Waste and recycled materials have recently been used in the construction industry to comply with the principles of circular economy and sustainable development. The aim of this paper is to examine the potentials of solidified wastewater treatment sludge (SWWTS) as a supplementary cementitious material (SCM) in the production of lightweight pervious concrete pavers (LWPCP) suitable for pedestrian trails and rooftops (green) that comply with EU standards. Detailed characterization of SWWTS was performed, in order to understand its properties related to application as SCM, which led to the conclusion that it may be applied only as a filler, having 89.5% of Ca(OH)₂. After thorough characterization, LWPCP samples were prepared and testing of physical and mechanical properties was conducted. The research showed that partial replacement of cement with SWWTS led to the decrease of all mechanical properties, ranging between 3.91 and 5.81 MPa for compressive strength and 0.97 to 1.23 MPa for flexural strength. However, all of the investigated mixtures showed a value higher than 3.5 MPa, which was defined as the lowest compressive strength in the range of pervious concrete properties. The addition of SWWTS led to a slight decrease in bulk density of the mixtures and an increase in water absorption. This could be explained by the reduction in hydration products that would fill in the micropores of the matrix, since SWWTS showed no pozzolanic reactivity. Pore sizes that prevail in the tested binder matrices are in accordance with the results measured on ordinary pervious concrete (the largest fraction of pores had a diameter between 0.02 and 0.2 μm). Low thermal conductivity nominates produced pavers as potential rooftop elements.

The inflow of infiltration and rainwater into the foul sewers cannot be completely avoided, but if this inflow is excessive, it can lead to serious consequences for the operation of sewerage and municipal wastewater treatment plants. The paper presents the causes and consequences of clean water inflow into the sewage, with an emphasis on their impact on the sewer system performance and the efficiency of municipal wastewater treatment processes. In the context of accelerated construction of sewage systems and treatment plants, it is highlighted that urgent and systematic attention must be paid to this issue in the Republic of Serbia.

The paper presents challenges that urban drainage has to solve under altering hydrological regime due to urbanization. The need for reducing the negative impacts of urbanization on the quantity and quality of urban runoff is emphasized. Innovative methods of urban drainage have been presented, together with general recommendations for their application. The requirements from the proposal of the new EU Directive on urban wastewater related to the integrated management of urban wastewater, including rainwater, are presented in more detail.

Urbanization increases pluvial flood risk by expanding impermeable surfaces, which is a trend likely to intensify with climate change. Permeable pavement (PePav) made from industrial byproducts, in accordance with circular economy principles, may improve soil permeability. Public acceptance remains a critical barrier to its implementation. Existing measures of willingness to accept (WtA) new technologies are inconsistent, limiting interdisciplinary collaboration. Therefore, a concise WtA scale was adapted from the Bogardus Social Distance Scale to assess acceptance of PePav at varying levels of proximity in residential contexts, from public flood-prone roads to private yards. The scale was evaluated across three studies: Study 1 (N = 195) and Study 2 (N = 187) utilized mixed student samples, while Study 3 (N = 625) involved a non-student sample. The 5-item solution, identified through factor analysis in Study 1, consistently demonstrated a unidimensional and cumulative structure and satisfactory reliability, even after the proposed PePav ingredient modification in subsequent studies. The scale correlated with recycling experience and professional background, indicating convergent validity, but not with flooding or informal construction experience, across all samples. Study 3 provided evidence of external validity by incorporating empirically well-established Theory of Planned Behavior (TPB) constructs and showing that WtA predicted PePav use beyond TPB variables and demographics. The scale also showed measurement invariance across sample type (student vs. general population) and different levels of construction experience. The constructed WtA scale is suitable for efficiently assessing professional and public acceptance of circular building materials and may have broad cross-disciplinary relevance. This enables timely, targeted interventions and informed policy decisions to advance sustainable technologies in the built environment, with substantial implications for education, professional policy, and sustainable engineering. Nevertheless, further validation is required.

Urban areas are increasingly challenged by pluvial flooding, driven by climate change and the expansion of impervious surfaces. Conventional sewer systems often lack the capacity to manage increased volumes of stormwater, resulting in water spills in the lowest floors of buildings, retention of water on the ground and potential contamination. Implementing nature-based solutions, such as porous concrete pavements, supports controlled infiltration and retention of stormwater, thereby reducing peak flows, lowering runoff volumes, and improving infrastructure durability. The integration of nature-inspired solutions and gray infrastructure leads to an increased use of recycled materials for the sustainability and resilience of urban environments to flooding.

The paper presents the causes and consequences of clean water inflow into the sewage system, with a particular focus on its impact on the functioning of the sewer network and the efficiency of the wastewater treatment process. Special emphasis is placed on the urgent need for a systematic and adequate response to this issue in the Republic of Serbia.