In many industrial applications most of the solid particles are separated by size and for this purpose there are used the oscillating sieves. The separation process based on sieves is a complex one and it depends on several factors, such as the properties of solid particles submitted to the separation process and on the operating regimes of the separating equipment. We have studied the separation process of the behaviour of solid particles on a flat oscillating surface by drawing up a series of mathematical models aiming at identifying the solid particle trajectory. This paper presents a study performed at the "Vasile Alecsandri" University in Bacau, aiming at determining the travel paths of the real particles compared to the ideal particle travel path. In order to determine the behaviour of the solid particles on oscillating surfaces within the experimental measurements we have used a blind screen. The experiments have been performed on a laboratory bench with flat oscillating sieves. The movement of the solid particle on the working surface has been monitored by two cameras positioned on perpendicular planes, the system aiming at obtaining the spatial trajectory of the particle on the operating surface. Films obtained from the experimental measurements have been processed using the SynthEyes software, resulting *.txt files, which contain the necessary data in order to visualize the trajectory of a particle studied on a working plan. By combining the two paths it was possible to view the three-dimensional trajectory of the solid particle. During the study, we have aimed to determine the trajectory for different types of particles, namely: ideal spherical particle, particle with cube form, various other forms of real particles: soy, pod and grain. Within the experimental measurements, we have also studied the solid particle behaviour for different operating conditions, like different angles of work surfaces and different operating modes of the block sieves. After processing the data obtained from experimental measurements one could calculate the velocity of solid particle on a flat oscillating surface.

In order to accomplish the water quality standards required for a specific use, the continental surface water is treated through a sequence of operations and unit processes. The treatment technological flowsheets carry out, partially or totally, the removal of various pollutants, every treatment step being used for improving one or more qualitative parameter. The treatment scheme is specific to water source type and water use. One of the basic operations for water treatment is the filtration, which is influenced by a series of parameters. The present paper aims at identifying the influence of the granular filtering material on the removal of solids in suspensions that are found in water in concentrations between 5 -50 mg/L. In order to accomplish the experimental program, the studies were carried out using three types of filtering materials with various shapes of granular particles, respectively: quartz sand, perlite and anthracite. Using this types of materials were constituted Granular filters with different thicknesses of the filtering layer were used at different water flow rates. The type of granular filtering material with the highest degree of retention of solids was identified and recommended for large scale application.

The sludge treatment processes represent a priority when we refer to the municipal wastewater treatment, but can implicate very complex studies and applications if we consider the industrial wastewater recovery and treatment processes. Even if the industrial sludges are seen as wastes, they can represent an important resource if are properly managed in the storage, treatment and recovery processes. This paper aims to identify some methods to optimize the coagulation and flocculation process used in petroleum slurry treatment. The application was carried out in real conditions of operation, aiming to establish the optimal concentrations for the chemical compounds used: the dispersant Drimax 1235, coagulant Magnafloc LT 32 and flocculant Magnafloc 120 L. The optimal concentration was established by analyzing the efficiency of the liquid and solid phase separation.

The most important aspect of the national environmental policy concerns air pollutant emission decrease. The studies led in order to identify the atmospheric pollution sources have revealed that the energy sector is one of the biggest pollutants in the economy. Given the negative impact of the pollutant emissions on the environment and the possibility of closing the large combustion plants in case necessary measures to comply with the legal regulations in the field are not taken will significantly reduce the amount of air pollutants from these installations. This paper presents a case study regarding the monitoring of emissions from the large combustion plants on the platform of S.C. CET S.A. in Bacau.