Journal of Environmental Engineering

Adopting and adapting emerging biotechnologies presents promise and challenges to the environmental engineer. Emerging biotreatment technologies that employ synthetic biology approaches, genetic engineering, and nanotechnologies present unique risk, reliability, and resilience profiles, especially given their unknown potential effects on human health and the environment. Decisions on whether and how to apply these technologies are challenging in light of the uncertainties about the potential environmental and health implications, including any downstream effects. Environmental engineers must balance the benefits of remediation, waste treatment, and other applications with these potential adverse effects by employing a systems view of the complexities in time and space to address the difficult-to-predict intended and unintended outcomes because these applications have few precedents. Insights and possible approaches to address these complexities and uncertainties are presented in this state-of-the-art review.

Methane (${\mathrm{CH}}_4$), a potent greenhouse gas, is globally available as both natural gas and biogas for residential, commercial, and industrial use. Though an excellent source of heat and power, ${\mathrm{CH}}_4$ is often flared or released into the air due to the lack of economically attractive end use options. One promising option is its use as a low-cost feedstock for growth of ${\mathrm{CH}}_4$-oxidizing microorganisms (methanotrophs) and production of single cell protein, methanol, bioplastics, and other bioproducts. However, such opportunities are impeded by the low aqueous solubility of ${\mathrm{CH}}_4$ and concerns about explosion hazards. To enable oxidation of ${\mathrm{CH}}_4$ at low levels, methane monooxygenase enzymes have evolved high affinities for ${\mathrm{CH}}_4$, as reflected in low half-saturation coefficients ($K_s<0.1–6\mathrm{mg}/\mathrm{L}$). Specific rates of ${\mathrm{CH}}_4$ consumption can therefore become maximum at low levels of dissolved ${\mathrm{CH}}_4$. For such kinetics, high volumetric productivities can be achieved by increasing biomass concentrations. Historically, this has been achieved by pressurizing ${\mathrm{CH}}_4$ feedstock. New methods include coupling high media recirculation rates with in-line mass transfer devices (static mixers, gas permeable membranes); recirculating fluid contactors, such as polymers or oils; and modifying fluid media with hydrophilic additives, such as electrolytes and alcohols. These new methods ensure that a flammable mixture is not created and provide many opportunities for innovation.

This study investigated the effectiveness of metal and nutrient removal from stormwater in bioretention systems amended with agricultural byproducts. Both batch and column studies were conducted to evaluate three amendments: hazelnut shells, pecan shells, and spent grain from the brewing process. Batch studies using buffered synthetic water containing copper and zinc evaluated adsorptive properties of the three amendments. Of the three amendments, hazelnut shells had the highest sorption coefficient based on $K_d$ ranges of $\mathrm{19,200}–\mathrm{106,000}\mathrm{L}/\mathrm{kg}$ and $\mathrm{8,610}–\mathrm{18,900}\mathrm{L}/\mathrm{kg}$ for zinc and copper, respectively. Both pecan shells and spent grain had significantly lower $K_d$ values for zinc ($\mathrm{2,160}–\mathrm{6,030}\mathrm{L}/\mathrm{kg}$ and $\mathrm{1,702}–\mathrm{55,932}\mathrm{L}/\mathrm{kg}$ for pecan shells and spent grain, respectively) and copper ($\mathrm{1,090}–\mathrm{1,760}\mathrm{L}/\mathrm{kg}$ and $\mathrm{1,270}–\mathrm{2,030}\mathrm{L}/\mathrm{kg}$ for pecan shells and spent grain, respectively). However, the spent grain contained zinc that potentially could add to zinc concentrations in the stormwater. Column studies using stormwater collected from an industrial site evaluated metal and nutrient removal from stormwater. Six columns were packed with 90% bioretention soil mix and 10% hazelnut shells, pecan shells, or spent grain, and two columns were packed with 100% bioretention soil mix as a control. Five tests were conducted with stormwater collected from a nearby industrial site. Influent and effluent samples were analyzed for copper, zinc, nitrate, ammonia, total nitrogen, phosphate, and total phosphorus. The columns with pecan shells had the highest removal, with 53% removal of copper and 87% removal of zinc. Removal in the columns with hazelnut shells and spent grain was 47% and 19% for copper and 83% and 65% for zinc, respectively. All columns exported nutrients. Although hazelnut shells had the highest sorption coefficient, the pecan shells removed more metals from the stormwater. This study indicates both hazelnut and pecan shells improve metals removal potential of bioretention systems.

In this research, the effect of operating variables, namely, inlet isoprene ($1–4\mathrm{g}/{\mathrm{m}}^3$) and acetone concentrations ($0.25–1\mathrm{g}/{\mathrm{m}}^3$), flow rates ($0.0785–0.157{\mathrm{m}}^3/\mathrm{h}$), and biofilter heights (25, 50, 75, and 100 cm) on the removal performance of an integrated biofilter was investigated. The use of chitosan beads have been attempted as a biosorbent and integrated at the tail end of the biofilter column. This novel modification proved to contribute better in improving the overall removal efficiency compared to a conventional biofilter. The maximum removal efficiency observed with acetone was higher than isoprene due to a better solubility reflected through Henry’s constants. An increase in inlet concentrations of isoprene and acetone, coupled with a reduced residence, produced lower removal efficiencies. The biomass profile confirmed better biomass distribution in the lower sections of the biofilter, and the same was related to contribute to the enhanced sectional removal efficiencies achieved. The integrated biofilter was tested at shock loads, and the efficiency achieved confirmed the suitability of this technique to handle real-time concentration variations.

Life-cycle assessment (LCA) was applied to assess the environmental impacts of a wastewater treatment plant (WWTP), along with 20 tertiary treatment options for reuse in agricultural irrigation, artificial recharge of groundwater, and industrial usages. Impact $2002+$ was adopted as the life-cycle impact assessment method. The results indicate that the energy consumed by the equipment accounts for 66.59% of environmental impacts of the WWTP. Moreover, consumption of the electricity generated by local biogas generators, instead of using the Iranian national grid, can be beneficial in mitigating the environmental impacts of the WWTP in the form of avoided impacts. LCA showed that a depth filter, granular activated carbon, and chlorination; a membrane bioreactor and chlorination; ultrafiltration, reverse osmosis, and chlorination; and ultrafiltration, reverse osmosis, a depth filter, coagulation/flocculation, and chlorination had the lowest environmental impacts for reuse in agricultural irrigation, artificial recharge of groundwater, cooling towers and other industries, and boilers, respectively. Energy consumption of tertiary treatment technologies is the primary contributor to the environmental impacts. This study indicated that because of high electricity and chemical consumption of the options for reuse in industries, their environmental impacts are higher than those of other options.

Chitosan-based silver nanocomposite beads were synthesized through the facile chemical precipitation method, and its efficiency was evaluated for removal of hexavalent chromium from synthetic and tannery industrial effluents in a packed bed reactor. The developed silver nanocomposite has been characterized through Fourier transform infrared spectroscopy (FTIR) and Brunauer-Emmett-Teller (BET) analysis. The effect of various process parameters, such as residence time (3–7 h), initial Cr (VI) concentration (10–30 ppm), silver nanocomposite dosage ($5–30\mathrm{g}/\mathrm{L}$), and flow rate ($5–20\mathrm{mL}/\min$), was investigated using synthetic effluent. Silver nanocomposite has the BET surface area and porosity of $0.710{\mathrm{m}}^2/\mathrm{g}$ and 88%, respectively. Maximum Cr (VI) removal was achieved with a residence time of 5 h, initial Cr (VI) concentration of 20 ppm, silver nanocomposite dosage of $30\mathrm{g}/\mathrm{L}$, and flow rate of $5\mathrm{mL}/\min$. The results exhibited that an increase in initial chromium concentration, the amount of bead, and residence time increased the efficiency of chromium removal, whereas an increase in the flow rate decreased sorption efficiency. Further, the evaluated process parameters exhibited almost 90% of Cr (VI) elimination from tannery industrial effluent [initial Cr (VI) concentration of 20 ppm] in a packed bed reactor. The study revealed that synthesized silver nanocomposite could be used as a potential sorbent for hexavalent chromium removal from synthetic and industrial effluents.

Stormwater runoff–induced polycyclic aromatic hydrocarbons (PAHs) increasingly raise concerns about groundwater quality and safety. Among stormwater management infrastructures and facilities, pavement plays an important role as the frontier of water protection. To remodel or reconstruct the current aging infrastructure, innovative construction materials with sustainable development capabilities are highly in demand. Recently, a multifunctional green-pervious concrete (MGPC), which is an organoclay-amended pervious concrete, has been proven to serve as a next generation pavement material at the lab scale. To simulate the long-term performance of MGPC, an ideal site under steady-state groundwater conditions was built up by using the finite-element method (FEM). Lab experiments were conducted to determine the adsorption function, diffusion coefficient, and other physicochemical parameters of the proposed MGPC. Three sorption isotherm models (linear, Freundlich, and Langmuir) were fitted to the sorption test data. FEM was used to analyze the PAHs removal by passing through the MGPC pavement and PAHs transport in the soil stratum under different scenarios. The simulation results revealed that the MGPC had a significant remediation efficiency on the PAHs. Other than the material properties of MGPC, the efficiency of contaminant remediation of MGPC was also influenced by the permeability of the subbase and the initial concentrations of PAHs. It was also found that the linear isotherm model would overestimate the removal efficiency of PAHs under higher concentration source ($100\mathrm{mg}/\mathrm{L}$).

Water-transmission main (WTM) failures transporting a much greater volume of water cause flooding roads, the inconvenience of daily activities, and economic loss. However, few studies have investigated factors affecting failure in steel WTMs and failure mechanisms based on field data. This study aimed to (1) evaluate the primary factors affecting a break rate of steel WTMs by statistical correlation analysis, (2) establish failure mechanisms of the influential factors with the steel WTM, and (3) quantify the failure causes based on the historical break data. It was found that water alkalinity, along with pipe age, significantly affected steel pipe deterioration, while other factors such as external load contributed to a lesser extent, which differs from previous studies based on small iron or plastic pipes. Additionally, this study proposed the holistic model for chemistry-based mechanisms between the key factors and steel pipe deterioration. The failure cause analysis also determined corrosion as the highest failure cause (52%). These findings will contribute to understanding steel pipe-failure mechanisms and extending the service life of steel WTMs.

Se(VI) and Se(IV) are the two major species of selenium in water. They are toxic to aquatic lives and human beings at high levels. Biological reduction of Se(VI) is a two-stage process, first from Se(VI) to Se(IV) and then to Se(0) with potential accumulation of the more toxic Se(IV) due to the slower rate of the second stage. Activated alumina, on the other hand, is more effective for Se(IV) adsorption than Se(VI). In this study, the effect of biological activities on selenium removal was investigated using continuous-flow reactors packed with alum-impregnated activated alumina (AIAA) and cultured with a Se(VI)-reducing strain, Shigella fergusonii strain TB42616, under various influent Se(VI) concentrations and hydraulic retention times (HRTs). A selenium removal efficiency of 92% was achieved in a bioreactor with initial biomass of $2.2\times {10}^6\mathrm{cells}/\mathrm{g}$ AIAA after a 70-day operation period. Little improvement was observed by lowering the influent Se(VI) concentration from 50 to $10\mathrm{mg}/\mathrm{L}$, while the removal efficiency was significantly enhanced by either extending the HRT from 3.2 to 5.0 days or increasing the attached biomass during the startup. An increase in mass ratios of Se(VI) reduction by immobilized cells to adsorption by AIAA was also observed from $1:2.2$ to $1:0.83$ with increasing cell mass during the operation.

Rhamnolipids, produced during biodegradation, enhance the removal of hydrocarbons by decreasing the surface tension and increasing the bioavailability. Unlike the synthetic surfactants, rhamnolipids are very promising for bioremediation because of low toxicity and biodegradability. Therefore, the need for eco-friendly and biodegradable surfactants like rhamnolipids for reliable environmental cleanup is increasing. The present work revealed that kerosene degraders were the potential source of rhamnolipids. For this finding, six kerosene degrading bacterial isolates were investigated for their biosurfactant production. All of the isolates namely Pseudomonas plecoglossicida Ag10, Raoultella planticola Ag11, Staphylococcus aureus Ba01, Enterococcus faecalis Cr07, Acinetobacter johnsonii Sb01, and Pantoea agglomerans Sn11 were determined as rhamnolipid producers through oil spreading activity, emulsification index, and microbial adhesion to hydrocarbon tests. Blue agar plate method, thin layer chromatography, and Fourier transform infrared spectroscopy analyses were also performed to characterize the rhamnolipids. The results revealed that mono-rhamnolipids were dominant among kerosene degraders.

Municipal solid waste (MSW) landfills are regarded as one of the major sources of greenhouse gas (GHG) emissions across the world. An innovative and sustainable biogeochemical cover system that consists of soil, biochar, and basic oxygen furnace (BOF) slag is being developed to mitigate fugitive landfill emissions such as methane (${\mathrm{CH}}_4$), carbon dioxide (${\mathrm{CO}}_2$), and hydrogen sulfide (${\mathrm{H}}_2\mathrm{S}$). Biochar-amended soil can mitigate ${\mathrm{CH}}_4$ emissions by oxidizing ${\mathrm{CH}}_4$ with the help of methanotrophs (${\mathrm{CH}}_4$-consuming microorganisms), whereas BOF slag can mitigate ${\mathrm{CO}}_2$ and ${\mathrm{H}}_2\mathrm{S}$ emissions by adsorption and various mineralogical reactions. However, BOF slag is highly alkaline in nature, with pH values usually above 12, and the effect of such high pH on the overall performance of biogeochemical cover system is not known. This study aims at investigating the effect of pH on ${\mathrm{CH}}_4$ oxidation and methanotrophic community structure in landfill cover soil and cultivated consortia through laboratory incubation experiments. In this regard, soil suspension and enrichment cultures were incubated at pH values ranging from 2 to 12, ${\mathrm{CH}}_4$ oxidation rates were measured, and the microbial community structure was analyzed using 16S rRNA gene amplicon sequencing. The optimal pH for ${\mathrm{CH}}_4$ consumption was found to be 7 in enrichment culture and 7.6 in soil suspensions. Very low or no ${\mathrm{CH}}_4$ consumption was observed at extreme pH values of 2 (enrichment culture) and 12 (enrichment culture and soil suspension). A shift in microbial community structure was observed in enrichment cultures initiated at different pH values. Type II methanotrophs were enriched under acidic pH conditions and Type I methanotrophs were enriched in incubations from pH 4 to 10. Soil suspensions were more stable, but also showed slight shifts in the microbial community dominated by Type I methanotrophs and methylotrophs at pH 7.6–10.0. These results demonstrate that at an extreme alkaline pH ($\sim 12$), ${\mathrm{CH}}_4$ oxidation is inhibited as growth of methane-oxidizing bacteria (MOB) is arrested in the landfill cover soil.

It is essential to understand the phenomena of adhesion, deadhesion, and transport of microorganisms in porous media to scale up bioengineering processes. In this study, the adhesion and deadhesion of two ureolytic microorganisms were investigated in loose sand using a set of flow-through column experiments by varying the pore fluid chemistry. An increase in the ionic strength altered the surface-charge properties of the microbes and the selected geomaterial, which in turn reduced the energy barrier, leading to significant adhesion of microbes on the sand surface. After microbial adhesion, permeation of a lower-ionic-strength solution exhibited considerable bacterial deadhesion from the sand column, indicating the reversible nature of the interaction between bacteria and the sand surface. The physicochemical adhesion and deadhesion mechanisms are elucidated in terms of extended Derjaguin-Landau-Verwey-Overbeek theory. The variation of the energy barrier between the microbe and sand, the appearance of primary and secondary energy minima attributed to the change in pore fluid chemistry, and its influence on microbial adhesion and deadhesion on to the sand were also studied.

Agroindustrial by-products have become an economical and ecofriendly alternative for wastewater treatment because their lignocellulosic structures are prone to adsorb metals and dyes from solutions. Mauritia flexuosa petioles are discarded during fiber extraction from leaves and are becoming an abundant agrowaste product. This study characterizes the biomass from Mauritia flexuosa petioles using different spectroscopic techniques and evaluates aqueous Cu(II) and methylene blue adsorption on this biomass. The results showed that Mauritia flexuosa petioles are a mesoporous and lignocellulosic biomass, rich in carboxyl and hydroxyl groups that adsorb Cu(II) and methylene blue primarily through physical and exothermic processes. Copper and methylene blue had adsorption rates of 0.016 and $0.733\mathrm{g}/\mathrm{mg}\min$ that are mainly controlled by the $─\mathrm{COOH}$ and $─\mathrm{OH}$ groups presented in the biomass surface. Copper adsorption occurs through liquid film diffusion and electrostatic attraction, whereas methylene blue adsorption occurs through electrostatic attraction and hydrogen bonding. The maximum Cu(II) and methylene blue adsorption capacity was 14.20 and $7.49\mathrm{mg}{\mathrm{g}}^{-1}$, respectively. These findings make this biomass a novel low-cost adsorbent and contributes to agrowaste valorization and reuse.

Computational fluid dynamics (CFD) simulations were employed in this paper to analyze the dynamic flow patterns within extremely thin slit spaces of two corrugated heat exchanger (HEx) plates. The entire plates are 1.0 m long and wide and 6.5 mm high, and the top and bottom parts consist of six unit plates of the same size (1.0 m long and 16.7 cm wide). A digital geometry of the assembled HEx was prepared as a stereolithography (STL) file (exported from AutoCAD), having excessive geometrical complexity. In this work, a numerical algorithm to reconstruct the STL file is developed, which converts a complex STL file consisting of skew triangles to one having a simple grid structure and an even size-distribution of surface triangles. The whole STL file is split into 36 square pieces (SPs), and each SP is meshed individually using NETGEN, and these meshes are merged as one for OpenFOAM-based CFD simulations. Finally, the flow and pressure profiles are obtained in the low Reynolds number region. The current CFD method with the split-and-merge scheme will be continuously used for the design and optimization for ocean thermal energy conversion technology in the future.

Researchers have observed that the biofilm nitrification rate (NR) in membrane-aerated biofilm reactor (MABR) systems did not deteriorate at low winter temperatures. Using the pilot data, the temperature impacts were studied in two different approaches. A close-to-unity temperature coefficient ($\theta =1.007$) and a constant half-velocity constant ($K_{N,BF}=5.7\mathrm{mgN}/\mathrm{L}$) were obtained from the semiempirical kinetic-based approach, indicating that the bulk ${\mathrm{NH}}_4^{+}\text{-}\mathrm{N}$ concentration, rather than temperature, was determining the biofilm NR. The pilot performance was also simulated in GPS-X 7.0 using all typical kinetic values from scientific literatures except the hydrolysis rate constant. A lower hydrolysis rate constant ($0.15{\mathrm{day}}^{-1}$) was used to match the data during calibration and it should be considered as a lumped effect of the pilot conditions. While the temperature effects on biological kinetics are well established, they were masked by the dynamic changes in the MABR biofilm. The apparently weak impact of temperature on the biofilm NR distinguishes the MABR technology as a novel solution for nitrification intensification. The two simulation approaches are proved effective as tools for the process design.

Phosphorus (P) surplus is a key factor in water eutrophication, and aqueous phosphate removal is a concern. In this study, ferrous ions (${\mathrm{Fe}}^{2+}$) were generated in situ by iron–air fuel cells and were used in the removal of P from synthetic P-containing wastewater. The P removal results indicated that different initial concentrations of P were more effectively removed by an in situ ${\mathrm{Fe}}^{2+}$ generation than by the addition of ${\mathrm{FeSO}}_4$. The main P removal products of ${\mathrm{FeSO}}_4$ were Fe hydroxides, whereas the main products with the iron fuel cell were vivianite and Fe hydroxides. These results suggested that ${\mathrm{Fe}}^{2+}$ formed in situ had a more conducive and stronger affinity to bond phosphate than ${\mathrm{FeSO}}_4$. The maximum power density reached $\mathrm{1,875}\mathrm{mW}/{\mathrm{m}}^2$ after 24 h of operation. The results indicate that the iron–air fuel cell can be used for P removal/recovery coupled with potential electricity generation.

This work attempts to optimize the traditional flow-reverse reactor by establishing a three-dimensional model of a toluene catalytic-combustion reactor through computational fluid dynamics (CFD). Four optimized structures are designed: (1) 20-mm grille; (2) 60-mm-long lattice plates; (3) 20-mm-long cross plate and 5-mm-thick cross plate; and (4) 20-mm-long lattice and 20-mm-long and 5-mm-thick cross plate. The velocity field, pressure drop, temperature field, and turbulent energy were calculated. The results show that the area-weighted evenness index of the four structures can reach (1) 0.910; (2) 0.901; (3) 0.909; and (4) 0.920. The results also show that the reactor with a 20-mm grid and 5-mm porous plate had the best optimization effect. Based on the reactor, the maximum resistance coefficient of the optimized flow direction conversion reactor was 0.030, meeting the engineering requirements. The results from the temperature fields show that the reactor with increased flow direction greatly improved the utilization of waste heat. It was also confirmed that the optimization had a certain guiding significance and value for practical application.

With the recent trend of increasing size for the dairy operations, dairy manure, due to its high content of phosphorus and relatively low nitrogen/phosphorus ratio, is limited when applied in the area where phosphorus is saturated in the soil. Electrocoagulation is a potential method to treat dairy manure for phosphorus removal and the operation parameters of this process can significantly affect the process efficiency. In this study, an 800 mL electrocoagulation reactor equipped with low carbon steel electrodes was investigated on its operation parameters, including current, agitation speed, initial pH, aeration time, and anaerobic digestion as pretreatment. The results showed that higher current and higher initial pH could improve the phosphorus removal efficiency. Agitation assisted the formation of coagulants, but high speed of agitation did not contribute further separation and removal of phosphorus. Pretreatment, i.e., aeration or anaerobic digestion before electrocoagulation, was beneficiary for phosphorus removal. The suggested operation parameters are with current under 1 A, agitation of 75 rpm, and higher initial pH. Pretreatment with 10 days of anaerobic digestion or 60 min of aeration before electrocoagulation is also recommended, and phosphorus removal efficiency in this condition can reach 97%. Overall, electrocoagulation with low carbon steel electrodes is an efficient method to remove phosphorus in dairy manure, and the process may potentially reduce the environmental impact of dairy operations on local water systems and increase the manure application scope and its competitiveness compared with chemical fertilizers.

Hydrogen sulfide (${\mathrm{H}}_2\mathrm{S}$) concentration in landfill gas (LFG) is predominately dependent on the biodegradation of gypsum drywall, a major component of construction and demolition (C&D) debris. This study focuses on the impacts of sulfur input on the generation of ${\mathrm{H}}_2\mathrm{S}$ in a landfill environment and proposes a unique method for future prediction of ${\mathrm{H}}_2\mathrm{S}$ concentration in LFG based on available historical data. The volume of LFG generated was estimated using EPA’s Landfill Gas Emissions Model (LANDGEM). Yearly sulfur input was estimated from the C&D waste landfilled assuming 10%, 20%, and 25% gypsum content and approximately 18.5% sulfur content in gypsum. ${\mathrm{H}}_2\mathrm{S}$ generation assumed to follow the first-order decay and projected for a series of decay rate ($k$) range from 0.45 to 0.90 and average ${\mathrm{H}}_2\mathrm{S}$ generation potential $S_0$ equal to $151.8{\mathrm{m}}^3\text{-}{\mathrm{H}}_2\mathrm{S}/\mathrm{t}$. Finally, an alternative analysis has been conducted by reviewing the available treatment technologies to select the most preferred treatment system to comply with the Title V air permit.

An Ag@AgBr/ZnO modified photocatalyst was prepared by a simple one-step hydrothermal method. The composites were well characterized by various analytical techniques, and the influence of an Ag@AgBr/ZnO system on the photocatalytic properties was also analyzed. The UV-vis diffuse reflectance spectra results clearly confirmed the red-shifted absorption edges transferred into the visible spectral region. The PL spectra results showed that Ag@AgBr/ZnO has a lower electron hole recombination rate than ZnO. With the cefuroxime sodium solution as the target pollutant, the mechanism of its catalytic effect and efficiency were studied. The results showed that the photocatalytic activity of Ag@AgBr/ZnO modified catalysts were greatly improved under visible light.

There is no existing applicable law that regulates compounds of emerging concern (CECs), so they remain a global concern because they are easily taken up by organisms. Because of the current need, different processes have been developed capable of removing CECs. A membrane bioreactor (MBR) system and a hybrid moving bed biofilm reactor–membrane bioreactor (MBBR–MBR) system with a 35% filling ratio were tested on real urban wastewater under 6 and 10 h of hydraulic retention time to remove pharmaceutical compounds. The mixed-liquor suspended solids changed between 5,200 and $\mathrm{5,700}\mathrm{mg}/\mathrm{L}$ and the temperature varied between 12.6°C and 28.1°C simulating real conditions. The plant received a shock with the mix of pharmaceutical compounds (carbamazepine, ibuprofen, and ciprofloxacin) used to study its behavior. The removal of ibuprofen, carbamazepine, and ciprofloxacin was above 83.7%, 48.6%, and 10.6%, respectively, regardless of the process and the operative variables; these removal rates increased when the temperature increased.

Permeable pavements are often developed as alternatives to traditional pavement (TP) systems for the mitigation of urban stormwater runoff impairment. The objective of this study was to evaluate the stormwater runoff and pollutant load-reduction performance of an enhanced permeable interlocking concrete pavement system with enlarged joints filled with gravel. This system was compared with an adjacent TP application located in La Feria, Texas. Both pavements were monitored for 2 years through a total of 65 storm events. Both pavement systems received some run-on stormwater flows from surrounding areas that included sediment and nutrients. Runoff volume was 80% lower than the TP. Furthermore, total suspended solids, 5-day biochemical oxygen demand, and Escherichia coli exhibited average reductions of 76% for 23 samples, 56% for 19 samples, and 12% for 11 samples, respectively. Field data were used to develop a Windows Source Loading and Management Model (WinSLAMM) method, which was in good agreement with the observed values.

Increasing sewage sludge production has become a new environmental problem in China because of its huge amounts of sludge, heavy metal concentrations, and potential pathogen risk. Composting with appropriate bulking agents is an effective method to treat sewage sludge. In this research project, wood chips, ceramsite, and plant ash were used as bulking agents during sewage sludge composting over a period of 44 days (in winter) at a pilot scale. The results indicated that wood chips were an efficient bulking agent to enhance composting performance while ceramsite failed to initialize sewage sludge composting. In addition, a lower weight ratio between sewage sludge and wood chips significantly improved the composting process. A ratio of $3:1$ (wet basis) resulted in an increase of composting temperature in two days from 13°C up to 67°C and maintained high temperatures of more than 55°C over some time. In addition, moisture content decreased from 78% to 50%, and a decline of volatile solids from 61% to 47% was observed. The addition of plant ash facilitated a further decrease in moisture content and the germination index of the compost rose from 85.3% to 106.3%. Furthermore, in the compost derived from the $3:1$ ratio of sludge to wood chips, all monitored heavy metal concentrations were far below the limit levels.

The study used a bench-scale biotrickling filter packed with mixed plastic chips with specific surface area of $610\pm 50{\mathrm{m}}^2/{\mathrm{m}}^3$ to test its performance for the removal of volatile organic compounds (VOCs) vented from paint-spraying operations. A paint containing ethyl acetate, butyl acetate, toluene, and xylenes as main solvents was used. The influent total hydrocarbon (THC) concentrations were in the range of 27–234 parts per million (ppm) (expressed as methane equivalent), and empty bed retention time (EBRTs) for the gas flowing through the empty bed space were 4.8–11.4 s in the experimental period of 125 days. Results show that a maximum THC removal capacity of 86 g as $\mathrm{methane}/{\mathrm{m}}^3\mathrm{h}$ with an EBRT of 4.8–8.2 s was obtained and the value implies that it is possible to effectively eliminate VOCs with the short EBRT compared with other related studies. Ethyl acetate and butyl acetate were more easily absorbed and removed by microbial films than toluene and xylenes because of the much lower volatility and higher water affinity of the former two compounds.

When treating drinking water using $\mathrm{UV}/{\mathrm{H}}_2{\mathrm{O}}_2$ advanced oxidation, the ${\mathrm{H}}_2{\mathrm{O}}_2$ residual is usually quenched to allow for downstream chlorine stability. In some utilities, monochloramine (${\mathrm{NH}}_2\mathrm{Cl}$) is used for secondary disinfection, and ${\mathrm{H}}_2{\mathrm{O}}_2$ may not need to be quenched because ${\mathrm{NH}}_2\mathrm{Cl}$ and ${\mathrm{H}}_2{\mathrm{O}}_2$ can coexist for some time. However, when ammonia and chlorine are applied to form ${\mathrm{NH}}_2\mathrm{Cl}$ in the ${\mathrm{H}}_2{\mathrm{O}}_2$-containing water, ${\mathrm{H}}_2{\mathrm{O}}_2$ will compete with ammonia to react with the applied chlorine, compromising the ${\mathrm{NH}}_2\mathrm{Cl}$ formation efficiency. This research combined theory and experiments to evaluate ${\mathrm{NH}}_2\mathrm{Cl}$ formation efficiency in the presence of ${\mathrm{H}}_2{\mathrm{O}}_2$ in Lake Ontario water and, after ${\mathrm{NH}}_2\mathrm{Cl}$ formation, its subsequent decay at different temperatures and pH. The results demonstrated that at many typical temperatures and pH, the presence of ${\mathrm{H}}_2{\mathrm{O}}_2$ does not significantly impair the formation of ${\mathrm{NH}}_2\mathrm{Cl}$. Furthermore, while ${\mathrm{H}}_2{\mathrm{O}}_2$ accelerates ${\mathrm{NH}}_2\mathrm{Cl}$ decay, the results suggest that under specific conditions, such as short to medium residence times (e.g., less than 48 h), it may be possible for ${\mathrm{NH}}_2\mathrm{Cl}$ to coexist with as much as $5\mathrm{mg}/\mathrm{L}$ ${\mathrm{H}}_2{\mathrm{O}}_2$ without compromising secondary disinfection.