The presented work is devoted to solving the actual problem of increasing the efficiency of rapid sand filters with granular filling, which operate at a constant filtration rate when cleaning suspensions with a relatively high concentration of contaminants. The proposed mathematical model for clarifying the suspension by filtration consists of three interconnected blocks: clarified, filtration, and hydraulic. Convenient dimensionless mathematical dependencies are obtained for calculating the concentrations of contaminants and sediment from the height of the filter and suspension in the filtrate; head loss in the filter loading; the effective time of the filter (the duration of the filter cycle). The design of the experimental setup and the methodology for conducting experimental studies and mathematical processing of the results are valid. The results of experimental studies of the suspension filtering process through the granular loading are presented, and the obtained data is analyzed. Measurement of pressure losses in the filter loading is performed when a suspension is passed with a relatively high concentration of contaminants at various filtration rates. The nature of the change in the filtration rate with time and height (length) loading at various filtration rates and initial contamination concentrations is determined. Measured variable concentration of suspended matter in filtered water and retained contamination over time. As a result of the experiments, it is confirmed that an increase in the concentration of retained contaminants S leads to an increase in the parameter Δn/n. Upon reaching a certain value of the concentration of the retained sediment S (in our case S=30 g/dm3), an increase in the relative specific volume of the sediment greater than Δn/n0=0.65 is not observed. It is established that an important characteristic of the retained sediment is the ratio of the volume concentration of the sediment to the volume concentration of solid particles in this sediment γ=Csd/Сs. The values of the adhesion and detachment of particles of contaminant in the particles of the material loading =4,9; =0,009. The results of experimental studies in general confirm the correctness and reliability of the obtained analytical dependencies.

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This paper reports the results of the experimental and theoretical studies of the characteristics of perforated pipelines, which are used to collect and dispose water from capacitive treatment structures of water supply and sewerage systems.The value and nature of the change in the flow rate through the perforation holes µ col lengthwise a pipeline have been examined depending on the design characteristics of the perforated pipes and parameters of a fluid flow in the pipeline. Measurements were carried out at a specially assembled experimental bench. The experiments determined the nature of changes in the flow rate value, as well as in the piezometric line along the collector. The obtained data showed that the flow rate factor µcol varies along the length of the collecting channel. Its value depends on the ratio of the velocity of the fluid jets that enter the pipe to the average velocity in the examined cross-section (U h /V). In this case, this ratio also changes along the path; it has a maximum value at the beginning of the pipe and a minimum value at its end. The variable flow rate factor of perforation holes, on the contrary, had a minimum at the beginning and a maximum at the end of the collector. The result of the analysis of initial equations and the findings based on experimental data has shown that calculations may assume, without a significant error, the flow rate factor value of perforation holes µ col to be constant lengthwise the collector. The impact of the transit flow rate on the value of this coefficient has also been estimated. It is shown that the increase in transit leads to a certain increase in the flow rate factor, which is averaged for the entire collector. The paper proposes empirical dependences that are convenient to use in order to calculate the flow rate factor, both variable and constant, for the case of the presence and absence of transit in the head drainage channel

The results of an experimental study of the hydraulic friction factor of perforated pipelines that work with the collection of fluid along the path are reported. Clarification of this issue will make it possible to solve an important engineering task – to devise a reliable procedure for the hydraulic calculation of perforated pipes. The experiments were carried out on an assembled experimental bench. A steel pipeline with a perforated part of 1–3 m was investigated. Perforation holes were taken with a diameter of 3.6 and 9 mm. In the experiments, fluid flow, pressure loss, and average velocity were measured. Based on the data obtained, the values of the coefficient under study were calculated. It has been established that it is significantly larger than its values with uniform movement and is variable in length of the pipeline. Experimental dependences λcol on the value of the ratio of the velocities of the flowing jets of liquid to the average flow velocity in the corresponding section (Uh/V), as well as on the design characteristics of the channel, were obtained. It is shown that the lower value of the degree of pipe perforation corresponds to the higher values of λcol. This result can be explained by the influence of the attached flow rate on the main flow. The confirmation of this conclusion is the resulting shapes of diagrams of the average flow velocity obtained in the experiments, which differ significantly from standard diagrams with uniform motion. Obviously, additional energy is spent on the reformation of the velocities, and this causes additional head losses. Dependences were obtained for calculating the considered coefficient for prefabricated pipelines, including in the presence of transit flow rate. Their use in the calculation of the pipes under consideration will increase the reliability and efficiency of the sewage treatment plant, in which they are important structural elements

Peculiarities of the diagrams of averaged fluid velocities in the cross-sections of pressure collecting perforated pipelines were determined on the basis of the experimental studies conducted by the authors. The most characteristic typical diagrams of averaged velocities in the pipelines cross-sections with their different design characteristics were given. A comparative analysis of the obtained diagrams with the diagrams of velocities that occur during uniform motion in pressure pipelines with solid walls was carried out. It is shown that the main difference between them occurs in the flow zones, which are located near the pipeline walls. It was explained by the connected liquid jets effect on the main flow. The degree of diagrams deformation was estimated by the value of the momentum coefficient α0 (Boussinesq coefficient) and the coefficient of kinetic energy α (Coriolis coefficient). It was determined that in the general case these coefficients will be variable in magnitude along the length of the studied pipes. Nevertheless, these coefficients are recommended to be constant in magnitude in engineering calculations. The limits of the structural characteristics of collecting perforated pipes for which this non-uniformity of the diagrams must be taken into account, and for which it can be neglected were determined on the basis of the analysis of the equation of fluid motion with a variable flow rate.