Journal of Environmental Engineering

Abstract

The coexistence of different foulant compositions in the feed water of reverse osmosis (RO) systems causes serious complications in the fouling process of the membranes. Hence, in this technical research, the phenomenon of combined inorganic (gypsum)-colloidal (silica particles) fouling (inorganic-colloidal fouling) of brackish water RO (BWRO) process was studied in the lab-scale experiments. Moreover, the effect of the presence of air micro–nano bubbles (AMNBs) in the feed water; as a new practical method for control of membrane fouling, was investigated on this phenomenon. For this purpose, a suspension with the potential of inorganic scaling [calcium sulfate, Saturation index $(\mathrm{SI})=0.96$] and colloidal fouling (colloidal silica, $50\mathrm{mg}/\mathrm{L}$) was used to form the inorganic and colloidal foulings (simultaneously) on the membrane surface during the inorganic-colloidal fouling process. All experiments were performed twice, once in the absence and once in the presence of AMNBs. Finally, the results of this research were compared with the results of the inorganic and colloidal fouling studies. Based on the results, the inorganic-colloidal fouling formed a dense and compact fouling layer on the membrane surface, which severely reduced the permeate flux (76.3%) and salt rejection (4%). The amount of decrease of these two parameters in inorganic-colloidal fouling was much higher than each of individual inorganic and colloidal foulings. In the presence of AMNBs, both types of inorganic and colloidal foulings greatly reduced and the major portion of inorganic-colloidal fouling was related to the colloidal fouling. Thus, a significant decline was observed in adverse effects of inorganic-colloidal fouling on the membrane performance and the permeate flux and salt rejection decreased by 18.5% and about 1%, respectively. The results of this study could introduce the micro–nano bubbles (MNBs) technology as an effective method to inhibit the inorganic-colloidal fouling in RO systems.

Practical Applications

Today, reverse osmosis processes are known as efficient technologies for supplying drinking water from brackish and sea water resources due to their high ability to remove various compounds. The separated compounds from the water accumulate near the membrane surface and consequently deposit on it and/or inside its pores. This phenomenon is called membrane fouling and has adverse effects on the performance of reverse osmosis processes. Water resources usually have different types of pollutants that simultaneous presence of them can intensify the membrane fouling process. Gypsum scaling and colloidal silica fouling are two major common types of reverse osmosis membrane fouling. Therefore, in this research, the effects of the inorganic-colloidal fouling were studied on the performance of a commercial brackish water reverse osmosis membrane, in presence and absence of air micro–nano bubbles. The results showed that the combined fouling formed a complex fouling layer on the membrane surface in absence of air micro–nano bubbles. In real-scale reverse osmosis process, this layer can severely reduce the membrane permeate flux and salt rejection which result to increase in the operational and maintenance costs. Alternatively, the presence of air micro–nano bubbles in the reverse osmosis feed flow could limit both inorganic and colloidal foulings and their synergetic effects on each other.

The stabilization/solidification method can improve the engineering properties and reduce the environmental risks of heavy metal-contaminated expansive soil. However, the solidification effects deteriorate for soils experiencing wetting–drying (W–D) cycles. For this objective, the expansion/shrinkage, cracking, and leaching behaviors, as well as the corresponding internal relations, of lime-solidified lead-contaminated expansive soil were investigated. The results showed that during the W–D process, the volumetric strain increased, particularly along the radial direction. The cracks gradually developed and increased in length, width, and surface-crack ratio. Contaminant leaching and mobility increased, increasing environmental risk. In addition, a higher Pb(II) concentration in the solidified soil exhibited a more notable expansion potential release, crack development, and leaching capacity. X-ray diffraction and scanning electron microscopy results revealed the redistribution of soil particles and pores rather than chemical changes in mineral components during the deterioration process, and increasing the lead concentration accelerated the deterioration of W–D cycles. Finally, based on the grey correlation analysis, deterioration effects in leaching behaviors were controlled by expansion/shrinkage exponential release for solidified soil experiencing lower W–D cycles and higher Pb(II) concentrations, whereas leaching behaviors were controlled by crack behavior for solidified soil experiencing higher W–D cycles and lower Pb(II) concentrations.

Abstract

Waterways and water bodies worldwide are impacted by anthropogenic litter (hereafter “litter” or “trash”), generated from nonpoint sources. This study analyzes litter loads across various land uses within two Los Angeles County watersheds: the Ballona Creek and the Los Angeles River. Our objective is to present a methodology to develop buildup and washoff parameters for densely populated urban areas, such as the coastal metropolitan area of Los Angeles, California. An assessment is also made to test how these model parameters perform when applied to another urbanized watershed with similar rainfall and climate patterns (i.e., the San Diego River Watershed in California). Using extensive litter collection data from small drainages (approximately 572 locations, each draining 0.05–8.5 ha), we estimate buildup and washoff model parameters. These parameters are used to simulate the buildup of litter and subsequent washoff (load) of litter in our selected watersheds. Simulated results are validated against observed data from different years in all three watersheds. To date, no study has used litter washoff data to develop these parameters for stormwater models and applied them on a regional scale. We compared linear and nonlinear power functions of litter buildup during interstorm periods. Although there were limited data to develop washoff parameters, an exponential washoff function was used and calibrated to the observed washoff. Generally, storm events with the greatest antecedent dry days had the largest litter loading. Buildup rates varied among land uses, and key calibration parameters included the maximum buildup, buildup rate constant, washoff exponent, and washoff coefficient. A parameter sensitivity analysis was conducted to reveal the washoff exponent as the most sensitive parameter. Annual litter loading estimates were $4.60\mathrm{kg}/\mathrm{ha}$ for the Ballona Creek and $11.50\mathrm{kg}/\mathrm{ha}$ for the Los Angeles River. Litter loading estimates for Ballona Creek were validated and calibrated to align with observed data from the Ballona Creek Trash Interceptor, resulting in an annual washoff load of $2.1\mathrm{kg}/\mathrm{ha}$. The estimated annual litter loading for the Lower San Diego River was $2.15\mathrm{kg}/\mathrm{ha}$ falling between the mean ($0.77\mathrm{kg}/\mathrm{ha}$) and the maximum ($3.56\mathrm{kg}/\mathrm{ha}$) observed values. When applying model parameters from one watershed to another, models require extensive calibration and validation data, as extrapolating data between watersheds can introduce errors.

Practical Applications

This research can inform stormwater modelers about the process for developing parameters to estimate water quality in numerical modeling software. We demonstrate how data from field sampling can be directly used to develop model parameters. Results show that with proper validation data, stormwater models can accurately simulate annual litter loads in modeled watersheds. Future studies can test model parameters in other urbanized watersheds to validate the potential for standardized buildup values. Field studies can be done in conjunction with the results from this survey to investigate and further validate litter loads mobilized by stormwater. This study highlights the need for long-term monitoring to improve and update models in the future. Although there is a risk of inaccurate results when extrapolating model parameters from one watershed to another, this research indicates the potential for developing buildup and washoff parameters that can be used as a starting point for parameter selection across urban watersheds.

A batch electrocoagulation (EC) process using aluminum electrodes was optimized for the removal of natural organic matter (NOM) and subsequent reduction in total trihalomethane (TTHM) formation potential from synthetic (SynW) and river water (RW) samples. Optimum operating conditions were found to be 45 min of electrolysis time, an initial NOM concentration of $10\mathrm{mg}/\mathrm{L}$, and an applied voltage of 15 V. Initial NOM concentrations tested were 3, 5, 10, 15, 20, 30, 40, and $50\mathrm{mg}/\mathrm{L}$ and treatment efficiency increased with increasing initial concentration. The kinetic study demonstrated that NOM removal followed second-order kinetics. NOM removal resulted in the reduction of trihalomethanes (THMs) formation in treated water. THM concentrations were measured in untreated and EC-treated water. Bromodichloromethane had the highest removal (92.4%) compared to trichloromethane (89.5%) after 10 min. The TTHM concentration after a 10–30 min treatment was below the US Environmental Protection Agency (USEPA) maximum contaminant level of $80\mathrm{\mu g}/\mathrm{L}$. After 60 min, the TTHM concentration in the RW samples was reduced by 77.5%, which was considerably less than the reduction in the SynW samples (89.7%) within 10 min. The lower THMFP removal from RW may be due to interference from natural or anthropogenic constituents. The total amount of sludge generated in experiments was compared with the estimate derived using Faraday’s equation. A current efficiency of 1.4 was obtained, indicating super-faradaic behavior of the EC process at the optimum operating conditions. Fourier-transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD) were used to characterize the generated sludge and entrapment of NOM in aluminum hydroxide [$\mathrm{Al}(\mathrm{OH}{)}_3$] flocs as the most likely removal mechanism. At optimum operating conditions, the energy consumption was $2.391\mathrm{kWh}/{\mathrm{m}}^2$. Thus, EC is an effective method for reducing NOM and THMFP from RW samples.

A heterogeneous condensation process facilitates the growth of fine particulate matter, making it more easily removable. The aim of this study was to effectively eliminate pre-existing fine particles in the atmosphere by investigating the growth characteristics of particles in turbulent water vapor environments using experimental and numerical methods. The results reveal that the presence of soluble and hydrophilic particles in atmospheric fine particulate matter enhances their growth compared to coal particles. Increasing temperature differences, reducing particle number concentrations, and elevating the proportion of soluble particle components contribute to particle growth. When the temperature difference is below 10K, particle growth is less effective. The beneficial impact of particle collision and coagulation, partly offsetting water vapor competition, was observed with an increase in particle number concentration. The addition of soluble and hydrophilic components promoted particle activation, further fostering particle growth. The region near the wall exhibited more significant particle growth due to higher supersaturation and lower flow velocity. These findings theoretically support the application of heterogeneous condensation processes in atmospheric purification.

In recent years, with the development of China’s industry, the pollution problem of heavy metal wastewater in the country has become increasingly serious. In this paper, peanut shells modified with zinc chloride were selected as an adsorbent for the adsorption of ${\mathrm{Ag}}^{+}$, and the optimal conditions for this adsorption were investigated. The results showed that the best adsorption effect was achieved at pH 4.0, an initial concentration of $250\mathrm{\mu g}/\mathrm{mL}$ of ${\mathrm{Ag}}^{+}$, a dosage of 0.10 g of peanut shell, a contact time of 40 min, and a temperature of 20°C. The prepared materials were also characterized by scanning electron microscopy and an X-ray diffraction analyzer. It was found that the skeleton did not change after the peanut shell treatment: the pores became larger; and the peanut shells had good adsorption capacity for ${\mathrm{Ag}}^{+}$ after being modified with zinc chloride. The kinetic, thermodynamic, and isothermal properties of the adsorption process were analyzed, showing that the adsorption conforms to the quasisecond-order kinetic equation and to the Freundlich adsorption isotherm. By this method, the heavy metal ${\mathrm{Ag}}^{+}$ in wastewater can be absorbed at low cost and with high efficiency, providing protection to the environment.

Abstract

Gelatin-based aerogel (G-Aerogel) from untanned proteinaceous solid wastes was applied as an adsorbent in batch and fixed-bed column systems to remove acid red 97 (AR97) from water. Adsorption was evaluated as a function of pH, adsorbent mass, contact time, temperature, and initial dye concentration. Maximum removal of AR97 was achieved at pH 3 after about 4 h. The pseudo-second-order equation provided the best adsorption kinetic model. The adsorption of AR97 onto G-Aerogel was best described with the Langmuir model, and the maximum adsorption capacity was about ${196\mathrm{mg}·\mathrm{g}}^{-1}$. A thermodynamic study showed an exothermic and spontaneous adsorption process. It was also demonstrated that G-Aerogel can be reused several times. The column study showed that breakthrough and saturation times decreased with increasing initial AR97 concentration. Thomas and Yoon-Nelson kinetic models were applied to the experimental data to predict the breakthrough curves and determine the characteristic parameters of column adsorption.

Practical Applications

Tannery solid wastes composed mainly of collagen are very abundant and constitute a material that should be valorized. In this study, we examined the transformation of untanned proteinaceous wastes into a biomaterial [Gelatin-based aerogel (G-Aerogel)] of environmental interest. The results demonstrated the promise of this material for dye adsorption because of its advantages in terms of its ease of preparation, its containing functional groups that are able to attract dye, its ability to be reused several cycles, and its high adsorption capacity. In addition to studying adsorption in static mode, we also studied dynamic adsorption, because the common industrial practice is to pass water to be treated through a column packed with an adsorbent, allowing the transport of the pollutant from the liquid to the solid. In summary, G-Aerogel can be applied as an environmentally friendly and efficient adsorbent for the removal of dyes from contaminated water.

The single-cycle transient high-concentration organic load shock test was conducted on the micropressure swirl reactor (MPSR) and sequencing batch reactor (SBR) to assess their capability to different levels of transient organic load shock (OLS), including pollutant removal, sludge characteristics, and microbial characteristics. The results indicated that the impact-resistance of biological treatment systems was related to reactor structure and microbial community distribution. When subjected to transient chemical oxygen demand (COD) load of 0.81, 1.28, and $1.70\mathrm{g}/(\mathrm{L}·\mathrm{d}\mathrm{a}\mathrm{y})$, respectively, both reactors exhibited effective organic removal capabilities. Compared with MPSR, within a certain shock range, nitrification in the SBR was less affected by shock and had a higher effect on nitrogen and phosphorus removal. However, when shock load reached $1.70\mathrm{gCOD}/(\mathrm{L}·\mathrm{d}\mathrm{a}\mathrm{y})$, the denitrification was sufficient in the MPSR, and microorganisms continued to secrete polysaccharides (PS), which was beneficial for adsorbing pollutants and resisting impacts. Under steady-state conditions, the SBR exhibited excellent nitrification with a relative abundance of 60.7% for nitrifying functional groups such as Thiothrix. Compared with the SBR, the MPSR displayed a higher microbial community diversity, with a variety of phosphorus-removing bacteria and denitrifying bacteria genera occupying aerobic and anoxic partitions within the same space, which was profitable for effective denitrification and phosphorus removal under high OLS. Besides, the enrichment of Flavobacterium and Zoogloea sp. at high concentrations significantly enhanced the MPSR’s resistance to OLS. This study provides a theoretical basis for effective measures by different processes in response to organic load shocks.

Bioretention is a type of stormwater best management practice that can reduce stormwater runoff volume, and with appropriate design, simultaneously reduce nitrogen loads. To meet the water quality potential of bioretention systems, improved simulation models of the transport and transformations of nitrogen are needed. In this work, two versions of a three-nitrogen-pool (3P) model (3P-1 and 3P-m) are applied to simulate observed nitrogen transport through a field bioretention system. The 3P models provide predictions of net export of dissolved organic carbon, dissolved organic nitrogen, and inorganic nitrogen species. The 3P-m model has promising results: (1) relative to the Storm Water Management Model (SWMM), it reduced the prediction error of percent removal of total dissolved nitrogen by up to 10.6% and reduces the scaled root-mean square error of total dissolved nitrogen loads by up to 53.0%; (2) it successfully captured the correlation between impactful environmental factors and event mean concentrations of total dissolved nitrogen and nitrate nitrogen in underdrain effluent; (3) its predictions on denitrification showed good alignment with observed isotope results; and (4) it demonstrated higher stability in simulated time series among calibration results than 3P-1. The 3P-m is expected to assist the design of bioretention system and valve control strategies by providing more accurate predictions on nitrogen removal under the impacts of soil moisture content and temperature. Future research and collaboration opportunities are also proposed in this article.

Activation of peroxymonosulfate (PMS) by catalysts for water treatment is very important for the sulfate radicals-based advanced oxidation technology. Constructing affordable and recyclable transition metal catalysts with high efficiency is highly desirable, but still challenging. In this study, a novel ${\mathrm{CoAl}}_2{\mathrm{O}}_4/{\mathrm{Co}}_2{\mathrm{O}}_3@\gamma {\text{-}\mathrm{Al}}_2{\mathrm{O}}_3$ catalyst for the activation of PMS was prepared with an excessive impregnation method, and its performance on the catalytic degradation of phenol in water was investigated. The composition and structure of the catalyst were characterized by X-ray diffraction, X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, and ${\mathrm{N}}_2$ adsorption-desorption experiments. It was found that the catalyst could greatly promote the phenol mineralization in water as the total organic carbon removal increased from 4.27% to 57.64% after 60 min of reaction. The presence of ${\mathrm{Cl}}^{-}$ inhibited the catalytic degradation of phenol in water at low concentrations, but promoted the catalytic degradation at high concentrations. However, ${\mathrm{HCO}}_3^{-}$ and ${\mathrm{CO}}_3^{2-}$ revealed inhibitory effects on the catalytic degradation because they could scavenge free radicals in the system. Based on the electron spin resonance technique and the quenching experiments, ${{}^1\mathrm{O}}_2$ and ${\mathrm{SO}}_4^{-}·$ were identified to be the primary reactive species for the catalytic degradation. The ${\mathrm{CoAl}}_2{\mathrm{O}}_4/{\mathrm{Co}}_2{\mathrm{O}}_3@\gamma {\text{-}\mathrm{Al}}_2{\mathrm{O}}_3$ could be easily recovered and reused. The toxicity evaluation verified that the toxicity of the treated water was greatly decreased after the catalytic degradation. Therefore, the ${\mathrm{CoAl}}_2{\mathrm{O}}_4/{\mathrm{Co}}_2{\mathrm{O}}_3@\gamma {\text{-}\mathrm{Al}}_2{\mathrm{O}}_3$ prepared in this study could be an effective catalyst for the catalytic degradation of phenol in water by activating PMS.

Inland oil spill accidents pose a negative impact on the health of the soil ecological system and human beings. The oil infiltration process is the main behavior of spilled oil, and its infiltration is influenced by many environmental factors like root netting and rainfall. This study was conducted to investigate the impact of these two important factors on the infiltration process and reduce the pollution of inland oil spill accidents. For root nettings, they can change the soil permeability and pore volume distribution, which are important in liquid infiltration, while rainwater can change the soil water content, thereby affecting the pressure, capillary force, and buoyancy force of spilled oil in the infiltration process. In the present study, these two unique factors of oil infiltration were investigated by detecting the infiltration front head and concentration distribution of spilled oil in soil layers with various root netting structures as well as the rainfall modes. It is found that root netting and surface rainfall critically affect oil infiltration in soil. The nettings with a finer mesh size and denser plant roots show a more significant effect on the infiltration process, particularly when their pore size is smaller than that of the soil. The netting’s position and soil particle size also play crucial roles, influencing where oil accumulates within soil layers. Rainfall timing and intensity further modify oil movement, with prior rainfall reducing infiltration, while subsequent rain can increase it. The findings can help better understand the transport of spilled oil transport and implement emergency response measures for inland oil spills.

Abstract

Sustainable remediation demonstrates that the benefit of undertaking remediation is more significant than its impact, and the optimum remediation solution is selected through a balanced decision-making process. Assessing sustainable remediation is site and project-specific and is strongly multifactorial across a wide range of categories, which may or may not be readily quantifiable. The applied socio-economic survey framework is based on the 2020 SuRF-UK guidance. The assessment was carried out in three steps. A small core team, an interim evaluation by the project of all beneficiaries, and a final assessment including the views of a broad range of external stakeholders developed an initial “pilot” sustainability assessment. The sustainability assessment process compared options across 45 individual criteria in 15 overarching “headline” categories: environmental, social, and economic. Members selected suitable criteria and the individual rankings of the project consortium from research, service providers and the site owner. The assessments compared $\mathrm{Wetland}+$ with the wastewater treatment plant (WWTP) and no-intervention scenario. $\mathrm{Wetland}+$ outranked the use of WWTP, and both performed significantly better than the no-intervention scenario. The quantitative data from LCA confirmed the results devoted to environmental impact.

Practical Applications

Remediation of contaminated sites is site-specific, and each site requires a specific targeted approach that should take into account not only the environmental benefits of the measures but also economic and social aspects. In the case of water contaminated with hexachlorocyclohexane (HCH) substances, there are various methods of dealing with it, ranging from removal and relocation to a secure site-to-site encapsulation to various methods of contaminated water treatment. In the case of mega-sites, the solution often reduces to water treatment, as other solutions are not acceptable, especially economically, but also environmentally (transporting large volumes of materials) and socially (large construction and material handling). The present paper gives guidance on the selection of the most accepted water treatment option from a sustainability point of view. A three-step process based on a multiparametric assessment shows how the subjective approach of technologists, activists, or the public can be eliminated. The paper shows that a wetland-based solution is accepted significantly more than a WWTP or a no-action scenario. The approach will be further applied to similar localities with HCH contamination but can be generalized to a much broader set of contaminated sites.