The sedimentation devices are commonly used in the clarifying of industrial suspensions and in the civil engineering. The sedimentation efficiency plays very important role in the environmental protection. The aim of the research was to investigate the possibilities of applying neural networks in computing the efficiency of sedimentation processes. Input data were the results of computer stimulation performed according to the mathematical model taking into account the overflow rate in the sedimentation facilities and physical parameters of the suspension, such as probability density function of solid particle size. Two probability density functions of solid particle size were compared: log-normal distribution and gamma distribution. Feed-forward neural networks (with no feedback and with one- stream flow of information) were applied in research work. Teacher-supervised teaching, according to back-propagation method with the use of Levenberg-Marquardt algorithm, was chosen. When neural networks were taught with the use of sets including less than 400 data elements, the errors were more than I%. Neural networks taught by means of series including more than 500 data sets would yield acceptable results and the error was less than I%. Accordingly, one can presume that the smallest teaching set is the one composed of 500 data elements. The best results were obtained when the number of data sets was about 5000- the differences in computed sedimentation efficiency were then less than 0.5%. A further increase in the number of data elements - above 5000 - would lead to lower accuracy of calculations.

Wastewater generated in the Warsaw metropolitan area is neutralized at one of the most modern treatment plants in Poland.

This study examined the process of filtering of infiltrated water containing excessive amounts or iron, manganese, and fulvic acids through two filtration beds-sand and zeolite-exhibiting catalytic properties. The fulvic acids that were added to the filtered water were extracted from mud in Kołobrzeg. The zeolite bed was modified with manganese oxide using our own technology and required periodic regeneration using 0.3% KMnO, solution. Our study showed the fulvic acids' negative effect on the process of water purification. The zeolite bed reduces this effect and is more effective than the quartz sand bed.

Environmental contamination is an urgent topic to be solved for sustainable society. Among various pollutants, microorganisms are believed to be the most dangerous and difficult to be completely inactivated. In this research, a new hybrid photoreactor assisted with rotating magnetic field (RMF) has been proposed for the efficient removal of two types of bacteria, i.e., gram-negative Escherichia coli and gram-positive Staphylococcus epidermidis. Three selfsynthesized photocatalysts were used, based on commercial titanium(IV) oxide - P25, homogenized and then modified with copper by photodeposition, as follows: 0.5Cu@HomoP25, 2.0Cu@HomoP25 and 5.0Cu@HomoP25 containg 0.5, 2.0 and 5.0 wt% of deposited copper, respectively. The response surface methodology (RSM) was employed to design the experiments and to deteremine the optimal conditions. The effects of various parameters such as copper concentration [% w/w], time [h] and frequency of RMF [Hz] were studied. Results: Analysis of variance (ANOVA), revealed a good agreement between experimental data and proposed quadratic polynomial model ((R2=0.86 for E. coli and R2=0.69 for S. epidermidis). Experimental results showed that with increasing copper concentration, time and decreasing of frequency of RMF removal efficiency was increased. Accordingly, the water disinfection efficiency of 100% in terms of the independent variables was optimized, including cooper concentration c =5 % and 2.5% w/w, time t = 3 h and 1.3 h and frequency of rotating magnetic field f = 50 Hz and 26.6 for E.coli and S. epidermidis, respectively. This study showed that response surface methodology is a useful tool for optimizing the operating parameters for photocatalytic disinfection process.

In this paper we studied the intensification of the water clarification process on contact clarifiers with quartz sand fil-tering bed, which was modified with a solution of aluminum sulphate coagulant. The modification of the quartz sand filter-ing bed was carried out by applying to the surface of grains of quartz sand solution of coagulant aluminum sulphate with different doses. Investigation of the electrokinetic potential of the filtering material (quartz sand) was carried out by the percolation potential method.

The influence of electrical properties (size and sign of the charge) of the filtering bed itself and suspended solids in the water on the filtration process was studied. The filter material – quartz sand used in contact clarifiers has a negative electric charge. When the electric charge of the particles decreases, that is, as the ζ-potential decreases, the repulsive forces de-crease and it the adhesion of particles becomes possible. This is the process of coagulation of the colloid. The forces of mu-tual gravity between the colloidal particles begin to predominate over the electric repulsive forces at the ζ-potential of thesystem less than 0.03 V.

Modification of quarts filtering bed with a solution of coagulant aluminum sulphate recommended for the purification of surface water allows: to intensify the process of water clarification, to reduce the consumption of reagents by 25–30%, with the obtaining purified water of the required quality, to reduce the production areas necessary for reagent management of treatment facilities, and to reduce the cost of water treatment by 20–25%.