The methodology of modelling and object analysis of management systems includes, inter alia, operations connected with the definition of special object types being an imitation of components (objects-sources of waste generation, objects for waste neutralisation, networks of roads, natural environment components, waste substances, etc.) [4, 6-7]. Since the systems are investigated in the GIS technology, some objects are assigned attributes of spatial representation (location coordinates, geometric and graphic attributes used for their recording on a map). Operations performed on the models of individual-class objects (e.g. topological operations) are interpreted (using object-related terminology) as the so-called methods (functions and procedures) which are in fact computer implementations of a range of algorithms used in system analyses

A B S T R A C TThe main threat to human health is associated with organic compounds, which are found in the natural water ecosystem. The law relating to drinking water quality protects consumers' health. Thus, the need to remove disinfection by-products (DBP) precursors requires the application of high-efficient water treatment processes. Usually, chlorine is used to disinfection, and then, haloforms are generated. Well-calibrated model, estimating the concentration of DBP in treated water, can be a useful tool for predicting the quantity of trihalomethanes in water in the distribution network. Such a model makes it also possible to identify the critical control points in the monitoring process. This paper presents the statistical analysis of chloroform formation in treated water, based on laboratory tests. The chloroform concentration is expressed as a function of factors, which determine kinetics of the chemical reaction of organic compounds with chlorine. Two new variables-the ratio of total organic carbon and chloroform and the ratio of chlorine consumption and chlorine dose, both obtained after 1 h of the reaction-were taken into account. From the function predicting the chloroform concentration, one can determine the optimal dose of chlorine in the disinfection of water in dynamic operational conditions.

Over the past years in Central and Eastern Europe, including Poland, it can be observed that there has been a considerable decrease in water consumption. This leads to high operational costs due to underutilised capacity of existing drinking water treatment plants (DWTP) or distribution systems. Under these conditions providing rational management of DWTP requires technical, economical and reliability analysis. The application of probability and statistical theories together with a decomposition method was the scientific basis of this paper. As a second step, Woodward's LCCA model, together with the Activity Based Costing (ABC) model, were applied.

In this work, attention has been paid to the problem of quality of groundwater, which is the main source of supply of drinking water for rural inhabitants. In particular, the important factors for the groundwater quality in rural areas have been presented. This paper also shows the impact of the quality and quantity of available water resources on the exploitation of chosen small water intakes. Results of research on the quality parameters of groundwater, obtained in 2012÷2016 for selected rural intakes in north-western Poland, were presented. There was an increase in the content of iron and manganese compounds, ammonium ions, as well as the presence of bacteriological contaminants in test water samples. For these reasons, problems with providing the receivers with water of appropriate quality parameters have been reported in described rural intakes. The paper is an attempt to show the relationship between the type and magnitude of changes in the groundwater quality and the efficiency of the water treatment. In addition, pro-quality activities undertaken by local water companies were emphasized.

A comprehensive method for safety assessment of water supply systems has been presented. The method includes both conditions of technical exploitation and quality of water delivered to consumers. In the analysis, the system capacity, appearance of failures on water mains as well as the chloroform concentration in transported water were taken into consideration. Four disjoint safety states have been defined (FS-full safety, ASM-acceptable safety menace, CSM-controlled safety menace, SL-safety loss) of water supply system. Moreover, the probabilities for the system to be in each of these states at the moment t were derived based on the Markov processes.