Engineered multifunctional sand for enhanced removal of stormwater runoff contaminants in fixed-bed column systems

Graphene-coated sand for enhanced water reuse: Impact on water quality and chemicals of emerging concern

This paper investigates the potential of graphene-coated sand (GCS) as an advanced filtration medium for improving water quality and mitigating chemicals of emerging concern (CECs) in treated municipal wastewater, aiming to enhance water reuse. The study utilizes three types of sand (Ottawa, masonry, and concrete) coated with graphene to assess the impact of surface morphology, particle shape, and chemical composition on coating and filtration efficiency. Additionally, sand coated with graphene and activated graphene coated sand were both tested to understand the effect of coating and activation on the filtration process. The materials were characterized using digital microscopy, Raman spectroscopy, scanning electron microscopy (SEM), and X-ray diffraction analysis. The material's efficiency in removing turbidity, nutrients, chemical oxygen demand (COD), bacteria, and specific CECs (Aciclovir, Diatrizoic acid, Levodopa, Miconazole, Carbamazepine, Diphenhydramine, Irbesartan, Lidocaine, Losartan, and Sulfamethoxazole) was studied. Our findings indicate that GCS significantly improves water quality parameters, with notable efficiency in removing turbidity, COD (14.1 % and 69.1 % removal), and bacterial contaminants (64.9 % and 99.9 % removal). The study also highlights the material's capacity to remove challenging CECs like Sulfamethoxazole (up to 80 % removal) and Diphenhydramine (up to 90 % removal), showcasing its potential as a sustainable solution for water reuse applications. This research contributes to the field by providing a comprehensive evaluation of GCS in water treatment, suggesting its potential for removing CECs from treated municipal wastewater.

Fate and cotransport of Pb(II) and Cd(II) heavy ions with bentonite colloidal flow in saturated porous media: The role of filter cake, counter ions, colloid concentration, and fluid velocity

This study examines the transport and retention of colloidal particles and heavy ions in porous sand, focusing on the environmental risks associated with waste from oil and gas drilling. Experimental and numerical models assess the influence of flow rate, external filter cake layer, and ionic strength on bentonite clay particles and heavy ions, such as cadmium (Cd) and lead (Pb), in near-wellbore (high-flux) and far-field (low-flux) scenarios. Colloidal filtration theory and the one-dimensional convection-dispersion equation with two-site kinetic model for attachment and detachment were utilized to calibrate and predict the transport of colloidal suspension in porous media. The research investigates the role of internal and external filter cakes on sand column pressure distribution and heavy ion absorption. Results indicate that the mobility of colloids and heavy ions is influenced by the ionic strength and pH of the carrying fluid. Colloidal clay suspensions show a higher affinity for Pb (II) absorption, while Cd (II) exhibits increased mobility in both clean sand and colloidal environments. Notably, the formation of an external filter cake significantly delays the breakthrough of heavy ions, up to four times longer than in clean sand, and reduces Cd (II) and Pb (II) outlet concentrations by 86% and 93%, respectively. This cake also limits clay concentration and particle size passage. High clay concentrations or injections under high ionic conditions induce clay bridging in pore throats, enhancing internal filtration and heavy ion retention. Conversely, low clay fluxes allow freer particle passage, increasing heavy ion loads and outlet concentrations.

Enhanced Escherichia coli removal from stormwater with bermudagrass-derived activated biochar filtration systems

Stormwater treatment and reuse can alleviate water pollution and scarcity while current sand filtration systems showed low treatment performance for stormwater. For enhancing E. coli removal in stormwater, this study applied the bermudagrass-derived activated biochars (BCs) in the BC-sand filtration systems for E. coli removal. Compared with the pristine BC (without activation), the FeCl3 and NaOH activations increased the BC carbon content from 68.02% to 71.60% and 81.22% while E. coli removal efficiency increased from 77.60% to 81.16% and 98.68%, respectively. In all BCs, the BC carbon content showed a highly positive correlation with E. coli removal efficiency. The FeCl3 and NaOH activations also led to the enhancement of roughness of BC surface for enhancing E. coli removal by straining (physical entrapment). The main mechanisms for E. coli removal by BC-amended sand column were found to be hydrophobic attraction and straining. Additionally, under 105-107 CFU/mL of E. coli, final E. coli concentration in NaOH activated BC (NaOH-BC) column was one order of magnitude lower than those in pristine BC and FeCl3 activated BC (Fe-BC) columns. The presence of humic acid remarkably lowered the E. coli removal efficiency from 77.60% to 45.38% in pristine BC-amended sand column while slightly lowering the E. coli removal efficiencies from 81.16% and 98.68% to 68.65% and 92.57% in Fe-BC and NaOH-BC-amended sand columns, respectively. Moreover, compared to pristine BC, the activated BCs (Fe-BC and NaOH-BC) also resulted in the lower antibiotics (tetracycline and sulfamethoxazole) concentrations in the effluents from the BC-amended sand columns. Therefore, for the first time, this study indicated NaOH-BC showed high potential for effective treatment of E. coli from stormwater by the BC-amended sand filtration system compared with pristine BC and Fe-BC.

Composting and green technologies for remediation of phthalate (PAE)-contaminated soil: Current status and future perspectives

Phthalate esters (PAEs) are hazardous organic compounds that are widely added to plastics to enhance their flexibility, temperature, and acidic tolerance. The increase in global consumption and the corresponding environmental pollution of PAEs has caused broad public concerns. As most PAEs accumulate in soil due to their high hydrophobicity, composting is a robust remediation technology for PAE-contaminated soil (efficiency 25%-100%), where microbial activity plays an important role. This review summarized the roles of the microbial community, biodegradation pathways, and specific enzymes involved in the PAE degradation. Also, other green technologies, including biochar adsorption, bioaugmentation, and phytoremediation, for PAE degradation were also presented, compared, and discussed. Composting combined with these technologies significantly enhanced removal efficiency; yet, the properties and roles of each bacterial strain in the degradation, upscaling, and economic feasibility should be clarified in future research.

Diagnosing trace metals contamination in ageing stormwater constructed wetlands by portable X-ray Fluorescence Analyzer (pXRF)

In the context of stormwater management in urban areas, more knowledge is needed about sustainable urban drainage systems (SUDS)' long-term performance. This article reports robust calibration of a portable X-ray Fluorescence Analyzer (pXRF) for a purpose of metal accumulation diagnosis in two stormwater constructed wetlands (SCWs). Two 9-year-old SCWs located in Eastern France and composed of a sedimentation pond and a vertical-flow reed-bed filter (RBF#1) respectively a horizontal-flow RBF (RBF#2) are studied. A focus is made on the RBFs where five target metals (Cr, Cu, Ni, Pb, Zn) are monitored to fulfill three objectives: i) develop a robust analyzing method for both field and laboratory scale; ii) compute a distribution mapping of the metals on the substrate; and iii) identify and quantify contamination hotspots. pXRF measurements present an opportunity for a quick field diagnosis of such ageing systems once calibrated. An optimal 63 s beam shooting time was selected for analyses, and optimal particle size distribution was set below 250 μm. As water content is known to be a critical factor influencing measuring quality, correction factors were determined to allow for field campaign up to 30 % of water content. Metals are more accumulated in RBF#1 than in RBF#2 because of the particle size distribution and hydraulic regime of the RBFs. Moreover, RBF#1 displays a higher metal accumulation at the water supply outputs while the distribution pattern in RBF#2 is more diffuse. Only 34 %, resp. 22 % of RBF#1 and RBF#2 surface is contaminated, with corresponding concentrations ranging among the highest 50 % and 25 % concentrations. Eventually, the RBF#1 upper layer (0-5 cm) higher organic matter content generates more metal retention than its deeper layer whereas in RBF#2 metal concentration is homogeneous along depth. These results can be useful to optimize the long-term maintenance and possibly the sizing of such systems.

The nitrogen cycle and mitigation strategies for nitrogen loss during organic waste composting: A review

Composting is a promising technology to decompose organic waste into humus-like high-quality compost, which can be used as organic fertilizer. However, greenhouse gases (N₂O, CO₂, CH₄) and odorous emissions (H₂S, NH₃) are major concerns as secondary pollutants, which may pose adverse environmental and health effects. During the composting process, nitrogen cycle plays an important role to the compost quality. This review aimed to (1) summarizes the nitrogen cycle of the composting, (2) examine the operational parameters, microbial activities, functions of enzymes and genes affecting the nitrogen cycle, and (3) discuss mitigation strategies for nitrogen loss. Operational parameters such as moisture, oxygen content, temperature, C/N ratio and pH play an essential role in the nitrogen cycle, and adjusting them is the most straightforward method to reduce nitrogen loss. Also, nitrification and denitrification are the most crucial processes of the nitrogen cycle, which strongly affect microbial community dynamics. The ammonia-oxidizing bacteria or archaea (AOB/AOA) and the nitrite-oxidizing bacteria (NOB), and heterotrophic and autotrophic denitrifiers play a vital role in nitrification and denitrification with the involvement of ammonia monooxygenase (amoA) gene, nitrate reductase genes (narG), and nitrous oxide reductase (nosZ). Furthermore, adding additives such as struvite salts (MgNH₄PO₄·6H₂O), biochar, and zeolites (clinoptilolite), and microbial inoculation, namely Bacillus cereus (ammonium strain), Pseudomonas donghuensis (nitrite strain), and Bacillus licheniformis (nitrogen fixer) can help control nitrogen loss. This review summarized critical issues of the nitrogen cycle and nitrogen loss in order to help future composting research with regard to compost quality and air pollution/odor control.

Enhanced nutrient removal from stormwater runoff by a compact on-site treatment system

Efficient and space-saving technologies for on-site treatment of stormwater runoff are required to control water pollution in the urban surface. The intermittent nature of stormwater runoff and extremely limited land available greatly hindered the application of current wastewater treatment technologies, and thus synchronous removal of multiple contaminants (especially for nutrient) efficiently was failed by current processes. In this study, a new compact CFFA treatment system, consisting of coagulation, flocculation, filtration and ammonium ion exchange units, was constructed for on-site treatment of stormwater runoff based on batch test optimization and pilot-scale test verification. The coagulation process effectively aggregated particles and precipitated phosphorus by dosing Al₂(SO₄)₃, while flocculation using anionic polyacrylamide further enlarged particle size for efficient micromesh filtration. The dynamic micromesh filtration obtained turbidity and phosphorus removal efficiencies comparable to 30 min gravity settling with greatly smaller footprint. Ion exchange by zeolite showed higher exchange capacity owing to lower initial ammonium nitrogen concentration in the stormwater runoff. The pilot-scale experiments with treatment capacity of 1 L/s showed that the CFFA treatment system achieved synchronous removal of particles (97.2%), nitrogen (79.7%), phosphorus (95.0%) and organic matters (83.3%) efficiently within short hydraulic retention time of 0.35 h, yielding effluent with chemical oxygen demand, suspended solids, total phosphorus and total nitrogen of 38.7, 7.80, 0.22 and 2.80 mg/L, respectively. The CFFA treatment system had the highest pollutant removal loads compared to reported runoff treatment processes in literatures, and was well suited to on-site treatment of stormwater runoff with high space utilization efficiency.

Enhanced Slow Sand Filtration for the Removal of Micropollutants from Groundwater

Remote areas, where centralized water supply cannot reach, rely heavily on decentralized supply systems such as slow sand filters (SSFs). Groundwater used to be a reliable water source; yet, the advent of micropollutants (MPs) has raised concerns over its quality. In this study, an enhanced slow sand filtration utilizing graphene oxide (GO)-coated sand prepared via a simple thermal method was employed to remove two representative MPs, atrazine (ATZ) and atenolol (ATL), from real groundwater for drinking water treatment. The removal of ATZ and ATL was studied in a bench-scale enhanced SSF using GO-coated sand in comparison with the conventional plain sand. The results showed that the GO-coated sand performed better in the removal of ATZ, ATL, and total organic carbon (TOC), as well as turbidity reduction. Moreover, in order to study the role of the schmutzdecke in MPs' removal small lab-scale columns with and without schmutzdecke growth were set up. The results indicated the enhanced removal capacity of the coated sand toward ATZ, ATL, and TOC could mainly be attributed to the GO coating layer, not the schmutzdecke. Hence, if the coated sand is to be used in field SSFs for the removal of organic contaminants, the schmutzdecke growing phase might not be needed. A preliminary techno-economic analysis was performed to evaluate the practicability of enhanced SSF and GO was found to dominate the overall cost. For a community-level or a household-level SSF, the extra cost using GO-coated sand may be $0.34 and $3.25 per m³ of water if the GO price is $10 and $100 per kg, respectively.

Treatment efficiency of synthetic urban runoff by low-cost mineral materials under various flow conditions and in the presence of salt: Possibilities and limitations

Urban runoff belongs to important carriers of pollutants that during infiltration can accumulate in the soil/water environment. One of the protection solutions may be the enhancement of infiltration systems by horizontal permeable treatment zones. The article presents the results of column tests carried out in order to determine (1) the influence of the hydraulic loading rate on the dynamic capacities of selected reactive materials: low-cost mineral materials (zeolite, limestone sand, halloysite) and reference material (activated carbon), and control soils (topsoil and Vistula sand) against Zn, NH₄⁺ and PO₄^3-, and (2) remobilization of contaminants under the influence of salt (NaCl 5 g/L) present in synthetic runoff water. The research has revealed that the most useful for the removal of zinc ions was limestone sand (>4.36 mg/g), of orthophosphates - halloysite (2.29 mg/g on the average), and of ammonium ions - zeolite (2.75 mg/g on the average). The control soils were characterized by low ability to immobilize the contaminants tested. In addition, increase in the hydraulic loading rate of synthetic runoff water reduced the dynamic capacity of materials to a variable degree depending on the material applied and the contamination removed (by 24% for limestone sand-PO₄^3- system to 95% for activated carbon-NH₄⁺ system). The presence of NaCl caused significant leaching of ammonium ions from zeolite and halloysite filter beds (up to 99.3%), and phosphates from the activated carbon filter bed (up to 41.3%). All tracer contaminants tested leached intensively from the Vistula sand filter bed, while only ammonium ions leached from the topsoil filter bed. It seems justified to support the performance of infiltration systems by layers of: limestone sand, to enhance the processes of heavy metal precipitation and ammonium ion volatilization by increasing the pH, and halloysite for the sorption of phosphates.

A critical review of contaminant removal by conventional and emerging media for urban stormwater treatment in the United States

Stormwater is a major component of the urban water cycle contributing to street flooding and high runoff volumes in urban areas, and elevated contaminant concentrations in receiving waters from contact with impervious surfaces. Engineers and city planners are investing in best management practices to reduce runoff volume and to potentially capture and use urban stormwater. However, these current approaches result in moderate to low contaminant removal efficiencies for certain classes of contaminants (e.g., particles, nutrients, and some metals). This review describes options and opportunities to augment existing stormwater infrastructure with conventional and emerging reactive media to improve contaminant removal. This critical analysis characterizes media physicochemical properties and mechanisms contributing to contaminant removal, describes possible candidates for new engineered media, highlights lab and field studies investigating stormwater media contaminant removal, and identifies possible limitations and knowledge gaps in media implementation. Following this analysis, information is provided regarding factors that may contribute to or adversely impact urban stormwater treatment by media. The review closes with insights into additional research directions and important information necessary for safe and effective urban stormwater treatment using media.

Joint effects of cadmium and copper on Apis mellifera forgers and larvae

Honey bees (Apis mellifera L.) are important ecological and agricultural resources. They are among the most widely available pollinators and provide products as well as services. Unfortunately, honey bee populations are susceptible to several environmental threats, including heavy metal exposure. Honey bees can be exposed to heavy metals when foraging on contaminated honey and pollen resources, and in some cases by airborne exposure. We studied the joint acute and chronic effects of cadmium (Cd) and copper (Cu) on A. mellifera. A 1:1 solution of the two heavy metals increased larval developmental duration and the mortality of both larvae and foragers in a dose-dependent way, decreased forager feeding, increased body metal burdens, and disrupted the sucrose response behavior of foragers. In combination, Cd and Cu demonstrated a weakly synergistic effect on foragers, but for larvae an initially antagonistic effect at low doses changed to strongly synergistic response at higher concentrations. The sucrose response threshold of foragers decreased significantly when they were dosed with increasing concentrations of the metal mixtures. Overall, the fitness of honey bee larvae and foragers is detrimentally affected when these metals co-occur.

Urban stormwater characterization, control, and treatment

This review summarizes over 280 studies published in 2019 related to the characterization, control, and management of urban stormwater runoff. A summary of quantity and quality concerns is provided in the first section of the review, serving as the foundation for the following sections which focus on the control and treatment of stormwater runoff. Finally, the impact of stormwater control devices at the watershed scale is discussed. Each section provides a self-contained overview of the 2019 literature, common themes, and future work. Several themes emerged from the 2019 literature including exploration of substrate amendments for improved water quality effluent from stormwater controls, the continued study of the role of vegetation in green infrastructure practices, and a call to action for the development of new models which generate reliable, computationally efficient results under the physical, chemical, biological, and social complexity of stormwater management. PRACTITIONER POINTS: Over 280 studies were published in 2019 related to the characterization, control, and treatment of urban stormwater. Studies on bioretention and general stormwater characteristics represented the two most common subtopics in 2019. Trends in 2019 included novel substrate amendments, studies on the role of vegetation, and advancements in computational models.

Hazardous wastes treatment technologies

A review of the literature published in 2019 on topics related to hazardous waste management in water, soils, sediments, and air. The review covered treatment technologies applying physical, chemical, and biological principles for the remediation of contaminated water, soils, sediments, and air. PRACTICAL POINTS: This report provides a review of technologies for the management of waters, wastewaters, air, sediments, and soils contaminated by various hazardous chemicals including inorganic (e.g., oxyanions, salts, and heavy metals), organic (e.g., halogenated, pharmaceuticals and personal care products, pesticides, and persistent organic chemicals) in three scientific areas of physical, chemical, and biological methods. Physical methods for the management of hazardous wastes including general adsorption, sand filtration, coagulation/flocculation, electrodialysis, electrokinetics, electro-sorption ( capacitive deionization, CDI), membrane (RO, NF, MF), photocatalysis, photoelectrochemical oxidation, sonochemical, non-thermal plasma, supercritical fluid, electrochemical oxidation, and electrochemical reduction processes were reviewed. Chemical methods including ozone-based, hydrogen peroxide-based, potassium permanganate processes, and Fenton and Fenton-like process were reviewed. Biological methods such as aerobic, anoxic, anaerobic, bioreactors, constructed wetlands, soil bioremediation and biofilter processes for the management of hazardous wastes, in mode of consortium and pure culture were reviewed. Case histories were reviewed in four areas including contaminated sediments, contaminated soils, mixed industrial solid wastes and radioactive wastes.

Assessment of heavy metal contamination and adverse biological effects of an industrially affected river

One of the most industrially affected rivers in Taiwan, the Houjing River, was studied in this research. The water and sediment samples were collected at five locations to measure the concentration of eight metals (As, Cd, Cr, Cu, Hg, Pb, Ni, and Zn). In order to assess the heavy metal contamination and its adverse biological effect, the heavy metal pollution index (HPI), the degree of contamination index (DC), the contamination factor (CF), the index of geo-accumulation (I_geo), and hazard quotients (HQs) were employed. The results showed that the Houjing River's water and sediment were contaminated with heavy metals. The annually averaged values of HPI (128.3) and DC (21.3) indicate that the water is unsafe for potable use and the sediment contamination level is at considerable degree of contamination. CF and I_geo calculation show that Zn, Cu, and Cd are the three main metals contributing to heavy metal contamination in sediment. Evaluation of adverse biological effects suggests that Zn, Cu, and Ni are the major metals that cause adverse effects on organisms. This study provides an overview of the synergistic heavy metal contamination degree of the Houjing River and its adverse biological effects, which should be a reliable reference for future contamination control and management plans.

Magnetic porous NiLa-Layered double oxides (LDOs) with improved phosphate adsorption and antibacterial activity for treatment of secondary effluent

The removal of phosphate (nutrient) and E. coli (pathogen) from secondary effluent is of great importance to control the water quality of the receiving water bodies. In this study, magnetic porous NiLa-layered double oxides (NiLa-LDOs/Fe₃O₄) were synthesized using a simple co-precipitation method. NiLa-LDOs/Fe₃O₄ exhibited a high phosphate adsorption capacity of 203.10 mg g^-1 in batch adsorption experiments, which can mostly be maintained within the pH range (5.5-8.5) and ionic strength range (5-20 mM) of secondary effluent, and in the presence of commonly co-existing species (anions and organics). NiLa-LDOs/Fe₃O₄ were further evaluated in real secondary effluent and the homogenous surface diffusion model (HSDM) was used to predict the performance in field applications. Under typical conditions, NiLa-LDOs/Fe₃O₄ can last for ∼1845-2448 bed volumes (BVs) before the phosphate concentration in the effluent exceeds the monthly average limit of 1 mg L^-1 P. Good regeneration capacities were also demonstrated in cyclic adsorption-desorption runs in both synthetic solution and secondary effluent. In addition, the presence of Ni and La species greatly enhanced the antibacterial performance of the NiLa-LDOs/Fe₃O₄ toward E. coli. Results obtained from this study indicate porous NiLa-LDOs/Fe₃O₄ can be a promising multifunctional material for the treatment of secondary effluent.

Comments on "Breakthrough analysis of continuous fixed-bed adsorption of sevoflurane using activated carbons"

This communication discusses the fixed bed modeling results of the recent paper published by Ang et al. (2020) in this journal.