Paper presents the results of investigations on sorption capacity of selected carcinogenic polycyclic aromatic hydrocarbons (PAHs) on microplastics fibers. Accumulation of organic micropollutants such as PAHs is indicated as one of the important problems in the case of microplastics present in surface water, including sea water. Concentrations of the micropollutants can reach even several mg/kg of microplastics. An unrecognized problem are sorption capacities of microfibers towards PAHs. Recent research works indicate that microfibers are commonly present in sewage sludge. Content of the fibers in this waste material can reach over 23000 particles per 1 kg of sludge dry matter. The fibers mainly come from cloth washing. It is obvious that the adsorption capacity of the fibers can affect the concentration of PAHs in sewage sludge. The aim of the study was to evaluate sorption capacities of polyester fibers towards PAHs. Adsorption of PAHs were provided under static conditions. After 24 h of adsorption 1255 μg/g of carcinogenic PAHs was adsorbed onto the polyster fibers. Amount of 6-ring PAHs was equal to 154 μg/g, whereas 5- i 4- ring ones, 562 and 539 μg/g, respectively. The results have confirmed that hydrophobic PAHs can be adsorbed onto polystyrene fibers and as a result cumulate in sewage sludge.

The results of investigations on heavy metals and polycyclic aromatic hydrocarbons (PAHs) content in mixed soil fertilized with sewage sludge are presented. The concentration of these micropollutants in various parts of a basket willow Salix viminalis grown on this substratum was also analyzed. Aerobically stabilized, dewatered, and hygienized sewage sludge (a dose of 90 tons of dry matter per hectare) was used to fertilize the soil. S. viminalis was planted on the soil amended with sewage sludge. The samples for analyses were taken after five vegetatives; they were both soil samples and parts of plants (roots, stems, and leaves). The concentration of heavy metals and PAHs was analyzed in the samples. The concentration of heavy metals in soil after five seasons of fertilizing with sewage sludge was at most cases higher than defined in soil at the beginning of the experiment. The concentration of Cr in soil after five years of S. viminalis cultivation was, however, lower than at the outset. The average concentration of Cr in biomass of a basket willow equaled to 9.3 mg/kg_d.m. and it was higher than the average content of this element in not fertilized soil samples (4.6 mg/kg_d.m.). The content of other heavy metals in willow biomass was lower than the soil concentration and was equal to 0.7, 7.9, 1.3, 13.2, and 47.0 mg/kg_d.m. for Cd, Cu, Ni, Pb, and Zn, respectively. The concentration of 15 PAHs total in soil did not exceed 700 μg/kg_d.m.. The total concentration of 15 PAHs was also analyzed in particular parts of S. viminalis. The average total concentration of these micropollutants in roots was equal to 67 μg/kg_d.m.. The total concentration of 15 PAHs in above ground parts of plants was equal to 115 and 55 μg/kg_d.m. for leaves and stems, respectively.

The results of investigations on the efficiency of the removal of polycyclic aromatic hydrocarbons (PAHs) from wastewater exposed to UV radiation are presented. The investigations were carried out using wastewater originating from an industrial treatment plant. Samples of wastewater were exposed to UV rays for 30, 60, and 90 s. After exposition to UV rays, PAHs concentration was determined in the samples. Extraction of PAHs from samples was made with the mixture of: cyclohexane and dichloromethane. The quantitative analysis of PAHs by high performance liquid chromatography with a fluorimetric detector was carried out. After exposition to ultraviolet rays, a decrease in PAHs concentration in the samples was observed. Exposure of wastewater to UV-rays resulted in a decrease in the concentration of PAHs in wastewater from an industrial wastewater treatment plant up to 50%. The efficiency of the removal for individual hydrocarbons was varied as it was in the range of 5–67%. The half-life time of hydrocarbons (without naphthalene) was in the range of 64–123 s under exposition to UV rays.

Wastewater treatment plants are considered to be not only as treatment facilities, but also essential elements of the circular economy. Wastewater treatment plants can be essential chains of the circular economy cycle. Despite this, sewage sludge management and utilization are mostly limited to biodegradation and further agricultural uses or incineration. The recovery of valuable products is mainly limited to nitrogen and phosphorus compounds. Fewer analyses focus on generating, recovering, and removing various polymers from sewage sludge, such as cellulose or extracellular polymeric substances (EPS). On the other hand, sewage sludge also contains polymeric pollutants, such as microplastics. The recovery and use of biopolymers is significant considering the problems connected with the presence and effects of artificial polymers (microplastics) in the environment. Despite the technical possibilities, not many technical scale installations are operated. Law regulations should make some incentives to develop the technologies and sell the recovered polymers in the market not as waste material, but as a valuable product. This paper presents state-of-the-art technologies for selected polymers’ recovery from sludge, including technical parameters of the processes and possible applications of recovered products, but it also considers the possibility of microplastics’ removal from this waste material.