Journal of Environmental Engineering

Soil pollution by organic matter is traditionally modeled through macroscale multiphase flow models, which rely on extensions of Darcy’s law and empirical relationships. The transfers between phases can be expressed by the phase equilibrium or by a kinetic model. In this study, initially, a two-phase model (air-water) is constructed to model water drainage from a two-dimensional (2D) geometry. Results from this are compared with experimental results from literature. In addition, a three-phase flow model was created and applied for the simulation of the infiltration of nonaqueous phase liquid (NAPL) through the unsaturated, capillary, and saturated zones. Again, simulation results are compared with experimental results both from tests performed in this study and from literature. These are 2D NAPL infiltration experiments in sand packs, in which toluene and Soltrol, respectively, are infiltrated in both the unsaturated and saturated zones. Comparisons were made based on visual observation of the outline of the progressing NAPL front and the water saturation data. A two-phase model for the drainage step through a 2D cell was first used to deduce the initial conditions of the soil. Subsequently, a three-phase model was created that can predict the water saturation and NAPL pressure within the 2D cell and reproduce the pollutant infiltration through the unsaturated, capillary, and saturated zones. Results show the effect of the capillary nature of soil on the vertical and lateral plume spread.

Excessive heavy metal ions in a bioleaching solution can negatively affect Acidithiobacillus ferrooxidans and consequently reduce the leaching rate. This work aims to verify the adsorption mechanisms of Rhodotorula sp. in collaborative bioleaching with A. ferrooxidans and Rhodotorula sp. and investigate the adsorption process with the competitive adsorption model. Experimental results indicate that collaborative bioleaching is more effective than bioleaching with A. ferrooxidans only. Results of Fourier transform infrared spectroscopy (FTIR) and energy-dispersive X-ray spectroscopy (EDX) characterization prove the adsorption ability of Rhodotorula sp. The calculation results of the adsorption experiment reveal that Cd does not participate in competitive adsorption among the heavy metals tested. The equilibrium adsorption concentration and the adsorption velocity constants of Cu, Mn, and Pb in competitive adsorption are lower than those in single-element biosorption. The adsorption capacities of Pb and Mn even decrease in later stages. The final competition coefficients of Cu, Mn, and Pb in the competitive adsorption of the three ions are 0.84, 0.14, and 0.02. Rhodotorula sp. can adsorb 67.4% Cd, 52.4% Cu, 1.0% Mn, and 8.6% Pb in the leaching solution, thereby increasing the bioleaching rate of A. ferrooxidans.

Management of inorganic dissolved nitrogen (${\mathrm{NH}}_4\text{-}\mathrm{N}$ and ${\mathrm{NO}}_3\text{-}\mathrm{N}$) in urban stormwater is challenging. This study investigated the role of bioretention plants and a saturated zone (SZ) on nitrogen removal and fate, under conditions of varying stormwater hydrology and nutrient loadings. Experiments were conducted using one plant species (Pennisetum alopecuroides), two media types, and with and without a saturated zone and organic carbon addition to examine the fate of ${\mathrm{NH}}_4\text{-}\mathrm{N}$ and ${\mathrm{NO}}_3\text{-}\mathrm{N}$ in stormwater applied to bioretention columns. During 1 year of synthetic stormwater applications, all bioretention treatments effectively captured ($>95\%$ concentration and mass) ${\mathrm{NH}}_4\text{-}\mathrm{N}$ from stormwater independent of the presence or absence of plants and SZ. In contrast, both plants and SZs were critical to the effective removal of ${\mathrm{NO}}_3\text{-}\mathrm{N}$ and total nitrogen. Planted systems removed 59.4% of the input dissolved N, compared with 28.9% of the unplanted control. Furthermore, when including plants and a SZ, 95.4% of the input dissolved N was removed, with 57.0% attributed to plant uptake and 33.5% to denitrification. The relative contribution of vegetation and a SZ to nitrogen removal was also controlled by stormwater event magnitude and nutrient loadings. These results suggest that both plants and saturated zones are needed to effectively and consistently remove nitrogen from urban stormwater over a wide range of environmental conditions.

This study investigates the use of extracellular polymeric substance (EPS), an eco-friendly and biodegradable bioflocculant, for the treatment of composting leachate [raw leachate (BR9) and biologically treated leachate (BB1)]. The removal of chemical oxygen demand (COD) (69% for BR9 and 92% for BB1), phosphorus (92% for BR9 and 94% for BB1) and ammoniacal nitrogen (65.7% for BR9 and 96% for BB1) was higher using a combination of slime-EPS (S-EPS) and ${\mathrm{FeSO}}_4$ than using slime-EPS alone for both leachates. However, removal of nitrates–nitrites (95% for BR9 and 99% for BB1) and metals (60%–98%) was higher using slime-EPS without the addition of ${\mathrm{FeSO}}_4$. In all experiments, slime-EPS performed better than broth-EPS (B-EPS). Further optimization of pH (5–9) and incubation time (0.5–12 h) revealed that the maximum removal of COD, phosphate, ammoniacal nitrogen, nitrates–nitrites, and metals was obtained using a slime-EPS concentration of $0.5\mathrm{g}/\mathrm{L}$ at pH 8 (leachate pH) and 8 h of incubation time. Moreover, the settled solids after EPS treatment produced a slime-EPS of $13\mathrm{g}/\mathrm{L}$ in 72 h, which could be used for the treatment of composting leachate.

Hydrolysis-acidogenesis of primary sludge is a suitable method to produce readily biodegradable organic matter. Sludge retention time (SRT) is a significant technological parameter: when it is too short, the sufficient amount of short chain volatile fatty acids (SCVFAs) will not be produced. When SRT is too long, part of the produced SCVFAs will be consumed by bacteria-producing methane. The objective of this research was to determine the optimal SRT of the hydrolysis-acidogenesis process for the highest production of organic carbon content. For research on the hydrolysis-acidogenesis process, two laboratory methods were applied, and primary sludge from two wastewater treatment plants (WWTPs) was investigated. The obtained results showed that the optimal SRT was six days under investigated conditions. The maximum SCVFAs production and biochemical oxygen demand (${\mathrm{BOD}}_7$) formation were achieved with the destruction of volatile suspended solids (VSS) of 5%.

This study used sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) analysis and a jar test apparatus to investigate the molecular weight (MW) and turbidity removal potential of Hibiscus seeds. Three Hibiscus species were assessed: okra crude extract (OCE), sabdariffa crude extract (SCE), and kenaf crude extract (KCE). Furthermore, purified versions of each [i.e., purified okra protein (POP), purified sabdariffa protein (PSP), and purified kenaf protein (PKP)] obtained from anionic exchange were evaluated. The results show that whereas the crude extracts had multiple proteins with MW sizes between 11 and 82 kDa, the purified samples consisted of a single coagulant protein band around 39 kDa. In each case, significant turbidity removal was recorded with the purified proteins; POP, PSP and PKP achieved approximately 98%, 94%, and 90% removal, respectively, at a reduced dosage of $\le 0.6\mathrm{mg}/\mathrm{L}$. However, OCE and SCE achieved lower turbidity removal of 86% and 85% using 40-mg/L doses, respectively, whereas KCE recorded only 73% turbidity removal with a 60-mg/L dose. Sludge generation by crude and purified proteins was approximately 25% of sludge produced by aluminum sulfate and had the additional benefit of being biodegradable. Therefore, the coagulant protein in Hibiscus plant seeds has potential applications for improvements to accessing clean water in developing countries.

Along with the increase of autoclaved aerated concrete (AAC) production, the amount of scrap waste (industrial by-products) is increasing. AAC waste, however, is not yet being fully reused or recycled and is discarded without any treatment in most developing countries. In this study, AAC fines were tested as effective and economic adsorbents for the removal of ${\mathrm{Cd}}^{2+}$ and ${\mathrm{Pb}}^{2+}$ from wastewater. A series of batch adsorption experiments were carried out using AAC with three different particle sizes ($<0.105$, 0.105–2, and 2–4.75 mm) to examine effects of the particle size, initial metal concentration ($C_i$), initial pH (${\mathrm{pH}}_i$), ionic strength, contact time, and competitive metals. For comparing the adsorption characteristics and capacities, crushed concrete fines and a fine sand were also used. Results showed that the adsorption kinetic data were well fitted to the pseudo–second-order kinetics model for all tested materials. ${\mathrm{Pb}}^{2+}$ adsorption was independent of ${\mathrm{pH}}_i$ and ionic strength for AAC fines, whereas ${\mathrm{Cd}}^{2+}$ adsorption varied depending on ${\mathrm{pH}}_i$ and decreased drastically at ${\mathrm{pH}}_i\le 7$. Based on the results from adsorption isotherms, the Freundlich model fitted well ($R^2>0.90$) to the data for $300\le C_i\le \mathrm{5,000}\mathrm{mg}/\mathrm{L}$, whereas the Langmuir model was applicable ($R^2>0.99$) to the data for $C_i\le \mathrm{2,000}\mathrm{mg}/\mathrm{L}$. The maximum adsorption capacity of each particle size of AAC exhibited almost the same adsorption capacity for ${\mathrm{Cd}}^{2+}$ ($15\mathrm{mg}/\mathrm{g}$) and ${\mathrm{Pb}}^{2+}$ ($>250\mathrm{mg}/\mathrm{g}$), which are similar to or higher than the values of other types of adsorbents in previous studies. The metal removal by AAC is controlled mainly by ion exchange, surface complexation, and surface precipitation. In particular, the ${\mathrm{Ca}}^{2+}$ ion exchange on the hydrated adsorbent surface is the dominant adsorption mechanism at the early stage of adsorption. The selectivity sequence of metal adsorptions became ${\mathrm{Pb}}^{2+}>{\mathrm{Cu}}^{2+}>{\mathrm{Ni}}^{2+}>{\mathrm{Cd}}^{2+}>{\mathrm{Zn}}^{2+}$ for AAC, and the existence of ${\mathrm{Pb}}^{2+}$ and ${\mathrm{Cu}}^{2+}$ in wastewater highly impeded the ${\mathrm{Cd}}^{2+}$ adsorption onto AAC fines.

Bisphenol S (BPS) is considered to be a persistent pollutant in the environment. In this study, an anaerobic bioelectrochemical system (BES) is established for BPS biotransformation with the goal of discovering a new pathway for BPS transformation and improving the removal efficiency of BPS. The results of the study suggest that the BES exhibits high-level BPS biotransformation that is better than that of conventional anaerobic cometabolism. The removal efficiency of BPS was as high as 92.9% at $0.1\mathrm{mg}/\mathrm{L}$ BPS. The intermediate products were analyzed comprehensively, and 4,4′-thiodiphenol, 1,2,3,4-tetrahydrodibenzo[b,d]thiophene, methyl(o-tolyl)sulfane, and phenol were found to be major products of BPS transformation, which indicated new pathways of biotransformation. In addition, the microbial diversity on the electrode biofilm was also identified. Rhodococcus and Chelatococcus are the major bacteria in BES, which further proves the new transformation process of BPS using BES. Therefore, the results of this study have great significance for improving BPS transformation in the environment.

In this study, the corrosion behavior of nickel-based alloys 625, 825, and 800 with a salt deposit layer was investigated in supercritical water containing a dissolved oxygen of 5,000 ppm at 400°C. Scanning electron microscopy, energy-dispersive spectroscopy, atomic force microscope, X-ray diffraction, and laser Raman spectroscopy were used to investigate the morphologies and compositions of samples. Control experiments were performed to investigate the effects of a salt deposit layer. The presence of one salt deposit layer on the sample surface resulted in the occurrence of an acidic and oxidizing microenvironment between the alloy surface and the salt deposit layer, evidently enhancing the corrosion of nickel-based alloys. A comparison of the corrosion resistances among Alloys 825, 800, and 625 indicated that Alloy 825 is the best. Additionally, a suggestion for materials selection in supercritical water oxidation plants for high-salinity organic wastewater treatment was proposed.

A reevaluation of the physical and chemical characteristics of individual components of municipal solid waste (MSW) is done, with a focus on the Indian subcontinent. Whereas previous studies reported average characteristics of the mixed-waste stream, the availability of characteristics of individual component fractions can be beneficial for the formulation of waste management strategies and policies. To facilitate an easy theoretical estimation of waste characteristics and simplify the decision making, physicochemical characteristics of individual components reported by previous researchers have been relied on. Accounting for the influence of source segregation, seasonal fluctuations, and economic constraints, this study aims to experimentally characterize individual components of mixed MSW generated in Delhi, Mumbai, Nagpur, Kochi, and Guwahati, which are located in different zones of India, over different seasons. This minimizes the uncertainties and increases the reliability of the characterization studies in India. The study gives a detailed account of the methodology for the same and indicates the application of the data thus derived in formulating sustainable waste management strategies. Proximate and ultimate analyses, heat content, C/N ratio, $\mathrm{H}/{\mathrm{C}}_{\mathrm{eff}}$ ratio, air requirement, potential flue-gas release, and potential ash generation, among others, are estimated using the characteristics of the individual component fractions. The moisture content varied significantly from the previously reported data, with the moisture content of plastic components varying by nearly 95%. The heat content reflected relatively lower deviation, with the paper fraction exhibiting 33%–36% variation. Inert content of the food wastes differed by 336% from the previous database. Differences in the source materials used, segregation practices, effect of climatic factors, instrumentation techniques, and analytical standards may have caused these variations.

Sudden gaseous contaminants are usually highly unpredictable and even very toxic. If unable to be responded to in time, they will seriously endanger the safety of occupants. In order to realize quick source identification based on very limited sensors, two indexes were established according to a combination of the traditional optimization method and probability method. The identification process consisted of two stages. In the pretreatment stage, computational fluid dynamics (CFD) was taken to simulate the contaminant release processes from 16 control-body centers and 16 actual sources, and the concentration information from three sensors, ${\beta }_1$, ${\beta }_2$, and ${\beta }_3$, was collected for later calculation. Then, in the source identification process, the identification index was solved based on the concentration information. The identification results show that when a single sensor is used for identification, the accuracy is greatly affected by the sensor position. When using dual-sensor combinations instead, the average accuracy rate can be increased by 13.5%. Dual-sensor combination scenarios can greatly improve accuracy and effectively eliminate the influence of sensor location.

In this study, the composition of actual pipeline sediment, the growth ring, was analyzed. According to this, we prepared and characterized a simulated growth ring. Adsorption or degradation behavior of the simulated growth ring for tetrachloroethylene (PCE) was conducted where the removal effect under different conditions was systematically studied. Adsorption behavior fitted the Freundlich isotherm and pseudo-second-order kinetic model and it was a spontaneous endothermic process of increased entropy. Adsorption reached saturation and the removal efficiency was 33.89% after 100 min. When the simulated growth ring was combined with ${\mathrm{H}}_2{\mathrm{O}}_2$ to build a Fenton-like system to degrade PCE, the degradation efficiency could attain 83.34% after 480 min. The van der Waals force and surface complex catalysis were the main adsorption and degradation mechanisms, respectively. The excellent pollutant removal capacity would make the growth ring become a potential candidate for water treatment and achieve the goal of water quality security in water distribution networks in the future.

Aqueous diffusivities were experimentally determined for perfluoroalkyl acids (PFAAs) with perfluorinated carbon chain lengths ranging from 3 to 8, including perfluorooctanoic acid (PFOA) and perfluorooctane sulfonic acid (PFOS). The capillary method was employed at room temperature. Measured aqueous diffusivities ranged from $2.5\times {10}^{\mathrm{-5}}{\mathrm{cm}}^2/\mathrm{s}$ (perfluorobutanoic acid) to $0.45\times {10}^{\mathrm{-5}}{\mathrm{cm}}^2/\mathrm{s}$ (perfluorohexane sulfonic acid). The experimental results were in good agreement with aqueous diffusivities determined from previously performed experiments that measured PFAA uptake into activated carbon. Although molecular simulations for PFOA and PFOS were in reasonable agreement with experimental measurements, the Wilke-Chang model was not able to accurately predict the values nor describe the trend for the PFAAs used in this study. The nonuniform trend in the PFAA diffusivities with respect to the molar volumes likely is reflective of unique molecular interactions associated with highly fluorinated compounds.