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Martin Jekel - One of the best experts on this subject based on the ideXlab platform.
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combination of granular activated carbon adsorption and deep bed filtration as a single advanced wastewater treatment step for organic micropollutant and phosphorus removal
Water Research, 2016Co-Authors: Johannes Altmann, Daniel Rehfeld, Kai Trader, Alexander Sperlich, Martin JekelAbstract:Abstract Adsorption onto granular activated carbon (GAC) is an established technology in water and advanced wastewater treatment for the removal of organic substances from the liquid phase. Besides adsorption, the removal of particulate matter by filtration and biodegradation of organic substances in GAC contactors has frequently been reported. The application of GAC as both adsorbent for organic micropollutant (OMP) removal and Filter medium for solids retention in tertiary wastewater filtration represents an energy- and space saving option, but has rarely been considered because high dissolved organic carbon (DOC) and suspended solids concentrations in the influent of the GAC adsorber put a significant burden on this integrated treatment step and might result in frequent backwashing and unsatisfactory filtration efficiency. This pilot-scale study investigates the combination of GAC adsorption and deep-bed filtration with coagulation as a single advanced treatment step for simultaneous removal of OMPs and phosphorus from secondary effluent. GAC was assessed as upper Filter Layer in dual-media downflow filtration and as mono-media upflow Filter with regard to filtration performance and OMP removal. Both filtration concepts effectively removed suspended solids and phosphorus, achieving effluent concentrations of 0.1 mg/L TP and 1 mg/L TSS, respectively. Analysis of grain size distribution and head loss within the Filter bed showed that considerable head loss occurred in the topmost Filter Layer in downflow filtration, indicating that most particles do not penetrate deeply into the Filter bed. Upflow filtration exhibited substantially lower head loss and effective utilization of the whole Filter bed. Well-adsorbing OMPs (e.g. benzotriazole, carbamazepine) were removed by >80% up to throughputs of 8000–10,000 bed volumes (BV), whereas weakly to medium adsorbing OMPs (e.g. primidone, sulfamethoxazole) showed removals
M Grundmann - One of the best experts on this subject based on the ideXlab platform.
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wavelength selective ultraviolet mg zn o photodiodes tuning of parallel composition gradients with oxygen pressure
Applied Physics Letters, 2016Co-Authors: Zhipeng Zhang, Holger Von Wenckstern, J Lenzner, M GrundmannAbstract:We report on ultraviolet photodiodes with integrated optical Filter based on the wurtzite (Mg,Zn)O thin films. Tuning of the bandgap of Filter and active Layers was realized by employing a continuous composition spread approach relying on the ablation of a single segmented target in pulsed-laser deposition. Filter and active Layers of the device were deposited on opposite sides of a sapphire substrate with nearly parallel compositional gradients. Ensure that for each sample position the bandgap of the Filter Layer blocking the high energy radiation is higher than that of the active Layer. Different oxygen pressures during the two depositions runs. The absorption edge is tuned over 360 meV and the spectral bandwidth of photodiodes is typically 100 meV and as low as 50 meV.
Hangseok Choi - One of the best experts on this subject based on the ideXlab platform.
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Experimental study on performance of sand Filter Layer to remove non-point source pollutants in rainwater
Water Supply, 2017Co-Authors: Jaeyoon Ahn, Dongseop Lee, Shinin Han, Youngwook Jung, Sangwoo Park, Hangseok ChoiAbstract:Clogging characteristics of conventional sand Filter Layers with different grain-size distributions were experimentally studied to estimate their filtration capacity to capture non-point source pollutants in an artificial rainwater reservoir. A series of laboratory-scale chamber tests was conducted for artificial urban runoff synthesized with non-point source pollutants collected from a real road in Seoul, Korea. In addition, an analytical filtration model for estimating removal of non-point source pollutants was adopted considering the clogging characteristics. To evaluate the performance of three types of sand Filter Layers with different grain size characteristics, the pollutant concentration was measured in terms of total suspended solids and chemical oxygen demand. The lumped parameter ( θ ) related to the clogging property was estimated by comparing the accumulated weight of pollutant particles obtained from the laboratory chamber experiments and the theoretical estimation from the analytical filtration model. Based on the experimental study and theoretical consideration, a double-sand-Filter Layer consisting of two separate Layers is proposed as the optimum system for removing non-point source pollutants in the pilot-scale rainwater reservoir.
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A Prediction Model for Removal of Non-point Source Pollutant Considering Clogging Effect of Sand Filter Layers for Rainwater Recycling
Journal of the Korean Geotechnical Society, 2014Co-Authors: Jaeyoon Ahn, Dongseop Lee, Shinin Han, Youngwook Jung, Hangseok ChoiAbstract:An artificial rainwater reservoir installed in urban areas for recycling rainwater is an eco-friendly facility for reducing storm water effluence. However, in order to recycle the rainwater directly, the artificial rainwater reservoir requires an auxiliary system that can remove non-point source pollutants included in the initial rainfall of urban area. Therefore, the conventional soil filtration technology is adopted to capture non-point source pollutants in an economical and efficient way in the purification system of artificial rainwater reservoirs. In order to satisfy such a demand, clogging characteristics of the sand Filter Layers with different grain-size distributions were studied with real non-point source pollutants. For this, a series of lab-scale chamber tests were conducted to make a prediction model for removal of non-point source pollutants, based on the clogging theory. The laboratory chamber experiments were carried out by permeating two types of artificially contaminated water through five different types of sand Filter Layers with different grain-size distributions. The two artificial contaminated waters were made by fine marine-clay particles and real non-point source pollutants collected from motorcar roads of Seoul, Korea. In the laboratory chamber experiments, the concentrations of the artificial contaminated water were measured in terms of TSS (Total Suspended Solids) and COD (Chemical Oxygen Demand) and compared with each other to evaluate the performance of sand Filter Layers. In addition, the accumulated weight of pollutant particles clogged in the sand Filter Layers was estimated. This paper suggests a prediction model for removal of non-point source pollutants with theoretical consideration of the physical characteristics such as the grain-size distribution and composition, and change in the hydraulic conductivity and porosity of sand Filter Layers. The lumped parameter related with the clogging property was estimated by comparing the accumulated weight of pollutant particles obtained from the laboratory chamber experiments and calculated from the prediction model based on the clogging theory. It is found that the lumped parameter has a significant influence on the amount of the pollutant particles clogged in the pores of sand Filter Layers. In conclusion, according to the clogging prediction model, a double-sand-Filter Layer consisting of two separate Layers: the upper sand-Filter Layer with the effective particle size of 1.49 mm and the lower sand-Filter Layer with the effective particle size of 0.93 mm, is proposed as the optimum system for removing non-point source pollutants in the field-sized artificial rainwater reservoir.
J. P. Rajapakse - One of the best experts on this subject based on the ideXlab platform.
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Stabilization of Stormwater BioFilters: Impacts of Wetting and Drying Phases and the Addition of Organic Matter to Filter Media
Environmental Management, 2015Co-Authors: D. N. Subramaniam, P. Egodawatta, P. Mather, J. P. RajapakseAbstract:Ripening period refers to a phase of stabilization in sand Filters in water treatment systems that follow a new installation or cleaning of the Filter. Intermittent wetting and drying, a unique property of stormwater bioFilters, would similarly be subjected to a phase of stabilization. Suspended solids are an important parameter that is often used to monitor the stabilization of sand Filters in water treatment systems. Stormwater bioFilters, however, contain organic material that is added to the Filter Layer to enhance nitrate removal, the dynamics of which is seldom analyzed in stabilization of stormwater bioFilters. Therefore, in this study of stormwater biofiltration in addition to suspended solids (turbidity), organic matter (TOC, DOC, TN, and TKN) was also monitored as a parameter for stabilization of the stormwater bioFilter. One Perspex bioretention column (94 mm internal diameter) was fabricated with Filter Layer that contained 8 % organic material and fed with tapwater with different antecedent dry days (0–40 day) at 100 mL/min. Samples were collected from the outflow at different time intervals between 2 and 150 min and were tested for total organic carbon, dissolved organic carbon, total nitrogen, total Kjeldhal nitrogen, and turbidity. The column was observed to experience two phases of stabilization, one at the beginning of each event that lasted for 30 min, while the other phase was observed across subsequent events that are related to the age of Filter.
Gary S V Coles - One of the best experts on this subject based on the ideXlab platform.
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the semistor a new concept in selective methane detection
Sensors and Actuators B-chemical, 1999Co-Authors: Geraint Williams, Gary S V ColesAbstract:Abstract Technology associated with both catalytic and semiconductor-based gas sensors has been combined to produce hybrid devices capable of detecting low levels of combustible gases. First-generation non-selective sensors, which respond to a wide range of reducing gases including hydrogen, carbon monoxide, lower hydrocarbons and ethanol vapour, were obtained by coating narrow diameter platinum wire coils with a low resistivity tin dioxide-based formulation. As in the case of catalytic sensors, semiconductor-based pellistors (semistors) are typically operated in a bridge-type circuit. However, in contrast to catalytic sensors, which are used to detect percentage levels of combustible gases, semistors are responsive to sub-100 ppm concentrations. Optimisation experiments have been carried out on factors affecting performance, such as sensing Layer composition, coil pitch and firing time. A further study on the effects of incorporating an additional catalyst-containing surface Filter Layer has led to the development of a second-generation methane-selective sensor. Undesirable humidity and ambient temperature effects, normally associated with tin dioxide-based sensors, can be eradicated by operating a semistor in conjunction with a compensating element. This utilises a Filter Layer, which removes all target gas response while retaining the same humidity and temperature dependence as the sensor.