Pollutant Removal Capacity Research Articles

Population dynamics in mixed cultures of Neochloris oleoabundans and native microalgae from water of a polluted river and isolation of a diatom consortium for the production of lipid rich biomass

The production of biodiesel utilizing microalgae has driven innovation worldwide, especially trying to overcome the current economic and technological limitations of the whole process. Within these efforts, the use of wastewater to cultivate oleaginous microalgae or the use of dual-purpose microalgae-bacteria-based systems that treat wastewater and produce oleaginous microalgae have become an attractive alternative. The aim of this work was to evaluate the population dynamics which occurred in mixed cultures of Neochloris oleoabundans with other native microalgae, in mixtures of a synthetic medium (BBM) and water of an urban polluted river. The effect of temperature, nutrient availability and the microscopic monitoring of the population dynamics in such mixed cultures were carried out. Furthermore, the isolation of the predominant consortium of diatoms and the evaluation of its kinetics of growth and its capacity for removal of pollutants was also performed. Results indicated that such green microalgae only predominated in mixtures containing 80% or 60% of the synthetic medium. In mixtures containing a volume of the polluted river higher than 40%, other microalgae predominated, especially diatoms of various genera. The diatom consortium isolated from a 100% of the river's water sampled in spring (April), was formed mainly by a population of Nitzchia frustulum and in less extent of Navicula sp. It showed a significantly higher specific growth rate when cultivated in water from the river, compared to cultures in synthetic modified diatom medium (MDM) and at 32°C, compared to cultures incubated at 25°C. The consortium was able to remove 95.45% and 95.78% of ammonia nitrogen, 60% and 62.5% of nitrates at 32°C and 25°C, respectively, after 2 days. It also removed 95% of phosphates at 32°C and 67% at 25°C after 4 days from the polluted river. Diatoms also showed significant accumulation of lipids after 10 days of cultivation when stained with Sudan III. In conclusion, such diatom consortium showed a large potential for being used in a dual-purpose system that could treat the water from polluted streams and that could produce lipid rich biomass.

New Nitrogen and Phosphorus Removal Process Development Based on Simulation

Nitrogen and phosphorus are the nutrients induced eutrophication, therefore the removal of nitrogen and phosphorus is the main target of domestic wastewater treatment. In order to achieve better nutrient removal effect with lower construction and operation cost, a new nitrogen and phosphorus removal process was developed based on simulation. New process named MUST was developed by mixing UCT and step-feed BNR technology together, and possessed the advantages of two processes. The results of simulation show that MUST can achieve similar treating effect with 20% shorter hydraulic retention time (HRT) compared with UCT process. The influent splitting ratio of 4:3:3 was recommended for MUST operation. A pilot experiment of MUST was also carried out according to simulation results, and achieved very good pollutant remove effect, the average COD, NH4+-N, TN, TP removal efficiency were 85.4%, 94.0%, 65.1%, 62.3% respectively under the condition of low influent COD/TN ratio. Considering the excellent pollutant removal capacity of MUST, an upgrade project chose it as wastewater treatment process. This paper just starts the research of MUST, further study is necessary and valuable.

Improving local air quality in cities: To tree or not to tree?

Vegetation is often quoted as an effective measure to mitigate urban air quality problems. In this work we demonstrate by the use of computer models that the air quality effect of urban vegetation is more complex than implied by such general assumptions. By modelling a variety of real-life examples we show that roadside urban vegetation rather leads to increased pollutant concentrations than it improves the air quality, at least locally. This can be explained by the fact that trees and other types of vegetation reduce the ventilation that is responsible for diluting the traffic emitted pollutants. This aerodynamic effect is shown to be much stronger than the pollutant removal capacity of vegetation. Although the modelling results may be subject to a certain level of uncertainty, our results strongly indicate that the use of urban vegetation for alleviating a local air pollution hotspot is not expected to be a viable solution.

Potential of a polyculture of Arundo donax and Typha latifolia for growth and phytotreatment of wastewater pollution

Arundo donax and Typha latifolia are emergent macrophyte species that commonly reproduce in humid areas during warm months. This study investigated the growth and pollutant removal capacity of these two species planted in polyculture in a vertical flow filter bed for rural wastewater treatment. Plant shoot height was monitored and biomass production and nutrient uptake were assessed. Water physicochemical parameters were also monitored. A. donax showed higher height elongation (288 cm), phytomass production (2.4 kg dry biomass/m²) and nitrogen uptake (21.1 mg/kg DW) than did T. latifolia. Phosphorus and potassium retention was identical for both species. The macrophyte bed achieved higher removal rates for biochemical oxygen demand (BOD) (76%), chemical oxygen demand (COD) (82%), total suspended solids (TSS) (96%), total Kjeldahl nitrogen (TKN) (33%) and total phosphorus (TP) (46%), compared to an unplanted basin. The macrophyte species used were able to grow and to contribute to the rural wastewater purification in the adopted experimental constructed wetland. Key words: Arundo donax , Typha latifolia , wastewater, phytotreatment, nutrient uptake, constructed wetland.

Rapid adsorption of anionic dyes by ordered nanoporous alumina

Here we show that the ordered nanoporous alumina has high adsorption capacity for removal of dye pollutants from aqueous solution. The removal percentage of dyes by ordered nanoporous alumina is more than 30% only after 30s and about 60% after 6min which means that the dye removal is too fast in comparison to the activated carbon. An ordered nanoporous alumina has been synthesized by a fast and facile method by using aluminum iso-propoxide, F127 triblock copolymer and ethanol as a solvent. The TEM, XRD and N2 adsorption/desorption techniques have been used for characterization and the UV–vis spectroscopy has been used to follow the adsorption process. N2 sorption measurements reveal that the pore size of the obtained nanoporous alumina is about 5nm and therefore can be categorized as mesoporous materials.

Removal of Agricultural Non-Point Source Pollutants by Ditch Wetlands of the Maixi River, Guizhou Province, China

A natural ditch wetland grown with nature annual bluegrass (Poa annua L.), alligator weed (Alternanthera philoxeroides (Mart.) Griseb.), common duckweed (Lemna minor L.) and curly pondweed (Potamogeton crispus L.) etc. were selected to study the removal capacity of agricultural non-point source pollutants in the Maixi River in Guiyang City, the capital of Guizhou Province, China. The removal characteristics and seasonal variation of chemical oxygen demand (COD), total phosphorus (TP), ammonia-nitrogen (NH+4-N), and suspended solids (SS) in the ditch water was studied. The results showed that there existed a certain seasonal diversity in the removal characteristics of nitrogen, phosphorus and organic pollutants by the ditch. The removal efficiency of TP, COD and SS demonstrated an increasing tendency with their increasing concentration at the ditch inlet, whereas that of the NH4+-N displayed contrary tendency as the concentration of NH4+-N increased.

Nutritional potential of Echinochloa pyramidalis (Lam.) Hitchc. & chase, a forage plant used in constructed wetlands treatment of faecal sludge and wastewater

In Cameroon, Echinochloa pyramidalis used in constructed wetlands as alternative macrophytes revealed an attractive market potentials because of its quality as forage in addition to its pollutant removal capacity. The effects of salinity and the combined effects of salinity and flooding on the nutritional potential of E. pyramidalis under drained and flooded conditions were evaluated after 45 and 100 days of faecal sludge treatment. Leaf and stem samples were analysed for their crude protein (CP) and chemical compositions, especially in terms of cell-wall components while their apparent digestible dry matter (DDM), total digestible nutrients (TDN) and metabolizable energy (ME) were estimated. The results showed that E. pyramidalis is potentially suitable for cattle feeding. Thus, its use on wetland systems provides an opportunity to link sanitation stewardship to animal feed production which may contribute to sustain sanitation infrastructures and development. However, further investigations are necessary to evaluate the digestibility of most nutrients, the harvesting period and the contamination risk of E. pyramidalis grown in such system. Keys words: Constructed wetlands, Echinochloa pyramidalis, flooding, nutritive value, salinity, treatment period.

Synthesis of mesoporous carbon capsules encapsulated with magnetite nanoparticles and their application in wastewater treatment

Mesoporous carbon capsules encapsulated with Fe3O4 nanoparticles were prepared by the successive coating of a silica layer and a subsequent mesoporous silica/carbon layer on the surface of Fe3O4 nanoparticles followed by chemical etching with NaOH solution. TEM observations show that the as-obtained samples had a rattle-like structure: Fe3O4 nanoparticles were encapsulated in the interior of the mesoporous carbon capsules. The typical nitrogen adsorption/desorption results demonstrate that the specific surface area for the as-prepared samples is up to 1570 m2 g−1, and the total pore volume is about 3.02 cm3 g−1. The porous wall structure of the lateral carbon capsules provides the sufficient spaces that contribute to high adsorption capacities and faster adsorption rates of pollutants molecules in aqueous media. The nanocomposites are superparamagnetic at room temperature with a saturation magnetization of 5.5 emu g−1, which provides the prerequisite for the fast magnetic separation in wastewater treatment application. Water treatment experiments indicated that the as-prepared samples exhibited higher adsorption rates and more effective removal capacity of organic pollutants compared with commercial activated carbon (AC), and their maximum adsorption capabilities for methylene blue (MB), congo red (CR), and phenol reached 608.04, 1656.9 and 108.38 mg g−1, respectively. The multifunctional nanocomposites can be potentially used as absorbents for fast, convenient, and highly efficient removal of pollutants from the wastewater, which will play important roles in the purification or desalination of natural water and industrial effluents.

Field evaluation of an innovative stormwater treatment device—the StormvaultTM system

Stormvault is a new volume-control-based underground stormwater treatment system, which is well suited for implementation in urban areas. In order to evaluate the hydrologic and hydraulic function of the system and assess the pollutant removal capacity of the system, a field monitoring program was implemented during both wet and dry weather conditions for 2 years. The pollutants of interest were total suspended solids (TSS), chemical oxygen demand (COD), total phosphorus (TP), and orthophosphate (OP). Data of 35 storms obtained were then analyzed by using several methods, such as the efficiency ratios, the summation of loads, and the relative achievable efficiency (RAE) methods to obtain estimates for the pollutant removal efficiencies of the Stormvault unit. Results show the following average efficiencies: TSS 82.46%, COD 73.10%, TP 47.37%, and OP 52.54%. Statistical significance and variation of removal efficiency with inlet concentration were also examined.

A New Method for Determination of Parameters in Sewer Pollutant Transformation Process Model

Understanding pollutant transformation in sewers is important in controlling odor emission from pressure mains as well as in assessing organic pollutant removal capacity of gravity sewers. Sewer process models have thus been developed to quantify the pollutant transformation processes under various sewer conditions. The quantification largely depends on model parameter values, in particular the kinetic and stoichiometric parameters related to microbial activities. The current approaches not only involve a large amount of experimental work but also may induce significant errors when microbial reactions cannot be differentiated effectively during the experiments. Therefore, this study is aimed at developing a new method that can reduce experimental work significantly. The proposed method utilizes a genetic algorithm (GA) to enable the determination with a single set of batch experiments. To study the feasibility of the proposed method, a set of 72-hr batch experiments was first conducted for determining the parameters of a sewer model developed in this study, which adopted a full version of the International Water Association (IWA) Activated Sludge Model No. 3 (ASM3) to describe the microbial activities in sewers. The results were then verified with two different sets of the batch experiments. Furthermore, dynamic variation data of dissolved oxygen level were collected at the outlet of a 1.5-km gravity sewer to validate the determined parameters. All the results showed that the proposed parameter determination method is effective.

Adsorption of phosphate and nitrate anions on ammonium-functionnalized mesoporous silicas

Surface modified mesostructured silica materials represent potential adsorbents offering an opportunity to remediate several important water pollutants. In the present work, ammonium-functionnalized MCM-41, MCM-48 and SBA-15 mesoporous silica materials were synthesized via post-synthesis grafting and co-condensation. Their efficiency to remove nitrate and phosphate anions in aqueous solutions was investigated. The adsorbent materials showed high adsorption capacities reaching 46.5 mg NO 3 − /g and 55.9 mg H2PO 4 − /g under the operating conditions explored. The mesoporous silica materials functionalized via post-synthesis grafting method exhibited higher performances in terms of percentage pollutant removal and adsorption capacities if compared to their analogs synthesized according to the co-condensation strategy.

The design of wetland systems for the treatment of urban run off

The results of studies of the pollution removal performance of constructed wetlands for urban runoff treatment are discussed. The design of urban runoff wetlands including primary treatment components, substrate composition and flow rate regulation are considered. The use of front-end treatment systems such as oil interceptors, spillage containment facilities and wetland forebays or lagoons are recommended to provide an initial pollutant removal capacity as well as attenuating the impact of high discharges. Design criteria which will ensure inlet flow velocities do not exceed 0.7m/s and which will achieve optimum retention times (10-15 hours) for maximum pollutant removal are described. The relative advantages of different soil types are discussed and an overall minimum substrate depth of 0.6m is recommended for sub-surface systems. Two case studies of urban runoff wetlands in the UK which are currently being monitored are described.

The design of wetland systems for the treatment of urban run off

The results of studies of the pollution removal performance of constructed wetlands for urban runoff treatment are discussed. The design of urban runoff wetlands including primary treatment components, substrate composition and flow rate regulation are considered.The use of front-end treatment systems such as oil interceptors, spillage containment facilities and wetland farebays or lagoons are recommended to provide an initial pollutant removal capacity as well as attenuating the impact of high discharges. Design criteria which will ensure inlet flow velocities do not exceed O.7m/s and which will achieve optimum retention times (10–15 hours) for maximum pollutant removal are described. The relative advantages of different soil types are discussed and an overall minimum substrate depth of 0.6m is recommended for sub-surface systems. Two case studies of urban runoff wetlands in the UK which are currently being monitored are described.