From Sewage Sludge to the Soil-Transfer of Pharmaceuticals: A Review.

Sewage sludge, produced in the process of wastewater treatment and managed for agriculture, poses the risk of disseminating all the pollutants contained in it. It is tested for heavy metals or parasites, but the concentration of pharmaceuticals in the sludge is not controlled. The presence of these micropollutants in sludge is proven and there is no doubt about their negative impact on the environment. The fate of these micropollutants in the soil is a new and important issue that needs to be known to finally assess the safety of the agricultural use of sewage sludge. The article will discuss issues related to the presence of pharmaceuticals in sewage sludge and their physicochemical properties. The changes that pharmaceuticals undergo have a significant impact on living organisms. This is important for the implementation of a circular economy, which fits perfectly into the agricultural use of stabilized sewage sludge. Research should be undertaken that clearly shows that there is no risk from pharmaceuticals or vice versa: they contribute to the strict definition of maximum allowable concentrations in sludge, which will become an additional criterion in the legislation on municipal sewage sludge.

The impact of sewage sludge processing on the safety of its use.

Particular attention is devoted to pharmaceutical residues in sewage sludge caused by their potential ecotoxicological effects. Diclofenac, ibuprofen and carbamazepine, 17-α-ethinylestradiol, ß-estradiol, were analysed in four types of fertilizers, based on sewage sludge commercial products, in compliance with Polish requirements. The release of active pharmaceutical compounds from fertilizers to water the phase after 24 h and 27 days was analysed. Solid-water partition coefficients (Kd) and partitioning coefficient values normalized on organic carbon content (log KOC) were evaluated. The environmental risk to terrestrial ecosystems, due to the application of fertilizers onto soils, was estimated. Cumulative mass of pharmaceuticals emitted to water from fertilizers ranged from 0.4 to 30.8 µg/kg after 24 h contact. The greatest amount of the material that was released, over 70%, was observed for carbamazepine. No presence of compounds except ibuprofen was observed after 27 days of testing. The highest environmental risk in fertilizers is due to carbamazepine, risk quotation, RQ = 0.93 and diclofenac RQ = 0.17. The values of risk quotation estimated for soil were below RQ = 0.01. This fact means that no risk to terrestrial ecosystems is expected to occur. The important decrease of the concentrations of active compounds after passing from sewage sludge to fertilizers [and] to fertilized soil could be observed.

Efficiency studies of modified IFAS-OSA system upgraded by an anoxic sludge holding tank.

An upgraded integrated fixed-film activated sludge-oxic settling anoxic (IFAS-OSA) system is a new technology for reducing nutrients and excess sludge. The results showed that the average TN removal efficiency of the IFAS-OSA system was gradually increased up to 7.5%, while the PO4-3-P removal efficiency increased up-to 27%, compared with that of the IFAS system. The COD removal efficiency of the IFAS-OSA system was slightly increased up-to 5.4% and TSS removal efficiency increased up to 10.5% compared with the control system. Biomass yield coefficient (Yobs) in the IFAS and IFAS-OSA systems were 0.44 and 0.24 (gr MLSS/ gr COD). Hence, sludge production decreased by 45%. The average SVI was decreased by 48% in IFAS-OSA system compared with IFAS. This study demonstrated the better performance of the IFAS-OSA system compared to that of the IFAS system.

Towards a bio-based circular economy in organic waste management and wastewater treatment - The Polish perspective.

Bio-based solutions are expected to ensure technological circularity in priority areas such as agriculture, biotechnology, ecology, green industry or energy. Although Poland, unlike the other EU member states, has not yet adopted a precise political strategy to promote bioeconomy, it has taken several actions to enable smart, sustainable and inclusive growth. This goal can be achieved by developing selected bioeconomy-related areas such as the biogas industry together with novel technologies implemented to optimize treatment of municipal sewage and management of organic solid waste. Here, the relatively strong status of the Polish biogas sector is presented. The widely used practice of sewage sludge biomethanation has led to construction of numerous complex installations combining biological wastewater treatment plants with anaerobic digesters. Based on physico-chemical processing of biostabilized sludges, a novel method for efficient granulated soil fertilizer production is elaborated, in line with the concept of circular economy and the notion of "waste-to-product". It is also shown that anaerobic fermentation of sewage sludges can be optimized by co-digestion with properly selected co-substrates to increase bioprocess yield and improve the resultant digestate fertilizer quality. The problem of post-fermentation eutrophic sludge liquors, environmentally hazardous waste effluents requiring proper treatment prior to discharge or field application, is addressed. Attempts to optimize biological treatment of digestate liquors with complex microbial consortia are presented. The Polish innovations described show that the "zero waste" path in circular bioeconomy may bring advantageous results in terms of transformation of waste materials into commercial, added-value products together with recovery of water resources.

Manufacturing of Lightweight Aggregates as an Auspicious Method of Sewage Sludge Utilization.

Sewage sludge is a high-volume and low-cost waste commonly generated worldwide, so its utilization is a vital issue. The application of this waste in the manufacturing of lightweight aggregates was investigated. The process was performed using intensive mixers with volumes of 5 and 30 L, as well as the industrial 500 L mixer. Then, granulates were sintered in a tube furnace. The influence of composition and mixer size on the particle size, microstructure, mechanical performance, and stability of lightweight aggregates in different environments was analyzed. The best results were obtained for a 500 L mixer, enhancing the industrial potential of the presented process. Increasing the share of sewage sludge in the composition of aggregates enhanced their porosity and reduced the specific weight, which caused a drop in compressive strength. Nevertheless, for all analyzed materials, the mechanical performance was superior compared to many commercial products. Therefore, sewage sludge can be efficiently applied as a raw material for the manufacturing of lightweight aggregates. The presented results confirm that a proper adjustment of composition allows easy the tailoring of aggregates' performance and cost.