Effet de l’irrigation par l’eau usée sur la biomasse aérienne et souterraine d’une culture intensive de saules en courtes rotations

Le but de cette étude est de comprendre l’effet d’une irrigation par les eaux usées et /ou de la fertilisation par les engrais chimiques sur la productivité aérienne et souterraine d’une plantation de saule Salix miyabeana SX67 en CICR dans un contexte de filtre végétal. Nous avons d’une part évalué l’impact de diverses doses d’eau usées et/ou de la fertilisation minérale sur les rendements en biomasse ligneuse d’une culture de saules au cours d’un cycle de croissance de deux ans. D’autre part et pour la même période nous avons comparé le développement racinaire (biomasse, morphologie et distribution dans le sol) suite aux divers traitements. Les résultats ont montré qu’au terme de deux ans de croissance, les traitements par les eaux usées aussi bien que celle par les engrais a permis l’augmentation des rendements de la biomasse aérienne de notre culture de saules avec un effet plus prononcé suite au traitements des eaux usées qu’à celui du fertilisant chimique. Nous avons mesuré des productivités en biomasse aussi élevées que 39,4 Mg ha-1 et 54,7 Mg ha-1 et ce pour les parcelles qui ont reçu la plus grande quantité d'eaux usées, respectivement pour les saules non fertilisé et fertilisé (D3-NF et D3-F). La majeure partie du système racinaire était en superficie avec 92-96% des racines (racine fine et racine grosse) concentrées dans les premiers 40 cm de sol et nous avons trouvé que la biomasse des racines fines était comprise entre 1,01 et 1,99 Mg ha-1. Généralement la fertilisation chimique n’a pas eu d’effet sur les rendements en biomasse des racines totales et/ou fines. Bien que l’irrigation par les eaux usées ait entraîné une réduction statistiquement significative de la biomasse racinaire, néanmoins cette réduction n'était pas linéaire (avec une réduction de la biomasse de D0 à D1, une augmentation de D1 à D2 pour réduire de nouveau de D2 à D3). Cette tendance porte à penser qu'au-delà d'une certaine quantité d'eau et de nutriments (suite à l’irrigation par les eaux usées), le développement du système racinaire des saules est affecté négativement, et bien que la biomasse aérienne soit restée élevée sous le traitement D3, nous pensons que le développement de la plante a été quelque peu déséquilibré. Aucun changement significatif n'a été constaté dans les traits morphologiques liés à l'irrigation par les eaux usées.The aim of this study was to understand the effect of both wastewater and/or mineral fertilisation on above- and belowground biomass of a Salix miyabeana SX67 willow SRC in a filter vegetation context. We firstly assessed the impact of various doses of wastewater and/or mineral fertilization on biomass yield after two season growth. On the other hand and during the same period we estimated root production and assessed vertical root distribution and roots morphology in response to various treatments doses. The results showed that after two years of growth both mineral fertilization and wastewater sewage fertilization enhanced willow aboveground biomass yields, with a more accurate effect due to wastewater irrigation than the mineral fertilization. We recorded high biomass yields such as 39.4 Mg ha-1 and 54.7 Mg ha-1 respectively for unfertilized and fertilized plants plots which benefits with the largest amount of wastewater (D3-NF and D3-F). We found that most of the roots were contained in top soil layers with 92-96% of the total roots (including fine and coarse roots) concentrated within the first 40 cm of soil depth, fine root biomass ranged between 1.01 and 1, 99 Mg ha-1. Neither mineral fertilization nor wastewater sewage irrigation showed an effect on total or fine roots biomass yields. Although we found a statistically significant decrease prior to wastewater treatments, this reduction was not linear (with a decrease of the biomass from D0 to D1, increased from D1 to D2 to go down again from D2 to D3). This pattern suggests that beyond a certain amount of water and nutrients (due to irrigation with wastewater) the development of the willow root system is negatively affected, and although the aboveground biomass remained high in the D3 treatment, we believe that the development of the plant was somewhat unbalanced. No significant changes were found in the deep morphological traits related to irrigation with sewage wastewater

Robust Asynchronous H∞ Observer-Based Control Design for Discrete-Time Switched Singular Systems with Time-Varying Delay and Sensor Saturation: An Average Dwell Time Approach

This work discuss the robust stabilization problem for discrete-time switched singular systems with simultaneous presence of time-varying delay and sensor nonlinearity. To this end, an observer-based controller was synthesized that works under asynchronous switching signals. Investigating the average dwell time approach and using a Lyapunov–Krasovskii functional with triple sum terms, sufficient conditions were derived for achieving the existence of such asynchronous controller and guaranteeing the resulting closed-loop system to be exponentially admissible with H∞ performance level. Subsequently, the effectiveness of the proposed control scheme was verified through two numerical examples

Optimization of the wastewater treatment capacity of a short rotation willow coppice vegetation filter

The objective of this study was to determine the conditions to optimize the wastewater treatment efficiency of a short rotation willow coppice (SRWC) plantation (Salix miyabeana ‘SX67’) used as a vegetation filter to treat small municipal primary effluents (with less than 800 population equivalent). With the aim of maximizing the annual amount of wastewater treated, the effect of adjusting the hydraulic loading rate (HLR) according to the estimated evapotranspiration was tested at demonstration scale under humid continental climate conditions. We proposed a new method to calculate the evapotranspiration rate from plant physiological data, introducing an α factor based on direct transpiration measurements. This method increased the accuracy of the water balance, with a prediction of the crop coefficient (kc) based on either an seasonal approach (R2 of 0.88) or a monthly approach (R2 of 0.94). This led to a more precise estimation of the pollutant loading reaching the groundwater and could be used after plantation establishment as a fine-tuning tool. Adjusting the HLR to that of evapotranspiration between May and October led to an annual increase of 2 mm/d (around 0.35 m3/m2 per growing season) in HLR, while maintaining a pollutant loading removal efficiency of at least 96% for organic matter, 99% for total phosphorus and 93% for total nitrogen. A high HLR at the end of the season caused nitrogen leaching into groundwater, indicating that the HLR should be decreased in October, when willow growth is greatly reduced

Sustainability analysis of primary wastewater treatment by willow plantations in Québec

Wastewater treatment is a necessary step to avoid environmental impacts of water consumption and usage. Traditional approaches are expensive and are limited to developed countries. Phytofiltration using fast-growing trees and shrubs like willows potentially offer an alternative. This paper aims to determine if wastewater treatment using phytofiltration can provide complementary environmental and economic benefits for rural communities in a Nordic climate such as the province of Québec, Canada. It looks at different perspectives of the wastewater treatment solution in a local and rural context. Based on life cycle analysis (LCA) and life cycle cost analysis (LCC), we found that, for an exemplar Québec municipality, the conventional wastewater treatment scenario impacted more on climate change, ecosystem quality and human health than the two phytofiltration of wastewater scenarios studied, where impact is highly dependant on the biomass valorization. The net present cost of the phytofiltration scenarios were lower than typical conventional treatment in Québec. For a biomass producer, conventional biomass production had the highest environmental impact on ecosystem quality, while biomass production from phytofiltration had the highest environmental impact on climate change, human health, and resources. We demonstrate that the phytofiltration is a viable and multifunctional technology that could provide good incentives for a local biomass value chain. it allows to both alleviate wastewater treatment burden and provide affordable biomass for bioenergy development for rural communities. Mobilizing local stakeholders will be key to make phytofiltration an alternative solution for both environmental burden alleviation and rural economic development

Box-Behnken design for extraction optimization of crude polysaccharides from Tunisian Phormidium versicolor cyanobacteria (NCC 466): Partial characterization, in vitro antioxidant and antimicrobial activities

© 2017 In this study, response surface methodology (RSM) based on Box-Behnken design (BBD) was employed to optimize the aqueous extraction of crude polysaccharides from Tunisian cyanobacteria Phormidium versicolor (NCC 466). The optimal extraction conditions with an extraction yield of 21.56 ± 0.92% were as follows: extraction temperature at 81.05 °C, extraction time of 3.99 h, and water to raw material ratio of 21.52 mL g−1. Crude Phormidium versicolor polysaccharides (CPv-PS) are found to be a hetero-sulfated-anionic polysaccharides that contained carbohydrate (79.37 ± 1.58%), protein (0.45 ± 0.11%), uronic acids (4.37 ± 0.19%) and sulfate (6.83 ± 0.28%). The carbohydrate fraction was composed of arabinose, xylose, ribose, rhamnose, N-acetyl glucosamine, galactose, glucose, mannose, glucuronic acid and saccharose with corresponding mole percentages of 2.41, 14.58, 2.18, 6.23, 7.04, 28.21, 26.04, 3.02, 0.86 and 5.07, respectively. Evaluation of the antioxidant activity in vitro suggested that CPv-PS strongly scavenged radicals, prevented bleaching of β-carotene and reduced activity. Furthermore, the CPv-PS exhibited effective antimicrobial properties