State of the reverse osmosis membrane of sea water corso plant desalination (Algiers)

AbstractSeawater reverse osmosis (SWRO) desalination is being increasingly emphasized as a strategy for conservation of limited resources of freshwater. Although desalination has been developed for the last few decades, the SWRO operation is still affected by membrane fouling. The membrane fouling of SWRO has a significant impact on operation of desalination plants. We follow the evolution of the permeate conductivity during three months of the sea water Corso (Algiers) plant desalination. The purpose of this work is to conduct an autopsy of fouled membranes in seawater using the scanning electron microscopy (SEM) coupled by an analysis EDX. This membrane shows a change of the surface morphology, which justifies the abrupt increase in the conductivity of the permeate in May 2006. In order to identify the nature of the fouling deposit, we analysed this deposit by Xrays diffraction (XRD)

Quantification of Outdoor Thermal Comfort Levels under Sea Breeze in the Historical City Fabric: The Case of Algiers Casbah

Thermal comfort in cities is an influential factor for citizens’ wellbeing and life quality. Urban microclimate studies have gained popularity following increasing urbanization trends and global climate change in recent years. Urban fabric and morphology in traditional cities represent a unique pattern both spatially and climatically. However, few studies have investigated traditional cities’ urban thermal comfort conditions. Therefore, this study aimed to assess the thermal comfort in different subspaces of Algiers Casbah’s historic urban fabric, which falls in the hot Mediterranean climate (Csa). This research evaluated the human thermal sensation by applying the physiological equivalent temperature (PET) index. The methodology used was a mixed approach, including field measurements, calculations, and a survey questionnaire. The results indicate the presence of a high-stress level during the measurement periods, and notable differences between the subspaces in January (ΔPETMax.Jan = 3.7 °C) and August (ΔPETMax.Aug = 2.2 °C). The highest discomfort was recorded in spaces with collapsed buildings, especially during the hot hours of the day. The findings also highlight a strong impact of the sky view factor on the mean radiant temperature (Tmrt) and the physiological equivalent temperature (PET). The study discusses recommendations and ways to improve the design of outdoor spaces and relieve heat stress in the streets of traditional cities. Finally, this work helps urban managers and heritage conservators in urban rehabilitation policies concerning outdoor microclimate improvement

Transient growth analysis of the flow past a circular cylinder

We apply direct transient growth analysis in complex geometries to investigate its role in the primary and secondary bifurcation/transition process of the flow past a circular cylinder. The methodology is based on the singular value decomposition of the Navier-Stokes evolution operator linearized about a two-dimensional steady or periodic state which leads to the optimal growth modes. Linearly stable and unstable steady flow at Re=45 and 50 is considered first, where the analysis demonstrates that strong two-dimensional transient growth is observed with energy amplifications of order of 10(3) at U-infinity tau/D approximate to 30. Transient growth at Re=50 promotes the linear instability which ultimately saturates into the well known von-Kaacutermaacuten street. Subsequently we consider the transient growth upon the time-periodic base state corresponding to the von-Kaacutermaacuten street at Re=200 and 300. Depending upon the spanwise wavenumber the flow at these Reynolds numbers are linearly unstable due to the so-called mode A and B instabilities. Once again energy amplifications of order of 10(3) are observed over a time interval of tau/T=2, where T is the time period of the base flow shedding. In all cases the maximum energy of the optimal initial conditions are located within a diameter of the cylinder in contrast to the spatial distribution of the unstable eigenmodes which extend far into the downstream wake. It is therefore reasonable to consider the analysis as presenting an accelerator to the existing modal mechanism. The rapid amplification of the optimal growth modes highlights their importance in the transition process for flow past circular cylinder, particularly when comparing with experimental results where these types of convective instability mechanisms are likely to be activated. The spatial localization, close to the cylinder, of the optimal initial condition may be significant when considering strategies to promote or control shedding

Evaluating Reuse of Alum Sludge as Coagulant for Tertiary Wastewater Treatment

International audienceUltrafiltration (UF) membrane processes have become an established technology in the treatment and reuse of secondary effluents from sewage treatment plants. However, without pretreatment, secondary-treated wastewater effluent shows high fouling potential and hence reduces the performance of UF membrane filtration significantly. This study investigates the potential reuse of alum sludge collected from a water treatment plant as primary coagulant in terms of membrane fouling reduction. The alum sludge was characterized by scanning electron microscopy with energy-dispersive spectroscopy and X-ray diffraction. A comparison was made between a conventional metal-ion coagulant - aluminum sulfate [Al2(SO4)3] - and alum sludge using a jar test and their performances were measured in terms of residual turbidity, UV254 (absorbance at 254 nm), and chemical oxygen demand (COD) removal. UF experiments were performed with CARBOSEP M3 (40 kDa) monotubular ceramic. It was shown that the application of coagulation by alum sludge restricted the fouling of membranes with a lowering of the permeate flux by only 34%. The results showed that alum sludge was effective in removal of organic matter; percent removal of COD and UV254 reached 90% and 60%, respectively, when combining alum sludge with UF. © 2018 American Society of Civil Engineers

Biomass activity and species assessment in a submerged membrane bioreactor operating at high SRT and low COD/N using respirometric analysis and modeling

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Effect of Recovery Duration on Muscular Power and Blood Lactate During the Bench Press Exercise

International audienceIn order to assess the effect of recovery on power and blood lactate, 10 males performed 10 sets (S1 to S10) of 6 repetitions of bench press at 70% of their maximal strength, with 1 (Prot1), 3 (Prot3) or 5 (Prot5) min rest between sets. From the measurements of force and displacement of the bar, mean power during each repetition (MPR) and set (MPS), were calculated. Blood lactate was evaluated before and immediately after each set. No significant variations in power or blood lactate occurred during prot3 and prot5. From S4 to S10, significantly lower MPS (27% decrease) and higher blood lactate (7.6 +/- 2.0 mmol/l) were demonstrated in prot1 vs prot3 or prot5. In spite of this, MPR in protl were significantly lower for repetitions 4, 5 and 6 only: MPR of repetitions 1, 2 and 3 were similar in the 3 protocols. During prot1 only, power decrease was related to lactate accumulation for all subjects (0.64 < or = r < or = 0.99, p < or = 0.05). These results indicate that although muscular power and blood lactate were both affected by the recovery interval, acidosis was not the direct cause of fatigue during the 1 min rest condition. The concomitant effects of lactate accumulation and insufficient time for a complete resynthesis may have resulted in a diminution of PCr stores, leading to power decrements