Natural apatites have previously shown a great capacity for phosphate retention from wastewater. However, its fine particle size distribution may lead to a premature clogging of the filter. Accordingly, a granulated apatite product was developed and manufactured in order to control the particle size distribution of the media. Experiments were conducted on laboratory columns to assess their phosphorus retention capacity, to identify the processes involved in phosphorus retention and to evaluate their kinetic rates. The results showed phosphorus retention capacities of 10.5 and 12.4 g PO4-P·kg−1 and kinetic rate coefficients in the range of 0.63 and 0.23 h−1 involving lower values than those found for natural apatites in previous studies. Scanning Electron Microscopy images showed that apatite particles in the granules were embedded in the binder and were not readily accessible to act as seeds for calcium phosphate precipitation. The retention processes differ depending on the supersaturation of the solution with respect to calcium phosphate phases: at low calcium concentrations (69.8 ± 3.9 mg·L−1), hydroxyapatite precipitates fill up the porosity of the binder up to a depth of 100–300 μm from the granule surface; at higher calcium concentrations (112.7 ± 7.4 mg·L−1) precipitation occurs at the granule surface, forming successive layers of hydroxyapatite and carbonated calcium phosphates.
El riesgo sanitario de los triatominos como vectores de Trypanosoma cruzi está relacionado con la domiciliación de especies originalmente selváticas que logran adaptarse a hábitats humanos, encontrando variadas fuentes de alimento y refugio. Para el control de estos insectos se utiliza la fumigación residual con insecticidas piretroides, pero debido a la resistencia de los triatominos a insecticidas químicos y altos costos de fumigaciones permanentes, alternativamente se ha probado con éxito el potencial de algunos hongos entomopatógenos como controladores biológicos. Sin embargo, se desconoce el efecto de dosis sub letales sobre parámetros reproductivos, siendo estos factores muy importantes en el crecimiento poblacional y colonización de nuevos hábitats. En este trabajo probamos el efecto de una concentración de conidios baja de Beauveria. bassiana (1 x 10⁸ conidios/ml) en los parámetros reproductivos de hembras de Meccus pallipennis inoculadas en el estadio adulto, contabilizando diariamente el número de huevos puestos y eclosionados en un periodo de 44 días. No se registró inhibición de la oviposición, todas las hembras pusieron huevos, pero la infección fúngica redujo un 63% la fertilidad de las hembras tratadas. El rendimiento reproductivo de las hembras control fue de 56.7 ± 3.8 huevos /hembra/vida mientras que el rendimiento de las hembras infectadas fue de 20.8 ± 2.9 huevos /hembra/vida encontrando diferencias significativas entre las medias de los grupos. (p<0.0008). No se detectaron diferencias significativas en el porcentaje de eclosión entre ambos grupos (p=.3737). El sistema reproductor de las hembras infectadas no presento variación en el tamaño de las estructuras, sin embargo, se observaron organismos sin filamento terminal, germario, y las ovariolas vacías, con algunos ovocitos desprendidos del vitelario. Confirmamos la presencia de B. bassiana en la genitalia y ovocitos. Durante el diseño experimental se observó que los machos tratados con B. bassiana no completaron el patrón de cópula.
<p>Wastewater management and treatment are key points in maintaining the quality and the sustainability of water resources. To preserve receiving water environments, efforts are being conducted to improve the treatment efficiency. Soil infiltration can therefore be used as a nature-based solution tertiary treatment, in some areas without surface water available, or with supplementary water bodies&#8217; protection regulations. Secondary wastewater effluents (SWE) infiltration surfaces&#160; mainly consist of infiltration trenches or flood-meadows. Among the main issues encountered with soil infiltration, two can be highlighted: the possible low hydraulic conductivity induced by soil clogging, on the one hand, and the use of non-renewable draining materials such as pebbles or gravel to ensure the distribution of water in trenches, on the other hand. In France, in order to overcome those issues, stakeholders are now considering the replacement of the gravel with woodchips, a renewable biodegradable material, also prone to biodiversity in soils. If there is no woodchip-filled soil infiltration surfaces downstream wastewater treatment plant in France, woodchips are however used for decentralized wastewater treatment, even though no study has quantified precisely their efficiency. The understanding of the flow processes and the risk of preferential flows in the woodchip-filled infiltration trenches is a prerequisite for a proper management of these works.</p> <p>Our study aims at investigating flow regimes in woodchip-filled infiltration trenches. Several woodchip-filled infiltration trenches were studied and analyzed with regards to their infiltration capacity in four decentralized wastewater treatment sites, located in South-West of France on silty-clay soil. Measurements of infiltration capacity of the soil below the woodchips-filled trenches were conducted with infiltration tests according to the Beerkan method (Braud et al., 2005). On each site, two tests were conducted on the bottom of the infiltration trenches after extracting woodchips and two others in the soil at a lateral distance of 1 m from the infiltration trench at the same soil depth, in order to sample the same type of soil. The soil hydraulic functions, i.e., water retention and hydraulic conductivity curves, below the woodchips and in the natural soil profiles were then calculated using the BEST method (Angulo-Jaramillo et al., 2019) and compared. Our findings showed that the use of woodchips locally maintains or even enhances the infiltration rate in the soil below. Moreover, the hydraulic conductivity was 5 to 14 times higher (up to 8600 mm.d<sup>-1</sup>) in soils under woodchip-filled infiltration trenches than in the reference soils. To explain such positive effects, several hypothesis were formulated and discussed against physical, biogeochemical and ecological factors (woodchips organic amendment, suitable moisture conditions, earthworm communities&#8217; activity). Dye tracer experiment, soil pit, and soil samples (chemical tracings and analyses) revealed the presence of preferential pathways induced by macro fauna and roots plants. An earthworm count showed that the majority of earthworms in the woodchips were 10 times higher than in the natural soil profile. Experiments also showed an organic carbon enrichment in woodchip-filled infiltration trenches soils that could lead to an improvement and stabilization of soils structure.</p>
Phosphorus retention in small- and medium-sized wastewater treatment plants is crucial to preventing the eutrophication of downstream catchments. One popular solution in combination with treatment wetlands is the use of reactive filters for phosphorus retention; however, identifying a suitable substrate is not an easy task in this process. Apatites have already proven to be an effective alternative for phosphorus retention, yet more in-depth research is needed. This article uses two natural apatite materials, NA1 and NA2, introduced in four fixed-bed laboratory columns to assess their phosphorus retention capacity. Various inflow conditions are set for the NA1 substrate to evaluate the impact of calcium and biomass development on performance. The substrates show high phosphorus retention (>16.8 g PO4-P/kg for NA1 and >17.5 g PO4-P/kg for NA2) as well as high kinetic rate coefficients (1.45 and 1.70 h−1 for NA1 and NA2, respectively), with performances above 80% for both substrates. The maximum phosphorus retention capacity is not attained at the end of the experiments, despite their long duration (230 days) and the short hydraulic residence times applied (∼2 h), thus suggesting a long-term removal capacity. The NA1 column fed with a calcium-deficient synthetic solution displays just slightly reduced kinetic rates, most likely due to calcite and dolomite dissolution from the media. The column fed with treated wastewater does not reveal any significant reduction in hydraulic conductivity due to biomass development. No loss of permeability due to chemical clogging was observed in the other columns. Scanning electron microscopy indicates that phosphorus retention occurs by the precipitation of amorphous calcium phosphate for both natural apatites, thereby clearly demonstrating the implementation of seeding mechanisms. Such a retention process is sustainable, which suggests it may proceed over even higher retention capacities.
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