Journal of Environmental Engineering

Biorefinery is a facility comprising industrial processes for the production of fuel and chemicals from biomass. Because there is a growing number of biorefineries worldwide, the related environmental aspects have to be studied. Following this context, this paper examines the application of horseradish peroxidase (HRP) for the treatment of high-phenol-content wastewaters from a biorefinery. The enzyme was characterized, and its optimal conditions for phenol removal were evaluated by an experimental design $2^{5-1}$ central composite rotatable design. The results showed a bioconversion yield above 99% using pH 6.32, enzyme concentration of 56.68 U, temperature of 28°C, $1.24\mathrm{g}/\mathrm{L}$ of hydrogen peroxide, and 35-min reaction time. The chromatographic analysis showed that, among total phenols, the 2-methoxyphenol was the majority compound, while many other phenolic compounds were present at trace levels. Furthermore, other physicochemical parameters were reduced after the enzymatic treatment, such as biochemical oxygen demand (98.13%) and chemical oxygen demand (49.39%). Enzymatic phenol removal using HRP can be a valuable strategy for biorefinery wastewater treatment.

Mill scale, an iron waste, was used to synthesize magnetite particles for the adsorption of phosphate from an aqueous solution. Several techniques were used to characterize the adsorbents. Mill scale–derived magnetite particles exhibited a strong uptake affinity to phosphate in a wide pH range of 3–7, with the maximum adsorptive removal of 100% at an adsorbent concentration of $1\mathrm{g}/\mathrm{L}$ and pH 3–5. The Langmuir isotherm model well described the equilibrium data, exhibiting maximum adsorption capacities for phosphate up to 4.95 and $8.79\mathrm{mg}/\mathrm{g}$ at 298 and 308 K, respectively. Kinetic data correlated well with the pseudo-second-order kinetic model, indicating that chemisorption is involved in the adsorption process. The phosphate adsorption was highly pH-dependent, and the presence of ${\mathrm{Cl}}^{-}$, ${\mathrm{SO}}_4^{2-}$, and ${\mathrm{CO}}_3^{2-}$ ions had no effect on phosphate removal. X-ray photoelectron spectroscopy (XPS) results revealed that phosphate was bonded onto the surface of magnetite predominantly through bidentate complexation. Desorption was performed on mill scale–derived magnetite to check recyclability. Five successive adsorption/regeneration cycles were successfully applied with a slight decrease in the adsorbent adsorption capacity.

This paper aimed to evaluate the process stability and microbial community structure during anaerobic digestion of food waste. Organic loading rate (OLR) disturbances were introduced into a mesophilic anaerobic digester treating food waste. The parameters evaluated included gas production, methane content, alkalinity, and volatile fatty acid (VFA) concentrations. The microbial community of each stage was analyzed by using 454-pyrosequencing. The results revealed that total VFA, acetate, and propionic acid displayed effective responses as indicators of process instability and system recovery. Process instability is closely related to high oil, high salt, and high protein concentrations. Total VFA, acetate, and propionic acid levels warned of impending process instability 7–8 days before system failure. They were also 3–8 days slower than other parameters during system recovery. The transition of the amino acid degradation pathway in bacterial communities was associated with the accumulation of VFA. Proteiniphilum gradually increased from 3 to 26% and became the dominant genus of the microbial community. The relative abundance of Syntrophomonas increased significantly to 2%, whereas Thermovirga decreased from 5 to 1%. This reduced protein and lipid degradation, resulting in an accumulation of long-chain fatty acids (LCFAs). Because of sodium salt intolerance, Methanospirillum dominance was replaced by that of Methanoculleus. Methanoculleus increased from 9.89 to 51.93%, whereas Methanospirillum gradually decreased from 35.35 to 0.46%.

As a consequence of increasing atmospheric ${\mathrm{CO}}_2$ and its subsequent sequestration, the oceans are undergoing changes that have not been seen for millennia, including temperature increases, ocean acidification, and localized alterations in salinity. Current methodologies for undertaking environmental-impact assessments may not be suitable for use under near-future (2100) conditions. This paper reviews and analyses what research has presently been undertaken to address these concerns. The authors find that little attention has previously been paid to chronic-exposure conditions that accurately reflect the near future, but the few available studies show that the consequences of oceanic climate change will not only be significant for marine life, but also impact humans who depend on it. The authors suggest that future research should target understanding how climate change will impact the physiological health of a wide array of species, important both economically and ecologically, going beyond the often-chosen model species and standardized testing. This information is necessary to accurately estimate the environmental risk of proposed engineering projects in changing environmental conditions.

This study focused on a pilot-scale infiltration of denitrified wastewater through artificially created soils. The hydraulic performance and sulfide production were evaluated to ensure the system’s longevity over the period needed for autotrophic denitrification. Experiments were carried out over a year in two reactors of 200-L capacity. Sandy and sandy loam soils were tested to represent highly permeable ($Ks=0.028\mathrm{cm}/\mathrm{s}$) and permeable ($Ks=0.0013\mathrm{cm}/\mathrm{s}$) soils, respectively. The infiltration of denitrified wastewater at a continuous hydraulic rate (130 and $70\mathrm{L}/{\mathrm{m}}^2/\mathrm{day}$) through these soils did not lead to the production of large amounts of gaseous hydrogen sulfide [$[{\mathrm{H}}_2\mathrm{S}]<2.1$ parts per million (ppm)] or aqueous sulfides ($[{\mathrm{HS}}^{-}+{\mathrm{H}}_2\mathrm{S}]<0.7\mathrm{mg}/\mathrm{L}$) sulfides in both feeding influent and effluents of the 200-L reactors. Considering the hydraulic performance, no loss in the infiltration capacity was recorded for the sandy soil, whereas a clogging phenomenon was observed after 37 days for the sandy loam soil. Two factors were responsible for this clogging phenomenon. A fine brown layer, known as a biomat, was formed on the infiltrative surface (IS) of the soil, which led to the formation of iron ochre at the bottom of the reactor. As an ascertainment attributed to the clogging phenomenon faced, sandy soil appeared to be the best choice as it did not contain organic matter, which could lead to the biomat formation and thus to a clogging phenomenon.

Roadside bioretention systems, also known as green streets are becoming increasingly popular, and have widespread potential to reduce pollutant loads coming from road runoff. However, the installation of these systems is outpacing the research regarding the comparative effectiveness of specific design features. Monitoring is a required component of many stormwater regulatory programs, and can provide vital feedback to designers and engineers, lower costs, and determine long-term effectiveness and maintenance requirements, yet very few bioretention systems are monitored. For professionals that are interested in performance assessment, there are very few descriptions of monitoring infrastructure for small drainage areas that are detailed enough to replicate during new bioretention construction projects. This research describes the innovative infrastructure used at the University of Vermont (UVM) Bioretention Laboratory to accurately measure pollutant mass load reduction by roadside bioretention systems. The inflow and outflow monitoring infrastructure designs are provided in enough detail to be adapted and/or replicated in other field settings. The steps taken to integrate the infrastructure into new construction are also provided. Ninety degree v-notch and compound weirs were installed at the inflow and outflow of eight bioretention systems, respectively. Differential pressure transducers related water height to flow rate. A time-based discrete sampling methodology was tested and found to adequately sample multiple points throughout the inflow and outflow hydrographs. This allowed for the comparison of pollutant mass removal among different bioretention designs on an equal volume basis.

Soil contamination by toxic metals is a major environmental issue, mainly due to inadequate methods of waste disposal and accidental spills. Studies on fate and transport of contaminants help prevent the spread of pollutants in subsurface soil and mitigate associated risks. Therefore, the objective of this study is to evaluate the sorption mechanisms involving seven metallic species (nickel, cadmium, lead, chromium, zinc, copper, and manganese) in a residual clayey soil, when available individually (single-species solution) or combined (multispecies solution), under different pH values in the acidic range. Batch equilibrium tests were conducted, from which sorption isotherms and partition coefficients—$K_d$ were determined and evaluated. The results showed that, for the clayey soil investigated, the pH of the contaminant solution significantly influenced $K_d$. For Cr, Pb, and Cu, higher retention capacities were observed for both single and multicomponent species solutions, while Zi, Ni, Cd, and Mn showed greater mobility.

This study consisted of two parts. First, pre-aeration tests were conducted to assess the space-time variability of water quality in a shallow lake. Chlorophyll-a concentration and cyanobacteria cell density varied from 40 to $80{\mathrm{\mu g}\mathrm{L}}^{-1}$ and $0.5–2.0\times {10}^6\text{cells}/\mathrm{mL}$, respectively. In the second and major part of the study, aeration tests were carried out to investigate the influence of artificial circulation on the flow hydrodynamics and water quality. Comparison of the measurements taken inside and outside the bubble plumes showed that artificial circulation promotes a faster decay of chlorophyll-a concentration over time. First-order kinetics fitted well the time-variation of depth-averaged chlorophyll-a, cyanobacteria, and pheophytin-a. The net reduction rate of chlorophyll-a and cyanobacteria could be described as a function of a dimensionless parameter $\beta$ that controls bubble plume hydrodynamics or, alternatively, as a function of the rate of dissipation of turbulent kinetic energy $ϵ$. This net reduction rate of chlorophyll-a could also be linearly related to the net growth rate of pheophytin-a. This suggests that algal removal was caused mainly by cellular death. Finally, the relationships obtained in this study were used to predict the impact of artificial circulation on algal removal in water-supply reservoirs.

Large spills at hydropower facilities can produce environmentally unfavorable supersaturated total dissolved gas (TDG) conditions. Enhanced coordination between adjacent hydropower facilities is required when a large, brief spill creates a pulse of TDG that is transported into a downstream reservoir. A premium is placed on quick and simple methods and relationships that can support short-term decision making under dynamic conditions. This paper presents an empirically based methodology to quantify and assess the relationship between mean hourly river flow and TDG travel time between an upstream hydropower spillway and a downstream dam. The analysis is conducted for reservoirs in the mid-Columbia River system and is limited to summer months when spill events that create high TDG are most common. A two-step filter and crosscorrelation procedure is used to isolate high-strength TDG events and characterize the time delay between when the TDG event is initiated upstream and when it is detected downstream. Spill flow, powerhouse flow, and TDG measurements are used to develop a bulk parameter estimation of mean TDG time delay as a function of mean river flow. The approach reveals an inverse power law relationship between mean river flow and mean TDG travel time. The relationship provides hydropower operators with a new, simplified decision support tool. The generalized methodology could be applied to other reservoir systems for which TDG minimization is a critical management objective.