SEWAGE SLUDGE MANAGEMENT AT THE CENTRAL WASTEWATER TREATMENT PLANT LJUBLJANA – CHARACTERIZATION OF ITS PROPERTIES, POSSIBILITIES FOR SUSTAINABLE UTILIZATION AND LEGISLATIVE OBSTACLES

The treated sewage sludge under consideration is a hygienized biodegradable waste in the form of pellets. It can be used as a fertilizer, but only for spreading on non-agricultural land. Regarding “waste to energy” philosophy, the specification of pellets as an alternative solid fuel according to EN 15359 resulted in “NCV4; Cl1; Hg3-4” class. The major problem regarding the final pellets utilization is the lack of facilities for energy and material recovery from this type of waste in Slovenia. According to the newest legislation regarding the waste management, a product status for residues generated in combustion and pyrolysis of pellets on a laboratory and semi-pilot scale was not achieved. The holistic approach to final pellets utilization was studied and regarding the full-scale level of self-sufficient sewage sludge management in Slovenia, some legislative provisions become significant obstacles

Basic Morphological, Thermal and Physicochemical Properties of Sewage Sludge for Its Sustainable Energy and Material Use in the Circular Economy

The treated sewage sludge is a smart material that provides sustainable use of energy and material that can be adapted to the needs of modern human life. Pyrolysis is one of the waste recovery operation that enables the generation of various useful groups of substances from treated sludge, which can then be utilized separately by final energy and material recovery processes: (i) solid residue (pyrogenic material), (ii) liquid fraction (bio-oil), and (iii) non-condensable gas. Those fractions are the basis for fertilizers and alternative fuel or new chemicals production. The chapter combines data on the quality of treated sludge as a case study of an urban wastewater treatment plant (UWWTP) with the capacity of 360,000 population equivalents (PE). The analytical results of dried anaerobically treated sludge over a 10-year period (from 2010 to 2020) are evaluated with respect to the limit values from directives, resolutions, guidelines, and national legislation related to specific processing procedures and quality of the final product. The data provide a comprehensive insight into the basic properties of treated sludge and allow thoughtful use of this smart material for WtE processes, organic matter material conversion, and agricultural use in terms of protecting the environment and human health

Specification and Classification of Pelletised Dried Sewage Sludge: Identifying Its Key Properties as a Renewable Material for Enabling Environmentally Non-Harmful Energy Utilisation

Renewable active sludge is a smart material for wastewater treatment and the protection of surface water bodies. The generated pellets (dried and pelletised dehydrated anaerobically stabilised excess sludge) are produced in a quantity of 31.4 ± 5.6 g dry matter (DM) per one Population equivalent (PE) calculated to COD (PECOD) in one day. As pellets are combustible material, their energy utilisation must reach the sustainable development goals (SDGs)—a bridge must be created between “treated sewage sludge as the tool to remove pollutants and nutrients from wastewater” and “preparation of the valuable material as a solid recovered fuel (SRF) that meets customer-specific requirements”. Technical Report CEN/TR 15508 and Technical Standard EN ISO 21640 set up methods for specifying and classifying pellets as an SRF. In the last eleven years (2010–2021), pellets’ net calorific value (NCV) is 13.0 ± 0.7 MJ kg−1 as received (ar). In 2021, the 80th percentile of the Hg/NCV ratio was 0.079 mg Hg MJ−1. In 2010–2021, the annual amount of Hg transferred to stakeholders reduced by 64.3% m/m—from 10.1 kg to 3.67 kg. The halogen contents of the pellets do not threaten corrosion to the incineration facility. Stable pellets’ energy potential and perspective ash composition for critical raw materials recovery qualify pellets as a specific waste stream and a renewable material for SRF production

Specification and Classification of Pelletised Dried Sewage Sludge: Identifying Its Key Properties as a Renewable Material for Enabling Environmentally Non-Harmful Energy Utilisation

Renewable active sludge is a smart material for wastewater treatment and the protection of surface water bodies. The generated pellets (dried and pelletised dehydrated anaerobically stabilised excess sludge) are produced in a quantity of 31.4 ± 5.6 g dry matter (DM) per one Population equivalent (PE) calculated to COD (PECOD) in one day. As pellets are combustible material, their energy utilisation must reach the sustainable development goals (SDGs)—a bridge must be created between “treated sewage sludge as the tool to remove pollutants and nutrients from wastewater” and “preparation of the valuable material as a solid recovered fuel (SRF) that meets customer-specific requirements”. Technical Report CEN/TR 15508 and Technical Standard EN ISO 21640 set up methods for specifying and classifying pellets as an SRF. In the last eleven years (2010–2021), pellets’ net calorific value (NCV) is 13.0 ± 0.7 MJ kg−1 as received (ar). In 2021, the 80th percentile of the Hg/NCV ratio was 0.079 mg Hg MJ−1. In 2010–2021, the annual amount of Hg transferred to stakeholders reduced by 64.3% m/m—from 10.1 kg to 3.67 kg. The halogen contents of the pellets do not threaten corrosion to the incineration facility. Stable pellets’ energy potential and perspective ash composition for critical raw materials recovery qualify pellets as a specific waste stream and a renewable material for SRF production

First inter-laboratory comparison exercise for the determination of anticancer drugs in aqueous samples

The results of an inter-laboratory comparison exercise to determine cytostatic anticancer drug residues in surface water, hospital wastewater and wastewater treatment plant effluent are reported. To obtain a critical number of participants, an invitation was sent out to potential laboratories identified to have the necessary knowledge and instrumentation. Nine laboratories worldwide confirmed their participation in the exercise. The compounds selected (based on the extent of use and laboratories capabilities) included cyclophosphamide, ifosfamide, 5-fluorouracil, gemcitabine, etoposide, methotrexate and cisplatinum. Samples of spiked waste (hospital and wastewater treatment plant effluent) and surface water, and additional non-spiked hospital wastewater, were prepared by the organising laboratory (Jožef Stefan Institute) and sent out to each participant partner for analysis. All analytical methods included solid phase extraction (SPE) and the use of surrogate/internal standards for quantification. Chemical analysis was performed using either liquid or gas chromatography mass (MS) or tandem mass (MS/MS) spectrometry. Cisplatinum was determined using inductively coupled plasma mass spectrometry (ICP-MS). A required minimum contribution of five laboratories meant that only cyclophosphamide, ifosfamide, methotrexate and etoposide could be included in the statistical evaluation. z-score and Q test revealed 3 and 4 outliers using classical and robust approach, respectively. The smallest absolute differences between the spiked values and the measured values were observed in the surface water matrix. The highest within-laboratory repeatability was observed for methotrexate in all three matrices (CV ≤ 12 %). Overall, inter-laboratory reproducibility was poor for all compounds and matrices (CV 27–143 %) with the only exception being methotrexate measured in the spiked hospital wastewater (CV = 8 %). Random and total errors were identified by means of Youden plots