The treatment of wastewater and the utilization of the by-products of these processes are an important part of the circular economy. The sewage sludge, a result of wastewater treatment, could be used as a material for plant nutrient supply and/or soil-improving products. The city of Nyíregyháza, Hungary, with 120,000 citizens, has a well-planned water treatment plant operated by Nyírségvíz Ltd., which, in cooperation with the Research Institute of Nyíregyháza, developed a municipal sewage sludge compost (SSC). The closed loop of sewage water treatment and the agricultural utilization of its by-product has been developed and managed. The compost product called Nyírkomposzt was planned for acidic sandy soils. Beyond the agronomic benefits, the sustainable and environmentally sound utilization of SSC reduces sewage sludge disposal. This active involvement of a water utility company demonstrates the potential of cross-sectoral cooperation in solving environmental problems. The quality of the compost fits the Hungarian legislation. To study the effects of 0, 9, 18, and 27 t ha⁻¹ doses of compost on acidic sandy soil, a long-term small plot experiment was started in 2003. The cumulative effects of the regular (every third year, last treatment before sampling in 2021) application of the SSC showed positive changes in basic soil properties, depending on the doses used. Increasing values were found in the case of pH from 4.5 to 6, plant available P₂O₅ from 240 to 690 ppm, and plant available K₂O from 180 to 200 ppm. The plant-available zinc and copper content also increased. Soil organic matter and total N content stabilized at around 0.9% and 0.08%, respectively. The grain yields of winter rye also increased in both investigated years. The yields of 18 t ha⁻¹ treatment were about two times higher compared to the control, but only in 2022 was the difference significant. Our findings underscore the potential of well-planned SSC applications to improve the fertility of ploughed, acidic sandy soil, taking into account the theory of the circular economy by utilizing wastes and decreasing landfilling.

Pharmaceutical agents accumulate in wastewater after consumption, but the conventional sewage treatment process is unable to remove them completely. The occurrence of certain compounds in the environment brings forth serious problems even at low concentrations. In this study, the microbiological elimination ability of four non-steroidal anti-inflammatory drugs (NSAIDs)—ibuprofen, naproxen, ketoprofen and diclofenac—were investigated under laboratory, pilot and plant conditions. Mixed cultures from environmental matrices presumably have the ability to reduce the concentration of target agents effectively. According to our analytical measurements, certain mixed cultures gained from natural habitats were even capable of reducing the amount of diclofenac efficiently, after being enriched to a 10⁹ colony-forming unit—CFU/mL scale, and inoculated in adequate quantity. Target NSAIDs were detected at µg/L levels in both influents and effluents from wastewater treatment plants (WWTPs). The results showed that inoculated conventional activated sludge sewage treatment technologies have high efficiency for removing ibuprofen, ketoprofen and naproxen. The diclofenac-specific bacteria mix exhibited mild but positive removal efficiency compared to the control plant. This removal ability is also influenced by the hydraulic retention time (HRT).