M. BEKRENTCHIR Khalida

Wastewater reuse is a useful tool for minimizing the amount of wastewater discharged into the environment. However, it is associated with threats to the environment and public health; consequently, effluent quality assessment is essential prior to reuse. The aim of this study is to assess the physicochemical and microbiological quality of treated wastewater from Cap Falcon wastewater treatment plant for reuse in irrigation. The suitability of treated wastewater from Cap Falcon plant for irrigation was assessed based on its composition and Algerian irrigation water quality standards. The average biochemical oxygen demand (BOD5) and chemical oxygen demand (COD) values decrease from 316 mg/L to 21 mg/L with a mean removal efficiency of 93.0% and from 659 to 40 mg/L with
removal efficiency of 93.7% respectively. For total suspended solids (TSS), the concentration at the inlet of the treatment plant is very high but reduces greatly after biological treatment with a removal efficiency over 94.5%. The physicochemical analyses of treated wastewater samples from the storage reservoir indicated that pH varied from 6.81 to 8.20 with an average value of 7.43, which is slightly alkaline in nature. Electrical conductivity is one of the criteria used to evaluate the suitability of water for agricultural use; the average value was found less than 1500 μS/cm, indicating that the treated wastewater is considered as suitable for irrigation use. On the other hand, microbiological analyses indicate that faecal coliforms are high compared with Algerian water quality reuse
standards. Furthermore, the overall quality of tertiary treated wastewater was analyzed by calculating the water quality index. The calculated index for the physicochemical and microbiological parameters was 96, which corresponds to a water quality type “very poor” signifying that this effluent can only be used for restricted irrigation practices

In this article, we present a mathematical model applied to the concentration of solar energy. This system is designed to prepare steam to meet the sterilization needs of medical instruments. A conical concentrator coupled to an autoclave in cylindrical form is placed in the conical reflector axis. We present a mathematical model explaining the thermal behaviour of water in a medical autoclave. The validation of the model was well done with the literature results. Our results indicate that the system produces saturated steam and takes 20 to 30 min, depending on climatic conditions and autoclave dimensions. The sufficient time to reach a temperature of more than 121 °C where no organism reproduces after being kept in an autoclave at 126 °C for 6 min or at 121 °C for at least 20 min. The simulation results encourage us to optimize the concentrator device to obtain a useful solar sterilizer, using the theoretical model as a safe guide to achieve this.

Surface aerators are commonly used in activated sludge systems to supply oxygen needed for all aerobic bacterial process and also ensure sufficient mixing of the sludge suspension with wastewater. Power consumption by surface aerator is one of the significant design parameters for surface aeration tank reactor which is affected by the physical properties, operating parameters, and geometrical parameters. The knowledge of the power consumption is essential for the determination of overall rates of heat and mass transfer and circulating and mixing times and is directly, related to the operating cost. In this work, computational fluid dynamics (CFD) techniques were employed to study the effect of the surface aerator submergence depth ratio and rotation speed on power consumption in a full scale aeration tank equipped with a low speed surface aerator, model Landy-7. The multiple reference frames approach coupled with the volume of fluid model and k-ε turbulence model is applied to predict the flow induced by the surface aerator and the free surface motion. The simulation results were compared with experimental data reported in the literature. The CFD results show that, the maximum values of power consumption are achieved for the optimal submergence depth ratios which correspond to of 0 and 0.031 for N1=20 rpm and N2=33 rpm, respectively. This indicates that power consumption can be considered as a judgment criterion to determine the optimal surface aerator submergence depth ratio.

abattement de la pollution carbonée azotée et phosphate par un réacteur biologique à boue activée

L’eau est devenue le réceptacle universel de tout type de pollution, surtout dans les pays hydro-sensibles.Ces eaux sont souvent chargées en matières organiques, azotées et phosphorées en quantités importantes dont leur rejet direct dans les milieux récepteurs n’est pas sans risques pour les organismes et l’environnement. Pour répondre `a cette situation, le recours `a l’épuration des eaux usées urbaines est devenu inévitable. L’objectif de notre étude est de traiter par boues activées les eaux ayant subies un traitement primaire. Le traitement par boue activée fait intervenir les micro-organismes (traitement biologique) en utilisant un réacteur biologique avec un système d’injection d’air. Le dispositif assure l’apport en oxygéné nécessaire aux bactéries épuratrices et provoque une turbulence au sein du liquide pour maintenir en suspension la boue activée. Plusieurs paramètres ont ´ et´e pris en considération tels que la DCO, la DBO5, Les MES, la température, les phosphates, les ions ammonium, les nitrates et les orthophosphates. Les résultats ont révélé un abattement de 44.3% pour l’azote ammoniacal et 80.63% pour l’azote nitrique par la réaction de dénitrification. Par ailleurs, la nitrification obtenue est de 70.34% et le relargage des orthophosphates par les micro-organismes avoisine 87.8%. L’´étape de précipitation du phosphore a permis d’obtenir un abattement de 99.6%. Ces résultats montrent l’efficacité du réacteur biologique de type boue activée répondant ainsi à la norme algérienne.

Algeria is considered one of the hottest countries in the world due to the abundance of solar hours, especially in the south of the country. Therefore, the process of cooling homes and buildings is
considered very important, but it is very expensive for the state. One of the solutions to reduce unwanted internal heat from buildings is to use solar energy. In this study, we used a solar chimney
connected to a ground pipe to provide ventilation and cooling for a room in a house. Three different regions of the country were chosen: Algiers, M'Sila and Ouargla. To know the effect of climatic
conditions on air flow in a room with limited dimensions. We simulated the air temperature distribution inside a room equipped with a solar chimney and connected to a ground pipe using the
Fluent program. Finally, the percentage of energy consumption in the three regions mentioned above was discussed.

Surface aeration tanks (SATs) are one of the main structures of activated sludge treatment process. The main functions of these bioreactors are to supply oxygen needed for all aerobic bacterial process and also ensure sufficient mixing of the sludge suspension with wastewater. This study presents a computational fluid dynamics (CFD) model of a full-scale SAT equipped with a low speed surface aerator, model Landy-7. The multiple reference frames approach coupled with the volume of fluid model and k-ε turbulence model is applied to predict the flow induced by the surface aerator and the free surface motion. After validation, the CFD model is used to optimize the submergence depth ratio of the aerator. Two different flow cases are observed depending on the aerator rotation speed. For low rotational speeds, the Landy-7 aerator acts as a surface aerator affecting mainly the water near the surface and has little effect on the shallow layers and the air-water interface is identified as the optimal position for the surface aerator. For high aerator rotation speeds, this effect persists longer in the SAT, even for large submersion depth ratios, which means that the Landy-7 aerator acts as an agitator as well as a surface aerator.

The criteria for choosing a coagulant are numerous. Aluminum-based coagulants iron and even synthetic polymers have adverse effects on human health and the environment. Our goal is to look for a plant substituent. For this, we used the seeds of Moringa oleifera for the treatment of raw water from the WWTP of El Karma (Oran) by the coagulation/flocculation process in jar-test. The seeds were used in powder and solution at different concentrations. We optimized the pH parameter for different doses of bioflocculant. The stirring speed was maintained at 250 rpm for coagulation and 50 rpm for flocculation. The results obtained showed that the use of bioflocculant in solution is more effective than its use in powder. The pH optimization showed that at pH 7 turbidity decreases from 4096 NTU to 25 NTU. While at pH 5, turbidity decreases from 4096 NTU to 238 NTU. With the bioflocculant powder, the turbidity obtained is 218 NTU at pH 7 and 278 NTU at pH 5.
Keywords – Moringa oleifera, Optimization, Bioflocculants, Raw water, Turbidity.

This research is to incorporate three efficient ways that will increase the performance of baffled heat exchangers. The 1st technique is represented by baffle perforating to create pores through which secondary streams pass in order to reduce main stream pressure on the flow areas. A 2nd technique represented in redesigning the baffle structure by replacing its square edge with the arched edge in order to increase the X-velocity to facilitate the flow towards the outlet and reduce the Y-velocity to reduce the values of fluid friction with the solid areas. Finally, a 3rd way was demonstrated by using the inclined baffle model. Reinforcement of the baffle structure allowed for enhanced vortices, increased thermal gradients, and thus a reinforced thermodynamic structure over the entire heat exchanger

Domestic wastewater generated by human activities, especially household wastewater like; baths, washing machines, and kitchens; consists of large levels of pollutants (organic, inorganic and microbial) and that harm the natural environment and the health of human beings. Therefore, these wastewaters must be treated before discharging to avoid adverse effects in the receiving environment. In integrated modern township, domestic wastewater is treated separately, but in most of the places it is mixed with municipal wastewater and it is sent for treatment by means of physical, chemical, physico-chemical, or biological methods. Among physicochemical processes, electrocoagulation appears as an alternative technique due to their effectiveness in removing inorganic and organic contaminants from various types of wastewater with less energy consumption, its lower maintenance cost, less need for labor and rapid achievement of results.
This technique is based on the electrochemical dissolution of sacrificial metal electrodes using just electric current and produce a coagulant species that destabilizes and traps pollutants in the form of suspended particles in wastewater, forcing them to form flocs and precipitate, resulting in the removal of pollutants. The iron, stainless steel, and aluminium electrodes are the most commonly used because of their low cost, easy availability, and proven efficiencies. In this work, treatment of a domestic wastewater by electrocoagulation process was investigated using a square section batch tank stirred with two blades impeller as a laboratory electrochemical reactor and aluminum electrodes. The samples were supplied from the wastewater treatment plant of ElKerma in Algeria. The main objectif of this study is to determine the effects of operational parameters on treatment performance, in order to evaluate the applicability of the process on real scale. Effects of various parameters such as electrolysis time (0–360 s), initial pH (5–10), current density (2–7 A/m2), and impeller rotational speed (1,67–3,33 s-1), were evaluated to find optimum operating condition for Total Suspended Solids and other pollutants removal. The experimental results revealed that the greatest removal efficiencies of the Total Suspended Solids and turbidity attained, respectively, 99.68, and 96.28% at the optimum conditions (operating time of 180 s, initial pH of 6, current density of 7 A/m2, and impeller rotational speed of 3,33 s-1). In addition, the bubbles generated from hydrogen at the cathode increase turbulence in the system and as a result, they improve the flotation separation process. This results shown considerably the technical feasibility of this electrochemical reactor design as a potential method for domestic wastewater treatment by electrocoagulation/flotation without the need of air injection and thereby, low operational costs.

This study presents a computational fluid dynamics (CFD) model of a full-scale surface aeration tank (SAT) equipped with a low speed surface aerator, model Landy-7. The multiple reference frames (MRF) approach coupled with the volume of fluid (VOF) model and k-ε turbulence model is applied to predict the turbulent flow induced by the surface aerator and the free surface motion. Simulations are performed for different rotational speeds and the predicted results in terms of steady-state power consumption are compared with literature data. After validation, the CFD model is used to study in detail the flow behavior in the SAT and then to optimize the submergence depth ratio of the surface aerator. Two different flow cases are observed depending on the aerator rotation speed. For low rotational speeds, the Landy-7 aerator acts as a surface aerator affecting mainly the water near the surface and has little effect on the shallow layers and the air-water interface is identified as the optimal position for the surface aerator. For aerator rotation speeds above 24 rpm, this effect persists longer in the SAT, even for large submersion depth ratios, which means that the Landy-7 aerator acts as an agitator as well as a surface aerator.

Surface aeration tanks are one of the main structures of wastewater treatment plants, especially in activated sludge treatment process. The main functions of the surface aeration tanks are to supply oxygen needed for all aerobic bacterial process and also ensure sufficient mixing of the sludge suspension with wastewater. Effective aeration in these bioreactors is achieved by placing a surface aerator close to the free surface of the liquid. The selection of a particular surface aerator is made according to consideration of efficiency of its oxygen transfer rate and its power consumption. Low-speed surface aerators are commonly used in activated sludge systems because they offer excellent oxygen transfer and mixing of the fluid, require little operational control, and able to handle environmental extremes such as high temperatures. In this study, the flow field in a full-scale square section tank fitted with a low speed surface aerator model Landy-7 developed and designed by WesTech and Landustrie is simulated using ANSYS Fluent software. This surface aeration tank is located at the wastewater treatment plant of El-Karma city in Algeria. The 3D k–ε turbulence model coupled with the multiple reference frames (MRF) approach were used to represent the particular flow induced by the Landy-7 surface aerator and the free surface deformation was modeled with the volume of fluid (VOF) method. After validating the numerical modeling of the surface aeration tank with the experimental measurements reported in the literature, the numerical tool is used to investigate the effects of surface aerator submergence depth on the main features of the flow field in the surface aeration tank, like volumetric power consumption, flow number rate, energy dissipation, shear rate, etc.
Next, by solving numerical dispersion of a passive tracer, performance of the surface aeration tank is investigated in term of mixing time. The numerical results were presented for various rotation speeds and compared to predict the optimal submergence depth of surface aerator and to improve the energy efficiency of the wastewater treatment plants. Based on the simulation results of the flow field and mixing, an optimized operation scheme of the surface aeration was proposed.

As part of a comprehensive evaluation of post-treatment techniques for the removal of chemical and microbiological pollutants from lagoon effluents, an aerated biofilter was designed. The main objective of this study was to evaluate the performance of pozzolan and Luffa cylindrica as low-cost packing materials for the advanced treatment of Stidia natural lagoon effluent. The aerated biofilter operates in down-flow with HLRs of 11.37 to 28.43 m3 m−2 d−1 and an air/liquid flow ratio of 3 : 1. The different experiments performed on the pilot showed that the percentages of sCOD removal vary with the HLRs and the wastewater concentration at the biofilter inlet. In this study, sCOD removal efficiencies above 78.9 % were achieved depending on HLR, and a maximum removal efficiency of TSS of 71.5 % was obtained for 28.43 m3 m−2 d−1. At low HLR (11.37 m3 m−2 d−1), the treated effluent had the following average concentrations: sCOD of 29.5 mg l−1, BOD5 of 21.7 mg l−1 and TSS of 26.4 mg l−1. These experimental results were used with an empirical model to determine the media constant n and treatability factor K. The faecal coliforms and Escherichia coli detected in the treated effluent were less than 105 CFU/100 ml, which meet the national guidelines for wastewater reuse in irrigation.

Elimination des Micropolluants des eaux usées destinées à l’Irrigation

A numerical investigation of a scraped surface heat exchanger (SSHE) was undertaken, using the commercial CFD code FLUENT in order to characterize flow patterns and the shear rates. Regarding the operating conditions of the heat exchanger, Newtonian fluids and various geometric configurations were considered. A three-dimensional resolution of the continuity and momentum equations was conducted. After validation of the numerical strategy, a parametric study is made to better understanding the interactions between axial and rotation velocity. The simulation is achieved for various values of Taylor number for extended interval [0.09, 561.70] and axial Reynolds included [12, 2232]. Furthermore, the developed model has established the impact of the rotational speed and the mass flow rate on the shear rate.

Ultrasound assisted maceration was developed as a new and cleaner procedure for a green enrichment of an olive oil with rosemary essential oil. Ultrasound assisted maceration has been compared with conventional maceration. Ultrasound was then applied in order to accelerate diffusion of the rosemary volatile compounds into the olive oil. Then the enriched olive oil obtained by Ultrasound assisted maceration was qualitatively similar to those obtained by conventional maceration. However, the processing time is reduced from hours or days to few minutes when comparing traditional maceration and Ultrasound assisted maceration.

In this work, the mixing performance in a batch torus reactor was investigated using computational fluid dynamics (CFD). The two impellers applied in this study generated completely different flow patterns: one generates simultaneously axial and rotating motions and the other is particularly shaped for axial pumping.To validate the numerical model, the CFD results for the mean bulk velocity and power number were compared with the experimental data reported in the literature. Next, by solving the numerical dispersion of a passive tracer in an unsteady state, the performance of the torus reactor is investigated in terms of the mixing time. Finally, the numerical tool is used to study the effect of the system geometry and operating conditions on the power consumption and mixing energy. All investigations indicate that the classical three-blade marine impeller has the best mixing performances.

The effect of the impeller type on the flow behaviour in a torus reactor is evaluated using the commercial CFD code FLUENT. The two impellers applied in this study generated completely different flow patterns: one generates simultaneously axial and rotating motions and the other is particularly shaped for axial pumping. The evolution of the flow pattern along the reactor axis is investigated for different impeller rotation speeds, which shows the complex hydrodynamical interaction between the main rotating swirl motion involved by the impeller rotation and the bend curvature effects. Then, the effect of the particular flow generated by both impellers on the appearance of Dean vortices is investigated. The predicted results show different flow structures, which result from the evolution of the axial and the rotating motions when moving away from the impeller