Clarification of Biologically Treated Wastewater in a Clarifier with Suspended Sludge Layer

The article presents the results of an experimental study on the clarification of biologically treated wastewater in a clarifier with a suspended sludge layer. The pilot plant was receiving effluent from trickling filters treating municipal wastewater. An experimental clarifier worked under steady-state conditions considering the influent characteristics and variable operating parameters in terms of flow velocities and height of the suspended layer. From the experimental dependences between different technological parameters it was found that the optimum range of the upward flow velocities providing a dynamic equilibrium of the suspended layer was 0.6–1.4 mm/s. Upward flow velocities below 0.5 mm/s can lead to sludge compaction at the bottom of the unit, while values greater than 1.8 mm/s may cause sludge washout. It was also found that higher suspended layer height values favor higher efficiency of the clarifier and can achieve suspended solids in the discharge of less than 5.0 mg/L; this height should be greater than 0.6 m Technological efficiency of the experimental clarifier was significantly higher than the conventional unit and was comparable with tertiary treatment technologies.

Analysis of energy consumption during convective drying of fruits and berries

The work is dedicated to the calculation of energy costs for the realization of the process of convective drying of fruits and berries in a suspended layer. The energy consumption for the fan drive for organizing the air flow, providing the phenomenon of fluidization of fruits and berries, as well as the costs for supplying heat to the dehydration object have been calculated. The energy consumption was determined for various options of energy supply: using a heat pump and due to the operation of thermoelectric heaters (TEH). It is found that the largest proportion of the energy consumption for air circulation organization. It has been established that from the energy point of view, of all the investigated freons, the refrigerant R410 is the most efficient, the total energy consumption for dehydration of 1 kg of irgi berries with it is 7102 kJ, for honeysuckle - 9765 kJ / kg, for lingonberry - 7989 kJ / kg. Comparative analysis revealed that the use of a heat pump installation of convective drying fruits and berries in the fluidized bed reduces the power consumption by an average of 13% in comparison with drying by using heaters to heat the coolant.

MECHANICS OF THE SUSPENDED LAYER WITH POLYDISPERSE PARTICLES IN CONTINUOUS AIR MIXERS

The quality of mixing of dry building mixes largely depends on the specialized equipment that is used in this process. For the best mixing of dry building mixes, continuous pneumatic mixers are used. Continuous air mixers are the most effective equipment for producing dry building mixes with a higher degree of uniformity. This indicator allows to achieve a better final product. Currently, there are a large number of continuous air mixers that are actively being modernized both in our country and abroad. The article presents a technique that describes the mechanics of a suspended layer with polydisperse particles in the working volume of the displacement palette of a continuous air mixer. The method is based on research conducted by the authors of the article, taking into account experimental data obtained by other scientists. This paper summarizes an approach to numerical modeling of a suspended layer with particles of different dispersion (for example, for dry building mixes) and density. The dependences of the layer boundary, its porosity, and speed parameters on the particle diameters, geometric parameters of the mixing chamber, and other technological values that affect the suspended layer inside the chamber are established. The article presents an algorithm for calculating the mechanics of the weighted layer, which proved itself in numerical modeling of the layer with high accuracy of calculations, which is later confirmed by the necessary amount of experimental data.

Ensuring the Reliability of Pneumatic Classification Process for Granular Material in a Rhomb-Shaped Apparatus

This article is devoted to a detailed description of the developed physical model of the pneumatic classification process for detecting the rotating suspended layer and ensuring the frequency of loading and unloading of a pneumatic classifier. The related mathematical model is developed for estimating the non-stationary concentration of fine particles in a gas-dispersed flow with respect to time and height of the working space of the apparatus. The research is aimed at developing a pneumatic classification method for granular materials using a rhomb-shaped apparatus and ensuring the reliability of the operating process based on the influence of the flow on the granular material concentrations. The obtained experimental results allow evaluating the rational geometrical parameters of the working space in pneumatic granulators, as well as verifying the proposed mathematical model based on the implementation of the quasi-linear regression procedure. It is shown that the rhomb-shaped pneumatic classifier provides effective separation of granular material, reaching up to 95% of the target fraction. As a result, the proposed methodology can be implemented for optimizing geometrical profiles of pneumatic classifiers in terms of defining the required technological parameters of the pneumatic classification process.

Permissible parameters for the circulation rate of the sludge mixture in airlift reactor-clarifier with suspended layer

Factors affecting the permissible limits of sludge mixture circulation rate are given for airlift reactor-clarifier with a suspended layer. The upper limit of the circulation rate is justified as a function of some geometric dimensions of the bioreactor and the hydraulic load on the clarifier to comply with conditions of a suspended layer existence. The lower limit of the circulation rate was obtained on the basis of two conditions: the duration of the active sludge stay in anoxic conditions and the observance of recommended rates in the construction in order to avoid the settling of active sludge. Theoretical and empirical dependences of the maximum permissible values of the circulation rate on the main geometric parameters and on productivity of the airlift reactor-clarifier are presented.