Potential For Removal Of Pollutants Research Articles

Root vertical spatial stress: A method for enhancing rhizosphere effect of plants in subsurface flow constructed wetland

The depth of the substrate of subsurface flow (SSF) constructed wetlands (CWs) is closely related to their cost and operation stability. To explore the physiological regulation mechanism of wetland plants and pollutant removal potential of SSF CWs under “vertical spatial stress of roots” (by greatly reducing the depth of the substrate in SSF CWs to limit the vertical growth space of roots, VSSR), the physiological response and wetland purification effect of a 0.1 m Canna indica L. CW under VSSR were studied compared with conventional SSF CWs (0.6 m, 1.2 m). The results demonstrated that VSSR significantly enhanced the dissolved oxygen (DO) concentration (p < 0.05) within the SSF CWs, with the DO in 0.1 m CW remaining stable at over 3 mg/L. Under the same hydraulic retention time (HRT), VSSR significantly improved the removal effect of pollutants (p < 0.05). The removal rates of COD, NH4+-N, and total phosphorus (TP) remained above 87%, and the mean removal rates of total nitrogen (TN) reached 91.71%. VSSR promoted the morphological adaptation mechanisms of plants, such as significantly increased root-shoot ratio (p < 0.05), changed biomass allocation. Plants could maintain the stability of the photosynthetic mechanism by changing the distribution of light energy. The results of microbial community function prediction demonstrated that aerobic denitrification was the main mechanism of N transformation in the 0.1 m CW under VSSR. VSSR could induce the high root activity of plants, augment the concentration of root exudates, enhance the redox environment of the plant rhizosphere, further foster the enrichment of aerobic denitrifying bacteria, and strengthen the absorption efficiency of wetland plants and substrate, thus achieving an efficient pollutant removal capacity. Studies showed that VSSR was an effective means to enhance the rhizosphere effect of plants and pollutant removal in SSF CWs.

Municipal Wastewater Effects on the Performance of Nutrient Removal, and Lipid, Carbohydrate, and Protein Productivity of Blue-Green Algae Chroococcus turgidus

The use of microalgae in wastewater treatment (WWT) is seen as a promising and sustainable alternative to conventional WWTs, and the obtained biomass is gaining importance as a bio-product. The present study aimed to investigate the effectiveness of using municipal wastewater (MWW) as a nutritional supplement for the cultivation of the cyanobacteria Chroococcus turgidus (Kützing) Nägeli 1849 and the pollutant removal potential of the microalgae. The WW received from the different treatment stages (primary, secondary, and final effluent) was applied to the microalgae culture, and algal growth was compared with regard to growth rate, nutrient removal efficiency, and final algal lipid (%) and protein (%) content. In 7-day batch experiments, except for BOD5 analysis, COD, PO4-P, and N forms analyses were carried out daily in parallel with in vivo Chl-a and Chl-b, DO, pH, temperature, and conductivity measurements. The growth rates and Chl-a quotas of the microalgae grown in trials were different, and the highest growth rate was with a 1.03 ± 0.06 d−1 in the primary effluent (PE). The highest Chl-a and Chl-b quotas among WW trials of microalgae were obtained from the PE trial as 252.4 ± 2 µg L−1 and 112 ± 18 µgL−1, respectively. NH4-N, NO3-N, NO2-N, PO4-P, BOD5, and COD treatment efficiencies were in the ranges of (74.6–83%), (16–71.2%), (22.2–63.6%), (89–95.3%), (50–76.2%), and (70.3–78.6%), respectively. The microalgae were observed to accumulate the highest lipid (28.05 ± 2.26%DW) content in secondary effluent (SE), the highest carbohydrate (43.93 ± 1.02%DW) content in the effluent (E), and the highest protein content (35.25 ± 1.22%DW) in the PE. The results of this study suggested that C. turgidus is a new candidate for bioremediate pollution load of MWW, and its biomass has the potential to offer options in bio-product applications.

Leachate treatment potential of nanomaterial based assemblies: a systematic review on recent development.

Rapid development of the population has brought about a serious problem of waste generation and management. Open dumping and land filling are two of the preferred options for waste management and treatment. As a consequence of this, the accumulation of leachates has become one of the concerns for environmental sustainability. In this regard, various treatment methodologies have been developed in recent decades. Among them, the nanomaterial-based approaches are the emerging ones in the current scenario due to their various unique properties. Furthermore, nanomaterial-based assemblies (i.e., nanomaterials combined with microbes, chemical catalysts, enzymes, and so on) have been introduced as a novel modification for leachate treatment. This work, therefore, has been dedicated to comprehensively reviewing all nanomaterial based leachate treatment techniques. In this regard, the first part of this review will discuss the nano catalyst, nano adsorbent along with their synthesis and mechanistic view of pollutant removal potential. In the second part, the nanomaterial-based microbial conjugates applied in the leachate treatments have been discussed. Apart from this, various other nanomaterial-based methods have been discussed in the third part of the review. Hence this review is providing an insight of all the recent developments pertaining to the nano material based leachate treatment techniques.

Peroxydisulfate bridged photocatalysis of covalent triazine framework for carbamazepine degradation

Covalent triazine frameworks (CTFs) are appealing photocatalysts for environmental remediation. However, high recombination rate of photogenerated electrons and holes is the key limitation for its application. Notably, peroxydisulfate (PDS) can potentially act as electron withdrawing center to efficiently prevent the recombination. Herein, the photocatalysis of CTF under visible light (VL) coupled with PDS shows great potential for pollutants removal, taking carbamazepine (CBZ) as a case, in which the observed rate constant of CBZ degradation in VL/CTF/PDS process is 9.0 and 4.5 times to that in CTF/PDS and VL/CTF processes, respectively. PDS can construct a bridge to enhance the charge separation and transfer efficiency of CTF to prevent the recombination of electrons and holes, thus significantly improving the oxidation ability of the VL/CTF/PDS process. Moreover, the accepted electrons can initiate the PDS activation to generate more reactive species, thus contributing to higher oxidation capacity of the VL/CTF/PDS process. Furthermore, the VL/CTF/PDS process tends to attack the 1 N and 12C–15C atoms of CBZ to induce the cleavage of N-C bond and oxidation of CC bond, thus decomposing CBZ into lower molecules and finally being mineralized. This study will promote the development on applying photocatalysis of CTF materials and PDS activation in practical environmental remediation.

Water hyacinth biochar and Aspergillus niger biomass amalgamation potential in removal of pollutants from polluted lake water

The excess load of organic and inorganic pollutants in Chanramkudi Lake water creates eutrophication resulting from excess growth and spreading of water hyacinth and bad odor and provides favorable circumstances for the survival of disease spreading insect vectors and possibilities of disease occurrence. The results showed that the suitable temperature and residence time for the conversion of dried biomass of water hyacinth into useful biochar was 350 °C and 60 min, respectively, and 33.6% of water hyacinth biochar (WHBC) at stable organic content basis of 49.2% was produced. The WHBC produced under this condition had physicochemical properties such as 389.8 mmol kg−1 of CEC (Cation Exchange Capacity), 69.1 of C/N, 68.2 of C, 234.7 mg kg−1 of total P, 19.7% of ash, and 59.4% of volatiles with pH 7.9. The metal adsorbing competence of this WHBC with and without A. niger was tested with various concentrations (250, 500, 750, and 1000 mg L−1) of various metal (Cd, Cr, and Pb) containing solutions. The WHBC with A. niger amalgamation (15:3 g) effectively adsorbed the metals even at 1000 mg L-1 such as Cr (91.5%), Cd (95.6%), and Pb (93.9%) than individually. The metals were adsorbed and immobilized in the pores of WHBC and the outer layer of the cell wall of A. niger was observed under SEM analysis with various scaling (50, 100, and 150 µm). Further, the pollutant adsorbing functional groups were found in both WHBC and dead mycelia biomass of A. niger through FTIR analysis. The attained results concluded that the biochar produced from challenging water hyacinth could adsorb and minimize the pollutants with an amalgamation of A. niger. Significantly, more volume (33.6%) of biochar can be derived from water hyacinth. Furthermore, WHBC and A. niger are easily cultivable. Thus, it could be preferably useful for removing real-world organic and inorganic pollutants from polluted water.

Геоекологічний аналіз і оцінка території Чернігівської області

The main purpose of the geoecological research of Chernihiv region is a comprehensive analysis and assessment of the ecological state of geosystems in terms of human needs. Based on the analysis of natural features of geosystems of Chernihiv region and their geochemical properties, differences in self-cleaning ability of landscapes were revealed. The relatively high potential for removal of hazardous substances is peculiar to the elevated dissected landscapes of the southeastern and northeastern parts of the region. The landscapes of the Dnieper and Desna Polissya and the Northern region of the Dnieper terrace plain account for the greatest share of areas with low potential for pollutants removal. Anthropogenic impact on the environment of Chernihiv region is quite significant and diverse in type, intensity, and territorial distribution. The consequences of this impact are radioactive contamination of the western and northeastern parts of the region, high level of air pollution in cities, unsatisfactory ecological state of groundwater, especially in Chernihiv Polissya, degradation of land resources. Based on the analysis of the ecological state of individual natural components, the integrated indicator of pollution of geosystems of the administrative districts (as of the year 2019) of Chernihiv region was determined and its western and northeastern territories are defined to have the most severe ecological situation in the region. As a result of a correlation analysis between the indicators of environmental pollution of Chernihiv region and the state of public health, it was found that the radioactive contamination of the territory by 137Cs has the greatest influence on the morbidity of the region’s population. It causes high incidence rates of the endocrine system, blood and hematopoietic organs diseases. This feature should be considered when developing environmental policy of the region.

Potential nanomaterials application in wastewater treatment: Physical, chemical and biological approaches

Abstract The essential challenges in the 21st century are providing clean and affordable water to meet human needs that are mainly resulting from the rapidly increasing population, depleting water resources, and climate change. The development and implementation of advanced wastewater treatment technologies with high efficiency and low capital requirement is important in order to minimize the negative impacts of wastes on the environment. Nanotechnology offers a great potential for removal of pollutants and germs from waswater. High surface-to-volume ratio and photocatalytic properties of these nanomaterials introduced them as highly potent option for removal of heavy metal ions and organic dyes. This paper critically reviewed the application of nanomaterials as nano-adsorbent, nano-catalyst and nano-membrane in wastewater treatment. This review also provided an insight into a detailed description and application of these nanomaterials in chemical, physical and biological treatment for removal of pollutant from waswater. From the current review, it is evident that the nanomaterials possess exclusive properties, which can contribute to the high efficacy in treating high levels of different pollutants.

Space-confined synthesis of nitrilotriacetic acid immobilized magnetic sorbents in aqueous continuous phase of high internal phase emulsion for removing bivalent cadmium

• Space-confined synthesis of NAIMSs-E in aqueous continuous phase of HIPEs is conducted. • High quality sorbents are applied for removing Cd 2+ from aqueous solutions. • DA-NTA moieties not only endow abundant binding sites, but also act as robust anchor. • NAIMSs-E possess sensitive response under magnetic field, fast uptake and large adsorption amount. Monodispersed magnetic sorbents (MMSs) display great potential for adsorptive removal of pollutants, but the conventional methods cannot meet requirements of scalable, time-saving, and energy-efficient fabrication. In this work, space-confined synthesis of nitrilotriacetic acid immobilized magnetic sorbents (NAIMSs-E) in aqueous continuous phase of high internal phase emulsions (HIPEs) was conducted, and as-prepared high quality sorbents (sensitive response to magnetic field, abundant affinity groups, uniform shell size, and stable structure) were applied for removing bivalent cadmium (Cd 2+ ) from aqueous solutions. 2-(Bis-carboxymethyl-amino)-6-{3-[2-(3,4-dihydroxy-phenyl)-ethylcarbamoyl]-propionylamino}-hexanoic acid was firstly synthesized as a robust anchor and a functional modifier onto magnetic Fe 3 O 4 . The effects of synthesis conditions to the morphology and structure were studied, and the forming mechanism based on emulsion nano-reactor was demonstrated. NAIMSs-E are expected to possess fast equilibrium rate, and approximately 90% of the maximum adsorption capacity is achieved within 60 min. The maximum uptake amounts are 49.98 mg g −1 , 80.58 mg g −1 , 176.4 mg g −1 at 288 K, 298 K, and 308 K, respectively, and the monolayer chemisorption based on sharing and transferring of electrons is the main rate-limiting step. Moreover, NAIMSs-E have excellent regeneration and specific affinity towards Cd 2+ , even for actual water samples. In addition, the spontaneous, endothermic, and entropy increased adsorption process is also confirmed. Therefore, this work not only presents a new clue to fabricate MMSs via simple emulsion nano-reactor, but also provides a novel platform for Cd 2+ removal.

Silver nanoparticles-assembled graphene oxide sheets on TiO2 nanotubes: synthesis, characterization, and photocatalytic investigation

In this study, graphene oxide (GO) sheets were assembled with silver nanoparticles (AgNPs) and then combined with TiO2 nanotubes (TNTs) by γ-ray irradiation at different doses (5, 10, 15, 20, and 25 kGy), to form GO–AgNPs–TNTs nanocomposites. Their physical and chemical properties were investigated using Fourier-transformed infrared, ultraviolet–visible (UV–Vis) adsorption, Raman and X-ray diffraction (XRD) spectroscopies. Field emission scanning electron and transmission electron (TEM) microscopies were applied for their morphology and structure observation. The obtained results indicated successful assemblage of silver nanoparticles on both GO sheets and TNTs, as well as significant effects of irradiation dose on nanocomposites’ characteristics. Photocatalytic activity of the material was determined by the photodegradation efficiency on rhodamine B dye solution. All nanocomposite samples were revealed to possess good photocatalytic activity, with the highest obtained decoloration efficiency value of 81.21%. Noticeably, the photocatalytic activity of all nanocomposite samples was higher than that of their sole components. With all obtained results, γ-ray irradiation was demonstrated to be a good technique for the synthesis of nanocomposite materials and GO–AgNPs–TNTs nanocomposite proclaimed high potential for pollutants removal and wastewater purification.

Slow growers possess a high pollutant removal potential through granule formation for wastewater treatment

For the upgradation and building of wastewater treatment plants in limited areas, biological wastewater treatment processes with a high pollutant removal loading rate are required. Biofilm or membrane-based systems can achieve a high pollutant removal loading rate through high microbial biomass concentrations and/or activities. The sludge separation is the primary bottleneck for achieving high biomass concentrations inside the biological reactors. In addition, low growers including anaerobic ammonia oxidation bacteria and methanogens are usually easier to form granules and induce high nutrient removal loading rates. The possible granule formation mechanisms should be clarified through physical, chemical and biological aspects, including hydraulic control, microbial extracellular polymeric substances formation, biological energy utilization control, microbial interactions and also other microbial processes. In future, the possible mechanisms should be further clarified, and then high-efficient bioreactors, new microbial ecology control strategy and novel biofilm carriers should be developed for advancing biological wastewater treatment processes with high pollutant removal loading rates.

Identifying key environmental factors for enhancing the pollutant removal potential at a river confluence

The confluence area of river networks is a hot spot for pollutant removal. As an essential part of the river ecosystem, sediment bacterial communities played a crucial role in the removal of pollutants. However, how the potential of sediment bacterial communities can be enhanced toward the removal of pollutants remains unclear. Therefore, this study provides a new approach for the identification of key environmental factors that enhance the pollutant removal potential at a river confluence, integrating the bacteria-based index of biotic integrity (Ba-IBI), path model, support vector regression (SVR) model, and sensitivity analysis. The developed Ba-IBI could quantitatively evaluate the differences of both structure and function of bacterial communities before and after the confluence, with a range from 1.52 to 2.78. The flow regime, which was represented by the Froude number, exerted an indirect effect on Ba-IBI mediated through water nutrients and sediment nutrients according to path model results. Sediment nutrients and water nutrients were considered as the main environmental factors that directly affected sediment bacterial communities. A function that could predict the response of sediment bacterial communities to environmental factors in the best possible way was found through SVR modeling, with R2 = 0.8357. The results of the sensitivity analysis indicated that the total phosphorus in water and ammonia nitrogen in sediments were key environmental factors for enhancing the pollutant removal potential at the river confluence. The established approach aids the improvement of the bioremediation potential of river confluence area, and might provide a theoretical basis for watershed restoration.

Bacterial community structure in rotating biological contactor treating coke wastewater in relation to medium composition

Biological wastewater treatment using biofilm systems is an effective way to treat difficult wastewater, such as coke wastewater. The information about the structure and the dynamics of this microbial community in biofilm, which are responsible for wastewater treatment, is relevant in the context of treatment efficacy and the biochemical potential to remove various pollutants. However, physico-chemical factors can influence the biofilm community significantly, causing performance disturbances. Therefore, we decided to examine the structure of microbial community in rotating biological contactor (RBC) biofilm during coke wastewater treatment and to investigate the possible shift in the community structure caused by the feeding medium change from synthetic to real coke wastewater. The experiment performed with high-throughput next-generation sequencing (NGS) revealed that bacteria commonly present in wastewater treatment plant (WWTP) systems, responsible for nitrite oxidizing, such as Nitrospira or Nitrobacter, were absent or below detection threshold, while Nitrosomonas, responsible for ammonia oxidizing, was detected in a relatively small number especially after shift to real coke wastewater. This research indicates that medium change could cause the change from autotrophic into heterotrophic nitrification led by Acinetobacter. Moreover, biofilm systems can be also a potential source of bacteria possessing high biochemical potential for pollutants removal but less known in WWTP systems, as well as potentially pathogenic microorganisms.

Pollutant removal potential of single-size root zone media using Vetiveria zizanioides as emergent macrophyte and its validation

The purpose of this study was to evaluate the performance of horizontal flow constructed wetland system made up of single-size gravel media root zone using Vetiver (Vetiveria zizanioides) as emergent plant with focus on removal of biochemical oxygen demand, chemical oxygen demand, nitrate and orthophosphate of sewage in microcosms scale test bed. In this study, wetland was made of RCC tank [1.8 m (L) × 0.8 m (W) × 0.7 m (H)] and planted with vetiver in 20 mm gravel root zone media and another setup without plants was maintained as a control. Constructed wetland was subjected to a flow rate of 0.18 m3/day and 0.12 m3/day corresponding to hydraulic retention time of 2 and 3 days, respectively, and pollutant loading rates in gm/m3/d in the range of 20.04–30.8, 45.59–49.2, 3.48–4.94 and 1.13–1.4, respectively, for biochemical oxygen demand, chemical oxygen demand, nitrate and orthophosphate. Removal efficiency achieved for biochemical oxygen demand, chemical oxygen demand, nitrate and orthophosphate was in the range of 88.87–92.25%, 77.65–81.07%, 44.97–51.43% and 49.17–53.33%, respectively, for 2 and 3 days of hydraulic retention time for the wetland system. Removal efficiency of horizontal flow constructed wetland system with vetiver is statistically significant (p < 0.05: two-sample Student’s t test) compared to control. Results obtained are validated through Proff. Kickuth and K-C* model. Results of the present study are in closer agreement with K-C* models’ predictions.

Enhancement of Cr(VI) removal by mechanically activated micron-scale zero-valent aluminum (MA-mZVAl): Performance and mechanism especially at near-neutral pH

The dense oxide film greatly limits the strong reducibility of micron-scale zero-valent aluminum (mZVAl), especially at near-neutral pH. In this study, we found that the removal efficiency of Cr(VI) can be greatly enhanced over a wide pH range (3.00–11.00) by mechanically activated mZVAl (MA-mZVAl), which was prepared from mZVAl by ball milling (BM) in the presence of additive NaCl. Compared with mZVAl, at initial pH 7.00, MA-mZVAl removed Cr(VI) at a roughly 292-fold faster rate. The effects of BM parameters including the amount of additive NaCl, BM speed, BM time, and BM atmosphere on Cr(VI) removal were first evaluated. Then, the Cr(VI) removal mechanism was explored by measuring the concentration of different valent chromium, monitoring the changes of water chemical parameters including DO, pH, ORP, Al ions concentration, and by ascertaining the role of Cl− in solution. Furthermore, the structure evolution of mZVAl after BM and the surface corrosion mechanism of MA-mZVAl during reaction with Cr(VI) were unveiled through the characterization by means of SEM-EDS, BET, XRD, and XPS. Based on above tests, we found that Cr(VI) was reductively removed by MA-mZVAl to form Cr(OH)3(s) precipitated on the surface of MA-mZVAl. NaCl promoted the reactivity of MA-mZVAl not in corrosion process but in BM process. The dense oxide film was destroyed by BM, and changed into a rough Al-(hydr)oxide film after corrosion. The reusability of MA-mZVAl was hindered by the formation of Al and Cr (hydr)oxide, but can be easily and completely rejuvenated by BM. Overall, BM can not only break through the bottleneck of oxide film but recover the passivated MA-mZVAl. Therefore, MA-mZVAl particles are of considerable potential for pollutants removal.

Shape matters: Cr(VI) removal using iron nanoparticle impregnated 1-D vs 2-D carbon nanohybrids prepared by ultrasonic spray pyrolysis

Iron nanoparticles (Fe NPs) are used for treating water contaminated with metals or organic compounds. One-dimensional (1-D) carbon nanotubes (CNTs) and two-dimensional (2-D) graphenes act as useful nanocarbon (NC) supports for Fe NPs by resisting aggregation and enhancing adsorption and redox activity. However, no study showed how shape difference between tubular CNT and planar graphene structures dictates the physicochemical properties and pollutant removal potential of their iron-based nanohybrids. In this work, ultrasonic spray pyrolysis was used to continuously prepare Fe-CNT and Fe-rGO nanohybrids. Both NC shape and Fe/NC ratio influenced Fe NP size, loading, and oxidation states. High Fe content (precursor Fe/NC mass ratio = 2) resulted Fe NPs with diameters of 30.97 ± 7.00 and 24.11 ± 4.42 nm for Fe-CNT and Fe-rGO, respectively; however, low Fe content (Fe/NC = 0.2) provided more uniformly dispersed Fe NPs of 15.65 ± 3.06 and 9.67 ± 1.49 nm, respectively, while unsupported Fe NPs were 285.71 ± 132.42 nm. The USP-derived nanohybrids, for the first time, were used for removal of pollutant, i.e., chromium (Cr(VI)) from aqueous media. Both CNT and rGO provided synergistic effects to significantly enhance Fe NPs’ ability to remove Cr(VI); the effect was more pronounced in Fe-rGO than Fe-CNT and also for low Fe content in both cases. Fe-rGO with low Fe/NC ratio and smallest Fe NPs provided the highest Cr(VI) removal capacity (25 mg/g), which was a multifold improvement over bare Fe NPs and other synthesized nanohybrids (range 7–14 mg/g). Overall, 2-D rGO improved contaminant removal capacity of the nanohybrids more than 1-D CNT indicating towards shape effect of NC supports.

Natural treatment system models for wastewater management: a study from Hyderabad, India.

Wastewater generated on a global scale has become a significant source of water resources which necessitates appropriate management strategies. However, the complexities associated with wastewater are lack of economically viable treatment systems, especially in low- and middle-income countries. While many types of treatment systems are needed to serve the various local issues, we propose natural treatment systems (NTS) such as natural wetlands that are eco-friendly, cost-effective, and can be jointly driven by public bodies and communities. In order for it to be part of wastewater management, this study explores the NTS potential for removal of pollutants, cost-effectiveness, and reuse options for the 1.20 million m3/day of wastewater generated in Hyderabad, India. The pilot study includes hydro-geophysical characterization of natural wetland to determine pollutant removal efficiency and its effective utilization for treated wastewater in the peri-urban habitat. The results show the removal of organic content (76-78%), nutrients (77-97%), and microbes (99.5-99.9%) from the wetland-treated wastewater and its suitability for agriculture applications. Furthermore, the wetland efficiency integrated with engineered interventions led to the development of NTS models with different application scenarios: (i) constructed wetlands, (ii) minimized community wetlands, and (iii) single outlet system, suitable for urban, peri-urban and rural areas, respectively.

A spatially-explicit method to assess the dry deposition of air pollution by urban forests in the city of Florence, Italy

Urban forests (UF) provide a range of important ecosystem services (ES) for human well-being. Relevant ES delivered by UF include urban temperature regulation, runoff mitigation, noise reduction, recreation, and air purification. In this study the potential of air pollution removal by UF in the city of Florence (Italy) was investigated. Two main air pollutants were considered – particulate matter (PM10) and tropospheric ozone (O3) – with the aim of providing a methodological framework for mapping air pollutant removal by UF and assessing the percent removal of air pollutant.The distribution of UF was mapped by high spatial resolution remote sensing data and classified into seven forest categories. The Leaf Area Index (LAI) was estimated spatially using a regression model between in-field LAI survey and Airborne Laser Scanning data and it was found to be in good linear agreement with estimates from ground-based measurements (R2=0.88 and RMSE%=11%). We applied pollution deposition equations by using pollution concentrations measured at urban monitoring stations and then estimated the pollutant removal potential of the UF: annual O3 and PM10 removal accounted for 77.9t and 171.3t, respectively. O3 and PM10 removal rates by evergreen broadleaves (16.1 and 27.3g/m2), conifers (10.9 and 28.5g/m2), and mixed evergreen species (15.8 and 31.7g/m2) were higher than by deciduous broadleaf stands (4.1 and 10g/m2). However, deciduous forests exhibited the largest total removal due to the high percentage of tree cover within the city. The present study confirms that UF play an important role in air purification in Mediterranean cities as they can remove monthly up to 5% of O3 and 13% of PM10.

Removal of Pollutants from Water by Using Single-Walled Carbon Nanotubes (SWCNTs) and Multi-walled Carbon Nanotubes (MWCNTs)

Water crisis is one of the supreme challenges worldwide as clean water is the ultimate need for human civilization and all other life on earth. In the present study, continuous adsorption experiments were carried out in an adsorption column to survey the efficiency of the carbon nanotubes (CNTs) for removal of pollutants from water/wastewater in terms of physicochemical parameters, such as electrical conductivity, total dissolved solids (TDS), pH, chemical oxygen demand (COD) and total organic carbon (TOC), by using both single-walled carbon nanotubes and multi-walled carbon nanotubes. Sample solutions were allowed to flow in down-flow mode through the fixed-bed of CNTs. The CNTs column showed a reduction efficiency of electrical conductivity 80 % from effluent treatment plant (ETP) treated water sample, 69.23 % from raw effluent sample, and 53.33 % from the synthetic salt water sample. Similarly, the efficiency of TDS reduction was 78.61 % from raw effluent sample, 66.86 % from ETP treated water sample, and 62.02 % from the synthetic salt water sample. COD also reduced 84.71 % from raw effluent sample and 39.58 % from the ETP treated water sample. In case of TOC, the column showed a reduction efficiency of 85.88 % from the ETP treated water sample and 70.79 % from the raw effluent sample. These findings suggested that CNTs present a great potential in removal of pollutants in terms of physicochemical parameters from water/wastewater.

Impact of the hydraulic loading rate on pollutants removal in tropical horizontal subsurface flow constructed wetlands

This study assessed the pollutant removal potential of horizontal subsurface flow (HSSF) constructed wetland systems under tropical conditions subjected to various hydraulic loading rates (HLRs). Three HSSF wetland units, each 1.4m×0.5m×0.6m (length×width×height) in size, filled with 10–20mm gravel as bed media, were used. Two beds were planted with a local emergent macrophyte; narrow-leaf cattail (Typha angustifolia), while the remaining served as a control without plants. All units were tested with synthetic wastewater mixed with septage sludge at different hydraulic loading rates (2.5–30cm/day) over a period of six months. Results show that the planted HSSF wetland units removed pollutants substantially up to 25cm/day HLR. Removal efficiencies at planted wetlands were over 80%, 44%, 96.5% and 96.1%, in comparison to unplanted wetland removals of 70%, 38%, 95.1% and 94.5% for five day biochemical oxygen demand (BOD5), total suspended solids (TSS), fecal coliform (FC) and total coliform (TC), respectively.

A systematic approach for the comparative assessment of stormwater pollutant removal potentials

This paper describes the development of a methodology to theoretically assess the stormwater pollutant removal performances of structural best management practices (BMPs). The method combines the categorisation of the relative importance of the primary removal processes within 15 different BMPs with an evaluation of the ability of each process to remove a pollutant in order to generate a value representing the pollutant removal potential for each BMP. The methodology is demonstrated by applying it separately to a set of general water quality indicators (total suspended solids, biochemical and chemical oxygen demand, nitrates, phosphates and faecal coliforms) to produce a ranked list of BMP pollutant removal efficiencies. Given the limited amount of available monitoring data relating to the differential pollutant removal capabilities of BMPs, the resulting prioritisation will support stakeholders in making urban drainage decisions from the perspective of pollutant removal. It can also provide inputs to existing urban hydrology models, which aim to predict the treatment performances of BMPs. The level of resilience of the proposed approach is tested using a sensitivity analysis and the limitations in terms of BMP design and application are discussed.