Journal of Environmental Engineering

The objective of this research was to evaluate the characteristics of two conventional treatment systems of sewage sludge production to estimate contamination removal efficiency and compare it with the Brazilian legislation. For that purpose, physicochemical parameters such as pH, phosphorus, potassium, metal ions, total solids, total fixed solids, total volatile solids, moisture, organic matter, and total organic carbon were determined. The results in relation to the sludge presented a pH close to neutral, and the concentration of phosphorus, potassium, and organic matter in the sludge of the system operated with an anaerobic sludge mantle reactor (RALF) was superior to that of the system operated with stabilization ponds (SPs). The concentrations of the metal ions in the RALF sludge were higher than those of the sludge in the drying bed; in the SPs these concentrations decreased during the treatment process. When comparing the wastewater treatment plants (WWTPs), the concentrations of the metal ions were higher in the RALF sludge, except Mn and Ni, and the Fe concentration was similar in both systems.

Secondary roads play an important role for connecting local communities to principal county and state highways and, in some cases, may account for a large proportion of the state-maintained road systems. Existing swales alongside secondary roads can help mitigate the impact of roadway runoff. Limited information is available to characterize their runoff constituent concentrations and pollutant reduction potentials. Consequently, three secondary roadway segments typical of low-to-medium traffic volumes were monitored within the Piedmont region of North Carolina. Event mean concentrations (EMCs) of monitored constituents were found to be substantially lower than those reported for North Carolina primary roads and the national highway runoff data derived from the Federal Highway Administration. In general, secondary road runoff exhibited site-average EMCs of $32\mathrm{mg}/\mathrm{L}$ total suspended solids (TSS), $0.65\mathrm{mg}/\mathrm{L}$ total nitrogen (TN), and $0.13\mathrm{mg}/\mathrm{L}$ total phosphorus (TP). Roadside swales are effective to attenuate the inflow EMCs to $15\mathrm{mg}/\mathrm{L}$ TSS and $0.48\mathrm{mg}/\mathrm{L}$ TN, achieving EMC removal efficiencies of 53% TSS and 25% TP. There was essentially no change in TP EMCs as runoff passing through the swale. Pollutant-load reductions for runoff moving through roadside swales were 77% for TSS, 67% for TN, and 33% for TP. Runoff attenuation through infiltration in vegetated swales accounts for all or most of the load reductions and points to the importance of maximizing infiltration rates in roadside swales. As a result, state agencies can incorporate the water quality benefits of swale treatment with secondary roads when developing their watershed strategies for nutrient load reductions.

The well-known biorefractory organic material 1,4-Dioxane (1,4-D) is difficult to degrade in groundwater by classical treatment processes. The sono-activated persulfate process was applied to remediate 1,4-D-contaminated groundwater. The influences of the persulfate dose, solution pH, initial 1,4-D concentration, and ${\mathrm{H}}_2{\mathrm{O}}_2$ dose on the enhancement of 1,4-D degradation were studied. The degradation kinetic and remediation effectiveness were also investigated. Up to an 84% 1,4-D elimination was achieved with ${\mathrm{pH}}_0$ of 7.0, temperature of $25\pm 2°\mathrm{C}$, $7.40\mathrm{mmol}/\mathrm{L}$ persulfate, $39.2\mathrm{mmol}/{\mathrm{L}\mathrm{H}}_2{\mathrm{O}}_2$, 400 kHz ultrasonic frequency, 100 W of power, and $2.67\mathrm{W}/{\mathrm{cm}}^2$ ultrasonic density, with an initial 1,4-D of approximately $13\mathrm{mg}/\mathrm{L}$ after an 8-h reaction in aqueous solution. The material 1,4-D in groundwater was eliminated completely after 10 h, while the acute toxicity of the treated groundwater decreased by 99.87%. In this process, the sulfate radical (${\mathrm{SO}}_4^{•-}$) and hydroxyl radical ($•\mathrm{OH}$) were confirmed to be primary reactive species that degraded 1,4-D. A novel reaction kinetic model grounded on the radicals’ oxidation was developed to describe the 1,4-D degradation process from the point of view of math and chemistry. The sono-activated persulfate process successfully degraded the 1,4-D present in groundwater under mild conditions and was accompanied by a toxicity reduction. In conclusion, this is a promising method to remediate 1,4-D-contaminated groundwater.

In this study, a novel polyacrylonitrile/aluminum oxide ($\mathrm{PAN}/\mathrm{Al}-{\mathrm{O}}_{\mathrm{NPs}}$) nanofiber adsorbent modified with 2-amino-3-methyl-1-hexanethiol (AMH) was synthesized by a combination of hydrothermal and electrospinning and evaluated as an adsorbent for removing thorium (IV) (${\mathrm{Th}}^{4+}$) ion from aqueous solution. The $\mathrm{PAN}/\mathrm{Al}-{\mathrm{O}}_{\mathrm{NPs}}/\mathrm{AMH}$ was characterized by X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), and Brunauer–Emmett–Teller (BET) analysis. Response surface methodology (RSM) was used in the optimization of ${\mathrm{Th}}^{4+}$ adsorption for parameters such as pH, initial metal ion concentration (${\mathrm{Th}}^{4+}$ concentration), and contact time. Design-Expert 7 was used for modeling these three variables. Statistical measures validated the developed model ($R^2=0.9415$). In addition, the adsorption kinetics was well defined by the pseudo-second-order equation ($R^2=0.98$) whereas the adsorption isotherms were better fit by the Langmuir model ($R^2=0.95$). The adsorption capacity of $\mathrm{PAN}/\mathrm{Al}\text{-}{\mathrm{O}}_{\mathrm{NPs}}/\mathrm{AMH}$, $472\mathrm{mg}{\mathrm{Th}}^{4+}{\mathrm{g}}^{-1}$ composite, led to 98% removal at 25°C. Moreover, thermodynamic parameters were determined which showed the endothermic nature of the reactions. The loaded ${\mathrm{Th}}^{4+}$ can be easily regenerated with ${\mathrm{HNO}}_3/\mathrm{HCl}$. Also, the desorption level of ${\mathrm{Th}}^{4+}$ by the $\mathrm{PAN}/\mathrm{Al}\text{-}{\mathrm{O}}_{\mathrm{NPs}}/\mathrm{AMH}$ using $0.4\mathrm{M}{\mathrm{HNO}}_3/0.2\mathrm{M}\mathrm{HCl}$ was more than 92%.

Geosynthetic clay liner (GCL) is a lining material that consists of a bentonite layer sandwiched between two geotextiles. To simulate the interaction between an aqueous solution and a barrier material, triaxial permeability and free swell tests are performed on a GCL that is permeated with 0.5 M ${\mathrm{MgCl}}_2$ solution. The temperature of the solution is 20, 40, and 60°C, with 0.5, 1, and 2% anionic polymer by mass added to the GCL. Test results indicate that although temperature increase causes a slight increase in the swell index of the GCL, it results in a significant increase of up to 2 orders of magnitude in permittivity. The GCLs are also tested with deionized water. The increase in permittivity is attributed to a decrease in the viscosity of the permeation fluid. Adding 1% anionic polymer to the GCL results in almost 2 orders of magnitude decrease in permittivity. Anionic polymer–treated GCLs can be used effectively in aggressive ${\mathrm{MgCl}}_2$ solutions by both decreasing the permittivity and increasing the swell index of the GCLs.

Struvite precipitation is a promising approach to recover nitrogen (N) and phosphorus (P). However, poor solid−liquid separation of struvite precipitation crystallization can significantly decrease resource recovery efficiency. This study systematically investigates the recovery of N and P from urine through a combination of biochar with struvite precipitation. The N and P recovery efficiencies reach 40%–50% and 99%, respectively, and are stable with four different types of biochar at an optimized pH of 9.0. A second-order kinetics model is demonstrated to describe the N and P recovery processes, which supports the further development of the promising resource recovery process. N and P recovery are enhanced via biochar adsorption and struvite precipitation, respectively. These results indicate that biochar, as a carrier of struvite precipitation to recover N and P from urine and as a slow-release fertilizer in agriculture, is feasible and practical.

Methyl tertiary butyl ether (MTBE) is a chemical product and the most commonly used gasoline oxygenate. It is characterized as a pollutant for soil and water that has effects on human health. Research on the remediation of soil polluted with MTBE is relatively rare. This paper presents the results of laboratory experiments to study the feasibility of using the electrokinetic technique to remove MTBE from a clay soil. Tests are conducted on a clay soil contaminated with MTBE in a special apparatus, using different quality of electrolyte and direct current (DC) or alternating current (AC) electricity. The results of the tests reveal that, under laboratory conditions, MTBE can be removed from soil using the electrokinetic technique. The efficiency of remediation is dependent on the quality of electrolyte and type of applied electrical current.

Surface water conductivity measurements were used to evaluate the combined contribution of anions in western Pennsylvania from brines discharged by sources such as oil and gas wastewater treatment, coal-fired power plants, and coal mining activities. Conductivity sensor data were collected in the Allegheny River during a US Environmental Protection Agency and US Fish and Wildlife study that included seven sites covering 256 river km during the fall of 2012. Intermittent discharges, such as oil and gas wastewater, and continuous sources contributing to the conductivity were quantified using constrained and adaptive decomposition of time-series (CADETS) frequency analysis. CADETS was able to quantify the intermittent or short-term component of conductivity at sites where the intermittent fraction was 1 to 22% of the total conductivity. The demonstrated efficacy of the CADETS method for surface water quality analysis suggests it could be widely used to evaluate other water sensor data in rivers with both continuous and intermittent source impacts.

Activated carbon adsorption experiments were carried out with humic acid solutions to determine adsorption isotherms and kinetics. Four commercial coconut shell–based activated carbons were used: untreated, nitric acid–modified, sulfuric acid–modified, and base-treated. Adsorption capacities for humic acid were appraised for each type. Nitric acid and sulfuric acid modification increased humic acid adsorption capacity, as compared with untreated and base–modified activated carbon. Humic acid adsorption capacity for nitric acid– and sulfuric acid–modified powder activated carbon (PAC) was determined to be 50 and $70\mathrm{mg}/\mathrm{g}$, respectively. Adsorption capacity for the untreated carbon and the base-treated PAC was 28.7 and $7.6\mathrm{mg}/\mathrm{g}$, respectively. The zeta potential ($\delta$) of activated carbons indicates that when acid modified they exhibit a net positive charge due to numerous carboxylic acid functional groups and positively charged hydroxyl groups attached to the surface, ultimately enhancing humic acid adsorption. Scanning electron microscopy (SEM) images confirmed that acid treatment of activated carbon enlarges its micropores and removes contaminants embedded in them. The Langmuir isotherm model and pseudo-second-order model provided the highest correlation coefficient for adsorption and kinetics.

Ferrate(VI) (${\mathrm{FeO}}_4^{2-}$) is a greener oxidant in the treatment of wastewater. This paper presents electrochemical synthesis using two titanium ruthenium sheets as cathodes and a gray cast iron sheet as anode (two cathodes/one anode cell configuration). This electrolytic cell was demonstrated to produce more Fe(VI) than a one cathode/one anode cell configuration ($\sim 1.6\mathrm{mmol}/\mathrm{L}$ versus $0.4\mathrm{mmol}/\mathrm{L}$). In the cell, hydroxide ion concentration ($[{\mathrm{OH}}^{-}]$), current density ($I_d$), distance between cathodes and anode ($d$), and electrolyte NaCl concentration were varied to obtain optimum conditions to generate Fe(VI) efficiently. The optimum NaOH concentration was determined to be $6.2\mathrm{mol}/\mathrm{L}$ in using applied $\mathrm{voltage}=2.8\mathrm{V}$, $I=10.0\mathrm{A}$, $I_d=31.2\mathrm{mA}/{\mathrm{cm}}^2$, $d=2\mathrm{cm}$, and $[\mathrm{NaCl}]=100\mathrm{g}/\mathrm{L}$. The efficiency of Fe(VI) to remove ${\mathrm{SCN}}^{-}$ in petroleum wastewater was tested in the pH range from 7.0 to 12.0. Additions of coagulants, polyaluminum chloride (PAC), and polyacrylamide (PAM) to petroleum wastewater under alkaline conditions eliminated the large particles present in the wastewater. Fe(VI) treatment of particle-free wastewater showed almost complete removal of ${\mathrm{SCN}}^{-}$ at pH 7.0–9.0 using $[\mathrm{Fe}(\mathrm{VI})]:[{\mathrm{SCN}}^{-}]=4.7$. At $\mathrm{pH}>9.0$ of the reaction mixture of Fe(VI) and wastewater, incomplete removal of ${\mathrm{SCN}}^{-}$ in wastewater was observed.

High-flow media (HFM) are able to treat large runoff volumes using small-footprint systems. Four full-scale HFM stormwater control measures (SCMs) in a residential area were monitored over 11 months to assess the removal of total suspended solids (TSS), nitrogen, and phosphorus in first-flush (FF) stormwater runoff. Excellent removal of TSS and particulate-bound nutrients is noted, but, in most SCMs, removal of dissolved species is limited. Sorption of dissolved P occurs, although most likely on captured sediment and not on the HFM itself. N removal varies among the systems, but, in general, mineralization and nitrification of accumulated N species in the SCMs leads to nitrate export. FF is present in TSS (strongest), total nitrogen, and total phosphorous (weakest). HFM grain size and organic content do not significantly impact TSS or P removal, but higher organic content is associated with higher N removal. Optimal HFM SCM design incorporates sedimentation before filtration to minimize clogging concerns.

In this study, the suitability of paper industry wastewater for production of polyhydroxyalkanoate (PHA) was investigated in a pilot reactor in an industrial setting. The pilot plant was designed as a three-step process comprising (1) anaerobic fermentation for maximization of the volatile fatty acid (VFA) concentration, (2) enrichment of PHA-producing biomass, and (3) accumulation for maximization of the PHA content of the biomass. After fermentation, the paper mill process water contained a VFA fraction of 78% on a chemical oxygen demand (COD) basis. The length of the feast phase in the enrichment process stabilized at $45\min \pm 4\min$ after 18 days of operation. At the end of the feast phase all VFA was consumed and the PHA content of the volatile suspended solids (VSS) was $0.50\mathrm{g}\mathrm{PHA}/\mathrm{g}\mathrm{VSS}\pm 0.05\mathrm{g}\mathrm{PHA}/\mathrm{g}\mathrm{VSS}$. The acquired microbial community was dominated by Plasticicumulans acidivorans, a PHA-producing microorganism previously found to dominate VFA-fed laboratory reactors. The maximum PHA content achieved after accumulation was 0.70 to 0.80 g PHA/g VSS. An overall PHA yield of 34% on a COD basis was achieved. Improving the VFA fraction in the product spectrum of the fermentation and minimization of acid and base consumption for pH control were identified as major bottlenecks.

Anoxic microcosms and flow-through experiments were used to evaluate the ability of sugarcane bagasse to support biogenic sulfide production that can mitigate pH and immobilize heavy metals commonly found in acid mine drainage (AMD). The study was organized in three phases. Phases I and II used mine tailings to generate AMD solutions having a pH near 2, with total metals concentrations in excess of $150\mathrm{mg}/\mathrm{L}$. Fresh sugarcane bagasse was placed in AMD solutions contained in microcosms at various liquid:solid ratios, under controlled environmental conditions. Within 30 days, significant reductions ($>90\%$) in dissolved As, Cu, Pb, and Zn concentrations were achieved and pH was elevated to circumneutral conditions. Phase III used fresh AMD to challenge flow-through columns packed with bagasse. Reductions in dissolved Cd, Cu, U, and Zn concentrations between 1.5 to 2 orders of magnitude were observed and sustained for more than one year. Column performance was not significantly impacted by temperature fluctuations in the range between 5 and 22°C. Nucleic acid probes confirmed that sulfate reducing bacteria (SRBs) were active and present in the bagasse-containing microcosms. The relative abundance of SRBs suggests they were associated with the sulfide and alkalinity production and that biogenic sulfide was likely responsible for metal removal.

The sorption isotherms, kinetics, and thermodynamics of contaminants, e.g., strontium, lead, and uranium, for four different Indian soils (named S1, S2, S3, and S4) were investigated. Batch testing was performed to determine sorption properties of the soils. It was found that among the four soils, S1 has the maximum sorption at each contaminant metal. The uptake capacity for strontium, lead, and uranium was found to be 55.78, 103.6, and $2.07\mathrm{g}·{\mathrm{kg}}^{-1}$, respectively, after 24 h interaction at 45°C. The Langmuir and Freundlich isotherms have shown good fits ($R^2\ge 0.9$) in comparison with other isotherms, revealing the sorption characteristics of the soil–contaminant system (SCS). The experimental data of the SCS followed pseudo-second-order kinetics; however, Soils S1 and S2 exhibited a pseudo-first-order reaction on sorption of uranium. The effect of temperatures from 27°C to 45°C on sorption has revealed higher uptake of contaminant metals onto soils, and sorption of SCS is established to be spontaneous and endothermic. Moreover, the results revealed the physisorption regime in the SCS, and the soils exhibit good binding with the contaminants.

Constructed wetlands (CWs) are wastewater treatment ecotechnologies which use plants as a source of pollutants removal in the system. In these systems, the root zone acts in pollutant removal, interacting with the support medium, water, microorganisms, and contaminants. This study investigates the hypothesis of the absence of significant differences in the removal efficiencies of organic matter, turbidity, and apparent color between planted (Typha sp. and Eleocharis sp., individually and combined) and unplanted constructed wetlands with horizontal subsurface flow on the secondary wastewater treatment. The study was conducted on a pilot-scale system at a wastewater treatment plant (WWTP) located in São Paulo, Brazil. The experiment consisted of four treatment tanks: T0, the feeding tank, filled with raw sewage coming from the WWTP’s preliminary treatment; T1, containing gravel and Eleocharis sp.; T2, containing gravel and Typha sp.; T3, containing gravel, Eleocharis sp., and Typha sp.; and T4, containing only gravel (control tank). The system was monitored for three months and samples were collected from three locations in each tank: the influent, the middle of the process, and the effluent. Analyses of biochemical oxygen demand (${\mathrm{BOD}}_{5,20}$), turbidity, and apparent color are carried out on these samples. According to the studied parameters, there is an effective removal by the four constructed wetlands systems. Because these systems are designed for secondary sewage treatment, i.e., they mainly aim for organic matter removal, the four tanks perform equivalently, having over 90% ${\mathrm{BOD}}_{5,20}$ removal efficiency. Color and turbidity removal efficiencies vary from 55% to 71% and from 43% to 77%, respectively, and tanks T1 and T4 have higher levels of removal efficiency. The study validates partially the hypothesis because there is no significant difference in organic matter removal between the tanks cultivated with different plant species (isolated or combined) and the control tank (with gravel only). An ANOVA test shows no statistical difference ($p>0.05$) in organic matter removal among the tanks. The similar organic matter removal efficiencies for the four tanks demonstrate that the physical (filtration and sedimentation) and biological (biofilm) mechanisms play an important role in constructed wetlands wastewater treatment.