Removal of contaminants from liquid after hydrothermal carbonization of sewage sludge using a combination of membrane techniques and struvite precipitation - replication data

Poland's obligation to meet the EU's RES target has resulted in the growing interest in the biogas market. Simultaneously, the state's energy policy introduces solutions to support biogas plants. In addition, new developing technologies should also be applied to sufficiently increase the biogas production and to utilise the potential in generated biomass waste either from wastewater plant or agricultural production. That is why the detailed information of every aspect of the process including potential disposal of products and by-products from biogas plant and environmental impact has to be determined. Also, European energy policy is focussed on reduction of waste in the landfilling. Therefore, the thermal conversion of biogas plant waste is required thus hydrothermal carbonization (HTC) seems to be a promising method. This method is carried out in aqueous environment, that is why digestate is a suitable feedstock due to a high moisture content (c.a. 80%) and organic origin. The obtained products of HTC might be further process into biofuels, biofertilizers or absorbents. The researchers are interested in hydrothermal treatment of digestate from sewage sludge, mainly because it is proven to enhance its dewaterability, but the digestate derived from agriculture biogas plant is not so widely studied. Therefore, the scientific knowledge of the products properties and its formation is essential to fulfil this gap. The main aim of the project is to investigate the impact of the main parameters of the process (temperature and residence time) on the physical and chemical properties of HTC products from digestate. Additionally, the determination of its mechanism formation will be done by multifaceted description using highly advanced instrumental techniques. The tested material will be digestate from anaerobic treatment of municipal and agricultural wastes. The process will be conducted in a stainless steel Zipperclave Stirred Reactor equipped with a MagneDrive Agitator. Then, the wide description of physical and chemical properties of solid, liquid and gaseous products will be determined. Pathway formation and transformation of inorganic elements, in particular of heavy metals, in solid product-hydrochar will be analysed. The biofuel properties of hydrochar strongly depends on the process parameters and feedstock origin. Therefore, the in-depth discussion of those factors affecting the ultimate and proximate analysis, energy and mass yields, densification ratio, higher heating value for will be carried out. Also, the mechanism of combustion behaviour of hydrochar will be studied using thermal analysis. In addition, the gasification of hydrochar will be carried out to find out the potential of syngas production. The instrumental and chemical methods to study the fibre structure (van Soest method) and chemical bonds in hydrochar will be also used (FTIR) to investigate the mechanism of the pore structure formation in order to determine its sorptive and fertile properties (SSA and pores distribution). Furthermore, the impact of temperature and residence time of hydrothermal treatment will be studied on liquid phase when the complex reactions take place resulting in a high load of dissolved total organic carbon content and nutrients. That is why its chemical composition and main characteristic parameters will be analysed and discussed. In addition, the eco-toxicity properties and potential in a anaerobic digestion as a biomethane producer will be tested. Moreover, investigation of vacuum depth in vacuum distillation process of postprocessing liquid and its impact on rheological properties of distillation residue will be also studied. The elaboration of scientific dependences between digestates, process parameters and solid and liquid phases will be deeply discussed. The results will demonstrate the multicriterial analysis of tested materials giving a new fundamental knowledge about the hydrothermal process and its product properties. Moreover, the circular economic European goal to “reuse, replace and reduce” will be achieved by enhancing properties of digestate and its reduction in the landfilling.