Analysis of the dispersivity in soils by applying a modified test based on the pinhole method

The Pinhole test is an empirical probe with a qualitative classification foundation that identifies fine-grained soils with dispersive potential using hydraulic heads. However, the original technique was designed to identify dispersive clays. In some cases, it is misused as a quantitative test for measuring subsurface erosion rates. This paper presents a physicochemical modification to the exact test, based on adding a dispersant in the sample compaction water. For the quantitative evaluation of the susceptibility of the soil to generate internal tubification or piping, the effects of hydraulic load, flow, and orifice diameter before and after the execution of the test are explored—both for the samples treated with deflocculant and for those compacted using distilled water. Additionally, to complete the identification results, physical and chemical approaches were applied as methods of comparison. The results obtained from the altered soils indicate a significant increase in the clay fraction among the samples at the end of the test and gains of 3.7 and 6.2 times the initial diameter. The study demonstrates that the modified test is suitable for identifying non-dispersive soils before raising the percolation pressure. This modification is helpful for the improvement of the test because it helps to understand the procedure better and allows to calibrate the apparatus used.

Copper and Zinc Removal Efficiency of Two Reactive Filter Media Treating Motorway Runoff—Model for Service Life Estimation

The predominant techniques used for road runoff treatment are sedimentation and filtration. In filtration systems, the ability of the media to adsorb the contaminants is a finite process. Consequently, construction, operation and maintenance managers of such systems should know in advance the service life, i.e., when the used medium should be replaced, and associated costs of operation and maintenance. A batch experiment followed by a packed bed reactor (PBR) experiment addressed the kinetics of the studied media argon oxygen decarburization slag (AOD) and Polonite, followed by the development of a 1D-model to describe the change of concentration of Cu and Zn within time. The batch test results showed that Cu and Zn adsorption followed the Freundlich isotherms for AOD and Polonite. Those results coupled with the linear driving force model and the developed model resulted in good agreement between the PBR results and the simulation. The model was capable to predict (i), the service life at the hydraulic load of 0.18 m/h for AOD (Cu: 395 d; Zn: 479 d) and Polonite (Cu: 445 d; Zn: 910 d), to show (ii) the profile concentration in the PBR within time and the gradient of the concentration along the height of the reactor.

Experimental Investigation of a Double-Acting Vane Pump with Integrated Electric Drive

The article presents an innovative design solution of a balanced vane pump integrated with an electric motor that has been developed by the authors. The designed and constructed bench, which enables testing of the system: power supply, converter, ntegrated motor—pump assembly and hydraulic load at different motor speeds and different pressures in the hydraulic system, is described. The electromagnetic and hydraulic processes in the motor-pump unit are investigated, and new, previously unpublished, results of experimental studies at steady and dynamic states are presented. The results of the study showed good dynamics of the integrated motor-pump assembly and proved its suitability to control the pump flow rate, and thus, the speed of the hydraulic cylinder or the speed of the hydraulic motor.

Influence of the hydrodynamic efforts on the efficiency of the regeneration of the granular filtering material in a water treatment plant

This article aims to study the hydrodynamic conditions of the parameters that influence the removal of dirt particles and aggregates by the drainage of wash water into filter materials for better regeneration efficiency. The water treatment plant with a nominal capacity of 600 m3·h−1 is located in the city of Parakou in Benin. It appears that one of the causes of the poor performance of the methods used for water treatment is the insufficient value of the shear stresses of the movement created by the flow of washing water in the filter bed. The use of hydro-elevators and hydrocyclones for the removal of particles from the surface of the grains of the filtering material under hydraulic load makes it possible to reduce the quantity of remaining pollution respectively by 1.5 to 2.5 times compared with the combined washing of water and air. To this end, the performance of grain washing in the hydrocyclone is explained by the presence of centrifugal field, self-separation and the friction of the particles between them and on the wall of the apparatus. The regeneration of the filter material under the action of ultrasonic waves reduces the remainder of particles compared to washing with water and air about 6 times.

Assessment of the performance of intermittent planted filters in treating urban wastewater under arid climate

Intermittent planted filters are extensive biological purification techniques aimed at oxidizing and decontaminating urban wastewater at a low cost and with minimum environmental impacts. The main purpose of this study was to evaluate the performances of intermittent planted filters in treating urban wastewater under arid conditions of southern Tunisia. The experimental study was carried out on a pilot scale plant comprising five constructed gravel-sand basins. Screened urban wastewater effluent was intermittently applied with a daily hydraulic load of 400 L/m2. Several water quality parameters were monitored at the inlet and outlet of this treatment plant. The average removal rate were 94.8%, 92.3%, 99.3%, 89.9% and 93.3% for chemical and biological oxygen demand, total suspended solids, ammonium nitrogen and orthophosphate, respectively. Additionally, results demonstrated that this treatment system is capable to remove 3.67, 3.22 and 2.44 log units of total and faecal coliforms, and faecal streptococci, respectively. Results showed that Phragmites australis allowed the development of biofilm in the sand filter beds, improving their purification efficiency. Furthermore, no bio-sludge production, no mechanical aeration, low energy requirement (0.02 kW/m2) and green aesthetic ambience are the additional particular strengths of the proposed pilot-plant.

Removal efficiency of antibiotics from water through constructed wetlands, a review

<p>Contamination in water bodies with antibiotics and resistance genes is becoming an increasing threat to global health. Overuse of antibiotics has become a serious ecological problem worldwide. There is growing concern that antibiotics are losing their effectiveness due to increased antibiotic resistance in bacteria. During the last twenty years, the consumption of antibiotics has increased rapidly, which has been cited as one of the world’s worst abusers of antibiotics. Several studies have been conducted to solve this issue. Developed countries have introduced several methods but constructed wetlands have been found low cost technology. Although constructed wetlands (CWs) offer a potential way to remove these antibiotics from water supplies, knowledge of their mechanisms is limited. In this review, we highlight important aspects of antibiotic pollution in waters, the removal efficiency of constructed wetlands for antibiotic removal and that antibiotic pollution affects many things which taken together poses several challenges for environmental scientists. It has been discovered that four main factors are affecting the performance of constructed wetlands used for the treatment of antibiotics in water supplies, the types configurations of constructed wetlands, hydraulic load rates, substrates, plants, and microorganisms. Further researches focusing on these factors are recommended to improve the removal efficiency of antibiotics in constructed wetlands. Outcomes of the study could help wastewater treatment plant engineers with providing reliable design data and outline a road map for future researches.</p>

Slope deformation, reservoir variation and meteorological data at the Khoko landslide, Enguri hydroelectric basin (Georgia), during 2016–2019

The Greater Caucasus mountain belt is characterized by deep valleys, steep slopes and frequent seismic activity, the combination of which results in major landslide hazard. Along the eastern side of the Enguri water reservoir lies the active Khoko landslide, whose head scarp zone affects the important Jvari–Khaishi–Mestia road, one of the few connections with the interior of the Greater Caucasus. Here, we present a database of measurement time series taken over a period of 4 years (2016–2019) that enables us to compare slope deformation with meteorological factors and human-induced perturbations owing to variations in the water level of the reservoir. The monitoring system we used is composed of two digital extensometers, placed within two artificial trenches excavated across the landslide head scarp. The stations are also equipped with internal and near-ground surface thermometers. The dataset is integrated by daily measurements of rainfall and lake level. The monitoring system – the first installed in Georgia – was set up in the framework of a NATO-funded project, aimed at assessing different types of geohazards affecting the Enguri artificial reservoir and the related hydroelectrical plant. Our results indicate that the Khoko landslide displacements appear to be mainly controlled by variations in hydraulic load, in turn induced by lake level oscillations. Rainfall variations might also have contributed, though this is not always evident for all the studied period. The full databases are freely available online at the following DOI: https://doi.org/10.20366/unimib/unidata/SI384-2.0 (Tibaldi et al., 2020).

Moving and Fixed Biological Biofilm Systems in Wastewater Treatmentwhen dose an Application Makes Sense

This study demonstrates the optimization of different Biofilm applications in wastewater treatment for a cost-effective solution. The increase of wastewater treatment cost because of high treatment efficiency requested and energy consumption makes such applications very interested in this field. Therefore, aerated reactors for wastewater treatment units were designed to work as Submerged Fixed Biofilm Bed, on the basis of biofilm-microorganisms attached to monolithic plastic supports to increase the treatment efficiency. This application depends on the aerobic process and achieved by the aeration in BOD reduction and Nitrifications reactors (Oxidation of organic compounds and nitrification). This was implemented by mixing and transport treatment processes within the biofilm attached to the plastic fixed media. The anaerobic reactor in this study was designed also to be simultaneous the de-nitrification stage by the application of a moving bed de-nitrification reactor which was considered as a part of the wastewater treatment process to achieve high treatment efficiency for the study pilot plant. The one-year-scientific evaluation was conducted onsite for the municipal wastewater pilot plant includes a test series with well-defined treatment parameters (soft mixing of the suspending the moving bed carriers; intermediate solids removal unit prior to the nitrification reactors; the mechanism for preventing the carriers to move with the flow into the subsequent reactor) such as waste-water-flow, quality, temperature, salinity, organic and hydraulic load and extensive sampling). The above application of the compact-container-system is considered as a typical field of application, for the following reasons: Need of quality improvements discharged into water body, which is often in the vicinity of bathing beaches; Need for Nutrient-Removal-Systems to avoid algae growth going into water bodies and; Space limitations in a resort and saving the implementation capital cost). The comparison between the application of the biofilm concept and the activated sludge system saved more than 40% tank size; 85% space/area; and up to 30% construction cost.