In this research, the efficiency of the IFAS-OSA system in biological excess-sludge reduction with the addition of an anoxic sludge-holding tank to the return line of the system was studied. The results showed that the average oxidation reduction potentials (ORPs) in the ${\mathrm{IFAS}}_{\mathrm{Aerobic}}$, ${\mathrm{IFAS}}_{\mathrm{RAS}}$, $\mathrm{IFAS}\text{-}{\mathrm{OSA}}_{2\mathrm{h}}$, and $\mathrm{IFAS}\text{-}{\mathrm{OSA}}_{4\mathrm{h}}$ processes were $+80\pm 15$, $-62\pm 22,–102\pm 8$, and $-140\pm 13\mathrm{mV}$, respectively. The average values of $Y_{obs}$ in the IFAS, $\mathrm{IFAS}\text{-}{\mathrm{OSA}}_{2\mathrm{h}}$, and $\mathrm{IFAS}\text{-}{\mathrm{OSA}}_{4\mathrm{h}}$ processes were $0.43\pm 0.01$, $0.31\pm 0.02$, and $0.23\pm 0.01$ g MLSS/g COD, respectively. Accordingly, in the $\mathrm{IFAS}\text{-}{\mathrm{OSA}}_{2\mathrm{h}}$ and $\mathrm{IFAS}\text{-}{\mathrm{OSA}}_{4\mathrm{h}}$ processes, the sludge production was reduced by 27.9% and 46.5%, and the excess sludge was reduced by 13.65% and 22%, respectively, compared with the control system. Furthermore, as the average ${\mathrm{SVI}}_{\mathrm{s}}$ reached $95\pm 12,63\pm 6$, and $49\pm 4$ $\mathrm{mL}/\mathrm{g}$, the TSS values in the effluents of the IFAS, $\mathrm{IFAS}\text{-}{\mathrm{OSA}}_{2\mathrm{h}}$, and $\mathrm{IFAS}\text{-}{\mathrm{OSA}}_{4\mathrm{h}}$ processes reached $16.5\pm 3$, $7.2\pm 1.5$, and $5.5\pm 1.2$ $\mathrm{mg}/\mathrm{L}$, respectively. The average percentages of total nitrogen (TN) removal efficiency in the IFAS, $\mathrm{IFAS}\text{-}{\mathrm{OSA}}_{2\mathrm{h}}$, and $\mathrm{IFAS}\text{-}{\mathrm{OSA}}_{4\mathrm{h}}$ processes were $78.56\pm 2.46$, $83.60\pm 0.92$, and $85.03\pm 1.69$, respectively, whereas the percentages of phosphorus removal efficiency in these processes were $32.69\pm 8.25$, $36.35\pm 6.73$, and $39.87\pm 3.61$, respectively. This study revealed that the modified IFAS-OSA system had a more efficient performance than the IFAS system.

Stable and efficient performance of biological treatment plants requires optimization of treatment system operating parameters. Among the various operating parameters, temperature is an important factor that influences the treatment system microbial community, which is responsible for the efficient removal of organic pollutants. This study investigated the effect of temperature on the microbiome of a submerged membrane bioreactor (SMBR) treating hospital wastewater (HWW). Specifically, the effect of temperatures ($T=20°\mathrm{C}$, 15°C, and 10°C) on the removal of pharmaceuticals from HWW was examined. The maximum removal of chemical oxygen demand ($\sim 70\%$) and ammoniacal nitrogen ($\sim 75\%$) in the SMBR occurred at 20°C. The suspended solids (SS) concentration in the SMBR decreased from $8.5{\mathrm{g}\mathrm{L}}^{-1}$ SS at 20°C to $6.75{\mathrm{g}\mathrm{L}}^{-1}$ SS at 15°C and to $5.2{\mathrm{g}\mathrm{L}}^{-1}$ SS at 10°C. At the lowest temperature (10°C), there was moderate removal of ibuprofen, hydroxyl-ibuprofen estrone, and caffeine, but the removal of sulfamethoxazole, clarithromycin, diclofenac, hydroxy diclofenac, atenolol, venlafaxine, and desvenlafaxine was inhibited substantially relative to that at higher temperatures. The microbiome analysis indicated a reduction in the relative abundance of nitrifying bacteria (Nitrosospira, Rhodanobacter, and Sphingobium) at low temperatures, which appeared to be correlated with the decrease in performance. Analysis of the microeukaryote community revealed a massive decrease in the relative abundance of the ciliate population at the low temperature and an increase in the abundance of the fungal group (Basidiomycota and unclassified fungus). Despite the dominance of fungal groups at the lower temperature, the decreased SMBR performance suggests that those fungal groups did not play an important role in pharmaceutical degradation.

Sulfonated graphene oxide (SGO) was prepared using sulfuric acid and used as a nanofiller at various concentrations in self-fabricated sulfonated polyetheretherketone (SPEEK) to produce nanocomposite proton-exchange membranes for microbial fuel-cell (MFC) applications. The proton conductivity, water uptake, ion-exchange capacity (IEC), and MFC performance of the nanocomposite membranes (SPEEK-SGO) were compared with those of pristine SPEEK and SPEEK-graphene oxide (GO). The addition of sulfonated GO (2% by weight) in a SPEEK membrane enhanced the proton conductivity and showed the maximum power density of $\mathrm{1,028}\pm 7\mathrm{mW}·{\mathrm{m}}^{-2}$ compared with SPEEK ($570\pm 4\mathrm{mW}·{\mathrm{m}}^{-2}$) and SPEEK-GO ($704\pm 6\mathrm{mW}·{\mathrm{m}}^{-2}$) membranes in a single-chamber MFC. The SPEEK-SGO 2% membrane exhibited a onefold greater performance than the Nafion 115 (sulfonated tetrafluoroethylene) membranes ($512\pm 6\mathrm{mW}·{\mathrm{m}}^{-2}$) in the same MFC arrangement. The enhanced result of the SGO membranes was attributed to the presence of a high-density of sulfonic acid ${─\mathrm{SO}}_3\mathrm{H}$, $─\mathrm{OH}$, and $─\mathrm{COOH}$ on SGO, which facilitates higher water uptake, proton conductivity, and IEC of the membrane.

Understanding and quantifying particle–fluid interaction (PFI) is of fundamental importance for such geoenvironmental issues as polluted soil behavior, transport of organic contaminants in porous media, and the behavior of slurries in contact with nonaqueous-phase liquids (NAPLs). NAPLs have a very low dielectric permittivity in comparison with water, and therefore significant changes in soil properties can be expected as a consequence of PFI. This study evaluates interactions between soil particles and NAPLs using the rheology measurement of loess silt, zeolite, and bentonite particle concentrated dispersions. The dispersing liquids were kerosene, two paraffin oils with different viscosities, and deionized water (DIW) as a reference liquid. The results show the influence of the volumetric content of particles on the undrained shear strength of dispersions. The effects of suspending fluid viscosity and the magnitude of PFI were analyzed in a novel way by comparing the volume of particles for which the dispersion presents an undrained shear stress of 1 Pa determined for two different fluids. These results highlight the importance of PFI in the macroscopic properties of soils, hydraulic conductivity, and liquid limit.

Volatile fatty acids (VFAs) and ammonia accumulation showed high inhibition for the high-solid anaerobic digestion (HSAD) of waste-activated sludge. This study investigated the effects of an exogenous pH buffer system with the addition of ${\mathrm{K}}_2{\mathrm{HPO}}_4/{\mathrm{KH}}_2{\mathrm{PO}}_4$ at different initial pH values in order to mitigate the inhibition of VFAs and ammonia accumulation. Results showed that the addition of ${\mathrm{K}}_2{\mathrm{HPO}}_4/{\mathrm{KH}}_2{\mathrm{PO}}_4$ with an optimal initial pH of 7.0 could prevent the pH from decreasing at the initial stage or rising at the final stage. In this study, 30.6% higher cumulative methane production was obtained compared to the control. A volatile solid (VS) removal rate as high as 42.3% was also achieved. Three key enzymes’ activities in the HSAD process were investigated, including alkaline protease, acetate kinase, and Coenzyme ${\mathrm{F}}_{420}$. Moreover, a model simulation presented that a modified Gompertz model fit the actual methane production best, as supported by the highest $R^2$ value. The addition of phosphorus buffer substantially increased the hydrolysis rate ($k_{\mathrm{hyd}}$) and maximum methane potential ($f_{\mathrm{d}}$) by parameters analysis, which explained the increased VS removal and methane production. High-throughput sequencing analysis clearly showed differences in the microbial community between samples from different treatments. Tepidimicrobium and Rhodobacter were the dominant bacterial genera involved in the HSAD system, which presented a high degradation capacity of organic material. The archaea community was dominated by Methanosaeta and Methanoculleus, and these are the typical aceticlastic methanogens and hydrogenotrophic methanogens, respectively. Herein, ${\mathrm{K}}_2{\mathrm{HPO}}_4/{\mathrm{KH}}_2{\mathrm{PO}}_4$ addition proved to be an effective method to overcome the problems related to the free ammonia and VFA accumulation during the sludge HSAD process under thermophilic conditions on a lab-scale setting (using a 7-L bioreactor).

A biodigester consists of a closed chamber to anaerobically digest biomass into biogas and biofertilizer, and is an efficient alternative for organic waste treatment and energy generation. The new interest in decentralizing waste treatment and the restricted space of urban centers makes compact biodigesters a feasible alternative for sustainable cities. This paper presents the compact and low-cost Hexagonal Methane Collector biodigester and its operational capacity to produce biogas. The factorial experimental design results indicate that the volume of inoculum and mixture inside the reactor are important in controlling biogas yield, but the volume of water is not. The findings indicate that this novel biodigester technology has a practical operational mode based on a batch dry system. The space-saving hexagonal shape and the flexible design, which can serve a variable number of people in small places are other advantages of Hexagonal Methane Collector compared with available models. Therefore, this concept of biodigester could be an important tool to integrate organic waste treatment and energy sustainability goals in increasingly populated urban centers.

Waste stabilization ponds (WSPs) are a common wastewater treatment approach throughout the world. Typically, WSPs are designed with the aid of empirical equations that may not incorporate complex hydrodynamics. Whereas numerical models have been presented as an alternative, they have been limited to two dimensions or lacked validation. In the present study, field monitoring and a high-resolution three-dimensional Delft3D model, incorporating inflows, changing water levels, and wind, are combined to deepen the understanding of WSP hydrodynamics. Observed water levels varied considerably and rapidly, changing by up to 0.5 m within 36 h, and velocities were typically very low ($<0.01\mathrm{m}/\mathrm{s}$), reaching peak speeds of $0.03\mathrm{m}/\mathrm{s}$ during strong winds. Modeled velocities were in good agreement with observations in open water areas, with a root mean square error (RMSE) of $0.003\mathrm{m}/\mathrm{s}$ and an $R^2$ of 0.58. The results indicate that circulation was primarily driven by wind, with a smaller contribution from varying water levels, and circulation patterns were classified into four hydraulic regimes. A dimensionless empirical equation was developed relating the longitudinal current to wind speed, direction, and WSP outflows, providing a tool to predict hydraulics in shallow and enclosed water bodies and representing an important step toward incorporating hydraulic complexity into WSP design.

Biochar’s capacity to remove pathogens from stormwater can vary by orders of magnitude, which makes it challenging for stormwater managers to select specific biochar from suppliers. In this study, the removal of Escherichia coli (E. coli) in model biofilters packed with sand and biochar from four suppliers was tested and correlation equations were developed that link short-term and long-term bacterial removal capacities of biochar with its commonly reported properties: surface area, carbon content, ash content, and volatile organic carbon content. The E. coli removal capacity of biochar was positively correlated with its surface area and carbon content and negatively correlated with ash content and volatile organic matter. Despite the presence of nutrients in stormwater, E. coli in pore water in biofilter did not grow between infiltration events, indicating biochar may continue to remove pathogens after rainfall. Overall, the results could help the selection of biochar from suppliers for the treatment of stormwater and inform the suppliers to tailor biochar production conditions to enrich specific biochar properties.

Bench-scale experiments were performed to measure and evaluate the desorption kinetics of poly- and perfluoroalkyl substances (PFAS) from a vadose zone soil exposed decades ago to aqueous film-forming foams (AFFFs). Desorption kinetics in the shallow zone ($0.03–0.9\mathrm{m}$ below ground surface) that contained an elevated organic carbon (OC) content, and in an underlying deep zone ($0.9–2.4\mathrm{m}$ below ground surface) that contained a relatively low OC content, were evaluated for a wide range of anionic and zwitterionic compounds. Results showed that, for a given perfluorinated chain length, the head group impacted desorption. For the low-OC deep soil, desorption equilibrium generally occurred rapidly (within $48\mathrm{h}$), indicating that mass transfer limitations were minimal. However, for the high-OC shallow soil, less-hydrophobic and short-chained compounds (including $\mathrm{C}<8$ for the perfluorinated carboxylates, and $\mathrm{C}<7$ for the perfluorinated sulfonates) generally did not reach equilibrium within $400\mathrm{h}$, whereas longer-chained and more-hydrophobic PFAS appeared to reach equilibrium within $48\mathrm{h}$. Kinetic desorption modeling revealed that these observations likely were due to the depletion of shorter-chained PFAS in the rapid equilibrium sorption domain, coupled with their persistence in the kinetically controlled sorption domain. Kinetic modeling also showed that the rate of desorption was proportional to the PFAS aqueous diffusivity, confirming that diffusion limited the rate of release from the soils. Overall, the extent of desorption generally was substantially less than that predicted by published $K_{\mathrm{oc}}{f}_{\mathrm{oc}}$ relationships, suggesting that PFAS desorption from field-aged soils may have a less pronounced impact on underlying groundwater than anticipated, particularly for shorter-chained PFAS.