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Separation of Cellulose fromWastewater and Valorisation via Pyrolysis: A Case Study in the Czech Republic
(MDPI, 2024-04-05) Djordjevićová, Denisa; Miino, Marco Carnevale; Raček, Jakub; Chorazy, Tomáš; Hlavínek, Petr; Vranayová, Zuzana
Currently, the recovery of resources from urban wastewater (WW) represents a priority. On this topic, the potential recovery of cellulose for its subsequent reuse in different sectors is gaining interest. In this work, a large-size conventional wastewater treatment plant (WWTP) was selected as a case study. A preliminary mechanical treatment was used, with the aim of separating, quantifying, and characterizing cellulose in WW. The results suggest that the per-capita production of dry primary cellulosic sludge (D-PCS) is equal to 1.46 ± 0.13 kgD-PCS PE1 y1, with an average calorific value of 21.04 MJ kg1DM. Cellulosic fibres have an average length of >100 µm and a thickness of 2–5 µm. The D-PCS was subsequently treated via medium-temperature pyrolysis; a total of 29.5% of the initial D-PCS was converted into pyrolyzed primary cellulosic sludge (P-PCS) and only 26% into pyrolytic gas. More than 44.5% of the dried cellulose can be converted into pyrolytic oil. Moreover, three different scenarios of recovery have been considered, and the impact of cellulose separation in terms of COD fluxes entering the WWTP and potential energy recovery has been studied. The results suggested that, in this case study, the potential separation of the primary cellulosic sludge from the influent water flux would have no significant impact on COD load entering the biological treatments and biogas production in the anaerobic digestion of the secondary sludge.
Comparison of Trenchless and Excavation Technologies in the Restoration of a Sewage Network and Their Carbon Footprints
(MDPI, 2024-01-15) Chorazy, Tomáš; Hlavínek, Petr; Raček, Jakub; Pietrucha-Urbanik, Katarzyna; Tchórzewska-Cieślak, Barbara; Keprdová, Šárka; Dufek, Zdeněk
The restoration of aging sewer networks is a fundamental remediation approach with the aim of renewing or improving existing systems. Remediation methods include repair, renovation, and replacement (renewal). The restoration of a sewer network itself can be performed using either excavation or trenchless technologies. While these technologies offer various advantages, they also present disadvantages. The choice of a restoration technology depends on numerous parameters, including economic factors and local conditions (such as the construction of the existing sewage network, available working space, traffic load, and environmental safety restrictions). In addition to the parameters influencing the choice of restoration technology, recent considerations have been given to constraints related to greenhouse gas emissions and the corresponding carbon footprint. Carbon footprint serves as an indicator of the restoration activity’s dependence on fossil fuels, both during implementation and operation. In the 21st century, concerns regarding carbon footprints have rapidly escalated. The reduction in carbon footprints is a crucial objective from both an economic and an ecological point of view. This article specifically addresses the prospects of monitoring the carbon footprint concerning the partial restoration of a sewer network within the historical core of the city of Brno, located in the Czech Republic.
Investigation of the process of heat transfer in the structure of thermal insulation materials based on natural fibres
(Elsevier, 2016-08-03) Zach, Jiří; Slávik, Richard; Novák, Vítězslav
Thermal insulation materials based on natural fibres are some of the promising materials that are currently emerging on the construction market. These materials are important especially in terms of sustainable development, since they utilise renewable raw material resources or secondary materials and their production does not consume too much energy. However, a problem with these materials is the rather different behaviour during heat and moisture transport compared with conventional insulation, which is made from synthetic (foam polystyrene) or inorganic (mineral wool) materials. The paper presents the results of a practical investigation into the process of heat transfer through the structure of thermal insulation materials based on natural fibres.
Studying the Properties of Particulate Insulating Materials on Natural Basis
(Elsevier, 2016-08-03) Reif, Martina; Zach, Jiří; Peterková, Jitka
Recently, materials based on secondary raw materials have been the focus of attention of building companies and end users as well. The reason for this are mainly the low material costs, easy manufacture and application in building structures. Despite the lower cost compared to existing insulation materials, strict requirements are put on these thermal insulation materials. In response to the constantly increasing need for insulation materials and given the general requirement of sustainability in the use of natural resources, the Faculty of Civil Engineering in Brno has for many years been engaged in the development of insulation materials made from natural fibres of agricultural origin. These materials show great promise in civil engineering. They have a low carbon footprint and low primary energy input. Experimental testing conducted in the past has revealed that the properties of these materials are comparable to those of the synthetic insulations available on the market. However, in terms of thermal insulation properties, the natural-fibre materials have different hygrothermal behaviour, which is due to the different structure of the insulations as well as the low value of thermal conductivity of the natural fibres (compared with e.g. glass or mineral fibres). The paper deals with the development of particulate insulation based on natural fibers, their behavior under different conditions and mainly with the examination of the thermal properties depending on moisture and bulk density. The paper also presents the results of research in the dependency of thermal insulation, acoustic and mechanical properties of the experimentally manufactured insulations on their bulk density.
Alternative technology of constructing masonry structures designed for areas with increased seismic activity
(Elsevier, 2016-07-21) Sedlmajer, Martin; Zach, Jiří; Novák, Vítězslav; Peterková, Jitka; Horský, Antonín
The Czech Republic is a country which generally sees low seismic activity; however, this activity needs to be taken into account in ca 50 % of the country’s area with 10 districts being considered as having seismic activity higher than 0.08 g. In terms of masonry structures, this issue concerns mainly the execution of the head joints of the masonry and its reinforcement (both in the direction of the bed joint and in the perpendicular direction). All these technologies are rather difficult and expensive to implement. The research focuses on assessing the possibilities of constructing dry masonry and binding it with polyurethane foam. This method allows for significantly higher shear strength of the masonry and appears to be an interesting alternative in the area of constructing buildings in seismically active areas. The structure was stiffened by filling hollow masonry units with large cavities with polyurethane foam. The PUR foam was sprayed into the units during construction. The foam thus applied hardens perpendicularly to the bed joint of the masonry and, having expanded throughout the clay units, it functions as a binder and a stiffening component to the masonry as a whole. The initial shear and flexural strength of the masonry segments was determined. The newly developed method of filling the cavities of masonry units with PUR foam was compared with the conventional method of constructing masonry by means of bonding the blocks with mortar or PUR foam in the bed joints (with no cavities filled). The filling of the masonry unit cavities brought a significant increase in the shear and flexural strength of the masonry. This indicates the stiffness of the structure increased as well.

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