Journal of Environmental Engineering

Traditionally, flood protection measures have focused on high investment alternatives for control infrastructures that will benefit a certain amount of people, based in a gross cost-benefit (GCB) for the defined design flood. This gross cost-benefit approach, however, does not fully incorporate risk assessment into the analysis, given that it assumes that the chosen flood protection measures will provide protection against a design flood by avoiding flood damage every year during the project’s lifespan. This paper presents a probabilistic view of the benefits of implementing flood control measures, incorporating the risk concept to a full flood cost analysis, for an example region in Brazil. By combining analysis on annual expected damage, which considered the likelihood of $n$ flood events along the year—and not only the project one—and two flood management measures (levee and land zoning flood hazard), this paper evaluates why, and by how much, the inclusion of the probability of effectiveness of a given flood protection measure differs from traditional methods based on gross benefit. Results demonstrated a large difference between verifying a measure’s benefits by the GCB and the expected damage: whereas the former indicates the levee structure resulting in a lower accumulated damage from the fifth year of measure implementation, if the expected damage is used, investing in land zoning will be always most cost effective. These findings are useful to highlight that full flood costs should be based on risk evaluation, which is consonant with the latest perception of the assessment and management of flood risks, such as the Floods Directive present in the EU Water Framework Directive.

The increase of urban areas with high population concentration in small spaces in developing countries such as Brazil brings serious social and environmental problems. Based on this reality, simulations of four different urbanization scenarios were carried out: the current scenario, the future scenario made highly impervious by the occupation, the possible scenario with the insertion of LID (low-impact development) structures and zoning measures, and the planned scenario with territorial planning. In this respect, both real rainfall data and design storm data were used to test LID through a calibrated hydrological model. The expansion of urban occupation from the current scenario to the future caused a 16% increase in the volume of output hydrographs of the catchment under analysis. The insertion of LID structures and zoning measures decreased the surface runoff volume by 13.8%, from the future scenario to the possible. For real rainfall data, the hydrographs had their peaks retarded with the insertion of LID structures and occupancy control measurements. The performance of the LID structures was higher with lower total rainfall.

This paper deals with a laboratory-based investigation for the treatment of graywater generated from public housing in Turkey. In the first part of the study, ferrate(VI) has been synthesized electrochemically. The current efficiency (CE), energy consumption (EC), and ferrate(VI) yield during the electrochemical synthesis of ferrate(VI) was measured using cast iron shavings as anode materials. In terms of the highest CE, the lowest EC, and ferrate(VI) yield, 16-M NaOH media, applied current of 3 A, and 90 min of electrolysis time were found as optimum conditions for electrochemical synthesis of ferrate(VI) with cast iron shavings. This reactor configuration with cast iron shavings provided much higher CE values compared with the other studies. Ferrate(VI) was quite effective for the removal of constituents in graywater. Applying $75\mathrm{mg}/\mathrm{L}$ ferrate(VI) dose at pH 7 was successful at removing organic pollutants and total coliforms (TCs). Besides, more than 73% anionic surfactant degradation was achieved at the same conditions. According to reuse regulations, treated graywater by electrosynthesized ferrate(VI) can be used for unrestricted reuse options. Additionally, the greater removal of organics by ferrate(VI) reduced the potential of bacterial regrowth and additional chemical disinfectant demand.

This investigation involved a column study and model simulation to evaluate longevity of zero-valent ion (ZVI) and pervious concrete (PERVC) reactive barriers for treatment of acid mine drainage (AMD). Each of the reactive media were evaluated for sorption capacity and hydraulic performance under the dynamic flow conditions of a column setup. The test data obtained were applied to the one-dimensional advective-dispersion transport equation to predict geochemical changes in concentration of contaminants flowing through a reactive barrier, as a function of time and distance. PERVC was found to be more effective in contaminant removal from AMD than ZVI. PERVC raised the pH of AMD from 2.99 to an average value of 11, compared with a maximum pH of 9 attained by ZVI treatment. While both media achieved complete removal of the main contaminants comprising Al, Fe, and Zn, the PERVC containing 30% fly ash (30FA-PERVC) had greater retardation factors and higher overall removal efficiency than ZVI. The hydrodynamic dispersion coefficient for 30FA-PERVC was 0.4 to $4\times {10}^{-4}{\mathrm{m}}^2/\mathrm{s}$ compared with 0.2 to $5\times {10}^{-6}{\mathrm{m}}^2/\mathrm{s}$ for ZVI. A barrier wall of 1.5 m thickness was estimated to provide indicative treatment life spans of 5 and 10 years for ZVI and 30FA-PERVC reactive media, respectively. Based on these results, the longevity of 30FA-PERVC reactive barriers can be about twice that of ZVI barriers.

Biochar, which is rich in aromatic carbon and minerals, is a product of biomass pyrolysis at temperatures ranging from 350 to 1,000°C in oxygen-limited environments. In recent years, biochar has generated much interest in the field of water treatment in view of low production costs, availability of the feedstock (e.g., lignocellulosic biomass waste), and adsorptive properties. In this study, lignocellulosic feedstock from control and contaminated sites was pyrolyzed under 450°C for 2 h. The novelty of this study was consideration of the natural modifications of biochar and their influence on principal adsorptive characteristics of the biochar. The aim of this study was to determine the influence of intrinsic properties of lignocellulosic feedstock on adsorptive properties of biochar. Intrinsic properties of lignocellulosic feedstock, such as lignin, C, O, H, N, moisture and ash content, and Pb, Zn, Cu, Cr, Ni, Cd, Mg, and Fe concentrations, were analyzed. Adsorptive properties of biochar, such as cation exchange capacity (CEC), Brunauer–Emmett–Teller (BET) surface area, surface functionality, carbon, oxygen, hydrogen, nitrogen (COHN), moisture and ash content, and Pb, Zn, Cu, Cr, Ni, Cd, Mg, and Fe concentrations, were investigated. It was found that a larger amount of lignin (54–59%), ash (11.8–13.9%), nitrogen (0.4%), and Zn ($182\mathrm{mg}/\mathrm{kg}$) and a lower carbon content (75–76%) in lignocellulosic feedstock may favor the adsorptive characteristics of biochar.

Hydraulic and mixing efficiencies of contact tanks are evaluated using several indexes that are used in the literature. These indexes emphasize different aspects of flow and mixing processes in the mixing tank at different scales. Uniformity of the evaluations obtained from these indexes is necessary for unified characterization of the overall performance of contact tanks, which is very difficult to achieve. In this study, several contact tanks with different baffling configurations were studied using computational fluid dynamics (CFD) analysis in which three-dimensional hydrodynamic analysis of flow and transport of a conservative tracer within the flow field were studied. The performance data developed were extended by including the outcome of some of the earlier studies that are reported in the literature. The most common indexes that are used in the literature were used to evaluate the performance of these cases. The results indicate that the performance evaluation obtained for these cases was not consistent for all indexes. An analysis was performed to identify the suitability of the performance indexes for a specific performance parameter. Performance of the newly introduced AD index, which yields more consistent evaluations for both short-circuiting and dispersion evaluation in the contact tank, was compared with the performance of the Morrill index. A dimensionless energy-efficiency index was also proposed for the evaluation of the efficiency of the flow-through system in the tank.

Steel slag, one of the by-products from the production of steel, is crushed, sized properly, and treated in relation to its volume swelling potential to be used as a highly resistant aggregate called steel aggregate or steel gravel. This study analyzes the swelling mechanisms of steel aggregate. By laboratory testing, the volumetric swelling potential in samples of steel aggregate and samples of lateritic soil and steel aggregate mixtures was determined in two different proportions: 90% soil $+10\%$ steel aggregate (M9010); and 80% soil $+20\%$ steel aggregate, by weight (M8020). This analysis is part of a project that assesses the feasibility of the utilization of this coproduct in the construction industry in Brazil. Average swelling values of 0.92, 0.73, and 0.61% were obtained from the steel aggregate samples and from the M9010 and M8020 mixture samples, respectively. According to Brazilian and Japanese standard volumetric swelling limits, all tested materials are suitable for the use of paving as an alternative to the use of natural aggregates.

A profile probe (PP) is a handy instrument for simultaneously measuring volumetric water content ($\theta$) at shallow multiple depths in the field. The accuracy of the $\theta$ measurement is important for moisture migration and water balance studies associated with the multilayered cover system (MLCS) provided over nonoperational landfills. There are no guidelines or controlled procedure for evaluating the accuracy of a PP for varying layers of an MLCS. A simple laboratory setup is developed in this study to evaluate all six sensors of a PP simultaneously for a particular soil type and compaction state. The results obtained from this study were used to improve the accuracy of PP measurements for the type of soils generally used in MLCSs. The validity of the proposed procedure was further evaluated based on a new set of PP measurements. The procedure adopted in this study improved the accuracy of PP measurement from $\pm 6\%$ to $\pm 1\%$. The most interesting observation is the parity in sensor readings by following the proposed procedure, which was initially found to be different. The results from this study indicated that improper $\theta$ measurements can result in an error as high as 18% in the determination of change in soil water storage for different layers of a trial MLCS. Adopting the procedure proposed in this study ensures reliable and precise $\theta$ measurements for the materials used in MLCS for all the sensors of PP. In the absence of soil-specific calibration for PP, the equations proposed in this study can be used for the type of soils used in MLCSs.

This study investigated the sludge drying from a facultative pond in a dryer that employs two dehydration methods: thermal drying by infrared lamps and convective drying. For the tests, three thicknesses of sludge were used (10, 25, and 50 mm) and different drying times (6 and 12 h). From the results, the data obtained was compatible with the adjustment of eight mathematical models utilized for thin layers (Newton, Henderson and Pabis, Page, two-term Wang and Singh, logarithmic, diffusion approximation, and Midilli) by four statistical parameters: determination coefficient ($R^2$), reduced chi-square (${\chi }^2$), root mean square error (RMSE), and mean relative deviation modulus ($P$). Even though this work used sludge layers greater than those found in the literature, the results for any mathematical model were satisfactory ($R^2>0.9931$). The Midilli model was the best in describing the drying behavior of the three thicknesses ($R^2>0.9996$). These results support the use of thin layer models for facultative pond sludge drying, and it could be a practical tool for dryer projects using large thickness.

Municipal solid waste (MSW) permeability is influenced mainly by compaction, unit weight, overburden pressure, composition, and biodegradation of the waste. However, the variation of hydraulic conductivity with MSW biodegrading over time has not yet been sufficiently studied, and consequently not fully understood. This study aimed to present the saturated hydraulic conductivity ($K_{\mathrm{sat}}$) of the MSW, considering the influence of anaerobic biodegradation, by using two large-scale rigid wall permeameters (P1 and P2) in two experimental groups. The leachate produced was subjected to physicochemical analysis. The MSW confined in both permeameters presented similar gravimetric composition and total mass but diverse initial unit weight, ranging from 4.9 to $7.2\mathrm{kN}·{\mathrm{m}}^{-3}$. Maximum and minimum values of $K_{\mathrm{sat}}$ obtained for the confined MSW were $2.0\times {10}^{-2}{\mathrm{ms}}^{-1}$ and $7.4\times {10}^{-6}{\mathrm{ms}}^{-1}$, respectively. Physicochemical analysis indicated that MSW biodegradation in permeameters remained in the anaerobic acid phase. The methodology adopted for the permeability tests influenced the MSW biodegradation, and consequently its hydraulic behavior. It is believed that, during 7 days before the permeability tests, the drained gas changed the MSW mass structure into the permeameters and the $K_{\mathrm{sat}}$ values over time. Within the permeameters with higher unit weight MSW, the $K_{\mathrm{sat}}$ values increased for up to 3 months, tending to stabilization.

Water Infrastructures play an important role in serving societies, and ensuring the proper performance of these facilities has received great attention recently. Growing hydrometeorological hazards, including coastal flooding, have posed a challenge to the management of water infrastructures. Reliability and resilience are two concepts for analyzing systems performance and behavior. Although there are various and sometimes even contradictory definitions in literature, in general, reliability relates to the successful performance of infrastructure within a defined period, whereas resilience relates to the capability of a system to return to normal operation when it is subject to malfunction due to the impact of hazards. This paper presents a framework for assessing the resilience and reliability of a typical wastewater-treatment plant under coastal flooding. Two main causes of the plant malfunction include increasing flow rate of influent to the plant (operational failure) and inundation of unit operations (structural failure). The performance of the plant is analyzed during a storm, assuming the full operation of each unit operation and the effluent concentration is obtained and compared with the standards limit. Next, the impact of structural failure is considered by lowering the removal rate of those unit operations that become inundated. Finally, the effect of some interventions in wastewatertreatment plant control strategy is assessed by comparing the resilience and reliability after implementing these adaptations. For resilience assessment, the concept of performance curves is used and three indicators are computed; to estimate reliability, the load-resistance concept is used and compared with the classical expected compliance percentage method. The methodology is applied to a wastewater treatment plant in New York City. Results show high resilience and reliability of biological parameters, which means that they are not greatly affected by the storm compared with total suspended solids and the nitrogen parameter. Furthermore, although the duration of the structural failure is short, the consequence of flooding is severe, which is demonstrated by low resilience based on magnitude. The interventions have various effects on different effluent parameters, improving some and degrading others, so evaluating trade-offs and making informed decisions will be necessary.

This research assessed how design factors (i.e., soil media and vegetative composition) influenced flow rates and pollutant mass removal in eight roadside bioretention systems under simulated increases in precipitation due to climate change. Labile and nonlabile nitrogen and phosphorus (N and P) mass and total suspended solids (TSS) removal was evaluated on an equal volume basis. Results confirm that bioretention systems are a useful tool for increasing local climate change resiliency; peak flow rates and volumes were significantly reduced in all treatments. Water quality performance was highly dependent on the design factors. Sorbtive Media was found to significantly enhance soluble reactive phosphorus removal, which was exported in the conventional media treatments. Labile and nonlabile pollutant retention in the two-species plant palette was higher than in the seven-species palette. This was attributed to the deep, fibrous rooted systems of the Panicum virgatum. Nonlabile pollutant constituents (i.e., TSS and nonlabile N and P) were well retained in all treatments, yet the labile N and P in the compost amended soil media (60% sand and 40% compost) were found to exceed the mass loads in incoming stormwater.

The sulfate release from solidified/stabilized fluorogypsum was measured to develop the effective diffusion coefficients (${\mathrm{D}}_{\mathrm{e}}$) as a parameter to assess the dissolution potential in aquatic applications. Specimens from 11 compositions consisting of 60–90% pH-adjusted fluorogypsum (pFG), 2–10% Type I/II portland cement (PC), and 0–38% Class C fly ash (FA) were exposed to solutions of $30{\mathrm{g}\mathrm{L}}^{-1}$ (saltwater), $15{\mathrm{g}\mathrm{L}}^{-1}$ (brackish water), and $0.5{\mathrm{g}\mathrm{L}}^{-1}$ (freshwater) total dissolved solids (TDS). The effects of composition and salinity, measured as the TDS, on the sulfate ${\mathrm{D}}_{\mathrm{e}}$ were determined to select the compositions for use in various aquatic environments. The results indicated that the solidified/stabilized pFG had a lower dissolution potential in saltwater and freshwater in comparison with brackish water. On the basis of the low ${\mathrm{D}}_{\mathrm{e}}$ and low critical times (the time when the diffusion out of the specimen equals the precipitation onto the specimen), a composition of 80% pFG, 10% PC, and 10% FA is recommended as an alternative to limestone in saltwater and freshwater applications.

We modeled the transport of 12 organic compounds through five different reactive media under diffusion and advection using deterministic and Monte Carlo methods to evaluate their effectiveness for sediment capping and/or liners. A broad range of media contaminant site scenarios are provided to aid in the selection of reactive media to address a broad range of organic sediment contaminants under diffusion or advection scenarios. Organic compounds evaluated include monoaromatics, polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs), and alkanes covering a wide range of organic pollutants commonly found in contaminated sites. We investigated the performance of the reactive media granular activated carbon (GAC), organoclay (OC), shredded tires (ST), and apatite (AP) in comparison with the performance of conventional sand media. Based on the modeling results, a 2-cm GAC layer is predicted to be as effective to reduce organic contaminant transport as a 1- to 3-m-thick sand layer. Performances of GAC and OC were similar under both diffusion and advection due to their low observed diffusivity coefficients. As expected, low molecular weight compounds (e.g., monoaromatics and naphthalene) present a higher potential release risk. In contrast, pyrene, hexachlorobiphenyl, and tetradecane do not present toxicity concerns at the 95% confidence level after 100 years under diffusion and/or advection (except in AP/sand configurations). Lower acute toxicity contaminants such as benzene and dichlorobiphenyl are predicted to behave similarly for most media under advection, with partial breakthrough within 100 years. Performance uncertainty is substantially lower for organic contaminant transport simulations compared with those in a previous metal contaminant transport study. The relative GAC and OC effectiveness increases with increasing contaminant hydrophobicity. This behavior may be a key decision factor to select GAC and/or OC media at sites with highly hydrophobic and low toxicity/solubility ratio contaminants such as dichlorobiphenyls.

The feasibility of enhanced degradation of bis(2-ethylhexyl) phthalate (DEHP) by activated sludge inoculated with DEHP-degrading strains at a low temperature (10°C) and microbial community dynamics was investigated in a sequencing batch reactor. Bioaugmentation shortened the start-up period and significantly improved the DEHP degradation efficiency. At an influent DEHP concentration of $0.1\mathrm{mg}{\mathrm{L}}^{-1}$ and an operating temperature of 14°C, DEHP removal rates of 74.3 and 34.2% were recorded on Day 21 in the bioaugmented and noninoculated control reactors, respectively. Successive increases in the DEHP concentration to $0.4\mathrm{mg}{\mathrm{L}}^{-1}$ and the operational temperature to 10°C resulted in poor bioreactor performance. Only 57.4 and 16.3% of DEHP in the test and control reactors was removed on Day 78, respectively. The addition of glucose significantly improved the performance of the two bioreactors ($p<0.05$), and 79.8 and 36.4% DEHP removal was achieved in the test and control reactors on Day 100. Real-time quantitative polymerase chain reaction (q-PCR) analysis showed that the 3,4-phthalate dioxygenase gene (phtA) and DEHP removal were positively correlated ($r=0.95$, $p<0.05$) during Phase I (the start-up period) and Phase II (with increased DEHP concentration and decreased temperature). Illumina sequencing analysis revealed that there was an obvious shift in the bacterial community during the bioaugmentation process. The relative abundance of Thauera, Nitrospira, and Nitrosomonas gradually decreased with decreasing temperatures and increasing DEHP concentrations. In contrast, Rhodococcus, Arcobacter, and Acinetobacter species continuously increased, concomitantly with increased DEHP removal. Overall, Rhodococcus, Arcobacter, Acinetobacter, Alcaligenes, and Bordetella contributed to a significant increase in DEHP degradation and were probably the key genera responsible for DEHP wastewater treatment at low temperatures.

Perfluoro-alkyl substances (PFAS) have drawn increased concern in recent years. Due to resistance to many remediation methods and potential for long-range transport, there is need for continued in situ remediation technique development. One such method is enhanced sorption onto aquifer material, thereby sequestering a plume and preventing long-range migration. Batch tests and column studies were carried out to evaluate the ability of polydiallyldimethylammonium chloride (PDM) and polyamine (PA) to enhance the adsorption of six PFAS onto Ottawa sand. At a dosage of $\mathrm{2,000}\mathrm{mg}/\mathrm{L}$ of either PDM or PA, results show increases of adsorption of the tested PFAS in all batches by factors of 3.6–45. Column studies showed retention capacity increasing up to six times for perfluorooctanoic acid (PFOA) and 10 times for perfluorooctane sulfonic acid (PFOS). Normalizing partitioning coefficients from batch tests to fraction of organic carbon suggest that an interaction other than PFAS associating with organic matter may be the main driving force behind sorption enhancement. These results suggest that this method shows promise for in situ remediation of PFAS-contaminated groundwater.

In this paper, manganese oxide octahedral molecular sieves (OMS-2) as a novel catalyst were used in activation of persulfate (PS) for Remazol Brilliant Blue R (RBBR) dye removal. The dye removal efficiencies of different systems including OMS-2 only, PS only, and OMS-2/PS were evaluated, and complete removal using the OMS-2/PS system was achieved in 30 min. It was found that operation parameters such as pH, OMS-2, PS, and RBBR concentrations affected RBBR removal. The OMS-2/PS system exhibited excellent catalytic activity in the pH range of 2.52–8.09. The reaction time decreased with increasing OMS-2 and PS concentrations. Quenching tests using tert-butanol and ethanol suggested that sulfate radicals in the OMS-2/PS system are the dominant reactive species. The RBBR degradation reactions could be well-described by the first-order kinetic model. In the optimized condition, total organic carbon (TOC) removal efficiency was 56.8% after 60 min. Ultraviolet-visible (UV-vis) spectra were used to ascertain the OMS-2/PS system. The practical applicability of the OMS-2/PS system was also investigated for simulated wastewater.

Glycogen is a chief metabolic storage pool in bacteria performing enhanced biological phosphorous removal (EBPR) and is a potential resource for the production of bio-based fuels and chemicals. Quantifying glycogen at full-scale EBPRs is necessary to evaluate viability. To more fully understand resource potential, both sampling location and lab-scale quantification methods were compared to ensure suitable assessment. Sampling location, before and after final clarification, indicated that clarification selects for high-glycogen flocs and concentrates glycogen with respect to solids—in this case by 51%. Two assays were compared for glycogen quantification of lyophilized sludge: acid treatment (0.9 M HCl) and alkaline treatment [5 M potassium hydroxide (KOH)], both at 100°C for 3 h. Alkaline treatment recovered only 58% of glycogen in known standards versus 96% for acid treatment. The acid method was successfully applied to waste-activated sludge (WAS) from seven different treatment facilities, which ranged from 2.5 to 2.8% of solids as glycogen. The results represent the first broad survey of glycogen in full-scale EBPR systems and indicates that it is a modest resource potential.

The removal of Cr(VI) from synthetic wastewater using living cyanobacteria Limnococcus sp. was examined. Characterizations of the native and metal loaded cells were done using scanning electron microscopy, energy-dispersive spectroscopy, and Fourier transform infrared spectroscopy. The operating condition was optimized using one-factor-at-a-time analysis. Maximum Cr(VI) removal (63.23%) was achieved with initial Cr(VI) concentration $20\mathrm{mg}/\mathrm{L}$, pH 9.0, inoculum size 10% [volume per volume (v/v)], and incubation period 16 days. The distribution of Cr(VI) on the cell surface through biosorption and in the intracellular space through bioaccumulation were also determined. The logistic model was used to design the variation of growth of the biomass with time. Maximum specific growth rate (${\mu }_m$) was determined to be $0.31/\mathrm{day}$. The maximum carrying capacity of the synthetic wastewater observed was $0.857\mathrm{g}/\mathrm{L}$ with initial Cr(VI) concentration of $20\mathrm{mg}/\mathrm{L}$. An empirical power-law model was also developed to predict the interactive effect of the initial Cr(VI) concentration, pH, inoculum size, and incubation time with the cell dry mass (CDM), percentage removal of Cr(VI), and lipid content.

Manganese oxide adsorbent materials were prepared from alkaline battery manufacturing and postconsumer waste. Specifically, electrolytic manganese dioxide (EMD) was obtained from a battery manufacturing facility, and cryptomelane, a $2\times 2$ tunnel octahedral molecular sieve structure, was synthesized from postconsumer waste alkaline batteries. For comparison, cryptomelane was synthesized using purchased chemicals. The manganese oxide materials were characterized and investigated as adsorbents for heavy metals in water. Adsorption isotherms and column studies were conducted at room temperature for each manganese oxide material. The heavy metals selected for this study included lead (Pb), cobalt (Co), and cerium (Ce). The unique feature of this study was that the manganese oxide materials investigated were derived from preconsumer and postconsumer alkaline batteries. The study highlighted the impacts of the chemical and physical properties of the manganese oxide materials for adsorption capacity for the selected heavy metals. The results of this study support that adsorbents capable of removing heavy metals from water can be prepared from postconsumer alkaline batteries.

Accelerating the dewatering of oil sands tailings is a crucial challenge to the oil sands industry. Fresh tailings (15–20% by weight solids) and mature tailings (30–35% by weight solids) dewater slowly over a period of decades or centuries, and have resulted in the accumulation of $\mathrm{1,075}{\mathrm{Mm}}^3$ of tailings in tailings ponds, the equivalent of 430,000 Olympic-size swimming pools. UltraZyme Hydrocarbon Powder (UltraZyme), a proprietary biological amendment of microbes, enzymes, and organic carrier developed by Cypher Environmental Ltd., was tested for its ability to accelerate dewatering and improve expressed pore water quality in three types of tailings. The effects of varying temperature, nitrogen addition, initial solids content, and UltraZyme dosage were also investigated. A 30% increase of solids content could be achieved in 112 days in all three tailings sources using $1.0\mathrm{g}/\mathrm{L}$ of UltraZyme without physical mixing. Increasing the temperature to 55°C yielded similar results in only 14 days. High UltraZyme dosages and low initial solids contents had the most positive impact on dewatering rates, and UltraZyme addition caused detoxification of expressed pore water (toxicity $\text{unit}<1$, by Microtox bioassay) and improved dissolved organic carbon (DOC) (27% removal for MFT-D1 and 16% removal for MFT-D2) and naphthenic acids (NAs) (38–46% removal for MFT-Mix). UltraZyme was unable to degrade bitumen, but was capable of reducing bitumen-derived toxicity.

Retention tanks are constructed to mitigate peak floods and capture sediments by storing combined sewage overflows. A rotatable bucket is used to sweep the settled particles at the bottom of retention tanks. The bucket rotates naturally by the force of gravity when filled with water, and the water drops from the bucket, consequentially cleaning up the sediments that have sunk to the bottom of the retention tank. In this study, a numerical simulation and scaled-down experiments were performed to investigate the influence of the design parameters—bucket height, bucket size, and bottom slope of the retention tank—on cleaning efficiency. The numerical simulation was executed based on a sediment scour model using FLOW-3D commercial software. The sediment scour model was simultaneously combined with a renormalized group (RNG) model to express a viscous and turbulent flow and with a general moving object (GMO) model to describe the bucket rotation. The amount of sediment left on the bottom of the retention tank was strongly dependent on bucket radius and less dependent on bucket height and bottom slope. When the bucket was designed with a height of 5 m, radius of 0.5 m, and bottom slope of 5%, approximately 97% of the sediments were washed out. An experiment using a scaled-down model produced by a three-dimensional (3D) printer based on the law of similarity was also conducted to verify the numerical model’s accuracy. The relative error of the total amount of sediments left on the retention tank bottom between the simulation and experiment ranged from 4.6 to 9.7%. A retention tank with rotatable bucket could be used to store overflow water with less energy for maintenance of sediment buildup.

Ferrate(VI) ($[{\mathrm{FeO}}_4{]}^{2-}$) is one of the innovative oxidation processes that has a strong oxidizing power. In this study, degradation of toluene has been examined using liquid sodium ferrate(VI) and solid potassium ferrate(VI). The effects of pH, molar ratio, and temperature on toluene removal by both ferrates(VI) were investigated. The highest toluene removal efficiency was achieved at neutral pH condition ($\mathrm{pH}=6.8$) after a reaction period of 20 min. For the effect of molar ratio, the degradation efficiency increased as the molar ratio increased. The highest toluene degradation was achieved at molar ratio $[({\mathrm{FeO}}_4^{2-}]:[\mathrm{Toluene})]$ of 4.23:1 by both ferrates(VI). The optimal temperature was 45°C with ${\mathrm{k}}_{\mathrm{app}}$ value of $389.07{\mathrm{M}}^{-1}{\mathrm{s}}^{-1}$ and activation energy of $79.4\mathrm{kJ}/\mathrm{mol}$ for liquid ferrate(VI), and ${\mathrm{k}}_{\mathrm{app}}$ value of $567.21{\mathrm{M}}^{-1}{\mathrm{s}}^{-1}$ and activation energy of $76.8\mathrm{kJ}/\mathrm{mol}$ for solid ferrate(VI). The intermediate products such as heptanal, 3-methylbutanal, 2-methylhexane, 2-methylbutan-1-ol, 1-chlorobutane, 4-chlorobutane-1-ol, and 1-chloro-2-methylpropane were identified and the possible degradation pathways have been proposed.

Coastal eutrophication is an important problem, and nitrogen input from the watershed is a primary cause. Consequently, management efforts often focus on lowering watershed N export by reducing the N loading (e.g., from point sources), and models are used to evaluate alternative reduction scenarios at the watershed scale. Existing models generally assume lake export decreases proportionally with loading. However, reducing N loading lowers the N:P ratio, and N fixation by cyanobacteria may increase, which may change the effective N export fraction (export/external input). This paper explicitly considers how lake N fixation may change when N loading is reduced and estimates the reduction in lake and watershed N export. A simple model, Fixation and Export of Nitrogen from Lakes (FENL) is developed; implemented into a watershed model, Spatially Referenced Regression on Watershed Attributes (SPARROW) of the Chesapeake Bay Watershed; and applied to predict steady-state N export under various management scenarios. The results suggest that lake and watershed N export will not be reduced proportionally with N loading. Under a 60% N-only reduction scenario, the model predicts that the majority of the lakes in the watershed are pushed into the N-fixation regime, which increases lake N fixation rate by a factor of 5.6 and may result in an equal increase in the concentration and blooms of N-fixing cyanobacteria. The model-predicted response is heterogeneous and suggests there are more-vulnerable and less-vulnerable regions, which may be exploited for more cost-effective management. The added N by fixation counteracts the N loading reduction, but the effect on the watershed export is small for Chesapeake Bay. In contrasts to a watershed load reduction of N alone, a balanced $\mathrm{N}+\mathrm{P}$ reduction (say, of 60%) will not change the N-fixing state (fixing N or not fixing N) of lakes and result in the same percentage reduction in watershed N export (i.e., also 60%) as the watershed load reduction.

A major drawback to land application of biosolids is the potential environmental release of nonregulated organic contaminants that accumulate in the biosolids during the wastewater treatment process. In particular, because some of the substances found in biosolids are designed to kill microorganisms (i.e., are disinfectants), there is a risk that these compounds could disrupt microbial ecology and negatively impact nutrient cycling, impacting soil and plant health in the long term. This study takes samples from four agricultural fields receiving liquid biosolids over a 150-day period, measures initial triclosan concentrations, and characterizes impacts by assessing changes in the denitrifying microbial community structure and function. Overall, a decrease in denitrification activity and denitrifier abundance is observed after 100 days following application. Although these data suggest that biosolids may affect denitrification, the effects cannot be attributed to biosolids application nor to the triclosan contained within the biosolids.

When local sanitary sewers discharge to regional treatment systems, flow monitoring is performed for billing purposes, but the information content of these flow data is often overlooked. Wastewater flow data provide information to: (1) quantify rainfall-derived infiltration and inflow, (2) detect flow spikes that could indicate improperly connected sump pumps, and (3) observe long-term increases in peak flow that threaten a surcharge (i.e., when the sewer fills completely). These points are illustrated through a case study from the Mansfield Heights Water & Sanitation District, Arapahoe Country, Colorado using simple methods including novel refinements. It is shown how prophylactic analysis of wastewater flow data might have predicted a surcharge that resulted in public exposure to waterborne pathogens and extensive property damage. Anecdotal estimates from the Denver, Colorado metropolitan region suggest that approximately 80% of sanitation perform flow monitoring, but essentially none evaluates these data routinely. Considering the value of flowmeter data, it is recommended that such data should be analyzed at least annually.

The overall mass of sodium chloride salt used to treat icy roads can be significantly reduced by pretreating roads or prewetting dry rock salt with concentrated brine solutions. Brine solutions can be made from rock salt; however, an alternative source of brine for some communities is brine that is a waste product of oil and gas extraction. This study compares contaminant chemistry of brine made from rock salt with literature data on oil and gas well brine from conventional and unconventional wells. In addition to reviewing existing literature, this paper analyzes four rock salt samples for a suite of chemical constituents. Maximum reported levels of some harmful contaminants are higher for well brines than for rock salt brines and are higher for unconventional than for conventional well brines. Because the regulatory structure for using well brines varies among states, the authors recommend a consistent approval process for permitting the use of waste brines that includes specific maximum allowable limits for potentially harmful contaminants, and that each batch of solution be tested before use. Although the use of brine, including waste brine, can reduce the overall amount of salt needed for snow and ice control, adequate steps should be taken to ensure the safety of the brine solutions before they are used.