19,725 research outputs found
Assessment of tertiary reed beds in chemically-dosed wastewater treatment plants for phosphorus removal
No full textEutrophication is one of the problems affecting the environmental quality standards of fresh waters. Phosphorus (P) is considered a main nutrient contributing to this. In the UK, the Water Industry is responsible for c. 50% of the total phosphorus load to freshwater ecosystems. Within this, small wastewater treatment plants (WwTPs) (<2,000 population equivalent) have a significant role since they represent 75% of all WwTPs in the UK.
The current option for P removal from wastewater is chemical precipitation through the dosing of iron (Fe) salts in combination with a tertiary filtration treatment step. This study aims to determine the transformation processes whereby tertiary reed beds permanently store or release iron and phosphorus in chemically-dosed sites to provide recommendations regarding the conditions where reed beds can be used as such final filtration treatment in small WwTPs. This was carried out through sampling campaigns in 14 full-scale tertiary reed beds.
Chemically-dosed WwTPs with tertiary reed beds can perform satisfactorily achieving phosphorus removals above 85% and average P and Fe final effluent concentrations of 0.7 mg P/L and 0.2 mg Fe/L, respectively, both well below consents (2 mg TP/L and 4 mg Fe/L). The majority of the total phosphorus in the reed bed influents was associated to either suspended solids or dissolved fractions, whereas 60¬90% of the effluent TP is in the dissolved form. Occasional episodes of phosphorus release from the reed bed can occur, as evidenced in an increase in soluble reactive phosphorus in the effluent. The main mechanism for trapping of Fe and P in mature beds was settlement of suspended particles, with phosphorus and iron concentrations in the accumulated sludge being up to 55.9 g P/kg dry matter and 246.6 g Fe/kg DM. The removal of particulate pollutants was successful in the reed beds studied, but colloidal and dissolved particles passing through the beds untreated. This could compromise the use of reed beds with future tightening P consents if the current chemical dosing practices are unchanged
Preliminary study on fractal character of growth pattern of reed
No full textThe researches about reed (Phragmites communis) growth were mainly concentrated on seasonal dynamics, investigation of large area resource, and comparison of different ecological forms of reed. The study on size distribution of reed, however, was scarcely reported. By means of fractal geometric theory of non-linear science, we studied the fractal character of growth pattern of reed, for the purpose of quantitatively exploring the mechanism of reed growth. The classical method of studying size distribution is to draw histogram and then to fit distribution curve. it is well known, however, that the obtained histogram is strongly depended on the number of class interval and its correspondent width. The determination of rational number and width of class interval is somewhat arbitrary, since it is gotten according to analyst's experience. In general, there are a certain similarity among histograms described at different class number of class interval and width somehow. It implies that we could use the fractal geometry to analyze the relationship among them, and reach more reliable conclusion. The data we used in our analyses is from the monthly sampling in Caogang Lake (114degreeE, 35degreeN), an emergent macrophyte dominated lake in Fengqiu Experimental Area of the Huanghuaihai Plain, Henan Province, P.R. China. The way to calculate ct-actal dimension (FD) of reed growth is box-dimension (BD) and information dimension (ID). Because the longest reed occasionally exceeds 400cm, for the reason of convenience, we define the largest scale S = 400 cm. Halving the scale S until it could recognize each individual reed (S 0.8), but is irregular in the middle and later growth season (fractal dimension < 0.7). These results are benefit to reach the goal of rational use of reed resources and to protect the biodiversity in wetland ecosystem
Low temperature hot-wire polysilicon waveguides
No full textWe fabricated and measured low loss polysilicon waveguides deposited using Hot-Wire Chemical Vapor Deposition (HWCVD) at 240 °C. The optical propagation loss was measured to be 11.9 dB/cm at lambda = 1550 nm
Raw data for "Low-loss silicon slot waveguide realized by surface roughness reduction"
No full textThis dataset contains the raw data used for the figures in the paper Debnath K, Khokhar A, Reed G, Saito S. Low-loss silicon slot waveguide realized by surface roughness reduction. In 2016 IEEE 13th International Conference on Group IV photonics (GFP). Piscataway, US: IEEE. 2016. Available from DOI: 10.1109/GROUP4.2016.7739069
Abstract: We demonstrate low-loss slot waveguides on silicon-on-insulator (SOI) platform. Waveguides oriented to the <;11-2> direction on the Si (110) plane are fabricated by a combination of dry and wet etching to realize propagation loss of 4dB/cm for a waveguide with a slot width of 120nm.</span
Assessment of Aquatic Reed Stands from Airborne Photogrammetric 3K Data
No full textAquatic reed beds provide important ecological functions, yet their monitoring by remote sensing methods remains challenging. In this study, we propose an approach of assessing aquatic reed stand status indicators based on data from the airborne photogrammetric 3K-system of the German Aerospace Center (DLR). By a Structure from Motion (SfM) approach, we computed stand surface models of aquatic reeds for each of the 14 areas of interest (AOI) investigated at Lake Chiemsee in Bavaria, Germany. Based on reed heights, we subsequently calculated the reed area, surface structure homogeneity and shape of the frontline. For verification, we compared 3K aquatic reed heights against reed stem metrics obtained from ground-based infield data collected at each AOI. The root mean square error (RMSE) for 1358 reference points from the 3K digital surface model and the field-measured data ranged between 39 cm and 104 cm depending on the AOI. Considering strong object movements due to wind and waves, superimposed by water surface effects such as sun glint altering 3K data, the results of the aquatic reed surface reconstruction were promising. Combining the parameter height, area, density and frontline shape, we finally calculated an indicator for status determination: the aquatic reed status index (aRSI), which is based on metrics, and thus is repeatable and transferable in space and time. The findings of our study illustrate that, even under the adverse conditions given by the environment of the aquatic reed, aerial photogrammetry can deliver appropriate results for deriving objective and reconstructable parameters for aquatic reed status (Phragmites australis) assessment
The politics and economics of regulatory impact assessment
No full textThis is the author accepted manuscript. The final version is available from the publisher via the link in this record
0.15 dB/cm loss in Unibond SOI waveguides
No full textThe optical loss of Unibond waveguides is measured and reported for the first time, using grating couplers. At a wavelength of 1.3 µm, a loss of 0.15 ±0.05 dB/cm is obtained for TE polarisation. This allows good quality low loss integrated optical circuits to be fabricated at low cost
Nitrogen removal from wastewater in vertical flow constructed wetlands containing LWA/gravel layers and reed vegetation
No full textThe influence of light weight aggregates made of fly ash from sewage sludge thermal treatment (FASSTT LWA) on the nitrogen removal efficiency from artificial wastewater in constructed wetlands (CW) with vertical flow reed bed was investigated. Thirty lysimeters with six different double-layer bed constructions (upper layer of FASSTT LWA with thicknesses of: 0 cm, 12 cm, 25 cm, 50 cm, and 100 cm of the total depth of the lysimeter, above a lower gravel layer), either with or without reed plants were operated with wastewater hydraulic loading rate of 4.67 mm/d. During a six-month experiment, high efficiency of ammonia removal was observed. The influence of FASSTT LWA as a bed material and the presence of reed on CW treatment efficiency was determined. The highest total nitrogen removal efficiency, 59.5%, was obtained in the CW with double-layer lysimeters consisting of 25% FASSTT LWA (upper layer), and 75% gravel (lower layer), and planted with reed
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