Étude de la qualité des eaux épurées par le lagunage naturel en Algérie

L’Algérie est l’un des pays les plus affecté par la rareté des ressources en eau, et la mauvaise répartition des précipitations, à laquelle il faut ajouter le problème de pollution des ressources en eau. Les procédés d’épuration les plus utilisé en Algérie sont les stations des boues activées et les stations de lagunage naturel. En Algérie, le lagunage naturel se présente comme la meilleure solution, il n’exige que des efforts minimaux d’entretien, d’opération et de maintenance, la mécanisation est presque’ absente. En plus ce système est le meilleur procédé d’épuration du côté bactériologique, pour cette raison nous avons effectué une recherche sur les performances épuratoires de lagunage naturel en Algérie. Pour aboutir à ce but, nous avons choisi deux stations de lagunage naturel fonctionnel, station de Sidi Senoussi et station d’El Emir Abel Kader. Nous avons analysé les eaux entrantes et sortantes des deux lagunages, les paramètres analysés sont : (MES, DBO ; DCO, PH , N-NH4+ N-NO3) durant les années 2010 ,2011 et 2012 pour le lagunage d’El Emir et 2010 ,2011 pour Sidi Senoussi. D’après les résultats nous avons conclu que le lagunage naturel ne suffit pas pour préserver l’environnement, il faut ajouter d’autres ouvrages d’épuration pour aboutir à la qualité requise pour la préservation de l’environnement, ou bien pour une éventuelle réutilisation. Nous proposons l’ajout des bassins de filtre planté à l’aval des bassins de lagunage naturel.Mots-clés : lagunage naturel, performances, eaux usées, Algérie.The quality of treated waste water by natural lagoon in AlgeriaAlgeria is one of the most affected by the scarcity of water resources countries sand poor rainfall distribution, which must be added the problem of pollution of water resources. Processes the ost used in Algeria purification stations are activated sludge stations and natural lagoons. In Algeria, the natural lagoon looks like the best solution, it requires only minimal maintenance efforts, operation and maintenance, mechanization is almost absent in most systems this is the best treatment processes of bacteriological side, for this reason we search don the treatment performance of waste stabilization ponds in Algeria. To achieve our goal, we have chose’n two stations lagoon natural functional station and station Senussi Sidi El Emir AbelKader. We analyzed the in-coming and out-going water from the two lagoons, the parameters analyzed are:(Contents suspensions and biological oxygen demand and chemical oxygen demand and ammonia and nitrates, alkalinity),during the years 2010 and 2011 and2012 for the lagoons of El Emir and 2010, 2011 to Sidi Senussi,based on the results we conclude that the natural lagoon is not enough to protect the environment, we must add another treatment works to achieve the quality required for the preservation of environment, or for reuse. We propose adding ponds planted filter downstream basins natural lagoon. Keywords : natural lagoon, performances, waste water, Algeria

Study of Flow and Energy Dissipation in Stepped Spillways

We present in this work the quantitative and qualitative study of the flow in the stepped spillways. The experimental measurement is realized on the reduced model. Different flow configurations on a spillway are described. New experimental results linked to the flow aspect and to the energy dissipation after the passage over the spillway are presented. The experimental results relative to the energy dissipation are analysed. They are compared thereafter to the results of the experiences and models found in other research works

Obtaining evapotranspiration and surface energy fluxes with remotely sensed data to improve agricultural water management

The quantification of evapotranspiration from irrigated areas is important for agriculture water management, especially in arid and semiarid regions where water deficiency is becoming a major constraint in economic welfare and sustainable development. Conventional methods that use point measurements to estimate evapotranspiration are representative only of local areas and cannot be extended to large areas because of heterogeneity of landscape. Remote sensing based energy balance models are presently most suited for estimating evapotranspiration at both field and regional scales. In this study, SEBAL (Surface Energy Balance Algorithm for Land), a remote sensing based evapotranspiration model, has been applied with Landsat ETM+ sensor for theestimation of actual evapotranspiration in the Habra plain, a semiarid region in west Algeria with heterogeneous surface conditions. This model followed an energy balance approach, where evapotranspiration is estimated as the residual when the net radiation, sensible heat flux and soil heat flux are known. It involves in the input the remote sensing land surface parameters such as surface temperature, NDVI and albedo. Different moisture indicators derived from the evapotranspiration were then calculated: evaporative fraction, Priestley-Taylor parameter and surface resistance to evaporation. These calculated indicators facilitate the quantitative diagnosis of moisture stress status in pixel basis. Thestudy area contains extremes in surface albedo, vegetation cover and surface temperature. The land uses in this study area consists of irrigated agriculture, rain-fed agriculture and livestock grazing. The obtained results concern the validation of the used model for spatial distribution analysis ofevapotranspiration and moisture indicators. The evaluation of dailyevapotranspiration and moisture indicators are accurate enough for the spatial variations of evapotranspiration rather satisfactory than sophisticated models without having to introduce an important number of parameters in input with difficult accessibility in routine. In conclusion, the results suggest that SEBAL can be considered as an operational method to predict actual evapotranspiration from irrigated areas having limited amount of ground information

Mapy zasięgu w przypadku ekstremalnych powodzi: przykład miasta Sidi Bel Abbes w Algierii

Hydrodynamic modelling is used to analyse the inundation behaviour of Sidi Bel Abbes city (North-West of Algeria) during extreme flood events. The study reach, 5.4 km in length, is a section of Wadi Mekerra through Sidi Bel Abbes city. Land and bathymetric surveys were used to create a digital terrain model (DTM) of the river channel and the floodplain. By coupling the geometry with hydrologic data, a two dimensional hydrodynamic model was built. The model is based on integrating Saint-Venant shallow waters (depth averaged) equations through Runge–Kutta discontinuous Galerkin numerical scheme. It was calibrated in terms of roughness coefficients on measured values of water surface elevation and discharge registered in the Sidi Bel Abbes gauging station. The objective is to draw the flood maps under extreme river flood event. The results are helpful for local authorities in order to take the appropriate defence measures in the future.Wykorzystano modelowanie hydrodynamiczne do analizy zasięgu ekstremalnych zjawisk powodziowych w mieście Sidi Bel Abbes w północnozachodniej Algierii. Teren badań stanowił odcinek okresowej rzeki Mekerra długości 5,4 km płynącej przez miasto. Badania naziemne i batymetryczne wykorzystano do zbudowania cyfrowego modelu terenu (DTM) koryta rzeki i obszarów zalewowych. Łącząc geometrię z danymi hydrologicznymi, zbudowano dwuwymiarowy model hydrodynamiczny. Model oparto na integracji równań Saint-Venanta (o uśrednionej głębokości) poprzez nieciągły schemat liczbowy Galerkina wg metody Rungego– Kutty. Model był kalibrowany na współczynnik szorstkości dla zmierzonych wysokości poziomu wody i na odpływ rejestrowany w posterunku pomiarowym Sidi Bel Abbes. Celem pracy było sporządzenie map powodzi w warunkach ekstremalnych zjawisk powodziowych. Wyniki mogą być przydatne władzom lokalnym w podejmowaniu odpowiednich zabiegów ochronnych przed powodzią w przyszłości