Swimming pools are very expensive, in terms of operation, sports facilities. Therefore, investors and managers of these facilities are looking for methods of reducing the costs of their use. One of the proposed methods is the managing of washings previously discharged to the sanitary sewage system. The assessment of possibilities for reuse of washings from swimming pool filtration system is based on the limits of basic indicators of pollutants in wastewater discharged to water and soil (temperature, pH, TSS, BOD5, COD, TN, TP, free chlorine). The conducted research of washings quality from 26 tested swimming pools have shown that washings quality is dependent on the operating conditions of the pool circuit, including the filter cycle duration and types of filter bed. A direct discharge to water or soil may be impossible due to excessive amounts of total suspended solids (above 35 mg/dm 3 ) and free chlorine concentration (above 0.2 mg Cl2/dm 3 ). However, the quality of supernatant water of washings subjected to sedimentation in the laboratory shows that the washings are suitable for reuse. The installation of settling tanks in swimming pool facilities could relieve the sewage systems and allow for the discharge of supernatant water to surface waters or for the irrigation of green areas in an environmentally friendly way.

The necessity of regular filter backwashing in the pool water technological systems generates enormous, unproductive water losses. In order to properly wash the filter bed, a water consumption of 4÷6 m 3 per 1 m 2 of bed is required. According to the guidelines, such backwashing should take place every 2÷3 days [1-6]. It can be estimated that the monthly water consumption for a typical installation, consisting of two filters with a diameter of 1800 mm, can be over 450 m 3. Every year, it is over 5 000 m 3 of unproductive wastewater discharged usually into the sanitary sewage system. In Poland, there are over 560 pools equipped with at least 2 filters [7]. Therefore it can be estimated that annually more than 2 800 000 m 3 of backwash water is lost. Assuming the average price for wastewater discharges in large cities, 1.48 €/m 3 , it is easy to estimate that over 4 million € per year is spent on discharging "pool" washings [8]. In addition, the water used to backwash filtration beds is usually taken from the technological system where it was previously heated. The temperature of washings ranges from 25°C to 36°C (average about 30°C). For this reason, its discharging into the sewage system is also a waste of energy used to heat it. In the Institute of Water and Wastewater Engineering of the Silesian University of Technology, the research on the quality of backwash water from swimming pool installations is being conducted. Their main purpose is to check the possibility of managing the backwash

This paper presents the influence of the type of filtration beds, used in swimming pool water treatment systems, on the quality and the possibility of reuse of washings. The research covered 4 pool cycles with sand, sand and anthracite, glass and diatomaceous beds. The degree of contamination of washings was assessed on the basis of physical, chemical and bacteriological tests. The possibility of washings drainage into the natural environment was considered, and the results of the research were compared with the permissible values of pollution indicators for wastewater discharged to water or ground. A direct management of washings from the analysed filters proved impossible mainly due to the high content of TSS (total suspended solids) and free chlorine. Washings were subjected to sedimentation and then the supernatant was stirred intensively. As a result of these processes, the quality of washings was significantly improved. This allowed planning to supplement the pool water installations with systems for washings management.

The paper has determined the suitability of membrane processes (UF ultrafiltration, UF, and nanofiltration, NF) for the purification of waste streams, so-called backwash water, obtained from washing filtration beds in a swimming pool water system. The backwash water samples were taken from the circuits located in two indoor facilities with a different purpose of the basins. Moreover, the samples were characterized by varying quality, as described by selected physicochemical parameters (such as turbidity and ultraviolet absorbance UV254). Commercial membranes were used for the tests. The transport-separation properties of the membranes were determined based on the volumetric flux of the permeate. In addition, backwash water samples before and after the membrane process were subjected to toxicological assessment using the Microtox ® screening test. The performed processes contributed to a significant reduction in turbidity and the value of UV254 ultraviolet absorbance, both in the ultrafiltration and nanofiltration processes. Whereas, significant differences in transport properties were noted within individual processes. A great influence of backwash water quality, including physicochemical parameters, on the course and results of the membrane filtration processes was demonstrated. In all of the nanofiltration cycles carried out, the removal of the toxic properties of the backwash water with respect to bacteria in the Microtox ® test was found. Nevertheless, samples with high values of resultant physicochemical parameters after the ultrafiltration process were still characterized by high toxicity. Pressure membrane processes show high effectiveness in the removal of contaminants from backwash water. However, it is necessary to introduce supporting processes aimed at reducing membrane pore blocking by deposits and organic compounds, and in the case of ultrafiltration, assuring the safety of the purified stream in terms of the toxicological effect.