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ab s t r ac tOrganic compounds, which are considered water pollutants, have the ability to react with chlorine or other oxidants leading to the formation of products which pose a significant threat to human health. Humic substances play an important role in the formation of disinfection by-products. Therefore, the removal of organic compounds in the process of water treatment is of great importance. The application of ultrasound initiates a number of physicochemical processes in water which can be used in water treatment technologies, e.g. coagulation or adsorption. These methods, as well as the ion-exchange process, are applied in order to remove organic contaminants. With reference to the theoretical fundamentals of ultrasound, some sonochemical processes can result in a decrease in the content of color organic compounds in water. Increasing the intensity of ultrasonic field enhances the occurrence of sonochemical processes including the destruction of high-molecular organic compounds or the oxidation reactions with radicals. The effect of the ultrasonic field is investigated as a method of water treatment by removal of color contaminants from water. Water samples were subjected to an ultrasonic field generated by the UP-400S ultrasound generator with a frequency of 24 kHz and useful power of 300 W. The samples were exposed to sonification for the time periods of 1 and 5 min; the range of the applied amplitude vibration was 18-90 μm, and the ultrasonic field intensity was in the range 21-105 W/cm 2 . The applied parameters allowed for the observation of changes in the content of organic compounds in water. The effect of the ultrasonic field was investigated for surface water. The water analysis included TOC, oxygen consumption and color. The efficiency of the investigated process (30-40%) was achieved for the highest value of the applied amplitude.

In this paper, we discuss the effect sewage sludge (SS) application has on the contamination of polycyclic aromatic hydrocarbons in fertilized soils and groundwater. Morver, the contents of these compounds in plant biomass was analyzed. For six months, composted sewage sludge was introduced into sandy soil. The research was conducted under lysimetric experiment conditions with the possibility of collecting soil leachate in natural conditions. The following doses of sewage sludge were used: 0, 10, 20, 30, and 40 t/ha calculated per experimental object containing 10 kg of sandy soil. The examinations were carried out within a three-year time frame. Dactylis glomerata grass was grown on the fertilized soils. Every year, the content of polycyclic aromatic hydrocarbons (PAHs) was collected from fertilized objects and analyzed in soil leachate, which can contaminate surface water. The following six polycylic aromatic hydrocarbons defined by Polish standards were determined: benzo(b)fluoranthene, benzo(k)fluoranthene, benzo(a)pyrene, dibenz(a,h)anthracene, and benzo(g,h,i)perylene, indeno(1,2,3-cd)pyrene. Further, the content of PAHs in soils and the bioaccumulation of these compounds in cultivated plants were evaluated after each year. The results of the study showed that the increase in the dose of sewage sludge used for soil fertilization led to the rise in the amount of polycyclic aromatic hydrocarbons analyzed in the soil. The compounds migrated to cultivated plants. This phenomenon was observed especially in the first year following soil fertilization with sewage sludge. Excessive accumulation of PAHs (especially benzo(a)pyrene) was observed in plant biomass in the first year of a lysimetric experiment after sewage sludge fertilization with doses greater than 10 t/ha. The increase in bioaccumulation of this compound in plant biomass compared to control objects was 138%, 288%, and 505% after application of 20, 30, and 40 t/ha, respectively. Fertilization with sewage sludge did not cause contamination with PAHs in water leachates from the soils.

Many publications point out to sewage sludge as a significant sources of polycyclic aromatic hydrocarbons (PAH). Some authors note that the amount of PAHs in plants increases as their concentration in the soil increases. It was often believed that as they are high-molecular compounds, their ability to migrate to plants is limited. In their studies, the authors of the present work took note of the contents of PAHs in sewage sludges used for agricultural purposes. They were used to fertilize a sandy soil in a dose of 10, 50, 100 and 200 t/ha, respectively. The tests were conducted in pot cultures under natural conditions. Osier willow (salix) and dactylis were grown on the sludge-soil mixtures. The use of sewage sludges for fertilization caused a significant increase in the contents of polycyclic aromatic hydrocarbons in the soils. The application of manure for fertilization resulted in the lowest increase in the contents of these components in the fertilized grounds. It was also found that fertilization with manure did not cause any significant increase in PAH contents in the plants grown. No increase in PAH contents in plants with increasing manure dose was noted either.