Journal of Environmental Engineering

In recent years, miniaturized particulate matter (PM) sensors have been studied intensively as an alternative device for air quality measurement due to their price advantage, moderate accuracy, and portable size. The accuracy of these sensors has been studied by calibration against conventional laboratory instruments. Such sensors have been connected in a network for spatiotemporal air quality measurements or used as personal monitors for exposure estimation. Another important application is combining low-cost PM sensors with drones or other unmanned vehicles for sampling environments where the setup of a static sensor network may not be viable. In this study, a mobile robot cart with a low-cost PM sensor (AAQRL-ROBOPM) was developed to map spatial PM distributions over time. The robot can be moved either manually via Bluetooth inputs from an Android device, autonomously by following preprogrammed instructions, or with basic artificial intelligence (AI) and an algorithm. PM concentration readings are sent to the Android device for monitoring and storage. The mobile sensor module was tested for both indoor and outdoor environments, and effectively found the locations of the highest PM concentrations. Using such a device has advantages over a sensor network, such as lower overall cost and lesser complexity of setup. This mobile sensor module provides a more cost-efficient and time-efficient method of finding PM hotspots. Once hotspots are located in the sampled environment, static sensors can be placed for the greatest effectiveness in measuring PM concentration over time. Furthermore, the mobile sensor module was manufactured with low-cost components, making it broadly affordable.

At present, wet flue gas desulfurization (FGD) systems offer insufficient control of the oxidation process. This study proposes to optimize the oxidation process of desulfurization slurry by an oxidation reduction potential (ORP) control strategy. By designing a ${\mathrm{L}}_{16}(4^5)$ orthogonal test, the effects of temperature, concentration, rotation speed, air flow rate, and pH on ORP were investigated at different oxidation stages of ${\mathrm{CaSO}}_3$. Based on the analysis of variance, the order of contribution of different influencing factors at the specific oxidation stage was obtained. The influence degree of specific influencing factors on ORP was different, and the trend is explained for each different oxidation stage as well. The results indicate that only the temperature plays a significant role in the change of ORP during the whole oxidation process, which clarifies that the temperature affects the oxidation process of ${\mathrm{CaSO}}_3$ by affecting the dissolution of ${\mathrm{O}}_2$ and ${\mathrm{CaCO}}_3$ and the transformation of S(IV) to S(VI). The results also provide theoretical guidance for precise oxidation control of the FGD slurry system.

This study investigates the exothermic laws involved when Fenton’s reagent is employed in the degradation of organic substances to achieve positive energy in wastewater treatment. It analyzes the effects of Fenton’s reagent concentration, target pollutant ($o$-phenylenediamine) concentration, initial reaction temperature, and reaction time to evaluate the observed temperature elevation and its exothermic law for $o$-phenylenediamine degradation by Fenton’s reagent. It was found that the Fenton oxidation process is accompanied by a rapid temperature elevation of the solution, which was mainly influenced by the concentration of added hydrogen peroxide and the concentration of the target pollutant. More specifically, when [${\mathrm{H}}_2{\mathrm{O}}_2$] is $0.15\mathrm{mol}·{\mathrm{L}}^{-1}$, [${\mathrm{Fe}}^{2+}$] is $10\mathrm{mmol}·{\mathrm{L}}^{-1}$, and the reaction time is 30 min, the degradation efficiency of $o$-phenylenediamine (200 mL and $0.04\mathrm{mol}·{\mathrm{L}}^{-1}$) was 95.87%, and the temperature increased by 9.2°C. It was also found that the heat produced during $o$-phenylenediamine degradation by Fenton’s reagent mainly originated from the exothermic reaction between the ${}^{•}\mathrm{OH}$ radicals (and other reactive oxygen species) and $o$-phenylenediamine (and its intermediate product), in addition to the exothermic production of ${}^{•}\mathrm{OH}$ free radicals and the consumption of other active groups.

The percentage removal metric is widely used in engineering practice for stormwater control measure (SCM) selection and design, because it has been adopted by regulatory agencies and because it is straightforward to use for load reduction calculations. Various studies have shown that the metric is poorly suited to the episodic and stochastic nature of stormwater flows, but the extent of uncertainty introduced by the use of the metric has not been quantified. This study evaluated SCM performance uncertainty for total phosphorus (TP), total nitrogen (TN), and total suspended solids (TSS) load reduction in 14 regulator-defined SCM categories, based on data from 176 SCM monitoring studies aggregated using a subjective weighting scheme. Uncertainty was characterized according to the cumulative distribution of percentage removal values from these studies, and defined as the probability that SCMs will perform equal to or below credit values. SCM uncertainty based on these probabilities ranged from 0 to 0.95 and was generally between 0.31 and 0.84, although data were limited for several SCM categories. Probabilities that percentage load reduction was less than or equal to zero ranged from 0 to 0.61, and were generally between 0 and 0.30 across all SCM categories. Probabilities that TSS removal was less than or equal to 80% were generally between 0.35 and 0.77.

Changing circumstances and the availability of new technologies are causing urban water systems to transition from managing system components in a separate and linear fashion to an integrated “One Water” approach that focuses much more on recovering resources, including water, energy, nutrients, and other materials. These systems often include both distributed and centralized components and are referred to as hybrid systems. The components of these integrated One Water and resource recovery systems are described, along with the benefits that they provide. Enabling factors, along with impediments, are described, including new technologies, the need to balance human services and environmental needs, the continuing evolution of optimal system configurations, concerns created by new and emerging issues, and the need to adapt existing institutions and practices. The literature reviewed illustrates the growing research interest in these topics, along with progress translating these approaches into practice.

In this study, cooling degree day (CDD) and life cycle cost (LCC) analyses are applied to refrigerated warehouses in Turkey to determine the optimum insulation thickness. The external wall of refrigerated warehouses is considered as a sandwich wall and the insulation material is taken to be expanded polystyrene. Also, the base temperatures are assumed to be $-20°\mathrm{C}$, $-18°\mathrm{C}$, $-12°\mathrm{C}$, 0°C, and 6°C, while coefficient of performance (COP) values are 1.2, 1.5, 1.8, 2.1, and 2.5. As a result: (1) the insulation thickness is directly proportional to the insulation cost; (2) insulation thickness is inversely proportional to the electricity cost; (3) the maximum annual energy saving is found for a COP of 1.2, and the minimum rate is determined for a COP value of 2.5; (4) the maximum and minimum energy savings are found for $-20°\mathrm{C}$ and 6°C, respectively; (5) the maximum total cost is found for $\mathrm{COP}=1.2$; (6) ${\mathrm{CO}}_2$ emissions increase with increases in CDD for the unit surface area; and (7) an increase in COP values reduces ${\mathrm{CO}}_2$ emissions.

To solve problems regarding the urgent need for deep dewatering of massive urban dewatered sewage sludge in the temporary sludge lagoon (UDSS-TSL), this study investigated the effects of various chemical conditioners on the deep dewatering of UDSS-TSL. The study used sludge-specific resistance to filtration, coefficient of consolidation, permeability coefficient, bound-water content, total nitrogen (TN), total phosphorus (TP), and chemical oxygen demand (COD) in the filtrate as indices to evaluate the conditioning effect. It was found that the influence of flocculation conditioners on the deep dewatering of UDSS-TSL is relatively low. Skeleton-builder conditioners, coal powder for example, did not improve the dewaterability of UDSS-TSL. Since CaO has the capabilities of flocculation, skeleton building, and cell disruption, the experimental results showed that, compared with other conditioners used in this study, CaO had the most significant effect. With a CaO dosage of 67% dry solids, specific resistance to filtration decreased by 80% compared with that of the raw sludge, the consolidation coefficient at each level of stress increased 3.5–8.2 times that of the raw sludge, and the water content was 40% after complete consolidation under 100 kPa. These results indicate that CaO conditioning for deep dewatering of UDSS-TSL is feasible.

Combined sewer overflow (CSO) negatively impacts water quality during wet weather. An end-of-pipe treatment train with settleable particle removal and peracetic acid (PAA) disinfection was investigated for treatment of Escherichia coli (E. coli), sul1 gene-carrying E. coli, and total coliform (TC) in simulated CSO effluent. Settling reduced chemical oxygen demand by $49\%\pm 11\%$ and total suspended solids by $78\%\pm 7\%$. Overall removals of $3.1\pm 0.14$-log and $2.5\pm 0.37\text{-}\log$ were achieved for E. coli and TC, respectively, with settling and disinfection, but these removals were not significantly different from removals with disinfection only. After disinfection, the fraction of E. coli carrying the antibiotic-resistance gene (ARG) sul1 increased. Treated samples were spiked into estuarine water to determine regrowth potential of target bacteria following release. After 7 days, E. coli was not detected in reactors with treated CSO, and TC concentrations decreased significantly. This research provides insight into a potential end-of-pipe treatment and suggests that disinfection rather than settling is more effective for microbial treatment of the wastewater component of CSO effluent.

The effects of the McKinney baffle on the limiting flux of secondary settling tanks (SSTs) are evaluated by comparing the predictions of the maximum solids loading rate (SLR) determined by a Fluent-based, two-dimensional computational fluid dynamics (CFD) model with limits calculated by one-dimensional idealized flux theory (1DFT). SLR stress tests are simulated using three different stress testing methods to adjust flow rate, SLR, recycle ratio, and concentration of mixed liquor suspended solids. For each method, different flow conditions are used as the starting points for the CFD stress test. Limiting fluxes of the SST without and with the McKinney baffle are compared, and the SSTs failure mechanisms are analyzed. The simulations show that the McKinney baffle improves SST limiting flux by 1.4–2 times over the limiting of the original SST. Also, different (1) baffling structures; (2) stress testing methods; and (3) initial flow conditions for CFD stress tests influence the prediction of the limiting SLR. Therefore, routinely assuming a flux rating of 80% of the 1DFT limit is not recommended for all SSTs.

In this study, the combination of capture mechanisms in ceramic water filters (doped with hydroxyapatite and alumina) was considered for the removal of contaminants from drinking water. It was found that hydroxyapatite and alumina were conserved during the firing process of the ceramic water filters up to 950°C. The nanopores resulting from the conservation of the additives increased the specific surface area of the ceramic water filters from 3.7 to $21.0{\mathrm{m}}^2·{\mathrm{g}}^{-1}$. On the other hand, the microscopic pores associated with the processing of the ceramic water filters (i.e., pressing and drying) and the combustion of the sawdust reduced the filtration time from 24 to 4 h. The efficiency of the resulting filters in removing bacterial, chemical, and viral contaminants from water was investigated using E. coli, fluoride, and MS2 as model contaminants. The contaminants were found to be captured from water by trapping in the pores, substitution in the hydroxyapatite, and adsorption on the surface of alumina. Hence, the ceramic water filters incorporating hydroxyapatite and alumina combined the different capture mechanisms. They had an efficiency of 99.998%, 99.970%, and 99.450% in the removal of bacterial, chemical, and viral contaminants, corresponding to log reduction values (LRVs) of 4.69, 3.47, and 2.26, respectively.

Limited qualified water resources have necessitated industries to use unconventional water resources such as wastewater. The aim of this study is to evaluate the risk of using urban treated wastewater to replace freshwater as a water source of cooling systems for industrial cooling water consumptions considering three main risks: corrosion, scaling, and biofouling. To perform this research, a risk analysis framework has been developed in three stages: identification of risks and the influential parameters, evaluation of the consequences of failure, and calculation of the probability of failure. The identified parameters were weighted using a paired comparison matrix, and the consequences of failure have been calculated using defined criteria. Questionnaires were used for scoring risks. In this research, the Isfahan Mobarakeh Steel Complex was chosen as the case study. The results of the risk assessment indicated that biofouling failure had the largest score. Furthermore, among the influential major failures, ammonium, phosphate, and chlorine, respectively, had the maximum risk. Based on the results, the developed framework can be used for ranking the risks of using urban treated wastewater instead of freshwater in industrial cooling systems.

In this paper, modified dynamic models of those used for traditional activated-sludge systems are proposed by adapting the oxic-anoxic phases to the sequencing batch reactor (SBR), where the nitrification-denitrification biochemical processes occur. The modification of Activated-Sludge Model 1 (ASM 1) to adapt to the operation performance of a sequencing batch reactor in the oxic-anoxic phases has yielded as results mathematical equations that allow estimation of the concentration of the removed nitrogenated forms such as ammonium and nitrate in the aeration and anoxic phases of the SBR. It is found that the determination coefficient ($R^2$) and $R^2$-adjusted trends vary from a qualified statistical adjustment ranging from good to excellent. It has been found that the estimated values of average saturation coefficients $K_{{\mathrm{NO}}_3}$, $K_{{\mathrm{O}}_{\text{2H}}}$, $K_{{\mathrm{NH}}_{\text{4AUT}}}$, and $K_{{\mathrm{O}}_{\text{2AUT}}}$ have the most influence in the estimation of the removed ${\mathrm{NO}}_3^{-}$ and ${\mathrm{NH}}_4^{+}$ concentrations in both oxic and anoxic phases of a SBR.

Multiorganic compounds are commonly found in contaminated environments, and the utilization of pure microbial strains for their removal is inefficient. The present study was conducted to evaluate whether the use of a consortium of Aspergillus fumigatus HD2, Ophiostoma stenoceras LLC, and Zoogloea resiniphila HJ showed improved removal of a mixture of alpha ($\alpha$)-pinene, n-butyl acetate, and ortho (o)-xylene in water when compared to the use of each strain. Carbon balance analysis indicated that more mineralized compounds were produced by the consortium. Microbial analysis indicated the ratio of A. fumigates and Z. resiniphila remained $1:1$, while O. stenoceras grew more slowly than the other two strains. Substrate inhibition models showed that the Levenspiel model was optimal for $\alpha$-pinene and n-butyl acetate, while the Edwards model was better for o-xylene. Finally, gaseous ternary mixture removal was achieved in a continuous-flow system, indicating that this consortium would have great potential in future full-scale applications of organic treatments.

Ultrasonic (US) irradiation is effective for the degradation of a variety of problematic pollutants, and simultaneous US low and high frequencies can lead to improved degradation yields. Hydroxyl radical ($·\mathrm{OH}$) is critical to the efficiency of ultrasonic oxidation processes. We monitored $·\mathrm{OH}$ production and carried out calorimetric measurements during dual-frequency ultrasonic (DFU) irradiation using probe- (20 kHz) and transducer (640 kHz)-type sources. The conditions were optimized based on calorimetric measurements to determine real power density dissipation to the solution for our dual-frequency ultrasonic reactor (DFUR) (20 and 640 kHz) with a power density of $10.1\mathrm{W}·{\mathrm{mL}}^{-1}$ in which the observed synergistic index reached a maximum of 0.991, whereas it was only 4.1 and $8.1\mathrm{W}·{\mathrm{mL}}^{-1}$, respectively, for 20 and 640 kHz individually. The production of $·\mathrm{OH}$ was measured using coumarin (COU) as trapping agent under simultaneous and sequential operation of low and high frequencies under different gas saturating conditions (Ar, ${\mathrm{O}}_2$, and ${\mathrm{N}}_2$). Distribution of $·\mathrm{OH}$ within the cavitational zones was assessed by comparing $·\mathrm{OH}$ trapping by hydrophobic COU and ionic terephthalic acid (TA) under DFU. Based on the approximately 6 times more effective trapping of $·\mathrm{OH}$ by COU compared to TA during DFU irradiation, the majority of $·\mathrm{OH}$ leading to degradation appears to be generated at the gas–liquid interface. Methylene blue (MB) and $N$, $N$-diethyl-meta-toluamide (DEET) were selected as hydrophilic and hydrophobic model target compounds to probe individual degradation zones within the cavitation process during DFU irradiation. The addition of peroxides ${\mathrm{H}}_2{\mathrm{O}}_2$ (PO), persulfate (PS), and monoperoxysulfate (MPS) to the DFU reactor had minimal or modest effects on the DFU-induced degradation of target compounds. The results revealed that combining low and high frequency US has a positive effect on enhancing the cavitational yields of $·\mathrm{OH}$ and is favorable for treatment of both hydrophilic and hydrophobic compounds.

Numerical models based on integrated applications of computational fluid dynamics and fluence rate field models (CFD-I models) are often used to simulate process performance in ultraviolet (UV) disinfection systems and other photoreactors. However, the predictions of these models are often presented as deterministic endpoints, whereas actual performance in these systems is variable. The central hypothesis of this research was that CFD-I models can be applied via a stochastic approach [Monte Carlo (MC) simulations] to simulate process performance of large-scale UV disinfection reactors including variability, by allowing appropriate variations in input variables, including UV dose-response behavior of target or challenge microbes, as well as the initial microbial count. The results of these stochastic simulations indicated that variability in E. coli dose-response model parameters and initial viable E. coli concentration play important roles in the variability among predictions of disinfection efficacy. MC simulation predictions indicated that the likelihood of violating the regulatory permits for viable E. coli concentration for a large-scale UV disinfection system was negligible for many operating conditions that span the range of common use, which suggests that it may be possible to reduce the amount of UV power applied in treatment, hence reducing input electrical power while retaining compliance with treatment objectives.

With the increase in transport of oil by rail, the probability of oil spills in rivers has increased. Traditionally, focus has been placed on oil slicks moving on the water surface. However, the density of bitumen oil carried by rail within and from Canada to the United States can exceed that of freshwater, causing this oil to get submerged in the water column. This also has the potential of forming oil particle aggregates (OPAs) upon interaction with suspended sediments. The energy-dissipation rate is a key parameter for predicting the formation of oil droplets, and for this purpose, expressions are developed to estimate the energy-dissipation rate at various depths in the river using easily measured quantities such as water depth, streambed slope, and streambed roughness. The formulation showed that for a stream 30 m wide with a natural slope of 1/1,000 and roughness height of 1.0 cm, the average and maximum energy-dissipation rates are 0.01 and $0.22\mathrm{W}/\mathrm{kg}$, respectively. The average value is comparable to spilling breakers of height around 0.3 m, and the maximum value is comparable to those obtained from plunging breakers of 0.30-m-high waves. The large average value suggests that breakup of droplets in streams is higher than in the open sea under regular waves.