Journal of Environmental Engineering

The goal of this research was to elaborate an effective and economical treatment system to eliminate nitrates from a large marine basin at the Aquarium du Québec. Several configurations of an autotrophic denitrification system using elemental sulfur were tested. Results showed that inoculums taken from various environments (soil, sewage sludge, wetland, pig manure, marine sediment) could be used to prepare denitrifying microbial cultures for a marine environment. Subsequent trials using a continuous-flow configuration with columns containing sulfur granules showed that a hydraulic retention time (HRT) of 16–19 h allowed the removal of nearly all of the nitrates present in the water (${[{\mathrm{NO}}_3\text{-}\mathrm{N}]}_i=25–30\mathrm{mg}{\mathrm{L}}^{-1}$). Furthermore, this study demonstrated that the insertion of oyster shell columns between the sulfur-containing columns led to an increase in pH and alkalinity of the treated water, maintaining a favorable denitrifying environment.

Heterogeneous photo-Fenton process with structured catalyst was investigated in the removal of two typical food azo dyes, red allura (RED) and tartrazine (TRZ). The influence of ${\mathrm{LaFeO}}_3$ loading (with and without Pt) on corundum honeycombs monolithic support was evaluated in the discoloration and mineralization of the target azo dyes. The results for discoloration were reported for different experimental conditions: UV, $\mathrm{UV}+{\mathrm{H}}_2{\mathrm{O}}_2$, $\mathrm{UV}+{\mathrm{H}}_2{\mathrm{O}}_2+\text{structured}\text{catalysts}$. In the case of UV alone the discoloration occurs very slowly and not completely (approximately 36 and 20% in 120 min of irradiation for RED and TRZ, respectively); but the process efficiency has been enhanced in the presence of ${\mathrm{H}}_2{\mathrm{O}}_2$ (approximately 77 and 80% in 5 min of irradiation for RED and TRZ, respectively). The best efficiency in RED dye discoloration and mineralization by heterogeneous photo-Fenton process was observed for a ${\mathrm{LaFeO}}_3$ loading equal to 4.5% by weight (complete discoloration and 95% of TOC removal in 60 min of irradiation time), whereas for TRZ dye the optimal ${\mathrm{LaFeO}}_3$ loading was lower (2.2% by weight) (total discoloration and TOC removal in 60 min of irradiation time). Pt loading of 0.1 wt% resulted in the highest total organic carbon (TOC) removal rate during RED dye solution treatment with together the highest ${\mathrm{CO}}_2$ selectivity. For TRZ, the higher the content of Pt on the catalyst, the better is the removal of TOC. The efficiency improvement obtained in presence of Pt can be explained considering that the noble metal suppresses to some extent the charge carriers’ recombination rate determining an increase of photo Fenton activity.

Management goals for many distribution systems include maintaining a minimum level of free chlorine and limiting disinfection by-products. As water resources become scarce and quality deteriorates, blends are often required, so achieving these goals becomes increasingly difficult. The augmented two-reactant (2RA) model describes chlorine decay in a single water, for various dosing levels and water temperatures. However, it is not known whether there is any effect on chlorine decay (either synergistic or antagonistic) arising from blending waters of distinctly different quality. Linked 2RA models of source waters were used to determine whether bulk decay in blends of various source waters could be accurately and generally modeled. Results showed that chlorine decay in blends of various waters could be described accurately without synergistic or antagonistic effects, implying that each water’s reactants reduced chlorine independently. This held for pairs of surface waters, groundwaters, and raw or treated surface water blended with desalinated water, for various initial chlorine doses and temperatures. Linked models can be incorporated immediately into system models, to predict bulk chlorine decay and trihalomethane (THM) formation in distribution systems supplied from several water sources.

The spread of aquatic invasive species during wildland firefighting activities is a concern when water sources and equipment are transported across watersheds or into pristine areas. In the present study, we investigated the capability of wildland firefighting foams to inactivate organisms in bench-scale laboratory experiments. Specifically, Escherichia coli and coliphage $\mathrm{\Phi }\mathrm{X}174$ were used to test the disinfection potential of foams against bacteria and virus species as an indicator of their efficacy against more resistant organisms. The U.S. Department of Agriculture Forest Service firefighting foams tested in this study did not inactivate E. coli or coliphage during maximum exposure conditions that are feasible during firefighting activities, i.e., 10% (v:v) mix ratio and a 60-min contact time. We did not examine whether firefighting foams were effective at displacing bacterial and viral organisms when used solely as a surfactant on solid surfaces. We conclude that fire retardant foams are not effective disinfection agents and will not reduce the risk of spreading aquatic invasive viral species during firefighting activities.

Pump and treat (P&T) is one of the most commonly used technologies to remove and/or contain contaminated groundwater. An appropriate delineation of capture zones is necessary to design an effective P&T system. The study presented in this paper focuses on developing a feasibility level methodology to estimate capture zone widths for photovoltaic (PV)-powered P&T systems without energy storage throughout the continental United States as a function of daily average solar insolation data, transmissivity, and hydraulic gradient. Maps depicting predicted capture zone widths for specified transmissivity values and a hydraulic gradient are developed. The applicability of the developed methodology is illustrated with two actual sites where groundwater remediation has taken place. The methodology presented in this study can be used to assess the feasibility of PV-powered P&T systems without energy storage, in terms of capture zone width, anywhere within the continental United States. Detailed capture zone analysis should be performed during system design.

Numerical simulations of the sediment-air-water buoyant jet released through the hopper dredgers’ overflow shaft have been performed. The release of sediments into the marine environment due to skimming the excess water from the dredging vessel’s hopper can lead to increased turbidity and adverse effects on the adjacent environment. Base-case simulations have been validated using in situ field observations. Simulations have been performed using the large-eddy simulation technique, which allows including the effect of large turbulent structures on the sediment dispersion. The complex nature of the flow field poses challenges for numerical simulations, such as the presence of propeller jets and three different phases: water, sediment, and air bubbles. The model has been applied to simulate the effect of a so-called environmental valve, which reduces air inclusion. This valve has been used in the past, but its efficiency as a function of the boundary conditions was never analyzed before. It is shown in this article that this type of valve can be very effective in reducing the generated turbidity, but only under given combinations of dredging speed, sediment concentration, overflow shaft diameter and overflow-stern distance.

The activated sludge process constitutes the most widely used wastewater treatment. The main drawback of this biological technology, however, is the excess sludge produced (ESP). In fact, disposal and management of this waste is one of the most expensive management costs at wastewater treatment plants (WWTP). Cell lysis based on the lower net biomass growth under cryptic conditions is one way to minimize the ESP directly in the water line. Ozone is a powerful oxidant used for this purpose. This paper reports the long-term data obtained at a full-scale plant (50,000 PE) where a fraction of the recycled sludge is treated with a low specific ozone dosage and a high treated sludge rate of approximately $0.5\mathrm{kg}{\mathrm{MLVSS}}_{\text{ozonated}}/\mathrm{kg}{\mathrm{MLVSS}}_{\text{biological}}/\mathrm{d}$. The study presents results in terms of ESP reduction and the effect of ozone on the main WWTP performance parameters. Specific tests at different specific ozone dosages (SOD), ranging between 0.7 and $5\mathrm{g}{\mathrm{O}}_3/\mathrm{Kg}\mathrm{MLVSS}$, were carried out to assess biomass activity changes (AUR, NUR, and PAO activity), gravitational behavior, soluble chemical oxygen demand (SCOD) release, and variation in the nonbiodegradable chemical oxygen demand (NBCOD) fraction. The main kinetic parameters under study did not change above a threshold of SOD of $2\mathrm{g}{\mathrm{O}}_3/\mathrm{Kg}{\mathrm{MLVSS}}_{\text{treated}}$. Furthermore, a comprehensive full-scale analysis determined an overall ESP reduction of 10% in terms of dry solids. Finally, an analysis of the energy consumption and economic feasibility of this technique is also reported.

The Shafdan wastewater treatment system treats the municipal wastewater of the Tel-Aviv metropolitan area, which contains 22 cities with a population of about two million. The conventional mechanical–biological treatment is followed by managed groundwater recharge. The effluent undergoes soil aquifer treatment (SAT) by controlled passage through the unsaturated zone and an average retention time of 960 days in the aquifer. The SAT provides effluent polishing treatment as well as seasonal and multiannual storage, which are much needed in the semiarid Mediterranean climate. The Shafdan SAT operates without disinfection prior to the land spreading of the secondary effluents or after the water is reclaimed from the aquifer. Despite that, since 1995 there has not been even a single positive test of fecal coliforms (FC) in any of the reclamation wells, and since 2001, all of the enterovirus tests in an observation well located midway between the infiltration basins and the reclamation wells were negative. The few positive cases of fecal coliforms that were reported before 1995 are well within the anticipated rate of the method’s false positives. The reclaimed water complies with all of the water quality specifications of drinking water except for the provision of a disinfection step. The SAT provides efficient reagentless physical pathogen removal, superior to chlorination and without its adverse health effects. It is therefore maintained that even without predisinfection and post-disinfection, the reclaimed water is safe for unrestricted irrigation of crops that are consumed raw and also for unrestricted nonpotable urban reuse. The high stability provided by the long retention time and reagentless disinfection obviates the need for frequent sampling, though assurance of no bacterial regrowth in the distribution system should be effected by monitoring and/or maintaining residual disinfectant. The endorsement of leading water reuse guidelines should be considered in view of these findings.

Subsurface processes alter the physical and chemical properties of fluid injected for hydraulic fracturing, with implications for its transport and fate in fractured or porous media. Models used to evaluate potential hydraulic fracturing–fluid migration lack formation-specific data to constrain temporal and thermal variation of the physical parameters that govern fluid movement. Density increases of 9.8% and viscosity increases of 26.5% were observed in produced water samples from three horizontally-drilled wells in the Marcellus shale, Pennsylvania, USA over a period of 11 months after hydraulic fracturing. Fluid density and viscosity rapidly increased during the first two weeks after fluid injection because of greater concentrations of dissolved inorganic ions, and plateaued within two months. When experimentally subjected to formation-relevant temperatures, mean density and viscosity decreased by up to 2.7 and 44.4%, respectively, between 20 and 60°C. These measurements yield new data to better constrain constitutive relations in flow and transport models evaluating the migration of hydraulic-fracturing fluid between a wellbore terminus and other subsurface locations.

The effectiveness of the Bacillus thermoamylovorans-enabled digested sludge in catalyzing cellulosic fermentation was tested under batch, mesophilic (40 plus or minus 1°C), unacclimatized, and high-loading (1.6 g cellulose in 80 mL aqueous solution) conditions. B. thermoamylovorans isolated from a molasses-fed anaerobic bioreactor was capable of quickly converting cellulose to alcohols and volatile organic acids (VOAs) at an overall rate of $0.32\mathrm{g}{\mathrm{COD}}_{\mathrm{S}}/\mathrm{g}$ VSS-day [volatile suspended solids (VSS), soluble chemical oxygen demand (${\mathrm{COD}}_{\mathrm{S}}$)] without producing ${\mathrm{H}}_2$. The digested sludge grown on pig manure, after an initial lag of 6 days, was able to produce ${\mathrm{H}}_2$, alcohols, and VOAs from cellulose at the rates of $0.021\mathrm{L}{\mathrm{H}}_2/\mathrm{g}$ VSS-day and $0.16\mathrm{g}{\mathrm{COD}}_{\mathrm{S}}/\mathrm{g}$ VSS-day, respectively. The experiment which used a mixture of 0.014 g B. thermoamylovorans and 0.172 g digested sludge yielded the best results, with about 11-fold and sevenfold rate increases in ${\mathrm{H}}_2$ production and acid fermentation, respectively, compared to the digested sludge. Moreover, the initial lag of the B. thermoamylovorans-enabled digested sludge was reduced to about 3.0 days. In addition to ${\mathrm{H}}_2$, the main end products included ethanol ($\mathrm{2,300}\mathrm{mg}/\mathrm{L}$), acetic acid ($\mathrm{2,300}\mathrm{mg}/\mathrm{L}$), and butyric acid ($\mathrm{3,600}\mathrm{mg}/\mathrm{L}$). Under the conditions tested, the presence of cooperative interactions between B. thermoamylovorans and digested sludge was evident, provided that the mass of the former was small relative to that of the latter in the mixture cultures (i.e., 3–8%).

This paper introduces the use of hierarchical Bayesian modeling as a method to estimate how kinetic properties of environmental contaminants vary across experimental factors. The hierarchical modeling framework utilizes a multilevel statistical structure, in which kinetic rate constants represent contaminant degradation behavior for individual, lower-level experiments, but also exhibit a higher-level structure across different experimental conditions. The main benefit of this modeling approach is the ability to pool information between experiments in order to reduce the influence of outliers and produce more robust predictions of degradation rate constants in an out-of-sample context. The Bayesian estimation method is also very flexible, with the ability to relax distributional assumptions on parameters, account for heteroscedasticity in model residuals, include prior information or expert knowledge when available, and propagate all uncertainties into model predictions, all with relative ease. The benefits of the hierarchical Bayesian approach are demonstrated in a case study examining the pH dependence of hydrolysis rates of haloacetamides (HAMs). A comparison is provided against a simpler least-squares method to highlight the differences and benefits of the proposed method.