Journal of Environmental Engineering

Per- and polyfluoroalkyl substances (PFAS) are compounds of emerging concern based on ubiquitous distribution and potential human health impacts. Whereas manufacturing plants and fire-training/suppression areas are recognized as primary sources of PFAS contamination of the environment, understanding the role of water treatment plants (WTPs) and water resource recovery facilities (WRRFs) in PFAS cycling is important. Literature on the presence and pathways of PFAS within and between WTPs and WRRFs was reviewed and synthesized to address this knowledge gap. The production, use, and disposal of PFAS was connected to the water cycle via aquifers/surface water/sediment, drinking water treatment, domestic/industrial water use, domestic/industrial wastewater treatment, the atmosphere, land application, landfills, thermal treatment of wastes, and food production. WTP and WRRF flows release PFAS in liquid-phase, solid-phase, and gas-phase matrices. The purpose of this review is to educate and inform readers of the fate and transport of PFASs throughout the urban water cycle emphasizing the WTP–WRRF connection. Source reduction programs, treatments that interrupt the PFAS cycle, and comprehensive analytical methods are future research needs.

Wetlands play an important role in biodiversity protection and ecosystem services provision but are susceptible to continuous degradation from the urban environment. In this study, objectives have been made to evaluate the spatial and seasonal (dry and wet periods) variations of diffusive fluxes of methane (${\mathrm{CH}}_4$) and carbon dioxide (${\mathrm{CO}}_2$) in water–atmosphere interface and limnological variables (water and sediment) in densely urbanized wetland areas of a tropical reservoir located in the São Paulo metropolitan area. Three sampling stations (S1, S2, and S3) covering areas with different levels of aquatic pollution and land use were evaluated. Nonparametric analysis and one-way analysis of variance indicated the spatial and temporal influence of limnological variability on ${\mathrm{CH}}_4$ and ${\mathrm{CO}}_2$ fluxes. In general, S2 presented higher mean emissions for ${\mathrm{CH}}_4(0.31\mathrm{g}{\mathrm{m}}^{-2}{\mathrm{day}}^{-1})$ and ${\mathrm{CO}}_2(60.9\mathrm{g}{\mathrm{m}}^{-2}{\mathrm{day}}^{-1})$ compared with the other two stations in both sampling periods, in which maximum mean fluxes in S1 were ${0.20\mathrm{g}\mathrm{m}}^{-2}{\mathrm{day}}^{-1}$ and ${18.3\mathrm{g}\mathrm{m}}^{-2}{\mathrm{day}}^{-1}$, whereas in S3 the mean values were ${<0.09\mathrm{g}\mathrm{m}}^{-2}{\mathrm{day}}^{-1}$ and ${3.5\mathrm{g}\mathrm{m}}^{-2}{\mathrm{day}}^{-1}$ for ${\mathrm{CH}}_4$ and ${\mathrm{CO}}_2$, respectively. These higher emissions in S2 are related to the proximity to point source discharge of raw sewage from a very urbanized area, as well as lower dilution capacity (water $\mathrm{depth}=0.4\mathrm{m}$). S3 showed lower gases emissions, while S1 presented the intermediate gases flows due to the deepest water column (2.5 m) and higher capacity of pollutant dilution. Thus, we associate higher ${\mathrm{CH}}_4$ and ${\mathrm{CO}}_2$ emissions with the proximity of pollution discharges and lower dilution capacity. The results indicate higher emissions for shallow water, highlight the influence of disorderly occupation in urban areas, and clarify that adequate wastewater treatment is urgent to prevent wetland degradation and to minimize ${\mathrm{CH}}_4$ and ${\mathrm{CO}}_2$ emissions.

The ferric-nitrilotriacetate (${\mathrm{Fe}}^{3+}\text{-}\mathrm{NTA}$)-catalyzed homogenous Fenton-like reaction (i.e., ${\mathrm{Fe}}^{3+}\text{-}\mathrm{NTA}/{\mathrm{H}}_2{\mathrm{O}}_2$) has received increasing interest for environmental applications, but its potential in degrading trichloroethylene (TCE) in groundwater still is not well known. The results of this study showed that ${\mathrm{Fe}}^{3+}\text{-}\mathrm{NTA}/{\mathrm{H}}_2{\mathrm{O}}_2$ was more effective than other ${\mathrm{Fe}}^{3+}\text{-}\mathrm{chelate}/{\mathrm{H}}_2{\mathrm{O}}_2$ processes (e.g., including ethylenediaminetetraacetate, ethylenediamine-$N,N^{\prime }$-disuccinate, citrate, malonate, and tartrate) in degrading TCE in groundwater at natural pH ($\sim 8.0$). The effects of important parameters including the ratio of $\mathrm{NTA}:{\mathrm{Fe}}^{3+}$, and the dosages of ${\mathrm{Fe}}^{3+}\text{-}\mathrm{NTA}$ and ${\mathrm{H}}_2{\mathrm{O}}_2$ were investigated. Greater than 98% degradation efficiency of TCE in actual groundwater was obtained after 60 min of reaction time under the given conditions of $\mathrm{NTA}:{\mathrm{Fe}}^{3+}=1.5:1$, $0.1\mathrm{mM}{\mathrm{Fe}}^{3+}\text{-}\mathrm{NTA}$, $5\mathrm{mM}{\mathrm{H}}_2{\mathrm{O}}_2$, and pH 8.0. Hydroxyl radical (${\mathrm{HO}}^{•}$) was responsible for the degradation of TCE, and the by-products were identified as formic acid and chloride ion (${\mathrm{Cl}}^{-}$). Greater than 90% degradation efficiency of TCE in a sand column was achieved under dynamic conditions [$0.5\mathrm{mM}{\mathrm{Fe}}^{3+}\text{-}\mathrm{NTA}$ ($1:1.5$), $4\mathrm{mM}{\mathrm{H}}_2{\mathrm{O}}_2$, and hydraulic retention time of 4 h], resulting in stoichiometric ratios of $\mathrm{\Delta }{\mathrm{Cl}}^{-}:\mathrm{\Delta }\mathrm{TCE}$ and $\mathrm{\Delta }\mathrm{TCE}:\mathrm{\Delta }{\mathrm{H}}_2{\mathrm{O}}_2$ of $\sim 3:1$ and 4%, respectively. Compared with iron mineral (e.g., magnetite)-catalyzed Fenton-like processes, ${\mathrm{Fe}}^{3+}\text{-}\mathrm{NTA}/{\mathrm{H}}_2{\mathrm{O}}_2$ led to much smaller consumption of ${\mathrm{H}}_2{\mathrm{O}}_2$ (at least 1 order of magnitude smaller). In addition, the buffering capacity of bicarbonate anions (${\mathrm{HCO}}_3^{-}$) in groundwater had a positive effect on the degradation of TCE by ${\mathrm{Fe}}^{3+}\text{-}\mathrm{NTA}/{\mathrm{H}}_2{\mathrm{O}}_2$.

The present study investigated the effects of air micro–nanobubbles (AMNBs) on calcium sulfate dehydrate (gypsum) scaling over a reverse-osmosis (RO) membrane in a lab-scale plate-and-frame module processing brackish water. Membrane performance for the treatment of a synthetic solution sample with high gypsum scaling potential was evaluated by measuring permeate flux and salt rejection and high-resolution scanning of fouled membrane surface in the presence and absence of AMNBs. The results show that AMNBs significantly reduce gypsum scaling on the membrane surface due to enhanced dispersion effect in flow and decrease the effect of concentration polarization ($CP$), especially in central areas and the outlet of the channel flow. In the absence of AMNBs, after 20 h of scaling, the membrane permeate flux and salt rejection reduced to 70% and 96.4%, respectively. However, the presence of AMNBs in the solution improved these values notably in the same conditions (flux-83% and rejection-98%). The results indicate that the application of AMNBs is able to play an effective role in the control of gypsum scaling and improvement of membrane performance in the RO desalination process.

Bench-scale experiments were performed to evaluate poly- and perfluoroalkyl substance (PFAS) desorption from vadose zone soils collected at a site historically impacted with aqueous film-forming foam (AFFF). A sequential dilution batch method was employed to obtain PFAS desorption isotherms from a shallow surface soil [0.03 to 0.9 m below ground surface (bgs)] and from a deep soil (0.9–2.4 m bgs). Results showed that the desorption isotherms were reasonably described by a linear model, and that a fraction of the soil-bound PFAS mass was not readily desorbed (or, non-labile); the recalcitrance of this non-labile fraction was evaluated on a subset of samples and shown to persist for up to 9 months. The non-labile fraction of PFAS mass sorbed to the soil (non-labile PFAS sorbed mass divided by the total PFAS sorbed mass) ranged from $0.17\mathrm{g}{\mathrm{g}}^{-1}$ for perfluorohexane sulfonamide in the deep soil to $0.87\mathrm{g}{\mathrm{g}}^{-1}$ for $8:2$ fluorotelomer sulfonate in the shallow soil, and generally increased with the PFAS organic carbon:water partitioning coefficient (${\mathrm{K}}_{\mathrm{oc}}$). The fraction of the PFAS within the non-labile fraction was generally greater in the shallow soil than in the deep soil, likely due to the elevated organic carbon content of the shallow soil. The slopes of the desorption isotherms associated with the readily-desorbable (labile) PFAS fraction for the shallow soil were within the ranges predicted by ${\mathrm{K}}_{\mathrm{oc}}$-based models derived from adsorption data. Overall, results for the soils studied herein suggest that much of the PFAS mass present in the soil likely is not readily available for leaching into infiltrating waters. Such information could provide useful insight for developing PFAS soil cleanup standards.

Particulate matter (PM) recovery from street sweeping (SS), catch basin (CB), and unit operation (UO) is essential for sustainability of these urban hydrologic functional units (HFUs). PM inventory in HFUs is of increasing interest. PM granulometry and transformations thereof are needed to examine loads and export from HFUs. This study uniquely examines transformation of PM distributions recovered from SS, CB, and UO, representing serial HFUs coupled from up- to downstream in drainage systems. HFUs are also indexed to land uses (residential, highway, commercial) across Florida ($n=470$ samples). Results indicate the dominant PM mass is sand-size from 425 to 1,000 μm. Gravimetrically, particle size distributions (PSDs) are represented by a cumulative gamma distribution (CGD) (${\mathrm{R}}_{\mathrm{adj}}^2:0.98–0.99$). Particle number density (PND) is represented by a power law model (PLM) with a log-log transformation (${\mathrm{R}}^2:0.86–0.89$). Results indicate UOs ($n=163$) as a downstream HFU had PSDs that were less heterodisperse and finer than CB ($n=155$) and SS ($n=152$). PNDs are statistically consistent between SS, CB, and UO, given the transport of suspended PM from pavement through UOs, which cannot capture suspended PM. PM from SS is statistically more enriched in the suspended and sediment fractions than CBs and UOs due to export from these HFUs. Land use has been hypothesized as a factor impacting PSDs. However, results indicate that the impact of land use is not statistically significant for recovered PSDs. These findings are a useful resource of PM granulometry for urban PM residuals and facilitate implementation of more sustainable drainage systems.

Long-term experiments were undertaken to evaluate the role of polyurethane foam (PUF) on performance and in alleviation of fouling in a ceramic membrane integrated in an anaerobic hybrid membrane bioreactor (An-HMBR), treating high-strength wastewater. A mass balance equation was also developed to assess the mixed liquor suspended solids (MLSS) concentration in PUF effluent by taking into account the “sloughing” of the biofilm layer. Results showed that MLSS concentration was overpredicted by the equation in the final stages and this was attributed to the retention of microbial dead mass in the interstices of PUF. This study revealed that the pore-blocking mechanism was dominant during the initial stages of reactor operation followed by cake layer formation in the final stage of treatment. Reversible fouling (98%) dominated over irreversible fouling (0.9%), which also supported cake layer formation. Increasing hydraulic retention time (HRT) and decreasing sludge retention time (SRT) resulted in higher concentration of soluble microbial products (SMP) and extracellular polymeric substances (EPS) in the suspended sludge, PUF biomass, and cake layer attached to the membrane. This, in turn, resulted in increasing the membrane resistance and fouling.

In this study, sulfonated poly(styrene-isobutylene-styrene) (SIBS) was used to validate its performance as a novel desalination media for brackish water through ion exchange. The effect of counter-ion substitution in the ionic domains (e.g., ${\mathrm{Ba}}^{2+}$ and ${\mathrm{Mg}}^{2+}$) was used to change the nanostructure and the sodium removal percentage. Material characterization techniques were employed to evaluate the chemical structure and physical properties of the polymer membranes depending on sulfonation levels and counter-ion substitution. Infrared spectroscopy was used to confirm the presence of sulfonic groups and interactions with ${\mathrm{Ba}}^{2+}$ and ${\mathrm{Mg}}^{2+}$ counter-ions in the polymer nanostructure. An experimental design and ANOVA were executed to assess the effect on sodium removal percentage of (1) sulfonation level, (2) counter-ion substitution, and (3) sodium chloride concentration. The results show that high values of ion-exchange capacity and water absorption were directly related to the degree of sulfonation in the polymer. Maximum values obtained from ion-exchange capacity and water absorption were $1.75\mathrm{meq}/\mathrm{g}$ and 581.3%, respectively. The incorporation of ${\mathrm{Ba}}^{2+}$ and ${\mathrm{Mg}}^{2+}$ counter-ions considerably reduced these two properties due to the ionic cross-linking formed in the sulfonated polymer nanostructure, confirming the suitability of this polymer for water desalination.

For low-temperature flue gas, there is still no efficient and economic denitration technology. The oxidation absorption method can be believed as a new popular choice. Heterogeneous Fenton reaction is a more promising method for the oxidation and removal of NO. Based on a previous study on the absorption of ${\mathrm{NO}}_{\mathrm{x}}$ by urea in the tail, the NO oxidation and removal by heterogeneous Fenton reaction was investigated in detail. Experimental results showed that the denitrification efficiency increased with the increase of ${\mathrm{H}}_2{\mathrm{O}}_2$ injecting, while the concentration of ${\mathrm{O}}_2$ have little influence. In order to ensure that the hydrogen peroxide is fully vaporized in the atomization zone, the temperature of the atomization zone should be at 125°C–170°C. Due to the self decomposition of hydrogen peroxide, the temperature in the reaction zone should drop rapidly to below 100°C. Rapid cooling after atomization is the key to improve the denitration efficiency. For the Fenton catalysts, the denitrification efficiency increased with the increase of loading amounts, and the denitrification efficiency can be greatly improved by the doping of Ce. Among the studied catalysts, $15{\%\mathrm{Fe}}_2{\mathrm{O}}_3{+15\%\mathrm{CeO}}_2/{\mathrm{Al}}_2{\mathrm{O}}_3$ catalyst had the best performance. The experimental study in this paper can commendably promote the follow-up technology development.

Besides collecting legitimate wastewater, municipal sanitary sewer systems, even when separated from storm sewer systems, also receive unwanted inflow and infiltration ($\mathrm{I}/\mathrm{I}$) that adversely impact their sizing, economics, and operation. Although several statistical models have been proposed to quantify $\mathrm{I}/\mathrm{I}$, their advanced methods and intricate data requirements may be unrealistic for practitioners who need to investigate $\mathrm{I}/\mathrm{I}$ for individual sewer systems. Here, a practical regression model of daily sewer flow is developed with discrete terms for sanitary flow (based on winter water use), groundwater infiltration (based on sinusoidal seasonality), direct inflow (based on same-day precipitation), and delayed inflow (based on multiday moving-average precipitation). The terms are intuitive and the model performs well with flow observations from a case study. The model can help practitioners separate $\mathrm{I}/\mathrm{I}$ from other wastewater flows, customize measures to control $\mathrm{I}/\mathrm{I}$, and improve sewer system performance.