Journal of Environmental Engineering

Air, water, and soil pollution are worldwide problems. Of these, heavy metals and organic dyes are the main targets for removal. Graphene oxide (GO), especially functionalized GO, has shown great application potential for the removal of contaminants from wastewater. This study used Santa Barbara Amorphous-15 (SBA-15) with amino acid to functionalize GO, not only to increase the adsorption sites, but also chelate with heavy metals to improve the adsorption efficiency. The optimal experimental conditions for ${\mathrm{Cu}}^{2+}$ adsorption were obtained by response surface methodology (RSM): $\mathrm{pH}=5.8$, $C_0=38.38\mathrm{mg}/\mathrm{L}$, $M=0.56\mathrm{g}/\mathrm{L}$, and $T=35.68°\mathrm{C}$. The optimum experimental conditions for MB adsorption were $\mathrm{pH}=10.24$, $C_0=82.70\mathrm{mg}/\mathrm{L}$, $M=0.33\mathrm{g}/\mathrm{L}$, and $T=35.27°\mathrm{C}$, and absorption rates all above 70%. Also, the adsorption mechanism, desorption, and reusability of the complexes are reviewed. Finally, the application potential of GO/SBA-15 as an adsorbent in the field of industrial wastewater treatment is summarized and its prospects are discussed.

Wastewater treatment is important in terms of human and environmental health in the urban water management cycle. Appropriate methods should be applied based on accurate data in order to ensure efficiency. This study developed a novel current condition assessment system to evaluate the data quality and the implementation level of wastewater treatment plant (WWTP) management and operations practices. The developed system consists of 48 components including the basic processes used in the operation of WWTPs. A unique scoring system is proposed to evaluate the system. The developed system was tested in three pilot WWTPs. The performance of Utility 2 was better than that of the other utilities in terms of data quality and implementation level of methods. However, the scores of Utilities 1 and 2 generally were close to each other. The weaknesses and strengths were determined within the scope of WWTP management in each utility.

Abstract

In recent years, the emergence of COVID-19 has created disastrous health effects worldwide. Doxycycline, a member of the tetracycline group, has been prescribed as a treatment companion for attending this catastrophe. Due to extensive use and high solubility, a significant amount of un-metabolized doxycycline has been found to reach water bodies within a short time, and consumption of this water may lead to the development of fatal resistance in organisms and create health problems. Therefore, it has become necessary to develop suitable technologies from a geoenvironmental point of view to remove these unwanted antibiotics from wastewater. In this context, locally obtainable silty-sandy soil was explored as a low-cost material in a constructed wetland with Chrysopogon zizanioides (vetiver sp.) for phytoremediation to mitigate doxycycline spiked wastewater. The obtained soil hydraulic conductivity was $1.63\times {10}^{-7}\mathrm{m}/\mathrm{s}$. Batch adsorption tests conducted on silty-sandy soil, vetiver leaf, and vetiver root provided maximum removal efficiencies of 90%, 72%, and 80% percent, respectively, at optimal sorbent doses of $10\mathrm{g}/\mathrm{L}$, $17\mathrm{g}/\mathrm{L}$, and $16\mathrm{g}/\mathrm{L}$, and contaminant concentrations of $25\mathrm{mg}/\mathrm{L}$, $20\mathrm{mg}/\mathrm{L}$, and $23\mathrm{mg}/\mathrm{L}$, with a 30-min time of contact. The Freundlich isotherm was the best fit, indicative of sufficient sorption capacity of all the adsorbents for doxycycline. The best match in the kinetic research was pseudo-second-order kinetics. A one dimensional vertical column test with the used soil on doxycycline revealed a 90% breakthrough in 24 h for a soil depth of 30 mm. Studies on a laboratory-scale wetland and numerically modeled yielded removal of around 92% by the selected soil and about 98% combined with Chrysopogon zizanioides for $25\mathrm{mg}/\mathrm{L}$ of initial doxycycline concentration, which is considered quite satisfactory. Simulated results matched the laboratory tests very well. The study is expected to provide insight into remedies for similar practical problems.

Practical Applications

To explore a cost-effective method for abatement of aqueous doxycycline in the surrounding environment and groundwater, a locally accessible silty-sandy soil was selected. While investigating its suitability, it was found that this soil met current standards (${10}^{-4}$ to ${10}^{-5}\mathrm{cm}/\mathrm{s}$) for hydraulic conductivity of wetland adsorbent. The selected soil also had a relatively large surface area ($23.502{\mathrm{m}}^2/\mathrm{g}$), and the presence of higher percentages of finer particles (50%) resulted in an outstanding adsorptive and removal capacity for doxycycline, as indicated by several test findings and validated with numerical modeling. Furthermore, as evidenced by batch experiments, the vegetative cover, primarily provided by vetiver, was also found to be an effective adsorbent. Sorption of a particular contaminant in wastewater to wetland soil is problematic due to the simultaneous presence of various compounds and other wastewater contaminants. The competition effect among these compounds is of concern in any treatment wetland, where thousands of compounds are present. Hence, further studies are required to address the competition between these compounds and their cumulative effect on the efficacy of the wetland system over a long period. This has therefore cemented the fact that silty-sandy soil is a perfect choice as bed material for wetlands. Together with vetiver, it has the potential to become a stable and environment-friendly removal system against doxycycline. However, the investigation was carried out with a spiked doxycycline solution in the laboratory, the results of which are believed to provide a basic understanding and remedial measures for this problem. Based on that, if several field studies are conducted with the studied soil using phytoremediating plants in doxycycline-laden wastewater, a real-life solution to the doxycycline problem may be obtained that is very much needed for assuage of social health problems.

In urban coastal environments, sewer infrastructure is plagued by infiltration which seeps into aging and compromised pipes. Infiltration increases pumping costs, reduces treatment efficiency, and may trigger release of partially treated wastewater at water reclamation facilities. This study analyzed infiltration in a small urban sewershed in Pinellas County, Florida to assess the magnitude of the problem. Flowmeters were deployed in different sections of the sewershed during 2015 and 2016 to evaluate spatial and seasonal variabilities in infiltration. To abate excessive infiltration, three trenchless sewer rehabilitation technologies were applied in 2019, and the flowmeters were redeployed in 2021 at the same locations to compare pre- and postrehabilitation conditions. The applied technologies were joint grouting, expanded-in-place PVC lining (EX liner), and cured-in-place pipe (CIPP). Pipe rehabilitation reduced infiltration by 43% during the dry season and by 49% during the wet season, but effectiveness varied by technology. Data revealed that CIPP and EX liners were not as effective as joint grouting, probably because groundwater seeps into the space between the pipe and liner and at lateral connections.

Polycyclic aromatic hydrocarbons (PAHs) have been detected in municipal and industrial wastewater, and are widely known as a toxic and carcinogen contaminant to human health. Currently, PAHs are treated by suspended growth bacteria in the municipal and industrial wastewater, but this method is not effective due to the washed-out effect of the bacteria from the aeration treatment. Therefore, this study investigates the attached bacteria on biofilm surface to enhance the biodegradation of PAHs. Phenanthrene (phe) and Rhodococcus zopfii (R. zopfii) were selected as the target contaminant and bacteria due to their presence and an abundancy in the wastewater. Surface characterization study of the natural biofilm was conducted using Fourier transform infrared spectroscopy (FTIR) and environmental scanning electron microscope (ESEM). Chemical functional groups present on the surface of the natural biofilm were hydroxyl (O-H), carbonyls (C═O), and alcohol (C─ O). These chemical functional groups provide sources of carbon for R. zopfii. Pore sizes of the natural biofilm were in the range of 1.97 to $20.60\mathrm{\mu m}$, and they provide shelter for R. zopfii to grow and enhanced biodegradation rate of phe. The biodegradation kinetics of phe by R. zopfii with the natural biofilm ($k_{\mathrm{with}\mathrm{biofilm}}:0.26\mathrm{mg}/\mathrm{L}/\mathrm{day}$) was increased 1.52 times compared with without the natural biofilm ($k_{\mathrm{without}\mathrm{biofilm}}:0.17\mathrm{mg}/\mathrm{L}/\mathrm{day}$) within 7 days. The biodegradation of the phe by the R. zopfii with the natural biofilm was significantly affected by difference of pH conditions (pH 7–9). The greatest biodegradation kinetic rate of phe was observed at pH 7 ($k_{\mathrm{withbiofilm}}:0.441\mathrm{mg}/\mathrm{L}/\mathrm{day}$) compared with other pH conditions. Phe was significantly transformed to catechol, coumarin, and phthalic acid via dihydroxylation reaction. This study provides new knowledge on the role of the natural biofilm as a shelter for R. zopfii to grow and enhance biodegradation kinetic of phe by R. zopfii in the wastewater treatment system.

This paper presents an electromagnetic energy harvester (EMEH) using gravity-induced self-excited vibrational resonance. The EMEH is capable of harvesting vibration energy below 1 Hz. The structure is a cantilever-mass system, and the mass is comprised of a magnet array and its support. The EMEH is excited by the gravity of the cantilever-mass system intermittently sliding down along a central hub. To explain the output performance of the EMEH visibly, we formulated the motion process and built an eight-stage dynamics motion. The effect of the cantilever thickness on the open-circuit voltage is discussed, and the results agree with the theoretical description well. Additionally, to demonstrate the output performance of the harvester, more experiments were performed, i.e., matching impedance, charging capacitors, and powering light emitting diodes (LEDs). The EMEH delivers a maximum instantaneous output power of 144.1 mW at a beam thickness of 1 mm. For charging experiments, 47 LEDs were successfully lighted up in real-time. The high performance of the gravity-induced resonance scheme indicates tremendous low-frequency application potential.

This work investigated the treatment of a heterogeneous soil by multiphase extraction (MPE), which is a physical remediation method for soils containing volatile organic compounds. Experiments were conducted on a two-dimensional (2D) laboratory pilot. The soil was simulated by sand in which one or two clay barriers were introduced. The pollutant used was $n$-decane (concentration $50\mathrm{g}/\mathrm{L}$) in hexane, acting as the solvant. The mixture of $n$-decane in hexane was introduced in the soil, and the infiltration of the contaminant and its extraction were modeled and experimentally verified. The extraction time and the extraction yield were determined experimentally by monitoring the pollutant concentrations over time during treatment. The influence of barriers on the treatment time and on the adsorption in solid phase in both the vadose and the capillary zones was highlighted. The installation of a clay barrier increased the treatment time but produced an almost identical yield to that obtained with sand alone.

Nanoscale zero-valent iron (nZVI) is one of the most prevalently used engineered nanomaterials for heavy metals removal. Microplastics (MPs) have been detected extensively in the environment, such as soil, surface water, groundwater, and water treatment plant. PVC MPs and Cd coexist in a variety of environment, and Cd compounds are often used as stabilizers in PVC production, which increases the likelihood of their coexistence. In this work, the influence of aged PVC MPs on ${\mathrm{Cd}}^{2+}$ removal with nZVI was evaluated. Spent nZVI after reaction with ${\mathrm{Cd}}^{2+}$ with and without MPs was characterized with scanning transmission electron microscopy (STEM), energy-dispersive spectroscopy (EDS), scanning electron microscope (SEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectrometer (FTIR), and Brunauer-Emmett-Teller (BET). The results showed that when MPs coexisted, the removal rate of ${\mathrm{Cd}}^{2+}$ with nZVI increased by up to 73.4%. Spent nZVI has more extensive oxidation, and has looser structure and higher specific surface area in a mixed contamination solution with trace MPs, resulting in high removal efficiency of ${\mathrm{Cd}}^{2+}$. Interaction between PVC MPs and nZVI shows positive promotion toward removal of ${\mathrm{Cd}}^{2+}$ with nZVI; thus, nZVI may have great potential for remediation of Cd in the water environment rich in PVC MPs.

Escherichia coli O157:H7 is a major cause of foodborne disease outbreaks throughout the world, while methicillin-resistant Staphylococcus aureus (MRSA) is responsible for many difficult-to-treat infections in humans. Ultraviolet (UV) irradiation is commonly used for disinfection in food processing, medical facilities, and water treatment to prevent the transmission of these pathogen. With increased use of UV disinfection technologies over the last few years because of COVID-19 and concerns about other communicable disease, it has become a concern that microbial species could develop tolerance to UV irradiation, especially when it is applied continuously. To elucidate the effect of continuous UV exposure at different wavelengths and power levels on the tolerance development of bacteria, Escherichia coli O157:H7 and MRSA)USA300 growths were investigated by continuously exposing inoculated agar plates to six different commercially available UV sources at wavelengths of 222 nm, 254 nm, 275 nm, and 405 nm. The agar plates in these experiments were partially covered by a thin acrylic sheet, which provided either complete protection from the UV to the cells directly under the sheet, no protection if significantly away from the sheet, or partial protection near the edges of the sheet due to shading or small amounts of UV reflection under the sheet at the edges. In these experiments, tolerant cells of E. coli and S. aureus were found from the 222 nm, the 405 nm, and one of the 254 nm sources. Upon examination of the power of each UV source, it was shown that the 275 nm and 254 nm sources that resulted in no tolerant cells had surface power densities [at 25 cm (10 in.)] that were more than 10–200 times greater than those that had tolerant cells. These results suggests that bacterial cells have a higher chance to develop UV tolerance under lower power UV sources (under the experimental conditions in our laboratory). Genome investigation of the tolerant colonies revealed that there are no significant differences between the cells that developed tolerance and the original organism, hinting at the need to explore the role of epigenetics mechanisms in the development of UV tolerance in these bacteria.

In the present study, two catalysts, MCM-41 and ZSM-5/MCM-41, were prepared by the hydrothermal synthesis method and their catalytic ozonation performances on pesticide wastewater were investigated. MCM-41 and ZSM-5/MCM-41 were proved to be a mesoporous structure and a micro-mesoporous structure, respectively, by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, and nitrogen adsorption-desorption measurements. The experimental results indicated that the chemical oxygen demand (COD) removal rate increased from 57.46% without catalysts to 79.35% and 87.56%, respectively, in the presence of MCM-41 and ZSM-5/MCM-41 after 100 min of catalytic ozonation. The catalytic activity of ZSM-5/MCM-41 was found to be greater than that of MCM-41. ${}^{·}\mathrm{OH}$ played an important role in the catalytic ozonation, which was verified by the tert-butanol test. The catalysts had highest activity at pH of 7, and both higher and lower pH values reduced the catalytic ozonation. The optimal ozone dosage was found to be $22.0\mathrm{mg}{\mathrm{L}}^{-1}{\min }^{-1}$ for the COD removal of the pesticide wastewater. The catalysts could be reused five times without significant loss of the catalytic activity, suggesting that the catalysts could be promising catalysts for the catalytic ozonation of the pesticide wastewater.